| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Josh Poimboeuf | 10768 | 55.71% | 117 | 42.09% |
| Peter Zijlstra | 7095 | 36.70% | 93 | 33.45% |
| Julien Thierry | 471 | 2.44% | 12 | 4.32% |
| Marco Elver | 239 | 1.24% | 8 | 2.88% |
| Alexandre Chartre | 134 | 0.69% | 3 | 1.08% |
| Sami Tolvanen | 106 | 0.55% | 4 | 1.44% |
| Matt Helsley | 91 | 0.47% | 1 | 0.36% |
| Michal Kubeček | 62 | 0.32% | 1 | 0.36% |
| Allan Xavier | 57 | 0.29% | 1 | 0.36% |
| Jann Horn | 40 | 0.21% | 2 | 0.72% |
| Alexander Potapenko | 39 | 0.20% | 1 | 0.36% |
| Nicholas Piggin | 37 | 0.19% | 1 | 0.36% |
| Raphael Gault | 28 | 0.14% | 2 | 0.72% |
| Ilie Halip | 24 | 0.12% | 1 | 0.36% |
| Joe Lawrence | 21 | 0.11% | 1 | 0.36% |
| Thomas Gleixner | 21 | 0.11% | 2 | 0.72% |
| Linus Torvalds | 20 | 0.10% | 5 | 1.80% |
| Sathvika Vasireddy | 16 | 0.08% | 3 | 1.08% |
| Vasily Gorbik | 12 | 0.06% | 2 | 0.72% |
| Mikulas Patocka | 11 | 0.06% | 1 | 0.36% |
| Christophe Leroy | 6 | 0.03% | 2 | 0.72% |
| Arnd Bergmann | 4 | 0.02% | 1 | 0.36% |
| Simon Ser | 4 | 0.02% | 1 | 0.36% |
| Arnaldo Carvalho de Melo | 3 | 0.02% | 1 | 0.36% |
| Frédéric Weisbecker | 3 | 0.02% | 1 | 0.36% |
| Dan J Williams | 3 | 0.02% | 2 | 0.72% |
| Chen Zhongjin | 3 | 0.02% | 1 | 0.36% |
| Sam James | 2 | 0.01% | 1 | 0.36% |
| Petr Pavlu | 2 | 0.01% | 1 | 0.36% |
| Al Viro | 2 | 0.01% | 1 | 0.36% |
| Lu Hongfei | 2 | 0.01% | 1 | 0.36% |
| Mauro Carvalho Chehab | 1 | 0.01% | 1 | 0.36% |
| Andrey Konovalov | 1 | 0.01% | 1 | 0.36% |
| Borislav Petkov | 1 | 0.01% | 1 | 0.36% |
| Sergei Trofimovich | 1 | 0.01% | 1 | 0.36% |
| Total | 19330 | 278 |
// SPDX-License-Identifier: GPL-2.0-or-later /* * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com> */ #include <string.h> #include <stdlib.h> #include <inttypes.h> #include <sys/mman.h> #include <objtool/builtin.h> #include <objtool/cfi.h> #include <objtool/arch.h> #include <objtool/check.h> #include <objtool/special.h> #include <objtool/warn.h> #include <objtool/endianness.h> #include <linux/objtool_types.h> #include <linux/hashtable.h> #include <linux/kernel.h> #include <linux/static_call_types.h> struct alternative { struct alternative *next; struct instruction *insn; bool skip_orig; }; static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache; static struct cfi_init_state initial_func_cfi; static struct cfi_state init_cfi; static struct cfi_state func_cfi; static struct cfi_state force_undefined_cfi; struct instruction *find_insn(struct objtool_file *file, struct section *sec, unsigned long offset) { struct instruction *insn; hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) { if (insn->sec == sec && insn->offset == offset) return insn; } return NULL; } struct instruction *next_insn_same_sec(struct objtool_file *file, struct instruction *insn) { if (insn->idx == INSN_CHUNK_MAX) return find_insn(file, insn->sec, insn->offset + insn->len); insn++; if (!insn->len) return NULL; return insn; } static struct instruction *next_insn_same_func(struct objtool_file *file, struct instruction *insn) { struct instruction *next = next_insn_same_sec(file, insn); struct symbol *func = insn_func(insn); if (!func) return NULL; if (next && insn_func(next) == func) return next; /* Check if we're already in the subfunction: */ if (func == func->cfunc) return NULL; /* Move to the subfunction: */ return find_insn(file, func->cfunc->sec, func->cfunc->offset); } static struct instruction *prev_insn_same_sec(struct objtool_file *file, struct instruction *insn) { if (insn->idx == 0) { if (insn->prev_len) return find_insn(file, insn->sec, insn->offset - insn->prev_len); return NULL; } return insn - 1; } static struct instruction *prev_insn_same_sym(struct objtool_file *file, struct instruction *insn) { struct instruction *prev = prev_insn_same_sec(file, insn); if (prev && insn_func(prev) == insn_func(insn)) return prev; return NULL; } #define for_each_insn(file, insn) \ for (struct section *__sec, *__fake = (struct section *)1; \ __fake; __fake = NULL) \ for_each_sec(file, __sec) \ sec_for_each_insn(file, __sec, insn) #define func_for_each_insn(file, func, insn) \ for (insn = find_insn(file, func->sec, func->offset); \ insn; \ insn = next_insn_same_func(file, insn)) #define sym_for_each_insn(file, sym, insn) \ for (insn = find_insn(file, sym->sec, sym->offset); \ insn && insn->offset < sym->offset + sym->len; \ insn = next_insn_same_sec(file, insn)) #define sym_for_each_insn_continue_reverse(file, sym, insn) \ for (insn = prev_insn_same_sec(file, insn); \ insn && insn->offset >= sym->offset; \ insn = prev_insn_same_sec(file, insn)) #define sec_for_each_insn_from(file, insn) \ for (; insn; insn = next_insn_same_sec(file, insn)) #define sec_for_each_insn_continue(file, insn) \ for (insn = next_insn_same_sec(file, insn); insn; \ insn = next_insn_same_sec(file, insn)) static inline struct symbol *insn_call_dest(struct instruction *insn) { if (insn->type == INSN_JUMP_DYNAMIC || insn->type == INSN_CALL_DYNAMIC) return NULL; return insn->_call_dest; } static inline struct reloc *insn_jump_table(struct instruction *insn) { if (insn->type == INSN_JUMP_DYNAMIC || insn->type == INSN_CALL_DYNAMIC) return insn->_jump_table; return NULL; } static bool is_jump_table_jump(struct instruction *insn) { struct alt_group *alt_group = insn->alt_group; if (insn_jump_table(insn)) return true; /* Retpoline alternative for a jump table? */ return alt_group && alt_group->orig_group && insn_jump_table(alt_group->orig_group->first_insn); } static bool is_sibling_call(struct instruction *insn) { /* * Assume only STT_FUNC calls have jump-tables. */ if (insn_func(insn)) { /* An indirect jump is either a sibling call or a jump to a table. */ if (insn->type == INSN_JUMP_DYNAMIC) return !is_jump_table_jump(insn); } /* add_jump_destinations() sets insn_call_dest(insn) for sibling calls. */ return (is_static_jump(insn) && insn_call_dest(insn)); } /* * This checks to see if the given function is a "noreturn" function. * * For global functions which are outside the scope of this object file, we * have to keep a manual list of them. * * For local functions, we have to detect them manually by simply looking for * the lack of a return instruction. */ static bool __dead_end_function(struct objtool_file *file, struct symbol *func, int recursion) { int i; struct instruction *insn; bool empty = true; #define NORETURN(func) __stringify(func), static const char * const global_noreturns[] = { #include "noreturns.h" }; #undef NORETURN if (!func) return false; if (func->bind == STB_GLOBAL || func->bind == STB_WEAK) for (i = 0; i < ARRAY_SIZE(global_noreturns); i++) if (!strcmp(func->name, global_noreturns[i])) return true; if (func->bind == STB_WEAK) return false; if (!func->len) return false; insn = find_insn(file, func->sec, func->offset); if (!insn || !insn_func(insn)) return false; func_for_each_insn(file, func, insn) { empty = false; if (insn->type == INSN_RETURN) return false; } if (empty) return false; /* * A function can have a sibling call instead of a return. In that * case, the function's dead-end status depends on whether the target * of the sibling call returns. */ func_for_each_insn(file, func, insn) { if (is_sibling_call(insn)) { struct instruction *dest = insn->jump_dest; if (!dest) /* sibling call to another file */ return false; /* local sibling call */ if (recursion == 5) { /* * Infinite recursion: two functions have * sibling calls to each other. This is a very * rare case. It means they aren't dead ends. */ return false; } return __dead_end_function(file, insn_func(dest), recursion+1); } } return true; } static bool dead_end_function(struct objtool_file *file, struct symbol *func) { return __dead_end_function(file, func, 0); } static void init_cfi_state(struct cfi_state *cfi) { int i; for (i = 0; i < CFI_NUM_REGS; i++) { cfi->regs[i].base = CFI_UNDEFINED; cfi->vals[i].base = CFI_UNDEFINED; } cfi->cfa.base = CFI_UNDEFINED; cfi->drap_reg = CFI_UNDEFINED; cfi->drap_offset = -1; } static void init_insn_state(struct objtool_file *file, struct insn_state *state, struct section *sec) { memset(state, 0, sizeof(*state)); init_cfi_state(&state->cfi); /* * We need the full vmlinux for noinstr validation, otherwise we can * not correctly determine insn_call_dest(insn)->sec (external symbols * do not have a section). */ if (opts.link && opts.noinstr && sec) state->noinstr = sec->noinstr; } static struct cfi_state *cfi_alloc(void) { struct cfi_state *cfi = calloc(1, sizeof(struct cfi_state)); if (!cfi) { WARN("calloc failed"); exit(1); } nr_cfi++; return cfi; } static int cfi_bits; static struct hlist_head *cfi_hash; static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2) { return memcmp((void *)cfi1 + sizeof(cfi1->hash), (void *)cfi2 + sizeof(cfi2->hash), sizeof(struct cfi_state) - sizeof(struct hlist_node)); } static inline u32 cfi_key(struct cfi_state *cfi) { return jhash((void *)cfi + sizeof(cfi->hash), sizeof(*cfi) - sizeof(cfi->hash), 0); } static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi) { struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)]; struct cfi_state *obj; hlist_for_each_entry(obj, head, hash) { if (!cficmp(cfi, obj)) { nr_cfi_cache++; return obj; } } obj = cfi_alloc(); *obj = *cfi; hlist_add_head(&obj->hash, head); return obj; } static void cfi_hash_add(struct cfi_state *cfi) { struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)]; hlist_add_head(&cfi->hash, head); } static void *cfi_hash_alloc(unsigned long size) { cfi_bits = max(10, ilog2(size)); cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0); if (cfi_hash == (void *)-1L) { WARN("mmap fail cfi_hash"); cfi_hash = NULL; } else if (opts.stats) { printf("cfi_bits: %d\n", cfi_bits); } return cfi_hash; } static unsigned long nr_insns; static unsigned long nr_insns_visited; /* * Call the arch-specific instruction decoder for all the instructions and add * them to the global instruction list. */ static int decode_instructions(struct objtool_file *file) { struct section *sec; struct symbol *func; unsigned long offset; struct instruction *insn; int ret; for_each_sec(file, sec) { struct instruction *insns = NULL; u8 prev_len = 0; u8 idx = 0; if (!(sec->sh.sh_flags & SHF_EXECINSTR)) continue; if (strcmp(sec->name, ".altinstr_replacement") && strcmp(sec->name, ".altinstr_aux") && strncmp(sec->name, ".discard.", 9)) sec->text = true; if (!strcmp(sec->name, ".noinstr.text") || !strcmp(sec->name, ".entry.text") || !strcmp(sec->name, ".cpuidle.text") || !strncmp(sec->name, ".text..__x86.", 13)) sec->noinstr = true; /* * .init.text code is ran before userspace and thus doesn't * strictly need retpolines, except for modules which are * loaded late, they very much do need retpoline in their * .init.text */ if (!strcmp(sec->name, ".init.text") && !opts.module) sec->init = true; for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) { if (!insns || idx == INSN_CHUNK_MAX) { insns = calloc(sizeof(*insn), INSN_CHUNK_SIZE); if (!insns) { WARN("malloc failed"); return -1; } idx = 0; } else { idx++; } insn = &insns[idx]; insn->idx = idx; INIT_LIST_HEAD(&insn->call_node); insn->sec = sec; insn->offset = offset; insn->prev_len = prev_len; ret = arch_decode_instruction(file, sec, offset, sec->sh.sh_size - offset, insn); if (ret) return ret; prev_len = insn->len; /* * By default, "ud2" is a dead end unless otherwise * annotated, because GCC 7 inserts it for certain * divide-by-zero cases. */ if (insn->type == INSN_BUG) insn->dead_end = true; hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset)); nr_insns++; } // printf("%s: last chunk used: %d\n", sec->name, (int)idx); sec_for_each_sym(sec, func) { if (func->type != STT_NOTYPE && func->type != STT_FUNC) continue; if (func->offset == sec->sh.sh_size) { /* Heuristic: likely an "end" symbol */ if (func->type == STT_NOTYPE) continue; WARN("%s(): STT_FUNC at end of section", func->name); return -1; } if (func->embedded_insn || func->alias != func) continue; if (!find_insn(file, sec, func->offset)) { WARN("%s(): can't find starting instruction", func->name); return -1; } sym_for_each_insn(file, func, insn) { insn->sym = func; if (func->type == STT_FUNC && insn->type == INSN_ENDBR && list_empty(&insn->call_node)) { if (insn->offset == func->offset) { list_add_tail(&insn->call_node, &file->endbr_list); file->nr_endbr++; } else { file->nr_endbr_int++; } } } } } if (opts.stats) printf("nr_insns: %lu\n", nr_insns); return 0; } /* * Read the pv_ops[] .data table to find the static initialized values. */ static int add_pv_ops(struct objtool_file *file, const char *symname) { struct symbol *sym, *func; unsigned long off, end; struct reloc *reloc; int idx; sym = find_symbol_by_name(file->elf, symname); if (!sym) return 0; off = sym->offset; end = off + sym->len; for (;;) { reloc = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off); if (!reloc) break; func = reloc->sym; if (func->type == STT_SECTION) func = find_symbol_by_offset(reloc->sym->sec, reloc_addend(reloc)); idx = (reloc_offset(reloc) - sym->offset) / sizeof(unsigned long); objtool_pv_add(file, idx, func); off = reloc_offset(reloc) + 1; if (off > end) break; } return 0; } /* * Allocate and initialize file->pv_ops[]. */ static int init_pv_ops(struct objtool_file *file) { static const char *pv_ops_tables[] = { "pv_ops", "xen_cpu_ops", "xen_irq_ops", "xen_mmu_ops", NULL, }; const char *pv_ops; struct symbol *sym; int idx, nr; if (!opts.noinstr) return 0; file->pv_ops = NULL; sym = find_symbol_by_name(file->elf, "pv_ops"); if (!sym) return 0; nr = sym->len / sizeof(unsigned long); file->pv_ops = calloc(sizeof(struct pv_state), nr); if (!file->pv_ops) return -1; for (idx = 0; idx < nr; idx++) INIT_LIST_HEAD(&file->pv_ops[idx].targets); for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++) add_pv_ops(file, pv_ops); return 0; } static struct instruction *find_last_insn(struct objtool_file *file, struct section *sec) { struct instruction *insn = NULL; unsigned int offset; unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0; for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--) insn = find_insn(file, sec, offset); return insn; } /* * Mark "ud2" instructions and manually annotated dead ends. */ static int add_dead_ends(struct objtool_file *file) { struct section *rsec; struct reloc *reloc; struct instruction *insn; s64 addend; /* * Check for manually annotated dead ends. */ rsec = find_section_by_name(file->elf, ".rela.discard.unreachable"); if (!rsec) goto reachable; for_each_reloc(rsec, reloc) { if (reloc->sym->type != STT_SECTION) { WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } addend = reloc_addend(reloc); insn = find_insn(file, reloc->sym->sec, addend); if (insn) insn = prev_insn_same_sec(file, insn); else if (addend == reloc->sym->sec->sh.sh_size) { insn = find_last_insn(file, reloc->sym->sec); if (!insn) { WARN("can't find unreachable insn at %s+0x%" PRIx64, reloc->sym->sec->name, addend); return -1; } } else { WARN("can't find unreachable insn at %s+0x%" PRIx64, reloc->sym->sec->name, addend); return -1; } insn->dead_end = true; } reachable: /* * These manually annotated reachable checks are needed for GCC 4.4, * where the Linux unreachable() macro isn't supported. In that case * GCC doesn't know the "ud2" is fatal, so it generates code as if it's * not a dead end. */ rsec = find_section_by_name(file->elf, ".rela.discard.reachable"); if (!rsec) return 0; for_each_reloc(rsec, reloc) { if (reloc->sym->type != STT_SECTION) { WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } addend = reloc_addend(reloc); insn = find_insn(file, reloc->sym->sec, addend); if (insn) insn = prev_insn_same_sec(file, insn); else if (addend == reloc->sym->sec->sh.sh_size) { insn = find_last_insn(file, reloc->sym->sec); if (!insn) { WARN("can't find reachable insn at %s+0x%" PRIx64, reloc->sym->sec->name, addend); return -1; } } else { WARN("can't find reachable insn at %s+0x%" PRIx64, reloc->sym->sec->name, addend); return -1; } insn->dead_end = false; } return 0; } static int create_static_call_sections(struct objtool_file *file) { struct static_call_site *site; struct section *sec; struct instruction *insn; struct symbol *key_sym; char *key_name, *tmp; int idx; sec = find_section_by_name(file->elf, ".static_call_sites"); if (sec) { INIT_LIST_HEAD(&file->static_call_list); WARN("file already has .static_call_sites section, skipping"); return 0; } if (list_empty(&file->static_call_list)) return 0; idx = 0; list_for_each_entry(insn, &file->static_call_list, call_node) idx++; sec = elf_create_section_pair(file->elf, ".static_call_sites", sizeof(*site), idx, idx * 2); if (!sec) return -1; /* Allow modules to modify the low bits of static_call_site::key */ sec->sh.sh_flags |= SHF_WRITE; idx = 0; list_for_each_entry(insn, &file->static_call_list, call_node) { /* populate reloc for 'addr' */ if (!elf_init_reloc_text_sym(file->elf, sec, idx * sizeof(*site), idx * 2, insn->sec, insn->offset)) return -1; /* find key symbol */ key_name = strdup(insn_call_dest(insn)->name); if (!key_name) { perror("strdup"); return -1; } if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR, STATIC_CALL_TRAMP_PREFIX_LEN)) { WARN("static_call: trampoline name malformed: %s", key_name); free(key_name); return -1; } tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN; memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN); key_sym = find_symbol_by_name(file->elf, tmp); if (!key_sym) { if (!opts.module) { WARN("static_call: can't find static_call_key symbol: %s", tmp); free(key_name); return -1; } /* * For modules(), the key might not be exported, which * means the module can make static calls but isn't * allowed to change them. * * In that case we temporarily set the key to be the * trampoline address. This is fixed up in * static_call_add_module(). */ key_sym = insn_call_dest(insn); } free(key_name); /* populate reloc for 'key' */ if (!elf_init_reloc_data_sym(file->elf, sec, idx * sizeof(*site) + 4, (idx * 2) + 1, key_sym, is_sibling_call(insn) * STATIC_CALL_SITE_TAIL)) return -1; idx++; } return 0; } static int create_retpoline_sites_sections(struct objtool_file *file) { struct instruction *insn; struct section *sec; int idx; sec = find_section_by_name(file->elf, ".retpoline_sites"); if (sec) { WARN("file already has .retpoline_sites, skipping"); return 0; } idx = 0; list_for_each_entry(insn, &file->retpoline_call_list, call_node) idx++; if (!idx) return 0; sec = elf_create_section_pair(file->elf, ".retpoline_sites", sizeof(int), idx, idx); if (!sec) return -1; idx = 0; list_for_each_entry(insn, &file->retpoline_call_list, call_node) { if (!elf_init_reloc_text_sym(file->elf, sec, idx * sizeof(int), idx, insn->sec, insn->offset)) return -1; idx++; } return 0; } static int create_return_sites_sections(struct objtool_file *file) { struct instruction *insn; struct section *sec; int idx; sec = find_section_by_name(file->elf, ".return_sites"); if (sec) { WARN("file already has .return_sites, skipping"); return 0; } idx = 0; list_for_each_entry(insn, &file->return_thunk_list, call_node) idx++; if (!idx) return 0; sec = elf_create_section_pair(file->elf, ".return_sites", sizeof(int), idx, idx); if (!sec) return -1; idx = 0; list_for_each_entry(insn, &file->return_thunk_list, call_node) { if (!elf_init_reloc_text_sym(file->elf, sec, idx * sizeof(int), idx, insn->sec, insn->offset)) return -1; idx++; } return 0; } static int create_ibt_endbr_seal_sections(struct objtool_file *file) { struct instruction *insn; struct section *sec; int idx; sec = find_section_by_name(file->elf, ".ibt_endbr_seal"); if (sec) { WARN("file already has .ibt_endbr_seal, skipping"); return 0; } idx = 0; list_for_each_entry(insn, &file->endbr_list, call_node) idx++; if (opts.stats) { printf("ibt: ENDBR at function start: %d\n", file->nr_endbr); printf("ibt: ENDBR inside functions: %d\n", file->nr_endbr_int); printf("ibt: superfluous ENDBR: %d\n", idx); } if (!idx) return 0; sec = elf_create_section_pair(file->elf, ".ibt_endbr_seal", sizeof(int), idx, idx); if (!sec) return -1; idx = 0; list_for_each_entry(insn, &file->endbr_list, call_node) { int *site = (int *)sec->data->d_buf + idx; struct symbol *sym = insn->sym; *site = 0; if (opts.module && sym && sym->type == STT_FUNC && insn->offset == sym->offset && (!strcmp(sym->name, "init_module") || !strcmp(sym->name, "cleanup_module"))) WARN("%s(): not an indirect call target", sym->name); if (!elf_init_reloc_text_sym(file->elf, sec, idx * sizeof(int), idx, insn->sec, insn->offset)) return -1; idx++; } return 0; } static int create_cfi_sections(struct objtool_file *file) { struct section *sec; struct symbol *sym; int idx; sec = find_section_by_name(file->elf, ".cfi_sites"); if (sec) { INIT_LIST_HEAD(&file->call_list); WARN("file already has .cfi_sites section, skipping"); return 0; } idx = 0; for_each_sym(file, sym) { if (sym->type != STT_FUNC) continue; if (strncmp(sym->name, "__cfi_", 6)) continue; idx++; } sec = elf_create_section_pair(file->elf, ".cfi_sites", sizeof(unsigned int), idx, idx); if (!sec) return -1; idx = 0; for_each_sym(file, sym) { if (sym->type != STT_FUNC) continue; if (strncmp(sym->name, "__cfi_", 6)) continue; if (!elf_init_reloc_text_sym(file->elf, sec, idx * sizeof(unsigned int), idx, sym->sec, sym->offset)) return -1; idx++; } return 0; } static int create_mcount_loc_sections(struct objtool_file *file) { size_t addr_size = elf_addr_size(file->elf); struct instruction *insn; struct section *sec; int idx; sec = find_section_by_name(file->elf, "__mcount_loc"); if (sec) { INIT_LIST_HEAD(&file->mcount_loc_list); WARN("file already has __mcount_loc section, skipping"); return 0; } if (list_empty(&file->mcount_loc_list)) return 0; idx = 0; list_for_each_entry(insn, &file->mcount_loc_list, call_node) idx++; sec = elf_create_section_pair(file->elf, "__mcount_loc", addr_size, idx, idx); if (!sec) return -1; sec->sh.sh_addralign = addr_size; idx = 0; list_for_each_entry(insn, &file->mcount_loc_list, call_node) { struct reloc *reloc; reloc = elf_init_reloc_text_sym(file->elf, sec, idx * addr_size, idx, insn->sec, insn->offset); if (!reloc) return -1; set_reloc_type(file->elf, reloc, addr_size == 8 ? R_ABS64 : R_ABS32); idx++; } return 0; } static int create_direct_call_sections(struct objtool_file *file) { struct instruction *insn; struct section *sec; int idx; sec = find_section_by_name(file->elf, ".call_sites"); if (sec) { INIT_LIST_HEAD(&file->call_list); WARN("file already has .call_sites section, skipping"); return 0; } if (list_empty(&file->call_list)) return 0; idx = 0; list_for_each_entry(insn, &file->call_list, call_node) idx++; sec = elf_create_section_pair(file->elf, ".call_sites", sizeof(unsigned int), idx, idx); if (!sec) return -1; idx = 0; list_for_each_entry(insn, &file->call_list, call_node) { if (!elf_init_reloc_text_sym(file->elf, sec, idx * sizeof(unsigned int), idx, insn->sec, insn->offset)) return -1; idx++; } return 0; } /* * Warnings shouldn't be reported for ignored functions. */ static void add_ignores(struct objtool_file *file) { struct instruction *insn; struct section *rsec; struct symbol *func; struct reloc *reloc; rsec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard"); if (!rsec) return; for_each_reloc(rsec, reloc) { switch (reloc->sym->type) { case STT_FUNC: func = reloc->sym; break; case STT_SECTION: func = find_func_by_offset(reloc->sym->sec, reloc_addend(reloc)); if (!func) continue; break; default: WARN("unexpected relocation symbol type in %s: %d", rsec->name, reloc->sym->type); continue; } func_for_each_insn(file, func, insn) insn->ignore = true; } } /* * This is a whitelist of functions that is allowed to be called with AC set. * The list is meant to be minimal and only contains compiler instrumentation * ABI and a few functions used to implement *_{to,from}_user() functions. * * These functions must not directly change AC, but may PUSHF/POPF. */ static const char *uaccess_safe_builtin[] = { /* KASAN */ "kasan_report", "kasan_check_range", /* KASAN out-of-line */ "__asan_loadN_noabort", "__asan_load1_noabort", "__asan_load2_noabort", "__asan_load4_noabort", "__asan_load8_noabort", "__asan_load16_noabort", "__asan_storeN_noabort", "__asan_store1_noabort", "__asan_store2_noabort", "__asan_store4_noabort", "__asan_store8_noabort", "__asan_store16_noabort", "__kasan_check_read", "__kasan_check_write", /* KASAN in-line */ "__asan_report_load_n_noabort", "__asan_report_load1_noabort", "__asan_report_load2_noabort", "__asan_report_load4_noabort", "__asan_report_load8_noabort", "__asan_report_load16_noabort", "__asan_report_store_n_noabort", "__asan_report_store1_noabort", "__asan_report_store2_noabort", "__asan_report_store4_noabort", "__asan_report_store8_noabort", "__asan_report_store16_noabort", /* KCSAN */ "__kcsan_check_access", "__kcsan_mb", "__kcsan_wmb", "__kcsan_rmb", "__kcsan_release", "kcsan_found_watchpoint", "kcsan_setup_watchpoint", "kcsan_check_scoped_accesses", "kcsan_disable_current", "kcsan_enable_current_nowarn", /* KCSAN/TSAN */ "__tsan_func_entry", "__tsan_func_exit", "__tsan_read_range", "__tsan_write_range", "__tsan_read1", "__tsan_read2", "__tsan_read4", "__tsan_read8", "__tsan_read16", "__tsan_write1", "__tsan_write2", "__tsan_write4", "__tsan_write8", "__tsan_write16", "__tsan_read_write1", "__tsan_read_write2", "__tsan_read_write4", "__tsan_read_write8", "__tsan_read_write16", "__tsan_volatile_read1", "__tsan_volatile_read2", "__tsan_volatile_read4", "__tsan_volatile_read8", "__tsan_volatile_read16", "__tsan_volatile_write1", "__tsan_volatile_write2", "__tsan_volatile_write4", "__tsan_volatile_write8", "__tsan_volatile_write16", "__tsan_atomic8_load", "__tsan_atomic16_load", "__tsan_atomic32_load", "__tsan_atomic64_load", "__tsan_atomic8_store", "__tsan_atomic16_store", "__tsan_atomic32_store", "__tsan_atomic64_store", "__tsan_atomic8_exchange", "__tsan_atomic16_exchange", "__tsan_atomic32_exchange", "__tsan_atomic64_exchange", "__tsan_atomic8_fetch_add", "__tsan_atomic16_fetch_add", "__tsan_atomic32_fetch_add", "__tsan_atomic64_fetch_add", "__tsan_atomic8_fetch_sub", "__tsan_atomic16_fetch_sub", "__tsan_atomic32_fetch_sub", "__tsan_atomic64_fetch_sub", "__tsan_atomic8_fetch_and", "__tsan_atomic16_fetch_and", "__tsan_atomic32_fetch_and", "__tsan_atomic64_fetch_and", "__tsan_atomic8_fetch_or", "__tsan_atomic16_fetch_or", "__tsan_atomic32_fetch_or", "__tsan_atomic64_fetch_or", "__tsan_atomic8_fetch_xor", "__tsan_atomic16_fetch_xor", "__tsan_atomic32_fetch_xor", "__tsan_atomic64_fetch_xor", "__tsan_atomic8_fetch_nand", "__tsan_atomic16_fetch_nand", "__tsan_atomic32_fetch_nand", "__tsan_atomic64_fetch_nand", "__tsan_atomic8_compare_exchange_strong", "__tsan_atomic16_compare_exchange_strong", "__tsan_atomic32_compare_exchange_strong", "__tsan_atomic64_compare_exchange_strong", "__tsan_atomic8_compare_exchange_weak", "__tsan_atomic16_compare_exchange_weak", "__tsan_atomic32_compare_exchange_weak", "__tsan_atomic64_compare_exchange_weak", "__tsan_atomic8_compare_exchange_val", "__tsan_atomic16_compare_exchange_val", "__tsan_atomic32_compare_exchange_val", "__tsan_atomic64_compare_exchange_val", "__tsan_atomic_thread_fence", "__tsan_atomic_signal_fence", "__tsan_unaligned_read16", "__tsan_unaligned_write16", /* KCOV */ "write_comp_data", "check_kcov_mode", "__sanitizer_cov_trace_pc", "__sanitizer_cov_trace_const_cmp1", "__sanitizer_cov_trace_const_cmp2", "__sanitizer_cov_trace_const_cmp4", "__sanitizer_cov_trace_const_cmp8", "__sanitizer_cov_trace_cmp1", "__sanitizer_cov_trace_cmp2", "__sanitizer_cov_trace_cmp4", "__sanitizer_cov_trace_cmp8", "__sanitizer_cov_trace_switch", /* KMSAN */ "kmsan_copy_to_user", "kmsan_report", "kmsan_unpoison_entry_regs", "kmsan_unpoison_memory", "__msan_chain_origin", "__msan_get_context_state", "__msan_instrument_asm_store", "__msan_metadata_ptr_for_load_1", "__msan_metadata_ptr_for_load_2", "__msan_metadata_ptr_for_load_4", "__msan_metadata_ptr_for_load_8", "__msan_metadata_ptr_for_load_n", "__msan_metadata_ptr_for_store_1", "__msan_metadata_ptr_for_store_2", "__msan_metadata_ptr_for_store_4", "__msan_metadata_ptr_for_store_8", "__msan_metadata_ptr_for_store_n", "__msan_poison_alloca", "__msan_warning", /* UBSAN */ "ubsan_type_mismatch_common", "__ubsan_handle_type_mismatch", "__ubsan_handle_type_mismatch_v1", "__ubsan_handle_shift_out_of_bounds", "__ubsan_handle_load_invalid_value", /* STACKLEAK */ "stackleak_track_stack", /* misc */ "csum_partial_copy_generic", "copy_mc_fragile", "copy_mc_fragile_handle_tail", "copy_mc_enhanced_fast_string", "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */ "rep_stos_alternative", "rep_movs_alternative", "__copy_user_nocache", NULL }; static void add_uaccess_safe(struct objtool_file *file) { struct symbol *func; const char **name; if (!opts.uaccess) return; for (name = uaccess_safe_builtin; *name; name++) { func = find_symbol_by_name(file->elf, *name); if (!func) continue; func->uaccess_safe = true; } } /* * FIXME: For now, just ignore any alternatives which add retpolines. This is * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline. * But it at least allows objtool to understand the control flow *around* the * retpoline. */ static int add_ignore_alternatives(struct objtool_file *file) { struct section *rsec; struct reloc *reloc; struct instruction *insn; rsec = find_section_by_name(file->elf, ".rela.discard.ignore_alts"); if (!rsec) return 0; for_each_reloc(rsec, reloc) { if (reloc->sym->type != STT_SECTION) { WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!insn) { WARN("bad .discard.ignore_alts entry"); return -1; } insn->ignore_alts = true; } return 0; } /* * Symbols that replace INSN_CALL_DYNAMIC, every (tail) call to such a symbol * will be added to the .retpoline_sites section. */ __weak bool arch_is_retpoline(struct symbol *sym) { return false; } /* * Symbols that replace INSN_RETURN, every (tail) call to such a symbol * will be added to the .return_sites section. */ __weak bool arch_is_rethunk(struct symbol *sym) { return false; } /* * Symbols that are embedded inside other instructions, because sometimes crazy * code exists. These are mostly ignored for validation purposes. */ __weak bool arch_is_embedded_insn(struct symbol *sym) { return false; } static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn) { struct reloc *reloc; if (insn->no_reloc) return NULL; if (!file) return NULL; reloc = find_reloc_by_dest_range(file->elf, insn->sec, insn->offset, insn->len); if (!reloc) { insn->no_reloc = 1; return NULL; } return reloc; } static void remove_insn_ops(struct instruction *insn) { struct stack_op *op, *next; for (op = insn->stack_ops; op; op = next) { next = op->next; free(op); } insn->stack_ops = NULL; } static void annotate_call_site(struct objtool_file *file, struct instruction *insn, bool sibling) { struct reloc *reloc = insn_reloc(file, insn); struct symbol *sym = insn_call_dest(insn); if (!sym) sym = reloc->sym; /* * Alternative replacement code is just template code which is * sometimes copied to the original instruction. For now, don't * annotate it. (In the future we might consider annotating the * original instruction if/when it ever makes sense to do so.) */ if (!strcmp(insn->sec->name, ".altinstr_replacement")) return; if (sym->static_call_tramp) { list_add_tail(&insn->call_node, &file->static_call_list); return; } if (sym->retpoline_thunk) { list_add_tail(&insn->call_node, &file->retpoline_call_list); return; } /* * Many compilers cannot disable KCOV or sanitizer calls with a function * attribute so they need a little help, NOP out any such calls from * noinstr text. */ if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) { if (reloc) set_reloc_type(file->elf, reloc, R_NONE); elf_write_insn(file->elf, insn->sec, insn->offset, insn->len, sibling ? arch_ret_insn(insn->len) : arch_nop_insn(insn->len)); insn->type = sibling ? INSN_RETURN : INSN_NOP; if (sibling) { /* * We've replaced the tail-call JMP insn by two new * insn: RET; INT3, except we only have a single struct * insn here. Mark it retpoline_safe to avoid the SLS * warning, instead of adding another insn. */ insn->retpoline_safe = true; } return; } if (opts.mcount && sym->fentry) { if (sibling) WARN_INSN(insn, "tail call to __fentry__ !?!?"); if (opts.mnop) { if (reloc) set_reloc_type(file->elf, reloc, R_NONE); elf_write_insn(file->elf, insn->sec, insn->offset, insn->len, arch_nop_insn(insn->len)); insn->type = INSN_NOP; } list_add_tail(&insn->call_node, &file->mcount_loc_list); return; } if (insn->type == INSN_CALL && !insn->sec->init) list_add_tail(&insn->call_node, &file->call_list); if (!sibling && dead_end_function(file, sym)) insn->dead_end = true; } static void add_call_dest(struct objtool_file *file, struct instruction *insn, struct symbol *dest, bool sibling) { insn->_call_dest = dest; if (!dest) return; /* * Whatever stack impact regular CALLs have, should be undone * by the RETURN of the called function. * * Annotated intra-function calls retain the stack_ops but * are converted to JUMP, see read_intra_function_calls(). */ remove_insn_ops(insn); annotate_call_site(file, insn, sibling); } static void add_retpoline_call(struct objtool_file *file, struct instruction *insn) { /* * Retpoline calls/jumps are really dynamic calls/jumps in disguise, * so convert them accordingly. */ switch (insn->type) { case INSN_CALL: insn->type = INSN_CALL_DYNAMIC; break; case INSN_JUMP_UNCONDITIONAL: insn->type = INSN_JUMP_DYNAMIC; break; case INSN_JUMP_CONDITIONAL: insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL; break; default: return; } insn->retpoline_safe = true; /* * Whatever stack impact regular CALLs have, should be undone * by the RETURN of the called function. * * Annotated intra-function calls retain the stack_ops but * are converted to JUMP, see read_intra_function_calls(). */ remove_insn_ops(insn); annotate_call_site(file, insn, false); } static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add) { /* * Return thunk tail calls are really just returns in disguise, * so convert them accordingly. */ insn->type = INSN_RETURN; insn->retpoline_safe = true; if (add) list_add_tail(&insn->call_node, &file->return_thunk_list); } static bool is_first_func_insn(struct objtool_file *file, struct instruction *insn, struct symbol *sym) { if (insn->offset == sym->offset) return true; /* Allow direct CALL/JMP past ENDBR */ if (opts.ibt) { struct instruction *prev = prev_insn_same_sym(file, insn); if (prev && prev->type == INSN_ENDBR && insn->offset == sym->offset + prev->len) return true; } return false; } /* * A sibling call is a tail-call to another symbol -- to differentiate from a * recursive tail-call which is to the same symbol. */ static bool jump_is_sibling_call(struct objtool_file *file, struct instruction *from, struct instruction *to) { struct symbol *fs = from->sym; struct symbol *ts = to->sym; /* Not a sibling call if from/to a symbol hole */ if (!fs || !ts) return false; /* Not a sibling call if not targeting the start of a symbol. */ if (!is_first_func_insn(file, to, ts)) return false; /* Disallow sibling calls into STT_NOTYPE */ if (ts->type == STT_NOTYPE) return false; /* Must not be self to be a sibling */ return fs->pfunc != ts->pfunc; } /* * Find the destination instructions for all jumps. */ static int add_jump_destinations(struct objtool_file *file) { struct instruction *insn, *jump_dest; struct reloc *reloc; struct section *dest_sec; unsigned long dest_off; for_each_insn(file, insn) { if (insn->jump_dest) { /* * handle_group_alt() may have previously set * 'jump_dest' for some alternatives. */ continue; } if (!is_static_jump(insn)) continue; reloc = insn_reloc(file, insn); if (!reloc) { dest_sec = insn->sec; dest_off = arch_jump_destination(insn); } else if (reloc->sym->type == STT_SECTION) { dest_sec = reloc->sym->sec; dest_off = arch_dest_reloc_offset(reloc_addend(reloc)); } else if (reloc->sym->retpoline_thunk) { add_retpoline_call(file, insn); continue; } else if (reloc->sym->return_thunk) { add_return_call(file, insn, true); continue; } else if (insn_func(insn)) { /* * External sibling call or internal sibling call with * STT_FUNC reloc. */ add_call_dest(file, insn, reloc->sym, true); continue; } else if (reloc->sym->sec->idx) { dest_sec = reloc->sym->sec; dest_off = reloc->sym->sym.st_value + arch_dest_reloc_offset(reloc_addend(reloc)); } else { /* non-func asm code jumping to another file */ continue; } jump_dest = find_insn(file, dest_sec, dest_off); if (!jump_dest) { struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off); /* * This is a special case for retbleed_untrain_ret(). * It jumps to __x86_return_thunk(), but objtool * can't find the thunk's starting RET * instruction, because the RET is also in the * middle of another instruction. Objtool only * knows about the outer instruction. */ if (sym && sym->embedded_insn) { add_return_call(file, insn, false); continue; } WARN_INSN(insn, "can't find jump dest instruction at %s+0x%lx", dest_sec->name, dest_off); return -1; } /* * An intra-TU jump in retpoline.o might not have a relocation * for its jump dest, in which case the above * add_{retpoline,return}_call() didn't happen. */ if (jump_dest->sym && jump_dest->offset == jump_dest->sym->offset) { if (jump_dest->sym->retpoline_thunk) { add_retpoline_call(file, insn); continue; } if (jump_dest->sym->return_thunk) { add_return_call(file, insn, true); continue; } } /* * Cross-function jump. */ if (insn_func(insn) && insn_func(jump_dest) && insn_func(insn) != insn_func(jump_dest)) { /* * For GCC 8+, create parent/child links for any cold * subfunctions. This is _mostly_ redundant with a * similar initialization in read_symbols(). * * If a function has aliases, we want the *first* such * function in the symbol table to be the subfunction's * parent. In that case we overwrite the * initialization done in read_symbols(). * * However this code can't completely replace the * read_symbols() code because this doesn't detect the * case where the parent function's only reference to a * subfunction is through a jump table. */ if (!strstr(insn_func(insn)->name, ".cold") && strstr(insn_func(jump_dest)->name, ".cold")) { insn_func(insn)->cfunc = insn_func(jump_dest); insn_func(jump_dest)->pfunc = insn_func(insn); } } if (jump_is_sibling_call(file, insn, jump_dest)) { /* * Internal sibling call without reloc or with * STT_SECTION reloc. */ add_call_dest(file, insn, insn_func(jump_dest), true); continue; } insn->jump_dest = jump_dest; } return 0; } static struct symbol *find_call_destination(struct section *sec, unsigned long offset) { struct symbol *call_dest; call_dest = find_func_by_offset(sec, offset); if (!call_dest) call_dest = find_symbol_by_offset(sec, offset); return call_dest; } /* * Find the destination instructions for all calls. */ static int add_call_destinations(struct objtool_file *file) { struct instruction *insn; unsigned long dest_off; struct symbol *dest; struct reloc *reloc; for_each_insn(file, insn) { if (insn->type != INSN_CALL) continue; reloc = insn_reloc(file, insn); if (!reloc) { dest_off = arch_jump_destination(insn); dest = find_call_destination(insn->sec, dest_off); add_call_dest(file, insn, dest, false); if (insn->ignore) continue; if (!insn_call_dest(insn)) { WARN_INSN(insn, "unannotated intra-function call"); return -1; } if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) { WARN_INSN(insn, "unsupported call to non-function"); return -1; } } else if (reloc->sym->type == STT_SECTION) { dest_off = arch_dest_reloc_offset(reloc_addend(reloc)); dest = find_call_destination(reloc->sym->sec, dest_off); if (!dest) { WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx", reloc->sym->sec->name, dest_off); return -1; } add_call_dest(file, insn, dest, false); } else if (reloc->sym->retpoline_thunk) { add_retpoline_call(file, insn); } else add_call_dest(file, insn, reloc->sym, false); } return 0; } /* * The .alternatives section requires some extra special care over and above * other special sections because alternatives are patched in place. */ static int handle_group_alt(struct objtool_file *file, struct special_alt *special_alt, struct instruction *orig_insn, struct instruction **new_insn) { struct instruction *last_new_insn = NULL, *insn, *nop = NULL; struct alt_group *orig_alt_group, *new_alt_group; unsigned long dest_off; orig_alt_group = orig_insn->alt_group; if (!orig_alt_group) { struct instruction *last_orig_insn = NULL; orig_alt_group = malloc(sizeof(*orig_alt_group)); if (!orig_alt_group) { WARN("malloc failed"); return -1; } orig_alt_group->cfi = calloc(special_alt->orig_len, sizeof(struct cfi_state *)); if (!orig_alt_group->cfi) { WARN("calloc failed"); return -1; } insn = orig_insn; sec_for_each_insn_from(file, insn) { if (insn->offset >= special_alt->orig_off + special_alt->orig_len) break; insn->alt_group = orig_alt_group; last_orig_insn = insn; } orig_alt_group->orig_group = NULL; orig_alt_group->first_insn = orig_insn; orig_alt_group->last_insn = last_orig_insn; orig_alt_group->nop = NULL; } else { if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len - orig_alt_group->first_insn->offset != special_alt->orig_len) { WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d", orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len - orig_alt_group->first_insn->offset, special_alt->orig_len); return -1; } } new_alt_group = malloc(sizeof(*new_alt_group)); if (!new_alt_group) { WARN("malloc failed"); return -1; } if (special_alt->new_len < special_alt->orig_len) { /* * Insert a fake nop at the end to make the replacement * alt_group the same size as the original. This is needed to * allow propagate_alt_cfi() to do its magic. When the last * instruction affects the stack, the instruction after it (the * nop) will propagate the new state to the shared CFI array. */ nop = malloc(sizeof(*nop)); if (!nop) { WARN("malloc failed"); return -1; } memset(nop, 0, sizeof(*nop)); nop->sec = special_alt->new_sec; nop->offset = special_alt->new_off + special_alt->new_len; nop->len = special_alt->orig_len - special_alt->new_len; nop->type = INSN_NOP; nop->sym = orig_insn->sym; nop->alt_group = new_alt_group; nop->ignore = orig_insn->ignore_alts; } if (!special_alt->new_len) { *new_insn = nop; goto end; } insn = *new_insn; sec_for_each_insn_from(file, insn) { struct reloc *alt_reloc; if (insn->offset >= special_alt->new_off + special_alt->new_len) break; last_new_insn = insn; insn->ignore = orig_insn->ignore_alts; insn->sym = orig_insn->sym; insn->alt_group = new_alt_group; /* * Since alternative replacement code is copy/pasted by the * kernel after applying relocations, generally such code can't * have relative-address relocation references to outside the * .altinstr_replacement section, unless the arch's * alternatives code can adjust the relative offsets * accordingly. */ alt_reloc = insn_reloc(file, insn); if (alt_reloc && arch_pc_relative_reloc(alt_reloc) && !arch_support_alt_relocation(special_alt, insn, alt_reloc)) { WARN_INSN(insn, "unsupported relocation in alternatives section"); return -1; } if (!is_static_jump(insn)) continue; if (!insn->immediate) continue; dest_off = arch_jump_destination(insn); if (dest_off == special_alt->new_off + special_alt->new_len) { insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn); if (!insn->jump_dest) { WARN_INSN(insn, "can't find alternative jump destination"); return -1; } } } if (!last_new_insn) { WARN_FUNC("can't find last new alternative instruction", special_alt->new_sec, special_alt->new_off); return -1; } end: new_alt_group->orig_group = orig_alt_group; new_alt_group->first_insn = *new_insn; new_alt_group->last_insn = last_new_insn; new_alt_group->nop = nop; new_alt_group->cfi = orig_alt_group->cfi; return 0; } /* * A jump table entry can either convert a nop to a jump or a jump to a nop. * If the original instruction is a jump, make the alt entry an effective nop * by just skipping the original instruction. */ static int handle_jump_alt(struct objtool_file *file, struct special_alt *special_alt, struct instruction *orig_insn, struct instruction **new_insn) { if (orig_insn->type != INSN_JUMP_UNCONDITIONAL && orig_insn->type != INSN_NOP) { WARN_INSN(orig_insn, "unsupported instruction at jump label"); return -1; } if (opts.hack_jump_label && special_alt->key_addend & 2) { struct reloc *reloc = insn_reloc(file, orig_insn); if (reloc) set_reloc_type(file->elf, reloc, R_NONE); elf_write_insn(file->elf, orig_insn->sec, orig_insn->offset, orig_insn->len, arch_nop_insn(orig_insn->len)); orig_insn->type = INSN_NOP; } if (orig_insn->type == INSN_NOP) { if (orig_insn->len == 2) file->jl_nop_short++; else file->jl_nop_long++; return 0; } if (orig_insn->len == 2) file->jl_short++; else file->jl_long++; *new_insn = next_insn_same_sec(file, orig_insn); return 0; } /* * Read all the special sections which have alternate instructions which can be * patched in or redirected to at runtime. Each instruction having alternate * instruction(s) has them added to its insn->alts list, which will be * traversed in validate_branch(). */ static int add_special_section_alts(struct objtool_file *file) { struct list_head special_alts; struct instruction *orig_insn, *new_insn; struct special_alt *special_alt, *tmp; struct alternative *alt; int ret; ret = special_get_alts(file->elf, &special_alts); if (ret) return ret; list_for_each_entry_safe(special_alt, tmp, &special_alts, list) { orig_insn = find_insn(file, special_alt->orig_sec, special_alt->orig_off); if (!orig_insn) { WARN_FUNC("special: can't find orig instruction", special_alt->orig_sec, special_alt->orig_off); ret = -1; goto out; } new_insn = NULL; if (!special_alt->group || special_alt->new_len) { new_insn = find_insn(file, special_alt->new_sec, special_alt->new_off); if (!new_insn) { WARN_FUNC("special: can't find new instruction", special_alt->new_sec, special_alt->new_off); ret = -1; goto out; } } if (special_alt->group) { if (!special_alt->orig_len) { WARN_INSN(orig_insn, "empty alternative entry"); continue; } ret = handle_group_alt(file, special_alt, orig_insn, &new_insn); if (ret) goto out; } else if (special_alt->jump_or_nop) { ret = handle_jump_alt(file, special_alt, orig_insn, &new_insn); if (ret) goto out; } alt = malloc(sizeof(*alt)); if (!alt) { WARN("malloc failed"); ret = -1; goto out; } alt->insn = new_insn; alt->skip_orig = special_alt->skip_orig; orig_insn->ignore_alts |= special_alt->skip_alt; alt->next = orig_insn->alts; orig_insn->alts = alt; list_del(&special_alt->list); free(special_alt); } if (opts.stats) { printf("jl\\\tNOP\tJMP\n"); printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short); printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long); } out: return ret; } static int add_jump_table(struct objtool_file *file, struct instruction *insn, struct reloc *next_table) { struct symbol *pfunc = insn_func(insn)->pfunc; struct reloc *table = insn_jump_table(insn); struct instruction *dest_insn; unsigned int prev_offset = 0; struct reloc *reloc = table; struct alternative *alt; /* * Each @reloc is a switch table relocation which points to the target * instruction. */ for_each_reloc_from(table->sec, reloc) { /* Check for the end of the table: */ if (reloc != table && reloc == next_table) break; /* Make sure the table entries are consecutive: */ if (prev_offset && reloc_offset(reloc) != prev_offset + 8) break; /* Detect function pointers from contiguous objects: */ if (reloc->sym->sec == pfunc->sec && reloc_addend(reloc) == pfunc->offset) break; dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!dest_insn) break; /* Make sure the destination is in the same function: */ if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc) break; alt = malloc(sizeof(*alt)); if (!alt) { WARN("malloc failed"); return -1; } alt->insn = dest_insn; alt->next = insn->alts; insn->alts = alt; prev_offset = reloc_offset(reloc); } if (!prev_offset) { WARN_INSN(insn, "can't find switch jump table"); return -1; } return 0; } /* * find_jump_table() - Given a dynamic jump, find the switch jump table * associated with it. */ static struct reloc *find_jump_table(struct objtool_file *file, struct symbol *func, struct instruction *insn) { struct reloc *table_reloc; struct instruction *dest_insn, *orig_insn = insn; /* * Backward search using the @first_jump_src links, these help avoid * much of the 'in between' code. Which avoids us getting confused by * it. */ for (; insn && insn_func(insn) && insn_func(insn)->pfunc == func; insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) { if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC) break; /* allow small jumps within the range */ if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest && (insn->jump_dest->offset <= insn->offset || insn->jump_dest->offset > orig_insn->offset)) break; table_reloc = arch_find_switch_table(file, insn); if (!table_reloc) continue; dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc)); if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func) continue; return table_reloc; } return NULL; } /* * First pass: Mark the head of each jump table so that in the next pass, * we know when a given jump table ends and the next one starts. */ static void mark_func_jump_tables(struct objtool_file *file, struct symbol *func) { struct instruction *insn, *last = NULL; struct reloc *reloc; func_for_each_insn(file, func, insn) { if (!last) last = insn; /* * Store back-pointers for unconditional forward jumps such * that find_jump_table() can back-track using those and * avoid some potentially confusing code. */ if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest && insn->offset > last->offset && insn->jump_dest->offset > insn->offset && !insn->jump_dest->first_jump_src) { insn->jump_dest->first_jump_src = insn; last = insn->jump_dest; } if (insn->type != INSN_JUMP_DYNAMIC) continue; reloc = find_jump_table(file, func, insn); if (reloc) insn->_jump_table = reloc; } } static int add_func_jump_tables(struct objtool_file *file, struct symbol *func) { struct instruction *insn, *insn_t1 = NULL, *insn_t2; int ret = 0; func_for_each_insn(file, func, insn) { if (!insn_jump_table(insn)) continue; if (!insn_t1) { insn_t1 = insn; continue; } insn_t2 = insn; ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2)); if (ret) return ret; insn_t1 = insn_t2; } if (insn_t1) ret = add_jump_table(file, insn_t1, NULL); return ret; } /* * For some switch statements, gcc generates a jump table in the .rodata * section which contains a list of addresses within the function to jump to. * This finds these jump tables and adds them to the insn->alts lists. */ static int add_jump_table_alts(struct objtool_file *file) { struct symbol *func; int ret; if (!file->rodata) return 0; for_each_sym(file, func) { if (func->type != STT_FUNC) continue; mark_func_jump_tables(file, func); ret = add_func_jump_tables(file, func); if (ret) return ret; } return 0; } static void set_func_state(struct cfi_state *state) { state->cfa = initial_func_cfi.cfa; memcpy(&state->regs, &initial_func_cfi.regs, CFI_NUM_REGS * sizeof(struct cfi_reg)); state->stack_size = initial_func_cfi.cfa.offset; state->type = UNWIND_HINT_TYPE_CALL; } static int read_unwind_hints(struct objtool_file *file) { struct cfi_state cfi = init_cfi; struct section *sec; struct unwind_hint *hint; struct instruction *insn; struct reloc *reloc; int i; sec = find_section_by_name(file->elf, ".discard.unwind_hints"); if (!sec) return 0; if (!sec->rsec) { WARN("missing .rela.discard.unwind_hints section"); return -1; } if (sec->sh.sh_size % sizeof(struct unwind_hint)) { WARN("struct unwind_hint size mismatch"); return -1; } file->hints = true; for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) { hint = (struct unwind_hint *)sec->data->d_buf + i; reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint)); if (!reloc) { WARN("can't find reloc for unwind_hints[%d]", i); return -1; } insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!insn) { WARN("can't find insn for unwind_hints[%d]", i); return -1; } insn->hint = true; if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) { insn->cfi = &force_undefined_cfi; continue; } if (hint->type == UNWIND_HINT_TYPE_SAVE) { insn->hint = false; insn->save = true; continue; } if (hint->type == UNWIND_HINT_TYPE_RESTORE) { insn->restore = true; continue; } if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) { struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset); if (sym && sym->bind == STB_GLOBAL) { if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) { WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR"); } } } if (hint->type == UNWIND_HINT_TYPE_FUNC) { insn->cfi = &func_cfi; continue; } if (insn->cfi) cfi = *(insn->cfi); if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) { WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg); return -1; } cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset); cfi.type = hint->type; cfi.signal = hint->signal; insn->cfi = cfi_hash_find_or_add(&cfi); } return 0; } static int read_noendbr_hints(struct objtool_file *file) { struct instruction *insn; struct section *rsec; struct reloc *reloc; rsec = find_section_by_name(file->elf, ".rela.discard.noendbr"); if (!rsec) return 0; for_each_reloc(rsec, reloc) { insn = find_insn(file, reloc->sym->sec, reloc->sym->offset + reloc_addend(reloc)); if (!insn) { WARN("bad .discard.noendbr entry"); return -1; } insn->noendbr = 1; } return 0; } static int read_retpoline_hints(struct objtool_file *file) { struct section *rsec; struct instruction *insn; struct reloc *reloc; rsec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe"); if (!rsec) return 0; for_each_reloc(rsec, reloc) { if (reloc->sym->type != STT_SECTION) { WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!insn) { WARN("bad .discard.retpoline_safe entry"); return -1; } if (insn->type != INSN_JUMP_DYNAMIC && insn->type != INSN_CALL_DYNAMIC && insn->type != INSN_RETURN && insn->type != INSN_NOP) { WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop"); return -1; } insn->retpoline_safe = true; } return 0; } static int read_instr_hints(struct objtool_file *file) { struct section *rsec; struct instruction *insn; struct reloc *reloc; rsec = find_section_by_name(file->elf, ".rela.discard.instr_end"); if (!rsec) return 0; for_each_reloc(rsec, reloc) { if (reloc->sym->type != STT_SECTION) { WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!insn) { WARN("bad .discard.instr_end entry"); return -1; } insn->instr--; } rsec = find_section_by_name(file->elf, ".rela.discard.instr_begin"); if (!rsec) return 0; for_each_reloc(rsec, reloc) { if (reloc->sym->type != STT_SECTION) { WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!insn) { WARN("bad .discard.instr_begin entry"); return -1; } insn->instr++; } return 0; } static int read_validate_unret_hints(struct objtool_file *file) { struct section *rsec; struct instruction *insn; struct reloc *reloc; rsec = find_section_by_name(file->elf, ".rela.discard.validate_unret"); if (!rsec) return 0; for_each_reloc(rsec, reloc) { if (reloc->sym->type != STT_SECTION) { WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!insn) { WARN("bad .discard.instr_end entry"); return -1; } insn->unret = 1; } return 0; } static int read_intra_function_calls(struct objtool_file *file) { struct instruction *insn; struct section *rsec; struct reloc *reloc; rsec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls"); if (!rsec) return 0; for_each_reloc(rsec, reloc) { unsigned long dest_off; if (reloc->sym->type != STT_SECTION) { WARN("unexpected relocation symbol type in %s", rsec->name); return -1; } insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!insn) { WARN("bad .discard.intra_function_call entry"); return -1; } if (insn->type != INSN_CALL) { WARN_INSN(insn, "intra_function_call not a direct call"); return -1; } /* * Treat intra-function CALLs as JMPs, but with a stack_op. * See add_call_destinations(), which strips stack_ops from * normal CALLs. */ insn->type = INSN_JUMP_UNCONDITIONAL; dest_off = arch_jump_destination(insn); insn->jump_dest = find_insn(file, insn->sec, dest_off); if (!insn->jump_dest) { WARN_INSN(insn, "can't find call dest at %s+0x%lx", insn->sec->name, dest_off); return -1; } } return 0; } /* * Return true if name matches an instrumentation function, where calls to that * function from noinstr code can safely be removed, but compilers won't do so. */ static bool is_profiling_func(const char *name) { /* * Many compilers cannot disable KCOV with a function attribute. */ if (!strncmp(name, "__sanitizer_cov_", 16)) return true; /* * Some compilers currently do not remove __tsan_func_entry/exit nor * __tsan_atomic_signal_fence (used for barrier instrumentation) with * the __no_sanitize_thread attribute, remove them. Once the kernel's * minimum Clang version is 14.0, this can be removed. */ if (!strncmp(name, "__tsan_func_", 12) || !strcmp(name, "__tsan_atomic_signal_fence")) return true; return false; } static int classify_symbols(struct objtool_file *file) { struct symbol *func; for_each_sym(file, func) { if (func->bind != STB_GLOBAL) continue; if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR, strlen(STATIC_CALL_TRAMP_PREFIX_STR))) func->static_call_tramp = true; if (arch_is_retpoline(func)) func->retpoline_thunk = true; if (arch_is_rethunk(func)) func->return_thunk = true; if (arch_is_embedded_insn(func)) func->embedded_insn = true; if (arch_ftrace_match(func->name)) func->fentry = true; if (is_profiling_func(func->name)) func->profiling_func = true; } return 0; } static void mark_rodata(struct objtool_file *file) { struct section *sec; bool found = false; /* * Search for the following rodata sections, each of which can * potentially contain jump tables: * * - .rodata: can contain GCC switch tables * - .rodata.<func>: same, if -fdata-sections is being used * - .rodata..c_jump_table: contains C annotated jump tables * * .rodata.str1.* sections are ignored; they don't contain jump tables. */ for_each_sec(file, sec) { if (!strncmp(sec->name, ".rodata", 7) && !strstr(sec->name, ".str1.")) { sec->rodata = true; found = true; } } file->rodata = found; } static int decode_sections(struct objtool_file *file) { int ret; mark_rodata(file); ret = init_pv_ops(file); if (ret) return ret; /* * Must be before add_{jump_call}_destination. */ ret = classify_symbols(file); if (ret) return ret; ret = decode_instructions(file); if (ret) return ret; add_ignores(file); add_uaccess_safe(file); ret = add_ignore_alternatives(file); if (ret) return ret; /* * Must be before read_unwind_hints() since that needs insn->noendbr. */ ret = read_noendbr_hints(file); if (ret) return ret; /* * Must be before add_jump_destinations(), which depends on 'func' * being set for alternatives, to enable proper sibling call detection. */ if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) { ret = add_special_section_alts(file); if (ret) return ret; } ret = add_jump_destinations(file); if (ret) return ret; /* * Must be before add_call_destination(); it changes INSN_CALL to * INSN_JUMP. */ ret = read_intra_function_calls(file); if (ret) return ret; ret = add_call_destinations(file); if (ret) return ret; /* * Must be after add_call_destinations() such that it can override * dead_end_function() marks. */ ret = add_dead_ends(file); if (ret) return ret; ret = add_jump_table_alts(file); if (ret) return ret; ret = read_unwind_hints(file); if (ret) return ret; ret = read_retpoline_hints(file); if (ret) return ret; ret = read_instr_hints(file); if (ret) return ret; ret = read_validate_unret_hints(file); if (ret) return ret; return 0; } static bool is_special_call(struct instruction *insn) { if (insn->type == INSN_CALL) { struct symbol *dest = insn_call_dest(insn); if (!dest) return false; if (dest->fentry || dest->embedded_insn) return true; } return false; } static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state) { struct cfi_state *cfi = &state->cfi; int i; if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap) return true; if (cfi->cfa.offset != initial_func_cfi.cfa.offset) return true; if (cfi->stack_size != initial_func_cfi.cfa.offset) return true; for (i = 0; i < CFI_NUM_REGS; i++) { if (cfi->regs[i].base != initial_func_cfi.regs[i].base || cfi->regs[i].offset != initial_func_cfi.regs[i].offset) return true; } return false; } static bool check_reg_frame_pos(const struct cfi_reg *reg, int expected_offset) { return reg->base == CFI_CFA && reg->offset == expected_offset; } static bool has_valid_stack_frame(struct insn_state *state) { struct cfi_state *cfi = &state->cfi; if (cfi->cfa.base == CFI_BP && check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) && check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8)) return true; if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP) return true; return false; } static int update_cfi_state_regs(struct instruction *insn, struct cfi_state *cfi, struct stack_op *op) { struct cfi_reg *cfa = &cfi->cfa; if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT) return 0; /* push */ if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF) cfa->offset += 8; /* pop */ if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF) cfa->offset -= 8; /* add immediate to sp */ if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD && op->dest.reg == CFI_SP && op->src.reg == CFI_SP) cfa->offset -= op->src.offset; return 0; } static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset) { if (arch_callee_saved_reg(reg) && cfi->regs[reg].base == CFI_UNDEFINED) { cfi->regs[reg].base = base; cfi->regs[reg].offset = offset; } } static void restore_reg(struct cfi_state *cfi, unsigned char reg) { cfi->regs[reg].base = initial_func_cfi.regs[reg].base; cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset; } /* * A note about DRAP stack alignment: * * GCC has the concept of a DRAP register, which is used to help keep track of * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP * register. The typical DRAP pattern is: * * 4c 8d 54 24 08 lea 0x8(%rsp),%r10 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp * 41 ff 72 f8 pushq -0x8(%r10) * 55 push %rbp * 48 89 e5 mov %rsp,%rbp * (more pushes) * 41 52 push %r10 * ... * 41 5a pop %r10 * (more pops) * 5d pop %rbp * 49 8d 62 f8 lea -0x8(%r10),%rsp * c3 retq * * There are some variations in the epilogues, like: * * 5b pop %rbx * 41 5a pop %r10 * 41 5c pop %r12 * 41 5d pop %r13 * 41 5e pop %r14 * c9 leaveq * 49 8d 62 f8 lea -0x8(%r10),%rsp * c3 retq * * and: * * 4c 8b 55 e8 mov -0x18(%rbp),%r10 * 48 8b 5d e0 mov -0x20(%rbp),%rbx * 4c 8b 65 f0 mov -0x10(%rbp),%r12 * 4c 8b 6d f8 mov -0x8(%rbp),%r13 * c9 leaveq * 49 8d 62 f8 lea -0x8(%r10),%rsp * c3 retq * * Sometimes r13 is used as the DRAP register, in which case it's saved and * restored beforehand: * * 41 55 push %r13 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp * ... * 49 8d 65 f0 lea -0x10(%r13),%rsp * 41 5d pop %r13 * c3 retq */ static int update_cfi_state(struct instruction *insn, struct instruction *next_insn, struct cfi_state *cfi, struct stack_op *op) { struct cfi_reg *cfa = &cfi->cfa; struct cfi_reg *regs = cfi->regs; /* ignore UNWIND_HINT_UNDEFINED regions */ if (cfi->force_undefined) return 0; /* stack operations don't make sense with an undefined CFA */ if (cfa->base == CFI_UNDEFINED) { if (insn_func(insn)) { WARN_INSN(insn, "undefined stack state"); return -1; } return 0; } if (cfi->type == UNWIND_HINT_TYPE_REGS || cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL) return update_cfi_state_regs(insn, cfi, op); switch (op->dest.type) { case OP_DEST_REG: switch (op->src.type) { case OP_SRC_REG: if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP && cfa->base == CFI_SP && check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) { /* mov %rsp, %rbp */ cfa->base = op->dest.reg; cfi->bp_scratch = false; } else if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP && cfi->drap) { /* drap: mov %rsp, %rbp */ regs[CFI_BP].base = CFI_BP; regs[CFI_BP].offset = -cfi->stack_size; cfi->bp_scratch = false; } else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { /* * mov %rsp, %reg * * This is needed for the rare case where GCC * does: * * mov %rsp, %rax * ... * mov %rax, %rsp */ cfi->vals[op->dest.reg].base = CFI_CFA; cfi->vals[op->dest.reg].offset = -cfi->stack_size; } else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP && (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) { /* * mov %rbp, %rsp * * Restore the original stack pointer (Clang). */ cfi->stack_size = -cfi->regs[CFI_BP].offset; } else if (op->dest.reg == cfa->base) { /* mov %reg, %rsp */ if (cfa->base == CFI_SP && cfi->vals[op->src.reg].base == CFI_CFA) { /* * This is needed for the rare case * where GCC does something dumb like: * * lea 0x8(%rsp), %rcx * ... * mov %rcx, %rsp */ cfa->offset = -cfi->vals[op->src.reg].offset; cfi->stack_size = cfa->offset; } else if (cfa->base == CFI_SP && cfi->vals[op->src.reg].base == CFI_SP_INDIRECT && cfi->vals[op->src.reg].offset == cfa->offset) { /* * Stack swizzle: * * 1: mov %rsp, (%[tos]) * 2: mov %[tos], %rsp * ... * 3: pop %rsp * * Where: * * 1 - places a pointer to the previous * stack at the Top-of-Stack of the * new stack. * * 2 - switches to the new stack. * * 3 - pops the Top-of-Stack to restore * the original stack. * * Note: we set base to SP_INDIRECT * here and preserve offset. Therefore * when the unwinder reaches ToS it * will dereference SP and then add the * offset to find the next frame, IOW: * (%rsp) + offset. */ cfa->base = CFI_SP_INDIRECT; } else { cfa->base = CFI_UNDEFINED; cfa->offset = 0; } } else if (op->dest.reg == CFI_SP && cfi->vals[op->src.reg].base == CFI_SP_INDIRECT && cfi->vals[op->src.reg].offset == cfa->offset) { /* * The same stack swizzle case 2) as above. But * because we can't change cfa->base, case 3) * will become a regular POP. Pretend we're a * PUSH so things don't go unbalanced. */ cfi->stack_size += 8; } break; case OP_SRC_ADD: if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) { /* add imm, %rsp */ cfi->stack_size -= op->src.offset; if (cfa->base == CFI_SP) cfa->offset -= op->src.offset; break; } if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) { /* lea disp(%rbp), %rsp */ cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset); break; } if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { /* drap: lea disp(%rsp), %drap */ cfi->drap_reg = op->dest.reg; /* * lea disp(%rsp), %reg * * This is needed for the rare case where GCC * does something dumb like: * * lea 0x8(%rsp), %rcx * ... * mov %rcx, %rsp */ cfi->vals[op->dest.reg].base = CFI_CFA; cfi->vals[op->dest.reg].offset = \ -cfi->stack_size + op->src.offset; break; } if (cfi->drap && op->dest.reg == CFI_SP && op->src.reg == cfi->drap_reg) { /* drap: lea disp(%drap), %rsp */ cfa->base = CFI_SP; cfa->offset = cfi->stack_size = -op->src.offset; cfi->drap_reg = CFI_UNDEFINED; cfi->drap = false; break; } if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) { WARN_INSN(insn, "unsupported stack register modification"); return -1; } break; case OP_SRC_AND: if (op->dest.reg != CFI_SP || (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) || (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) { WARN_INSN(insn, "unsupported stack pointer realignment"); return -1; } if (cfi->drap_reg != CFI_UNDEFINED) { /* drap: and imm, %rsp */ cfa->base = cfi->drap_reg; cfa->offset = cfi->stack_size = 0; cfi->drap = true; } /* * Older versions of GCC (4.8ish) realign the stack * without DRAP, with a frame pointer. */ break; case OP_SRC_POP: case OP_SRC_POPF: if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) { /* pop %rsp; # restore from a stack swizzle */ cfa->base = CFI_SP; break; } if (!cfi->drap && op->dest.reg == cfa->base) { /* pop %rbp */ cfa->base = CFI_SP; } if (cfi->drap && cfa->base == CFI_BP_INDIRECT && op->dest.reg == cfi->drap_reg && cfi->drap_offset == -cfi->stack_size) { /* drap: pop %drap */ cfa->base = cfi->drap_reg; cfa->offset = 0; cfi->drap_offset = -1; } else if (cfi->stack_size == -regs[op->dest.reg].offset) { /* pop %reg */ restore_reg(cfi, op->dest.reg); } cfi->stack_size -= 8; if (cfa->base == CFI_SP) cfa->offset -= 8; break; case OP_SRC_REG_INDIRECT: if (!cfi->drap && op->dest.reg == cfa->base && op->dest.reg == CFI_BP) { /* mov disp(%rsp), %rbp */ cfa->base = CFI_SP; cfa->offset = cfi->stack_size; } if (cfi->drap && op->src.reg == CFI_BP && op->src.offset == cfi->drap_offset) { /* drap: mov disp(%rbp), %drap */ cfa->base = cfi->drap_reg; cfa->offset = 0; cfi->drap_offset = -1; } if (cfi->drap && op->src.reg == CFI_BP && op->src.offset == regs[op->dest.reg].offset) { /* drap: mov disp(%rbp), %reg */ restore_reg(cfi, op->dest.reg); } else if (op->src.reg == cfa->base && op->src.offset == regs[op->dest.reg].offset + cfa->offset) { /* mov disp(%rbp), %reg */ /* mov disp(%rsp), %reg */ restore_reg(cfi, op->dest.reg); } else if (op->src.reg == CFI_SP && op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) { /* mov disp(%rsp), %reg */ restore_reg(cfi, op->dest.reg); } break; default: WARN_INSN(insn, "unknown stack-related instruction"); return -1; } break; case OP_DEST_PUSH: case OP_DEST_PUSHF: cfi->stack_size += 8; if (cfa->base == CFI_SP) cfa->offset += 8; if (op->src.type != OP_SRC_REG) break; if (cfi->drap) { if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) { /* drap: push %drap */ cfa->base = CFI_BP_INDIRECT; cfa->offset = -cfi->stack_size; /* save drap so we know when to restore it */ cfi->drap_offset = -cfi->stack_size; } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) { /* drap: push %rbp */ cfi->stack_size = 0; } else { /* drap: push %reg */ save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size); } } else { /* push %reg */ save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size); } /* detect when asm code uses rbp as a scratch register */ if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP && cfa->base != CFI_BP) cfi->bp_scratch = true; break; case OP_DEST_REG_INDIRECT: if (cfi->drap) { if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) { /* drap: mov %drap, disp(%rbp) */ cfa->base = CFI_BP_INDIRECT; cfa->offset = op->dest.offset; /* save drap offset so we know when to restore it */ cfi->drap_offset = op->dest.offset; } else { /* drap: mov reg, disp(%rbp) */ save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset); } } else if (op->dest.reg == cfa->base) { /* mov reg, disp(%rbp) */ /* mov reg, disp(%rsp) */ save_reg(cfi, op->src.reg, CFI_CFA, op->dest.offset - cfi->cfa.offset); } else if (op->dest.reg == CFI_SP) { /* mov reg, disp(%rsp) */ save_reg(cfi, op->src.reg, CFI_CFA, op->dest.offset - cfi->stack_size); } else if (op->src.reg == CFI_SP && op->dest.offset == 0) { /* mov %rsp, (%reg); # setup a stack swizzle. */ cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT; cfi->vals[op->dest.reg].offset = cfa->offset; } break; case OP_DEST_MEM: if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) { WARN_INSN(insn, "unknown stack-related memory operation"); return -1; } /* pop mem */ cfi->stack_size -= 8; if (cfa->base == CFI_SP) cfa->offset -= 8; break; default: WARN_INSN(insn, "unknown stack-related instruction"); return -1; } return 0; } /* * The stack layouts of alternatives instructions can sometimes diverge when * they have stack modifications. That's fine as long as the potential stack * layouts don't conflict at any given potential instruction boundary. * * Flatten the CFIs of the different alternative code streams (both original * and replacement) into a single shared CFI array which can be used to detect * conflicts and nicely feed a linear array of ORC entries to the unwinder. */ static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn) { struct cfi_state **alt_cfi; int group_off; if (!insn->alt_group) return 0; if (!insn->cfi) { WARN("CFI missing"); return -1; } alt_cfi = insn->alt_group->cfi; group_off = insn->offset - insn->alt_group->first_insn->offset; if (!alt_cfi[group_off]) { alt_cfi[group_off] = insn->cfi; } else { if (cficmp(alt_cfi[group_off], insn->cfi)) { struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group; struct instruction *orig = orig_group->first_insn; char *where = offstr(insn->sec, insn->offset); WARN_INSN(orig, "stack layout conflict in alternatives: %s", where); free(where); return -1; } } return 0; } static int handle_insn_ops(struct instruction *insn, struct instruction *next_insn, struct insn_state *state) { struct stack_op *op; for (op = insn->stack_ops; op; op = op->next) { if (update_cfi_state(insn, next_insn, &state->cfi, op)) return 1; if (!insn->alt_group) continue; if (op->dest.type == OP_DEST_PUSHF) { if (!state->uaccess_stack) { state->uaccess_stack = 1; } else if (state->uaccess_stack >> 31) { WARN_INSN(insn, "PUSHF stack exhausted"); return 1; } state->uaccess_stack <<= 1; state->uaccess_stack |= state->uaccess; } if (op->src.type == OP_SRC_POPF) { if (state->uaccess_stack) { state->uaccess = state->uaccess_stack & 1; state->uaccess_stack >>= 1; if (state->uaccess_stack == 1) state->uaccess_stack = 0; } } } return 0; } static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2) { struct cfi_state *cfi1 = insn->cfi; int i; if (!cfi1) { WARN("CFI missing"); return false; } if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) { WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d", cfi1->cfa.base, cfi1->cfa.offset, cfi2->cfa.base, cfi2->cfa.offset); } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) { for (i = 0; i < CFI_NUM_REGS; i++) { if (!memcmp(&cfi1->regs[i], &cfi2->regs[i], sizeof(struct cfi_reg))) continue; WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d", i, cfi1->regs[i].base, cfi1->regs[i].offset, i, cfi2->regs[i].base, cfi2->regs[i].offset); break; } } else if (cfi1->type != cfi2->type) { WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d", cfi1->type, cfi2->type); } else if (cfi1->drap != cfi2->drap || (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) || (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) { WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)", cfi1->drap, cfi1->drap_reg, cfi1->drap_offset, cfi2->drap, cfi2->drap_reg, cfi2->drap_offset); } else return true; return false; } static inline bool func_uaccess_safe(struct symbol *func) { if (func) return func->uaccess_safe; return false; } static inline const char *call_dest_name(struct instruction *insn) { static char pvname[19]; struct reloc *reloc; int idx; if (insn_call_dest(insn)) return insn_call_dest(insn)->name; reloc = insn_reloc(NULL, insn); if (reloc && !strcmp(reloc->sym->name, "pv_ops")) { idx = (reloc_addend(reloc) / sizeof(void *)); snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx); return pvname; } return "{dynamic}"; } static bool pv_call_dest(struct objtool_file *file, struct instruction *insn) { struct symbol *target; struct reloc *reloc; int idx; reloc = insn_reloc(file, insn); if (!reloc || strcmp(reloc->sym->name, "pv_ops")) return false; idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *)); if (file->pv_ops[idx].clean) return true; file->pv_ops[idx].clean = true; list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) { if (!target->sec->noinstr) { WARN("pv_ops[%d]: %s", idx, target->name); file->pv_ops[idx].clean = false; } } return file->pv_ops[idx].clean; } static inline bool noinstr_call_dest(struct objtool_file *file, struct instruction *insn, struct symbol *func) { /* * We can't deal with indirect function calls at present; * assume they're instrumented. */ if (!func) { if (file->pv_ops) return pv_call_dest(file, insn); return false; } /* * If the symbol is from a noinstr section; we good. */ if (func->sec->noinstr) return true; /* * If the symbol is a static_call trampoline, we can't tell. */ if (func->static_call_tramp) return true; /* * The __ubsan_handle_*() calls are like WARN(), they only happen when * something 'BAD' happened. At the risk of taking the machine down, * let them proceed to get the message out. */ if (!strncmp(func->name, "__ubsan_handle_", 15)) return true; return false; } static int validate_call(struct objtool_file *file, struct instruction *insn, struct insn_state *state) { if (state->noinstr && state->instr <= 0 && !noinstr_call_dest(file, insn, insn_call_dest(insn))) { WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn)); return 1; } if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) { WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn)); return 1; } if (state->df) { WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn)); return 1; } return 0; } static int validate_sibling_call(struct objtool_file *file, struct instruction *insn, struct insn_state *state) { if (insn_func(insn) && has_modified_stack_frame(insn, state)) { WARN_INSN(insn, "sibling call from callable instruction with modified stack frame"); return 1; } return validate_call(file, insn, state); } static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state) { if (state->noinstr && state->instr > 0) { WARN_INSN(insn, "return with instrumentation enabled"); return 1; } if (state->uaccess && !func_uaccess_safe(func)) { WARN_INSN(insn, "return with UACCESS enabled"); return 1; } if (!state->uaccess && func_uaccess_safe(func)) { WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function"); return 1; } if (state->df) { WARN_INSN(insn, "return with DF set"); return 1; } if (func && has_modified_stack_frame(insn, state)) { WARN_INSN(insn, "return with modified stack frame"); return 1; } if (state->cfi.bp_scratch) { WARN_INSN(insn, "BP used as a scratch register"); return 1; } return 0; } static struct instruction *next_insn_to_validate(struct objtool_file *file, struct instruction *insn) { struct alt_group *alt_group = insn->alt_group; /* * Simulate the fact that alternatives are patched in-place. When the * end of a replacement alt_group is reached, redirect objtool flow to * the end of the original alt_group. * * insn->alts->insn -> alt_group->first_insn * ... * alt_group->last_insn * [alt_group->nop] -> next(orig_group->last_insn) */ if (alt_group) { if (alt_group->nop) { /* ->nop implies ->orig_group */ if (insn == alt_group->last_insn) return alt_group->nop; if (insn == alt_group->nop) goto next_orig; } if (insn == alt_group->last_insn && alt_group->orig_group) goto next_orig; } return next_insn_same_sec(file, insn); next_orig: return next_insn_same_sec(file, alt_group->orig_group->last_insn); } /* * Follow the branch starting at the given instruction, and recursively follow * any other branches (jumps). Meanwhile, track the frame pointer state at * each instruction and validate all the rules described in * tools/objtool/Documentation/objtool.txt. */ static int validate_branch(struct objtool_file *file, struct symbol *func, struct instruction *insn, struct insn_state state) { struct alternative *alt; struct instruction *next_insn, *prev_insn = NULL; struct section *sec; u8 visited; int ret; sec = insn->sec; while (1) { next_insn = next_insn_to_validate(file, insn); if (func && insn_func(insn) && func != insn_func(insn)->pfunc) { /* Ignore KCFI type preambles, which always fall through */ if (!strncmp(func->name, "__cfi_", 6) || !strncmp(func->name, "__pfx_", 6)) return 0; WARN("%s() falls through to next function %s()", func->name, insn_func(insn)->name); return 1; } if (func && insn->ignore) { WARN_INSN(insn, "BUG: why am I validating an ignored function?"); return 1; } visited = VISITED_BRANCH << state.uaccess; if (insn->visited & VISITED_BRANCH_MASK) { if (!insn->hint && !insn_cfi_match(insn, &state.cfi)) return 1; if (insn->visited & visited) return 0; } else { nr_insns_visited++; } if (state.noinstr) state.instr += insn->instr; if (insn->hint) { if (insn->restore) { struct instruction *save_insn, *i; i = insn; save_insn = NULL; sym_for_each_insn_continue_reverse(file, func, i) { if (i->save) { save_insn = i; break; } } if (!save_insn) { WARN_INSN(insn, "no corresponding CFI save for CFI restore"); return 1; } if (!save_insn->visited) { WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo"); return 1; } insn->cfi = save_insn->cfi; nr_cfi_reused++; } state.cfi = *insn->cfi; } else { /* XXX track if we actually changed state.cfi */ if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) { insn->cfi = prev_insn->cfi; nr_cfi_reused++; } else { insn->cfi = cfi_hash_find_or_add(&state.cfi); } } insn->visited |= visited; if (propagate_alt_cfi(file, insn)) return 1; if (!insn->ignore_alts && insn->alts) { bool skip_orig = false; for (alt = insn->alts; alt; alt = alt->next) { if (alt->skip_orig) skip_orig = true; ret = validate_branch(file, func, alt->insn, state); if (ret) { BT_INSN(insn, "(alt)"); return ret; } } if (skip_orig) return 0; } if (handle_insn_ops(insn, next_insn, &state)) return 1; switch (insn->type) { case INSN_RETURN: return validate_return(func, insn, &state); case INSN_CALL: case INSN_CALL_DYNAMIC: ret = validate_call(file, insn, &state); if (ret) return ret; if (opts.stackval && func && !is_special_call(insn) && !has_valid_stack_frame(&state)) { WARN_INSN(insn, "call without frame pointer save/setup"); return 1; } if (insn->dead_end) return 0; break; case INSN_JUMP_CONDITIONAL: case INSN_JUMP_UNCONDITIONAL: if (is_sibling_call(insn)) { ret = validate_sibling_call(file, insn, &state); if (ret) return ret; } else if (insn->jump_dest) { ret = validate_branch(file, func, insn->jump_dest, state); if (ret) { BT_INSN(insn, "(branch)"); return ret; } } if (insn->type == INSN_JUMP_UNCONDITIONAL) return 0; break; case INSN_JUMP_DYNAMIC: case INSN_JUMP_DYNAMIC_CONDITIONAL: if (is_sibling_call(insn)) { ret = validate_sibling_call(file, insn, &state); if (ret) return ret; } if (insn->type == INSN_JUMP_DYNAMIC) return 0; break; case INSN_CONTEXT_SWITCH: if (func && (!next_insn || !next_insn->hint)) { WARN_INSN(insn, "unsupported instruction in callable function"); return 1; } return 0; case INSN_STAC: if (state.uaccess) { WARN_INSN(insn, "recursive UACCESS enable"); return 1; } state.uaccess = true; break; case INSN_CLAC: if (!state.uaccess && func) { WARN_INSN(insn, "redundant UACCESS disable"); return 1; } if (func_uaccess_safe(func) && !state.uaccess_stack) { WARN_INSN(insn, "UACCESS-safe disables UACCESS"); return 1; } state.uaccess = false; break; case INSN_STD: if (state.df) { WARN_INSN(insn, "recursive STD"); return 1; } state.df = true; break; case INSN_CLD: if (!state.df && func) { WARN_INSN(insn, "redundant CLD"); return 1; } state.df = false; break; default: break; } if (insn->dead_end) return 0; if (!next_insn) { if (state.cfi.cfa.base == CFI_UNDEFINED) return 0; WARN("%s: unexpected end of section", sec->name); return 1; } prev_insn = insn; insn = next_insn; } return 0; } static int validate_unwind_hint(struct objtool_file *file, struct instruction *insn, struct insn_state *state) { if (insn->hint && !insn->visited && !insn->ignore) { int ret = validate_branch(file, insn_func(insn), insn, *state); if (ret) BT_INSN(insn, "<=== (hint)"); return ret; } return 0; } static int validate_unwind_hints(struct objtool_file *file, struct section *sec) { struct instruction *insn; struct insn_state state; int warnings = 0; if (!file->hints) return 0; init_insn_state(file, &state, sec); if (sec) { sec_for_each_insn(file, sec, insn) warnings += validate_unwind_hint(file, insn, &state); } else { for_each_insn(file, insn) warnings += validate_unwind_hint(file, insn, &state); } return warnings; } /* * Validate rethunk entry constraint: must untrain RET before the first RET. * * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes * before an actual RET instruction. */ static int validate_unret(struct objtool_file *file, struct instruction *insn) { struct instruction *next, *dest; int ret; for (;;) { next = next_insn_to_validate(file, insn); if (insn->visited & VISITED_UNRET) return 0; insn->visited |= VISITED_UNRET; if (!insn->ignore_alts && insn->alts) { struct alternative *alt; bool skip_orig = false; for (alt = insn->alts; alt; alt = alt->next) { if (alt->skip_orig) skip_orig = true; ret = validate_unret(file, alt->insn); if (ret) { BT_INSN(insn, "(alt)"); return ret; } } if (skip_orig) return 0; } switch (insn->type) { case INSN_CALL_DYNAMIC: case INSN_JUMP_DYNAMIC: case INSN_JUMP_DYNAMIC_CONDITIONAL: WARN_INSN(insn, "early indirect call"); return 1; case INSN_JUMP_UNCONDITIONAL: case INSN_JUMP_CONDITIONAL: if (!is_sibling_call(insn)) { if (!insn->jump_dest) { WARN_INSN(insn, "unresolved jump target after linking?!?"); return -1; } ret = validate_unret(file, insn->jump_dest); if (ret) { BT_INSN(insn, "(branch%s)", insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : ""); return ret; } if (insn->type == INSN_JUMP_UNCONDITIONAL) return 0; break; } /* fallthrough */ case INSN_CALL: dest = find_insn(file, insn_call_dest(insn)->sec, insn_call_dest(insn)->offset); if (!dest) { WARN("Unresolved function after linking!?: %s", insn_call_dest(insn)->name); return -1; } ret = validate_unret(file, dest); if (ret) { BT_INSN(insn, "(call)"); return ret; } /* * If a call returns without error, it must have seen UNTRAIN_RET. * Therefore any non-error return is a success. */ return 0; case INSN_RETURN: WARN_INSN(insn, "RET before UNTRAIN"); return 1; case INSN_NOP: if (insn->retpoline_safe) return 0; break; default: break; } if (!next) { WARN_INSN(insn, "teh end!"); return -1; } insn = next; } return 0; } /* * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter * VALIDATE_UNRET_END before RET. */ static int validate_unrets(struct objtool_file *file) { struct instruction *insn; int ret, warnings = 0; for_each_insn(file, insn) { if (!insn->unret) continue; ret = validate_unret(file, insn); if (ret < 0) { WARN_INSN(insn, "Failed UNRET validation"); return ret; } warnings += ret; } return warnings; } static int validate_retpoline(struct objtool_file *file) { struct instruction *insn; int warnings = 0; for_each_insn(file, insn) { if (insn->type != INSN_JUMP_DYNAMIC && insn->type != INSN_CALL_DYNAMIC && insn->type != INSN_RETURN) continue; if (insn->retpoline_safe) continue; if (insn->sec->init) continue; if (insn->type == INSN_RETURN) { if (opts.rethunk) { WARN_INSN(insn, "'naked' return found in RETHUNK build"); } else continue; } else { WARN_INSN(insn, "indirect %s found in RETPOLINE build", insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); } warnings++; } return warnings; } static bool is_kasan_insn(struct instruction *insn) { return (insn->type == INSN_CALL && !strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return")); } static bool is_ubsan_insn(struct instruction *insn) { return (insn->type == INSN_CALL && !strcmp(insn_call_dest(insn)->name, "__ubsan_handle_builtin_unreachable")); } static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn) { int i; struct instruction *prev_insn; if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP) return true; /* * Ignore alternative replacement instructions. This can happen * when a whitelisted function uses one of the ALTERNATIVE macros. */ if (!strcmp(insn->sec->name, ".altinstr_replacement") || !strcmp(insn->sec->name, ".altinstr_aux")) return true; /* * Whole archive runs might encounter dead code from weak symbols. * This is where the linker will have dropped the weak symbol in * favour of a regular symbol, but leaves the code in place. * * In this case we'll find a piece of code (whole function) that is not * covered by a !section symbol. Ignore them. */ if (opts.link && !insn_func(insn)) { int size = find_symbol_hole_containing(insn->sec, insn->offset); unsigned long end = insn->offset + size; if (!size) /* not a hole */ return false; if (size < 0) /* hole until the end */ return true; sec_for_each_insn_continue(file, insn) { /* * If we reach a visited instruction at or before the * end of the hole, ignore the unreachable. */ if (insn->visited) return true; if (insn->offset >= end) break; /* * If this hole jumps to a .cold function, mark it ignore too. */ if (insn->jump_dest && insn_func(insn->jump_dest) && strstr(insn_func(insn->jump_dest)->name, ".cold")) { struct instruction *dest = insn->jump_dest; func_for_each_insn(file, insn_func(dest), dest) dest->ignore = true; } } return false; } if (!insn_func(insn)) return false; if (insn_func(insn)->static_call_tramp) return true; /* * CONFIG_UBSAN_TRAP inserts a UD2 when it sees * __builtin_unreachable(). The BUG() macro has an unreachable() after * the UD2, which causes GCC's undefined trap logic to emit another UD2 * (or occasionally a JMP to UD2). * * It may also insert a UD2 after calling a __noreturn function. */ prev_insn = prev_insn_same_sec(file, insn); if (prev_insn->dead_end && (insn->type == INSN_BUG || (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest && insn->jump_dest->type == INSN_BUG))) return true; /* * Check if this (or a subsequent) instruction is related to * CONFIG_UBSAN or CONFIG_KASAN. * * End the search at 5 instructions to avoid going into the weeds. */ for (i = 0; i < 5; i++) { if (is_kasan_insn(insn) || is_ubsan_insn(insn)) return true; if (insn->type == INSN_JUMP_UNCONDITIONAL) { if (insn->jump_dest && insn_func(insn->jump_dest) == insn_func(insn)) { insn = insn->jump_dest; continue; } break; } if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len) break; insn = next_insn_same_sec(file, insn); } return false; } static int add_prefix_symbol(struct objtool_file *file, struct symbol *func) { struct instruction *insn, *prev; struct cfi_state *cfi; insn = find_insn(file, func->sec, func->offset); if (!insn) return -1; for (prev = prev_insn_same_sec(file, insn); prev; prev = prev_insn_same_sec(file, prev)) { u64 offset; if (prev->type != INSN_NOP) return -1; offset = func->offset - prev->offset; if (offset > opts.prefix) return -1; if (offset < opts.prefix) continue; elf_create_prefix_symbol(file->elf, func, opts.prefix); break; } if (!prev) return -1; if (!insn->cfi) { /* * This can happen if stack validation isn't enabled or the * function is annotated with STACK_FRAME_NON_STANDARD. */ return 0; } /* Propagate insn->cfi to the prefix code */ cfi = cfi_hash_find_or_add(insn->cfi); for (; prev != insn; prev = next_insn_same_sec(file, prev)) prev->cfi = cfi; return 0; } static int add_prefix_symbols(struct objtool_file *file) { struct section *sec; struct symbol *func; for_each_sec(file, sec) { if (!(sec->sh.sh_flags & SHF_EXECINSTR)) continue; sec_for_each_sym(sec, func) { if (func->type != STT_FUNC) continue; add_prefix_symbol(file, func); } } return 0; } static int validate_symbol(struct objtool_file *file, struct section *sec, struct symbol *sym, struct insn_state *state) { struct instruction *insn; int ret; if (!sym->len) { WARN("%s() is missing an ELF size annotation", sym->name); return 1; } if (sym->pfunc != sym || sym->alias != sym) return 0; insn = find_insn(file, sec, sym->offset); if (!insn || insn->ignore || insn->visited) return 0; state->uaccess = sym->uaccess_safe; ret = validate_branch(file, insn_func(insn), insn, *state); if (ret) BT_INSN(insn, "<=== (sym)"); return ret; } static int validate_section(struct objtool_file *file, struct section *sec) { struct insn_state state; struct symbol *func; int warnings = 0; sec_for_each_sym(sec, func) { if (func->type != STT_FUNC) continue; init_insn_state(file, &state, sec); set_func_state(&state.cfi); warnings += validate_symbol(file, sec, func, &state); } return warnings; } static int validate_noinstr_sections(struct objtool_file *file) { struct section *sec; int warnings = 0; sec = find_section_by_name(file->elf, ".noinstr.text"); if (sec) { warnings += validate_section(file, sec); warnings += validate_unwind_hints(file, sec); } sec = find_section_by_name(file->elf, ".entry.text"); if (sec) { warnings += validate_section(file, sec); warnings += validate_unwind_hints(file, sec); } sec = find_section_by_name(file->elf, ".cpuidle.text"); if (sec) { warnings += validate_section(file, sec); warnings += validate_unwind_hints(file, sec); } return warnings; } static int validate_functions(struct objtool_file *file) { struct section *sec; int warnings = 0; for_each_sec(file, sec) { if (!(sec->sh.sh_flags & SHF_EXECINSTR)) continue; warnings += validate_section(file, sec); } return warnings; } static void mark_endbr_used(struct instruction *insn) { if (!list_empty(&insn->call_node)) list_del_init(&insn->call_node); } static bool noendbr_range(struct objtool_file *file, struct instruction *insn) { struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1); struct instruction *first; if (!sym) return false; first = find_insn(file, sym->sec, sym->offset); if (!first) return false; if (first->type != INSN_ENDBR && !first->noendbr) return false; return insn->offset == sym->offset + sym->len; } static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn) { struct instruction *dest; struct reloc *reloc; unsigned long off; int warnings = 0; /* * Looking for function pointer load relocations. Ignore * direct/indirect branches: */ switch (insn->type) { case INSN_CALL: case INSN_CALL_DYNAMIC: case INSN_JUMP_CONDITIONAL: case INSN_JUMP_UNCONDITIONAL: case INSN_JUMP_DYNAMIC: case INSN_JUMP_DYNAMIC_CONDITIONAL: case INSN_RETURN: case INSN_NOP: return 0; default: break; } for (reloc = insn_reloc(file, insn); reloc; reloc = find_reloc_by_dest_range(file->elf, insn->sec, reloc_offset(reloc) + 1, (insn->offset + insn->len) - (reloc_offset(reloc) + 1))) { /* * static_call_update() references the trampoline, which * doesn't have (or need) ENDBR. Skip warning in that case. */ if (reloc->sym->static_call_tramp) continue; off = reloc->sym->offset; if (reloc_type(reloc) == R_X86_64_PC32 || reloc_type(reloc) == R_X86_64_PLT32) off += arch_dest_reloc_offset(reloc_addend(reloc)); else off += reloc_addend(reloc); dest = find_insn(file, reloc->sym->sec, off); if (!dest) continue; if (dest->type == INSN_ENDBR) { mark_endbr_used(dest); continue; } if (insn_func(dest) && insn_func(insn) && insn_func(dest)->pfunc == insn_func(insn)->pfunc) { /* * Anything from->to self is either _THIS_IP_ or * IRET-to-self. * * There is no sane way to annotate _THIS_IP_ since the * compiler treats the relocation as a constant and is * happy to fold in offsets, skewing any annotation we * do, leading to vast amounts of false-positives. * * There's also compiler generated _THIS_IP_ through * KCOV and such which we have no hope of annotating. * * As such, blanket accept self-references without * issue. */ continue; } /* * Accept anything ANNOTATE_NOENDBR. */ if (dest->noendbr) continue; /* * Accept if this is the instruction after a symbol * that is (no)endbr -- typical code-range usage. */ if (noendbr_range(file, dest)) continue; WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset)); warnings++; } return warnings; } static int validate_ibt_data_reloc(struct objtool_file *file, struct reloc *reloc) { struct instruction *dest; dest = find_insn(file, reloc->sym->sec, reloc->sym->offset + reloc_addend(reloc)); if (!dest) return 0; if (dest->type == INSN_ENDBR) { mark_endbr_used(dest); return 0; } if (dest->noendbr) return 0; WARN_FUNC("data relocation to !ENDBR: %s", reloc->sec->base, reloc_offset(reloc), offstr(dest->sec, dest->offset)); return 1; } /* * Validate IBT rules and remove used ENDBR instructions from the seal list. * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with * NOPs) later, in create_ibt_endbr_seal_sections(). */ static int validate_ibt(struct objtool_file *file) { struct section *sec; struct reloc *reloc; struct instruction *insn; int warnings = 0; for_each_insn(file, insn) warnings += validate_ibt_insn(file, insn); for_each_sec(file, sec) { /* Already done by validate_ibt_insn() */ if (sec->sh.sh_flags & SHF_EXECINSTR) continue; if (!sec->rsec) continue; /* * These sections can reference text addresses, but not with * the intent to indirect branch to them. */ if ((!strncmp(sec->name, ".discard", 8) && strcmp(sec->name, ".discard.ibt_endbr_noseal")) || !strncmp(sec->name, ".debug", 6) || !strcmp(sec->name, ".altinstructions") || !strcmp(sec->name, ".ibt_endbr_seal") || !strcmp(sec->name, ".orc_unwind_ip") || !strcmp(sec->name, ".parainstructions") || !strcmp(sec->name, ".retpoline_sites") || !strcmp(sec->name, ".smp_locks") || !strcmp(sec->name, ".static_call_sites") || !strcmp(sec->name, "_error_injection_whitelist") || !strcmp(sec->name, "_kprobe_blacklist") || !strcmp(sec->name, "__bug_table") || !strcmp(sec->name, "__ex_table") || !strcmp(sec->name, "__jump_table") || !strcmp(sec->name, "__mcount_loc") || !strcmp(sec->name, ".kcfi_traps") || strstr(sec->name, "__patchable_function_entries")) continue; for_each_reloc(sec->rsec, reloc) warnings += validate_ibt_data_reloc(file, reloc); } return warnings; } static int validate_sls(struct objtool_file *file) { struct instruction *insn, *next_insn; int warnings = 0; for_each_insn(file, insn) { next_insn = next_insn_same_sec(file, insn); if (insn->retpoline_safe) continue; switch (insn->type) { case INSN_RETURN: if (!next_insn || next_insn->type != INSN_TRAP) { WARN_INSN(insn, "missing int3 after ret"); warnings++; } break; case INSN_JUMP_DYNAMIC: if (!next_insn || next_insn->type != INSN_TRAP) { WARN_INSN(insn, "missing int3 after indirect jump"); warnings++; } break; default: break; } } return warnings; } static bool ignore_noreturn_call(struct instruction *insn) { struct symbol *call_dest = insn_call_dest(insn); /* * FIXME: hack, we need a real noreturn solution * * Problem is, exc_double_fault() may or may not return, depending on * whether CONFIG_X86_ESPFIX64 is set. But objtool has no visibility * to the kernel config. * * Other potential ways to fix it: * * - have compiler communicate __noreturn functions somehow * - remove CONFIG_X86_ESPFIX64 * - read the .config file * - add a cmdline option * - create a generic objtool annotation format (vs a bunch of custom * formats) and annotate it */ if (!strcmp(call_dest->name, "exc_double_fault")) { /* prevent further unreachable warnings for the caller */ insn->sym->warned = 1; return true; } return false; } static int validate_reachable_instructions(struct objtool_file *file) { struct instruction *insn, *prev_insn; struct symbol *call_dest; int warnings = 0; if (file->ignore_unreachables) return 0; for_each_insn(file, insn) { if (insn->visited || ignore_unreachable_insn(file, insn)) continue; prev_insn = prev_insn_same_sec(file, insn); if (prev_insn && prev_insn->dead_end) { call_dest = insn_call_dest(prev_insn); if (call_dest && !ignore_noreturn_call(prev_insn)) { WARN_INSN(insn, "%s() is missing a __noreturn annotation", call_dest->name); warnings++; continue; } } WARN_INSN(insn, "unreachable instruction"); warnings++; } return warnings; } /* 'funcs' is a space-separated list of function names */ static int disas_funcs(const char *funcs) { const char *objdump_str, *cross_compile; int size, ret; char *cmd; cross_compile = getenv("CROSS_COMPILE"); objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '" "BEGIN { split(_funcs, funcs); }" "/^$/ { func_match = 0; }" "/<.*>:/ { " "f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);" "for (i in funcs) {" "if (funcs[i] == f) {" "func_match = 1;" "base = strtonum(\"0x\" $1);" "break;" "}" "}" "}" "{" "if (func_match) {" "addr = strtonum(\"0x\" $1);" "printf(\"%%04x \", addr - base);" "print;" "}" "}' 1>&2"; /* fake snprintf() to calculate the size */ size = snprintf(NULL, 0, objdump_str, cross_compile, objname, funcs) + 1; if (size <= 0) { WARN("objdump string size calculation failed"); return -1; } cmd = malloc(size); /* real snprintf() */ snprintf(cmd, size, objdump_str, cross_compile, objname, funcs); ret = system(cmd); if (ret) { WARN("disassembly failed: %d", ret); return -1; } return 0; } static int disas_warned_funcs(struct objtool_file *file) { struct symbol *sym; char *funcs = NULL, *tmp; for_each_sym(file, sym) { if (sym->warned) { if (!funcs) { funcs = malloc(strlen(sym->name) + 1); strcpy(funcs, sym->name); } else { tmp = malloc(strlen(funcs) + strlen(sym->name) + 2); sprintf(tmp, "%s %s", funcs, sym->name); free(funcs); funcs = tmp; } } } if (funcs) disas_funcs(funcs); return 0; } struct insn_chunk { void *addr; struct insn_chunk *next; }; /* * Reduce peak RSS usage by freeing insns memory before writing the ELF file, * which can trigger more allocations for .debug_* sections whose data hasn't * been read yet. */ static void free_insns(struct objtool_file *file) { struct instruction *insn; struct insn_chunk *chunks = NULL, *chunk; for_each_insn(file, insn) { if (!insn->idx) { chunk = malloc(sizeof(*chunk)); chunk->addr = insn; chunk->next = chunks; chunks = chunk; } } for (chunk = chunks; chunk; chunk = chunk->next) free(chunk->addr); } int check(struct objtool_file *file) { int ret, warnings = 0; arch_initial_func_cfi_state(&initial_func_cfi); init_cfi_state(&init_cfi); init_cfi_state(&func_cfi); set_func_state(&func_cfi); init_cfi_state(&force_undefined_cfi); force_undefined_cfi.force_undefined = true; if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3))) goto out; cfi_hash_add(&init_cfi); cfi_hash_add(&func_cfi); ret = decode_sections(file); if (ret < 0) goto out; warnings += ret; if (!nr_insns) goto out; if (opts.retpoline) { ret = validate_retpoline(file); if (ret < 0) return ret; warnings += ret; } if (opts.stackval || opts.orc || opts.uaccess) { ret = validate_functions(file); if (ret < 0) goto out; warnings += ret; ret = validate_unwind_hints(file, NULL); if (ret < 0) goto out; warnings += ret; if (!warnings) { ret = validate_reachable_instructions(file); if (ret < 0) goto out; warnings += ret; } } else if (opts.noinstr) { ret = validate_noinstr_sections(file); if (ret < 0) goto out; warnings += ret; } if (opts.unret) { /* * Must be after validate_branch() and friends, it plays * further games with insn->visited. */ ret = validate_unrets(file); if (ret < 0) return ret; warnings += ret; } if (opts.ibt) { ret = validate_ibt(file); if (ret < 0) goto out; warnings += ret; } if (opts.sls) { ret = validate_sls(file); if (ret < 0) goto out; warnings += ret; } if (opts.static_call) { ret = create_static_call_sections(file); if (ret < 0) goto out; warnings += ret; } if (opts.retpoline) { ret = create_retpoline_sites_sections(file); if (ret < 0) goto out; warnings += ret; } if (opts.cfi) { ret = create_cfi_sections(file); if (ret < 0) goto out; warnings += ret; } if (opts.rethunk) { ret = create_return_sites_sections(file); if (ret < 0) goto out; warnings += ret; if (opts.hack_skylake) { ret = create_direct_call_sections(file); if (ret < 0) goto out; warnings += ret; } } if (opts.mcount) { ret = create_mcount_loc_sections(file); if (ret < 0) goto out; warnings += ret; } if (opts.prefix) { ret = add_prefix_symbols(file); if (ret < 0) return ret; warnings += ret; } if (opts.ibt) { ret = create_ibt_endbr_seal_sections(file); if (ret < 0) goto out; warnings += ret; } if (opts.orc && nr_insns) { ret = orc_create(file); if (ret < 0) goto out; warnings += ret; } free_insns(file); if (opts.verbose) disas_warned_funcs(file); if (opts.stats) { printf("nr_insns_visited: %ld\n", nr_insns_visited); printf("nr_cfi: %ld\n", nr_cfi); printf("nr_cfi_reused: %ld\n", nr_cfi_reused); printf("nr_cfi_cache: %ld\n", nr_cfi_cache); } out: /* * For now, don't fail the kernel build on fatal warnings. These * errors are still fairly common due to the growing matrix of * supported toolchains and their recent pace of change. */ return 0; }
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