| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Peter Zijlstra | 5122 | 59.67% | 46 | 26.29% |
| Gerd Hoffmann | 609 | 7.09% | 3 | 1.71% |
| Nadav Amit | 327 | 3.81% | 8 | 4.57% |
| Song Liu | 326 | 3.80% | 2 | 1.14% |
| Andi Kleen | 320 | 3.73% | 7 | 4.00% |
| Daniel Bristot de Oliveira | 303 | 3.53% | 2 | 1.14% |
| Rusty Russell | 228 | 2.66% | 4 | 2.29% |
| Mathieu Desnoyers | 195 | 2.27% | 5 | 2.86% |
| Borislav Petkov | 164 | 1.91% | 15 | 8.57% |
| Jan Beulich | 145 | 1.69% | 6 | 3.43% |
| Masami Hiramatsu | 138 | 1.61% | 6 | 3.43% |
| Jiri Kosina | 118 | 1.37% | 2 | 1.14% |
| Andrew Lutomirski | 114 | 1.33% | 3 | 1.71% |
| Thomas Gleixner | 86 | 1.00% | 7 | 4.00% |
| Adrian Hunter | 65 | 0.76% | 1 | 0.57% |
| Ingo Molnar | 45 | 0.52% | 6 | 3.43% |
| Juergen Gross | 43 | 0.50% | 4 | 2.29% |
| Jeremy Fitzhardinge | 37 | 0.43% | 6 | 3.43% |
| Zachary Amsden | 25 | 0.29% | 2 | 1.14% |
| H. Peter Anvin | 20 | 0.23% | 2 | 1.14% |
| Linus Torvalds | 17 | 0.20% | 3 | 1.71% |
| Luca Barbieri | 15 | 0.17% | 1 | 0.57% |
| Chris Wright | 13 | 0.15% | 1 | 0.57% |
| Zhou Chengming | 12 | 0.14% | 1 | 0.57% |
| Kees Cook | 11 | 0.13% | 1 | 0.57% |
| Joe Perches | 11 | 0.13% | 1 | 0.57% |
| Kirill A. Shutemov | 7 | 0.08% | 1 | 0.57% |
| Linus Torvalds (pre-git) | 7 | 0.08% | 4 | 2.29% |
| Dave Hansen | 6 | 0.07% | 2 | 1.14% |
| Pekka Paalanen | 6 | 0.07% | 1 | 0.57% |
| Pavel Tatashin | 6 | 0.07% | 1 | 0.57% |
| Steven Rostedt | 4 | 0.05% | 1 | 0.57% |
| Dave Jones | 4 | 0.05% | 1 | 0.57% |
| Ricardo Neri | 3 | 0.03% | 1 | 0.57% |
| Dan Aloni | 3 | 0.03% | 1 | 0.57% |
| Greg Kroah-Hartman | 3 | 0.03% | 1 | 0.57% |
| Josh Poimboeuf | 3 | 0.03% | 1 | 0.57% |
| Mike Travis | 2 | 0.02% | 1 | 0.57% |
| Prasanna S. Panchamukhi | 2 | 0.02% | 1 | 0.57% |
| David Woodhouse | 2 | 0.02% | 1 | 0.57% |
| Christoph Hellwig | 2 | 0.02% | 1 | 0.57% |
| Qiujun Huang | 2 | 0.02% | 2 | 1.14% |
| Arnd Bergmann | 2 | 0.02% | 1 | 0.57% |
| Dan Carpenter | 2 | 0.02% | 1 | 0.57% |
| Marco Ammon | 2 | 0.02% | 1 | 0.57% |
| Mark Rutland | 2 | 0.02% | 1 | 0.57% |
| Yue haibing | 1 | 0.01% | 1 | 0.57% |
| Fengguang Wu | 1 | 0.01% | 1 | 0.57% |
| Jiri Slaby | 1 | 0.01% | 1 | 0.57% |
| Ira Weiny | 1 | 0.01% | 1 | 0.57% |
| Pavel Skripkin | 1 | 0.01% | 1 | 0.57% |
| Total | 8584 | 175 |
// SPDX-License-Identifier: GPL-2.0-only #define pr_fmt(fmt) "SMP alternatives: " fmt #include <linux/module.h> #include <linux/sched.h> #include <linux/perf_event.h> #include <linux/mutex.h> #include <linux/list.h> #include <linux/stringify.h> #include <linux/highmem.h> #include <linux/mm.h> #include <linux/vmalloc.h> #include <linux/memory.h> #include <linux/stop_machine.h> #include <linux/slab.h> #include <linux/kdebug.h> #include <linux/kprobes.h> #include <linux/mmu_context.h> #include <linux/bsearch.h> #include <linux/sync_core.h> #include <asm/text-patching.h> #include <asm/alternative.h> #include <asm/sections.h> #include <asm/mce.h> #include <asm/nmi.h> #include <asm/cacheflush.h> #include <asm/tlbflush.h> #include <asm/insn.h> #include <asm/io.h> #include <asm/fixmap.h> #include <asm/paravirt.h> #include <asm/asm-prototypes.h> int __read_mostly alternatives_patched; EXPORT_SYMBOL_GPL(alternatives_patched); #define MAX_PATCH_LEN (255-1) #define DA_ALL (~0) #define DA_ALT 0x01 #define DA_RET 0x02 #define DA_RETPOLINE 0x04 #define DA_ENDBR 0x08 #define DA_SMP 0x10 static unsigned int __initdata_or_module debug_alternative; static int __init debug_alt(char *str) { if (str && *str == '=') str++; if (!str || kstrtouint(str, 0, &debug_alternative)) debug_alternative = DA_ALL; return 1; } __setup("debug-alternative", debug_alt); static int noreplace_smp; static int __init setup_noreplace_smp(char *str) { noreplace_smp = 1; return 1; } __setup("noreplace-smp", setup_noreplace_smp); #define DPRINTK(type, fmt, args...) \ do { \ if (debug_alternative & DA_##type) \ printk(KERN_DEBUG pr_fmt(fmt) "\n", ##args); \ } while (0) #define DUMP_BYTES(type, buf, len, fmt, args...) \ do { \ if (unlikely(debug_alternative & DA_##type)) { \ int j; \ \ if (!(len)) \ break; \ \ printk(KERN_DEBUG pr_fmt(fmt), ##args); \ for (j = 0; j < (len) - 1; j++) \ printk(KERN_CONT "%02hhx ", buf[j]); \ printk(KERN_CONT "%02hhx\n", buf[j]); \ } \ } while (0) static const unsigned char x86nops[] = { BYTES_NOP1, BYTES_NOP2, BYTES_NOP3, BYTES_NOP4, BYTES_NOP5, BYTES_NOP6, BYTES_NOP7, BYTES_NOP8, #ifdef CONFIG_64BIT BYTES_NOP9, BYTES_NOP10, BYTES_NOP11, #endif }; const unsigned char * const x86_nops[ASM_NOP_MAX+1] = { NULL, x86nops, x86nops + 1, x86nops + 1 + 2, x86nops + 1 + 2 + 3, x86nops + 1 + 2 + 3 + 4, x86nops + 1 + 2 + 3 + 4 + 5, x86nops + 1 + 2 + 3 + 4 + 5 + 6, x86nops + 1 + 2 + 3 + 4 + 5 + 6 + 7, #ifdef CONFIG_64BIT x86nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8, x86nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9, x86nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10, #endif }; /* * Fill the buffer with a single effective instruction of size @len. * * In order not to issue an ORC stack depth tracking CFI entry (Call Frame Info) * for every single-byte NOP, try to generate the maximally available NOP of * size <= ASM_NOP_MAX such that only a single CFI entry is generated (vs one for * each single-byte NOPs). If @len to fill out is > ASM_NOP_MAX, pad with INT3 and * *jump* over instead of executing long and daft NOPs. */ static void __init_or_module add_nop(u8 *instr, unsigned int len) { u8 *target = instr + len; if (!len) return; if (len <= ASM_NOP_MAX) { memcpy(instr, x86_nops[len], len); return; } if (len < 128) { __text_gen_insn(instr, JMP8_INSN_OPCODE, instr, target, JMP8_INSN_SIZE); instr += JMP8_INSN_SIZE; } else { __text_gen_insn(instr, JMP32_INSN_OPCODE, instr, target, JMP32_INSN_SIZE); instr += JMP32_INSN_SIZE; } for (;instr < target; instr++) *instr = INT3_INSN_OPCODE; } extern s32 __retpoline_sites[], __retpoline_sites_end[]; extern s32 __return_sites[], __return_sites_end[]; extern s32 __cfi_sites[], __cfi_sites_end[]; extern s32 __ibt_endbr_seal[], __ibt_endbr_seal_end[]; extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; extern s32 __smp_locks[], __smp_locks_end[]; void text_poke_early(void *addr, const void *opcode, size_t len); /* * Matches NOP and NOPL, not any of the other possible NOPs. */ static bool insn_is_nop(struct insn *insn) { /* Anything NOP, but no REP NOP */ if (insn->opcode.bytes[0] == 0x90 && (!insn->prefixes.nbytes || insn->prefixes.bytes[0] != 0xF3)) return true; /* NOPL */ if (insn->opcode.bytes[0] == 0x0F && insn->opcode.bytes[1] == 0x1F) return true; /* TODO: more nops */ return false; } /* * Find the offset of the first non-NOP instruction starting at @offset * but no further than @len. */ static int skip_nops(u8 *instr, int offset, int len) { struct insn insn; for (; offset < len; offset += insn.length) { if (insn_decode_kernel(&insn, &instr[offset])) break; if (!insn_is_nop(&insn)) break; } return offset; } /* * Optimize a sequence of NOPs, possibly preceded by an unconditional jump * to the end of the NOP sequence into a single NOP. */ static bool __init_or_module __optimize_nops(u8 *instr, size_t len, struct insn *insn, int *next, int *prev, int *target) { int i = *next - insn->length; switch (insn->opcode.bytes[0]) { case JMP8_INSN_OPCODE: case JMP32_INSN_OPCODE: *prev = i; *target = *next + insn->immediate.value; return false; } if (insn_is_nop(insn)) { int nop = i; *next = skip_nops(instr, *next, len); if (*target && *next == *target) nop = *prev; add_nop(instr + nop, *next - nop); DUMP_BYTES(ALT, instr, len, "%px: [%d:%d) optimized NOPs: ", instr, nop, *next); return true; } *target = 0; return false; } /* * "noinline" to cause control flow change and thus invalidate I$ and * cause refetch after modification. */ static void __init_or_module noinline optimize_nops(u8 *instr, size_t len) { int prev, target = 0; for (int next, i = 0; i < len; i = next) { struct insn insn; if (insn_decode_kernel(&insn, &instr[i])) return; next = i + insn.length; __optimize_nops(instr, len, &insn, &next, &prev, &target); } } static void __init_or_module noinline optimize_nops_inplace(u8 *instr, size_t len) { unsigned long flags; local_irq_save(flags); optimize_nops(instr, len); sync_core(); local_irq_restore(flags); } /* * In this context, "source" is where the instructions are placed in the * section .altinstr_replacement, for example during kernel build by the * toolchain. * "Destination" is where the instructions are being patched in by this * machinery. * * The source offset is: * * src_imm = target - src_next_ip (1) * * and the target offset is: * * dst_imm = target - dst_next_ip (2) * * so rework (1) as an expression for target like: * * target = src_imm + src_next_ip (1a) * * and substitute in (2) to get: * * dst_imm = (src_imm + src_next_ip) - dst_next_ip (3) * * Now, since the instruction stream is 'identical' at src and dst (it * is being copied after all) it can be stated that: * * src_next_ip = src + ip_offset * dst_next_ip = dst + ip_offset (4) * * Substitute (4) in (3) and observe ip_offset being cancelled out to * obtain: * * dst_imm = src_imm + (src + ip_offset) - (dst + ip_offset) * = src_imm + src - dst + ip_offset - ip_offset * = src_imm + src - dst (5) * * IOW, only the relative displacement of the code block matters. */ #define apply_reloc_n(n_, p_, d_) \ do { \ s32 v = *(s##n_ *)(p_); \ v += (d_); \ BUG_ON((v >> 31) != (v >> (n_-1))); \ *(s##n_ *)(p_) = (s##n_)v; \ } while (0) static __always_inline void apply_reloc(int n, void *ptr, uintptr_t diff) { switch (n) { case 1: apply_reloc_n(8, ptr, diff); break; case 2: apply_reloc_n(16, ptr, diff); break; case 4: apply_reloc_n(32, ptr, diff); break; default: BUG(); } } static __always_inline bool need_reloc(unsigned long offset, u8 *src, size_t src_len) { u8 *target = src + offset; /* * If the target is inside the patched block, it's relative to the * block itself and does not need relocation. */ return (target < src || target > src + src_len); } static void __init_or_module noinline apply_relocation(u8 *buf, size_t len, u8 *dest, u8 *src, size_t src_len) { int prev, target = 0; for (int next, i = 0; i < len; i = next) { struct insn insn; if (WARN_ON_ONCE(insn_decode_kernel(&insn, &buf[i]))) return; next = i + insn.length; if (__optimize_nops(buf, len, &insn, &next, &prev, &target)) continue; switch (insn.opcode.bytes[0]) { case 0x0f: if (insn.opcode.bytes[1] < 0x80 || insn.opcode.bytes[1] > 0x8f) break; fallthrough; /* Jcc.d32 */ case 0x70 ... 0x7f: /* Jcc.d8 */ case JMP8_INSN_OPCODE: case JMP32_INSN_OPCODE: case CALL_INSN_OPCODE: if (need_reloc(next + insn.immediate.value, src, src_len)) { apply_reloc(insn.immediate.nbytes, buf + i + insn_offset_immediate(&insn), src - dest); } /* * Where possible, convert JMP.d32 into JMP.d8. */ if (insn.opcode.bytes[0] == JMP32_INSN_OPCODE) { s32 imm = insn.immediate.value; imm += src - dest; imm += JMP32_INSN_SIZE - JMP8_INSN_SIZE; if ((imm >> 31) == (imm >> 7)) { buf[i+0] = JMP8_INSN_OPCODE; buf[i+1] = (s8)imm; memset(&buf[i+2], INT3_INSN_OPCODE, insn.length - 2); } } break; } if (insn_rip_relative(&insn)) { if (need_reloc(next + insn.displacement.value, src, src_len)) { apply_reloc(insn.displacement.nbytes, buf + i + insn_offset_displacement(&insn), src - dest); } } } } /* * Replace instructions with better alternatives for this CPU type. This runs * before SMP is initialized to avoid SMP problems with self modifying code. * This implies that asymmetric systems where APs have less capabilities than * the boot processor are not handled. Tough. Make sure you disable such * features by hand. * * Marked "noinline" to cause control flow change and thus insn cache * to refetch changed I$ lines. */ void __init_or_module noinline apply_alternatives(struct alt_instr *start, struct alt_instr *end) { struct alt_instr *a; u8 *instr, *replacement; u8 insn_buff[MAX_PATCH_LEN]; DPRINTK(ALT, "alt table %px, -> %px", start, end); /* * In the case CONFIG_X86_5LEVEL=y, KASAN_SHADOW_START is defined using * cpu_feature_enabled(X86_FEATURE_LA57) and is therefore patched here. * During the process, KASAN becomes confused seeing partial LA57 * conversion and triggers a false-positive out-of-bound report. * * Disable KASAN until the patching is complete. */ kasan_disable_current(); /* * The scan order should be from start to end. A later scanned * alternative code can overwrite previously scanned alternative code. * Some kernel functions (e.g. memcpy, memset, etc) use this order to * patch code. * * So be careful if you want to change the scan order to any other * order. */ for (a = start; a < end; a++) { int insn_buff_sz = 0; instr = (u8 *)&a->instr_offset + a->instr_offset; replacement = (u8 *)&a->repl_offset + a->repl_offset; BUG_ON(a->instrlen > sizeof(insn_buff)); BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32); /* * Patch if either: * - feature is present * - feature not present but ALT_FLAG_NOT is set to mean, * patch if feature is *NOT* present. */ if (!boot_cpu_has(a->cpuid) == !(a->flags & ALT_FLAG_NOT)) { optimize_nops_inplace(instr, a->instrlen); continue; } DPRINTK(ALT, "feat: %s%d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d)", (a->flags & ALT_FLAG_NOT) ? "!" : "", a->cpuid >> 5, a->cpuid & 0x1f, instr, instr, a->instrlen, replacement, a->replacementlen); memcpy(insn_buff, replacement, a->replacementlen); insn_buff_sz = a->replacementlen; for (; insn_buff_sz < a->instrlen; insn_buff_sz++) insn_buff[insn_buff_sz] = 0x90; apply_relocation(insn_buff, a->instrlen, instr, replacement, a->replacementlen); DUMP_BYTES(ALT, instr, a->instrlen, "%px: old_insn: ", instr); DUMP_BYTES(ALT, replacement, a->replacementlen, "%px: rpl_insn: ", replacement); DUMP_BYTES(ALT, insn_buff, insn_buff_sz, "%px: final_insn: ", instr); text_poke_early(instr, insn_buff, insn_buff_sz); } kasan_enable_current(); } static inline bool is_jcc32(struct insn *insn) { /* Jcc.d32 second opcode byte is in the range: 0x80-0x8f */ return insn->opcode.bytes[0] == 0x0f && (insn->opcode.bytes[1] & 0xf0) == 0x80; } #if defined(CONFIG_RETPOLINE) && defined(CONFIG_OBJTOOL) /* * CALL/JMP *%\reg */ static int emit_indirect(int op, int reg, u8 *bytes) { int i = 0; u8 modrm; switch (op) { case CALL_INSN_OPCODE: modrm = 0x10; /* Reg = 2; CALL r/m */ break; case JMP32_INSN_OPCODE: modrm = 0x20; /* Reg = 4; JMP r/m */ break; default: WARN_ON_ONCE(1); return -1; } if (reg >= 8) { bytes[i++] = 0x41; /* REX.B prefix */ reg -= 8; } modrm |= 0xc0; /* Mod = 3 */ modrm += reg; bytes[i++] = 0xff; /* opcode */ bytes[i++] = modrm; return i; } static int emit_call_track_retpoline(void *addr, struct insn *insn, int reg, u8 *bytes) { u8 op = insn->opcode.bytes[0]; int i = 0; /* * Clang does 'weird' Jcc __x86_indirect_thunk_r11 conditional * tail-calls. Deal with them. */ if (is_jcc32(insn)) { bytes[i++] = op; op = insn->opcode.bytes[1]; goto clang_jcc; } if (insn->length == 6) bytes[i++] = 0x2e; /* CS-prefix */ switch (op) { case CALL_INSN_OPCODE: __text_gen_insn(bytes+i, op, addr+i, __x86_indirect_call_thunk_array[reg], CALL_INSN_SIZE); i += CALL_INSN_SIZE; break; case JMP32_INSN_OPCODE: clang_jcc: __text_gen_insn(bytes+i, op, addr+i, __x86_indirect_jump_thunk_array[reg], JMP32_INSN_SIZE); i += JMP32_INSN_SIZE; break; default: WARN(1, "%pS %px %*ph\n", addr, addr, 6, addr); return -1; } WARN_ON_ONCE(i != insn->length); return i; } /* * Rewrite the compiler generated retpoline thunk calls. * * For spectre_v2=off (!X86_FEATURE_RETPOLINE), rewrite them into immediate * indirect instructions, avoiding the extra indirection. * * For example, convert: * * CALL __x86_indirect_thunk_\reg * * into: * * CALL *%\reg * * It also tries to inline spectre_v2=retpoline,lfence when size permits. */ static int patch_retpoline(void *addr, struct insn *insn, u8 *bytes) { retpoline_thunk_t *target; int reg, ret, i = 0; u8 op, cc; target = addr + insn->length + insn->immediate.value; reg = target - __x86_indirect_thunk_array; if (WARN_ON_ONCE(reg & ~0xf)) return -1; /* If anyone ever does: CALL/JMP *%rsp, we're in deep trouble. */ BUG_ON(reg == 4); if (cpu_feature_enabled(X86_FEATURE_RETPOLINE) && !cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE)) { if (cpu_feature_enabled(X86_FEATURE_CALL_DEPTH)) return emit_call_track_retpoline(addr, insn, reg, bytes); return -1; } op = insn->opcode.bytes[0]; /* * Convert: * * Jcc.d32 __x86_indirect_thunk_\reg * * into: * * Jncc.d8 1f * [ LFENCE ] * JMP *%\reg * [ NOP ] * 1: */ if (is_jcc32(insn)) { cc = insn->opcode.bytes[1] & 0xf; cc ^= 1; /* invert condition */ bytes[i++] = 0x70 + cc; /* Jcc.d8 */ bytes[i++] = insn->length - 2; /* sizeof(Jcc.d8) == 2 */ /* Continue as if: JMP.d32 __x86_indirect_thunk_\reg */ op = JMP32_INSN_OPCODE; } /* * For RETPOLINE_LFENCE: prepend the indirect CALL/JMP with an LFENCE. */ if (cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE)) { bytes[i++] = 0x0f; bytes[i++] = 0xae; bytes[i++] = 0xe8; /* LFENCE */ } ret = emit_indirect(op, reg, bytes + i); if (ret < 0) return ret; i += ret; /* * The compiler is supposed to EMIT an INT3 after every unconditional * JMP instruction due to AMD BTC. However, if the compiler is too old * or SLS isn't enabled, we still need an INT3 after indirect JMPs * even on Intel. */ if (op == JMP32_INSN_OPCODE && i < insn->length) bytes[i++] = INT3_INSN_OPCODE; for (; i < insn->length;) bytes[i++] = BYTES_NOP1; return i; } /* * Generated by 'objtool --retpoline'. */ void __init_or_module noinline apply_retpolines(s32 *start, s32 *end) { s32 *s; for (s = start; s < end; s++) { void *addr = (void *)s + *s; struct insn insn; int len, ret; u8 bytes[16]; u8 op1, op2; ret = insn_decode_kernel(&insn, addr); if (WARN_ON_ONCE(ret < 0)) continue; op1 = insn.opcode.bytes[0]; op2 = insn.opcode.bytes[1]; switch (op1) { case CALL_INSN_OPCODE: case JMP32_INSN_OPCODE: break; case 0x0f: /* escape */ if (op2 >= 0x80 && op2 <= 0x8f) break; fallthrough; default: WARN_ON_ONCE(1); continue; } DPRINTK(RETPOLINE, "retpoline at: %pS (%px) len: %d to: %pS", addr, addr, insn.length, addr + insn.length + insn.immediate.value); len = patch_retpoline(addr, &insn, bytes); if (len == insn.length) { optimize_nops(bytes, len); DUMP_BYTES(RETPOLINE, ((u8*)addr), len, "%px: orig: ", addr); DUMP_BYTES(RETPOLINE, ((u8*)bytes), len, "%px: repl: ", addr); text_poke_early(addr, bytes, len); } } } #ifdef CONFIG_RETHUNK /* * Rewrite the compiler generated return thunk tail-calls. * * For example, convert: * * JMP __x86_return_thunk * * into: * * RET */ static int patch_return(void *addr, struct insn *insn, u8 *bytes) { int i = 0; /* Patch the custom return thunks... */ if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) { i = JMP32_INSN_SIZE; __text_gen_insn(bytes, JMP32_INSN_OPCODE, addr, x86_return_thunk, i); } else { /* ... or patch them out if not needed. */ bytes[i++] = RET_INSN_OPCODE; } for (; i < insn->length;) bytes[i++] = INT3_INSN_OPCODE; return i; } void __init_or_module noinline apply_returns(s32 *start, s32 *end) { s32 *s; if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) static_call_force_reinit(); for (s = start; s < end; s++) { void *dest = NULL, *addr = (void *)s + *s; struct insn insn; int len, ret; u8 bytes[16]; u8 op; ret = insn_decode_kernel(&insn, addr); if (WARN_ON_ONCE(ret < 0)) continue; op = insn.opcode.bytes[0]; if (op == JMP32_INSN_OPCODE) dest = addr + insn.length + insn.immediate.value; if (__static_call_fixup(addr, op, dest) || WARN_ONCE(dest != &__x86_return_thunk, "missing return thunk: %pS-%pS: %*ph", addr, dest, 5, addr)) continue; DPRINTK(RET, "return thunk at: %pS (%px) len: %d to: %pS", addr, addr, insn.length, addr + insn.length + insn.immediate.value); len = patch_return(addr, &insn, bytes); if (len == insn.length) { DUMP_BYTES(RET, ((u8*)addr), len, "%px: orig: ", addr); DUMP_BYTES(RET, ((u8*)bytes), len, "%px: repl: ", addr); text_poke_early(addr, bytes, len); } } } #else void __init_or_module noinline apply_returns(s32 *start, s32 *end) { } #endif /* CONFIG_RETHUNK */ #else /* !CONFIG_RETPOLINE || !CONFIG_OBJTOOL */ void __init_or_module noinline apply_retpolines(s32 *start, s32 *end) { } void __init_or_module noinline apply_returns(s32 *start, s32 *end) { } #endif /* CONFIG_RETPOLINE && CONFIG_OBJTOOL */ #ifdef CONFIG_X86_KERNEL_IBT static void poison_cfi(void *addr); static void __init_or_module poison_endbr(void *addr, bool warn) { u32 endbr, poison = gen_endbr_poison(); if (WARN_ON_ONCE(get_kernel_nofault(endbr, addr))) return; if (!is_endbr(endbr)) { WARN_ON_ONCE(warn); return; } DPRINTK(ENDBR, "ENDBR at: %pS (%px)", addr, addr); /* * When we have IBT, the lack of ENDBR will trigger #CP */ DUMP_BYTES(ENDBR, ((u8*)addr), 4, "%px: orig: ", addr); DUMP_BYTES(ENDBR, ((u8*)&poison), 4, "%px: repl: ", addr); text_poke_early(addr, &poison, 4); } /* * Generated by: objtool --ibt * * Seal the functions for indirect calls by clobbering the ENDBR instructions * and the kCFI hash value. */ void __init_or_module noinline apply_seal_endbr(s32 *start, s32 *end) { s32 *s; for (s = start; s < end; s++) { void *addr = (void *)s + *s; poison_endbr(addr, true); if (IS_ENABLED(CONFIG_FINEIBT)) poison_cfi(addr - 16); } } #else void __init_or_module apply_seal_endbr(s32 *start, s32 *end) { } #endif /* CONFIG_X86_KERNEL_IBT */ #ifdef CONFIG_FINEIBT enum cfi_mode { CFI_DEFAULT, CFI_OFF, CFI_KCFI, CFI_FINEIBT, }; static enum cfi_mode cfi_mode __ro_after_init = CFI_DEFAULT; static bool cfi_rand __ro_after_init = true; static u32 cfi_seed __ro_after_init; /* * Re-hash the CFI hash with a boot-time seed while making sure the result is * not a valid ENDBR instruction. */ static u32 cfi_rehash(u32 hash) { hash ^= cfi_seed; while (unlikely(is_endbr(hash) || is_endbr(-hash))) { bool lsb = hash & 1; hash >>= 1; if (lsb) hash ^= 0x80200003; } return hash; } static __init int cfi_parse_cmdline(char *str) { if (!str) return -EINVAL; while (str) { char *next = strchr(str, ','); if (next) { *next = 0; next++; } if (!strcmp(str, "auto")) { cfi_mode = CFI_DEFAULT; } else if (!strcmp(str, "off")) { cfi_mode = CFI_OFF; cfi_rand = false; } else if (!strcmp(str, "kcfi")) { cfi_mode = CFI_KCFI; } else if (!strcmp(str, "fineibt")) { cfi_mode = CFI_FINEIBT; } else if (!strcmp(str, "norand")) { cfi_rand = false; } else { pr_err("Ignoring unknown cfi option (%s).", str); } str = next; } return 0; } early_param("cfi", cfi_parse_cmdline); /* * kCFI FineIBT * * __cfi_\func: __cfi_\func: * movl $0x12345678,%eax // 5 endbr64 // 4 * nop subl $0x12345678,%r10d // 7 * nop jz 1f // 2 * nop ud2 // 2 * nop 1: nop // 1 * nop * nop * nop * nop * nop * nop * nop * * * caller: caller: * movl $(-0x12345678),%r10d // 6 movl $0x12345678,%r10d // 6 * addl $-15(%r11),%r10d // 4 sub $16,%r11 // 4 * je 1f // 2 nop4 // 4 * ud2 // 2 * 1: call __x86_indirect_thunk_r11 // 5 call *%r11; nop2; // 5 * */ asm( ".pushsection .rodata \n" "fineibt_preamble_start: \n" " endbr64 \n" " subl $0x12345678, %r10d \n" " je fineibt_preamble_end \n" " ud2 \n" " nop \n" "fineibt_preamble_end: \n" ".popsection\n" ); extern u8 fineibt_preamble_start[]; extern u8 fineibt_preamble_end[]; #define fineibt_preamble_size (fineibt_preamble_end - fineibt_preamble_start) #define fineibt_preamble_hash 7 asm( ".pushsection .rodata \n" "fineibt_caller_start: \n" " movl $0x12345678, %r10d \n" " sub $16, %r11 \n" ASM_NOP4 "fineibt_caller_end: \n" ".popsection \n" ); extern u8 fineibt_caller_start[]; extern u8 fineibt_caller_end[]; #define fineibt_caller_size (fineibt_caller_end - fineibt_caller_start) #define fineibt_caller_hash 2 #define fineibt_caller_jmp (fineibt_caller_size - 2) static u32 decode_preamble_hash(void *addr) { u8 *p = addr; /* b8 78 56 34 12 mov $0x12345678,%eax */ if (p[0] == 0xb8) return *(u32 *)(addr + 1); return 0; /* invalid hash value */ } static u32 decode_caller_hash(void *addr) { u8 *p = addr; /* 41 ba 78 56 34 12 mov $0x12345678,%r10d */ if (p[0] == 0x41 && p[1] == 0xba) return -*(u32 *)(addr + 2); /* e8 0c 78 56 34 12 jmp.d8 +12 */ if (p[0] == JMP8_INSN_OPCODE && p[1] == fineibt_caller_jmp) return -*(u32 *)(addr + 2); return 0; /* invalid hash value */ } /* .retpoline_sites */ static int cfi_disable_callers(s32 *start, s32 *end) { /* * Disable kCFI by patching in a JMP.d8, this leaves the hash immediate * in tact for later usage. Also see decode_caller_hash() and * cfi_rewrite_callers(). */ const u8 jmp[] = { JMP8_INSN_OPCODE, fineibt_caller_jmp }; s32 *s; for (s = start; s < end; s++) { void *addr = (void *)s + *s; u32 hash; addr -= fineibt_caller_size; hash = decode_caller_hash(addr); if (!hash) /* nocfi callers */ continue; text_poke_early(addr, jmp, 2); } return 0; } static int cfi_enable_callers(s32 *start, s32 *end) { /* * Re-enable kCFI, undo what cfi_disable_callers() did. */ const u8 mov[] = { 0x41, 0xba }; s32 *s; for (s = start; s < end; s++) { void *addr = (void *)s + *s; u32 hash; addr -= fineibt_caller_size; hash = decode_caller_hash(addr); if (!hash) /* nocfi callers */ continue; text_poke_early(addr, mov, 2); } return 0; } /* .cfi_sites */ static int cfi_rand_preamble(s32 *start, s32 *end) { s32 *s; for (s = start; s < end; s++) { void *addr = (void *)s + *s; u32 hash; hash = decode_preamble_hash(addr); if (WARN(!hash, "no CFI hash found at: %pS %px %*ph\n", addr, addr, 5, addr)) return -EINVAL; hash = cfi_rehash(hash); text_poke_early(addr + 1, &hash, 4); } return 0; } static int cfi_rewrite_preamble(s32 *start, s32 *end) { s32 *s; for (s = start; s < end; s++) { void *addr = (void *)s + *s; u32 hash; hash = decode_preamble_hash(addr); if (WARN(!hash, "no CFI hash found at: %pS %px %*ph\n", addr, addr, 5, addr)) return -EINVAL; text_poke_early(addr, fineibt_preamble_start, fineibt_preamble_size); WARN_ON(*(u32 *)(addr + fineibt_preamble_hash) != 0x12345678); text_poke_early(addr + fineibt_preamble_hash, &hash, 4); } return 0; } static void cfi_rewrite_endbr(s32 *start, s32 *end) { s32 *s; for (s = start; s < end; s++) { void *addr = (void *)s + *s; poison_endbr(addr+16, false); } } /* .retpoline_sites */ static int cfi_rand_callers(s32 *start, s32 *end) { s32 *s; for (s = start; s < end; s++) { void *addr = (void *)s + *s; u32 hash; addr -= fineibt_caller_size; hash = decode_caller_hash(addr); if (hash) { hash = -cfi_rehash(hash); text_poke_early(addr + 2, &hash, 4); } } return 0; } static int cfi_rewrite_callers(s32 *start, s32 *end) { s32 *s; for (s = start; s < end; s++) { void *addr = (void *)s + *s; u32 hash; addr -= fineibt_caller_size; hash = decode_caller_hash(addr); if (hash) { text_poke_early(addr, fineibt_caller_start, fineibt_caller_size); WARN_ON(*(u32 *)(addr + fineibt_caller_hash) != 0x12345678); text_poke_early(addr + fineibt_caller_hash, &hash, 4); } /* rely on apply_retpolines() */ } return 0; } static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline, s32 *start_cfi, s32 *end_cfi, bool builtin) { int ret; if (WARN_ONCE(fineibt_preamble_size != 16, "FineIBT preamble wrong size: %ld", fineibt_preamble_size)) return; if (cfi_mode == CFI_DEFAULT) { cfi_mode = CFI_KCFI; if (HAS_KERNEL_IBT && cpu_feature_enabled(X86_FEATURE_IBT)) cfi_mode = CFI_FINEIBT; } /* * Rewrite the callers to not use the __cfi_ stubs, such that we might * rewrite them. This disables all CFI. If this succeeds but any of the * later stages fails, we're without CFI. */ ret = cfi_disable_callers(start_retpoline, end_retpoline); if (ret) goto err; if (cfi_rand) { if (builtin) cfi_seed = get_random_u32(); ret = cfi_rand_preamble(start_cfi, end_cfi); if (ret) goto err; ret = cfi_rand_callers(start_retpoline, end_retpoline); if (ret) goto err; } switch (cfi_mode) { case CFI_OFF: if (builtin) pr_info("Disabling CFI\n"); return; case CFI_KCFI: ret = cfi_enable_callers(start_retpoline, end_retpoline); if (ret) goto err; if (builtin) pr_info("Using kCFI\n"); return; case CFI_FINEIBT: /* place the FineIBT preamble at func()-16 */ ret = cfi_rewrite_preamble(start_cfi, end_cfi); if (ret) goto err; /* rewrite the callers to target func()-16 */ ret = cfi_rewrite_callers(start_retpoline, end_retpoline); if (ret) goto err; /* now that nobody targets func()+0, remove ENDBR there */ cfi_rewrite_endbr(start_cfi, end_cfi); if (builtin) pr_info("Using FineIBT CFI\n"); return; default: break; } err: pr_err("Something went horribly wrong trying to rewrite the CFI implementation.\n"); } static inline void poison_hash(void *addr) { *(u32 *)addr = 0; } static void poison_cfi(void *addr) { switch (cfi_mode) { case CFI_FINEIBT: /* * __cfi_\func: * osp nopl (%rax) * subl $0, %r10d * jz 1f * ud2 * 1: nop */ poison_endbr(addr, false); poison_hash(addr + fineibt_preamble_hash); break; case CFI_KCFI: /* * __cfi_\func: * movl $0, %eax * .skip 11, 0x90 */ poison_hash(addr + 1); break; default: break; } } #else static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline, s32 *start_cfi, s32 *end_cfi, bool builtin) { } #ifdef CONFIG_X86_KERNEL_IBT static void poison_cfi(void *addr) { } #endif #endif void apply_fineibt(s32 *start_retpoline, s32 *end_retpoline, s32 *start_cfi, s32 *end_cfi) { return __apply_fineibt(start_retpoline, end_retpoline, start_cfi, end_cfi, /* .builtin = */ false); } #ifdef CONFIG_SMP static void alternatives_smp_lock(const s32 *start, const s32 *end, u8 *text, u8 *text_end) { const s32 *poff; for (poff = start; poff < end; poff++) { u8 *ptr = (u8 *)poff + *poff; if (!*poff || ptr < text || ptr >= text_end) continue; /* turn DS segment override prefix into lock prefix */ if (*ptr == 0x3e) text_poke(ptr, ((unsigned char []){0xf0}), 1); } } static void alternatives_smp_unlock(const s32 *start, const s32 *end, u8 *text, u8 *text_end) { const s32 *poff; for (poff = start; poff < end; poff++) { u8 *ptr = (u8 *)poff + *poff; if (!*poff || ptr < text || ptr >= text_end) continue; /* turn lock prefix into DS segment override prefix */ if (*ptr == 0xf0) text_poke(ptr, ((unsigned char []){0x3E}), 1); } } struct smp_alt_module { /* what is this ??? */ struct module *mod; char *name; /* ptrs to lock prefixes */ const s32 *locks; const s32 *locks_end; /* .text segment, needed to avoid patching init code ;) */ u8 *text; u8 *text_end; struct list_head next; }; static LIST_HEAD(smp_alt_modules); static bool uniproc_patched = false; /* protected by text_mutex */ void __init_or_module alternatives_smp_module_add(struct module *mod, char *name, void *locks, void *locks_end, void *text, void *text_end) { struct smp_alt_module *smp; mutex_lock(&text_mutex); if (!uniproc_patched) goto unlock; if (num_possible_cpus() == 1) /* Don't bother remembering, we'll never have to undo it. */ goto smp_unlock; smp = kzalloc(sizeof(*smp), GFP_KERNEL); if (NULL == smp) /* we'll run the (safe but slow) SMP code then ... */ goto unlock; smp->mod = mod; smp->name = name; smp->locks = locks; smp->locks_end = locks_end; smp->text = text; smp->text_end = text_end; DPRINTK(SMP, "locks %p -> %p, text %p -> %p, name %s\n", smp->locks, smp->locks_end, smp->text, smp->text_end, smp->name); list_add_tail(&smp->next, &smp_alt_modules); smp_unlock: alternatives_smp_unlock(locks, locks_end, text, text_end); unlock: mutex_unlock(&text_mutex); } void __init_or_module alternatives_smp_module_del(struct module *mod) { struct smp_alt_module *item; mutex_lock(&text_mutex); list_for_each_entry(item, &smp_alt_modules, next) { if (mod != item->mod) continue; list_del(&item->next); kfree(item); break; } mutex_unlock(&text_mutex); } void alternatives_enable_smp(void) { struct smp_alt_module *mod; /* Why bother if there are no other CPUs? */ BUG_ON(num_possible_cpus() == 1); mutex_lock(&text_mutex); if (uniproc_patched) { pr_info("switching to SMP code\n"); BUG_ON(num_online_cpus() != 1); clear_cpu_cap(&boot_cpu_data, X86_FEATURE_UP); clear_cpu_cap(&cpu_data(0), X86_FEATURE_UP); list_for_each_entry(mod, &smp_alt_modules, next) alternatives_smp_lock(mod->locks, mod->locks_end, mod->text, mod->text_end); uniproc_patched = false; } mutex_unlock(&text_mutex); } /* * Return 1 if the address range is reserved for SMP-alternatives. * Must hold text_mutex. */ int alternatives_text_reserved(void *start, void *end) { struct smp_alt_module *mod; const s32 *poff; u8 *text_start = start; u8 *text_end = end; lockdep_assert_held(&text_mutex); list_for_each_entry(mod, &smp_alt_modules, next) { if (mod->text > text_end || mod->text_end < text_start) continue; for (poff = mod->locks; poff < mod->locks_end; poff++) { const u8 *ptr = (const u8 *)poff + *poff; if (text_start <= ptr && text_end > ptr) return 1; } } return 0; } #endif /* CONFIG_SMP */ #ifdef CONFIG_PARAVIRT /* Use this to add nops to a buffer, then text_poke the whole buffer. */ static void __init_or_module add_nops(void *insns, unsigned int len) { while (len > 0) { unsigned int noplen = len; if (noplen > ASM_NOP_MAX) noplen = ASM_NOP_MAX; memcpy(insns, x86_nops[noplen], noplen); insns += noplen; len -= noplen; } } void __init_or_module apply_paravirt(struct paravirt_patch_site *start, struct paravirt_patch_site *end) { struct paravirt_patch_site *p; char insn_buff[MAX_PATCH_LEN]; for (p = start; p < end; p++) { unsigned int used; BUG_ON(p->len > MAX_PATCH_LEN); /* prep the buffer with the original instructions */ memcpy(insn_buff, p->instr, p->len); used = paravirt_patch(p->type, insn_buff, (unsigned long)p->instr, p->len); BUG_ON(used > p->len); /* Pad the rest with nops */ add_nops(insn_buff + used, p->len - used); text_poke_early(p->instr, insn_buff, p->len); } } extern struct paravirt_patch_site __start_parainstructions[], __stop_parainstructions[]; #endif /* CONFIG_PARAVIRT */ /* * Self-test for the INT3 based CALL emulation code. * * This exercises int3_emulate_call() to make sure INT3 pt_regs are set up * properly and that there is a stack gap between the INT3 frame and the * previous context. Without this gap doing a virtual PUSH on the interrupted * stack would corrupt the INT3 IRET frame. * * See entry_{32,64}.S for more details. */ /* * We define the int3_magic() function in assembly to control the calling * convention such that we can 'call' it from assembly. */ extern void int3_magic(unsigned int *ptr); /* defined in asm */ asm ( " .pushsection .init.text, \"ax\", @progbits\n" " .type int3_magic, @function\n" "int3_magic:\n" ANNOTATE_NOENDBR " movl $1, (%" _ASM_ARG1 ")\n" ASM_RET " .size int3_magic, .-int3_magic\n" " .popsection\n" ); extern void int3_selftest_ip(void); /* defined in asm below */ static int __init int3_exception_notify(struct notifier_block *self, unsigned long val, void *data) { unsigned long selftest = (unsigned long)&int3_selftest_ip; struct die_args *args = data; struct pt_regs *regs = args->regs; OPTIMIZER_HIDE_VAR(selftest); if (!regs || user_mode(regs)) return NOTIFY_DONE; if (val != DIE_INT3) return NOTIFY_DONE; if (regs->ip - INT3_INSN_SIZE != selftest) return NOTIFY_DONE; int3_emulate_call(regs, (unsigned long)&int3_magic); return NOTIFY_STOP; } /* Must be noinline to ensure uniqueness of int3_selftest_ip. */ static noinline void __init int3_selftest(void) { static __initdata struct notifier_block int3_exception_nb = { .notifier_call = int3_exception_notify, .priority = INT_MAX-1, /* last */ }; unsigned int val = 0; BUG_ON(register_die_notifier(&int3_exception_nb)); /* * Basically: int3_magic(&val); but really complicated :-) * * INT3 padded with NOP to CALL_INSN_SIZE. The int3_exception_nb * notifier above will emulate CALL for us. */ asm volatile ("int3_selftest_ip:\n\t" ANNOTATE_NOENDBR " int3; nop; nop; nop; nop\n\t" : ASM_CALL_CONSTRAINT : __ASM_SEL_RAW(a, D) (&val) : "memory"); BUG_ON(val != 1); unregister_die_notifier(&int3_exception_nb); } static __initdata int __alt_reloc_selftest_addr; extern void __init __alt_reloc_selftest(void *arg); __visible noinline void __init __alt_reloc_selftest(void *arg) { WARN_ON(arg != &__alt_reloc_selftest_addr); } static noinline void __init alt_reloc_selftest(void) { /* * Tests apply_relocation(). * * This has a relative immediate (CALL) in a place other than the first * instruction and additionally on x86_64 we get a RIP-relative LEA: * * lea 0x0(%rip),%rdi # 5d0: R_X86_64_PC32 .init.data+0x5566c * call +0 # 5d5: R_X86_64_PLT32 __alt_reloc_selftest-0x4 * * Getting this wrong will either crash and burn or tickle the WARN * above. */ asm_inline volatile ( ALTERNATIVE("", "lea %[mem], %%" _ASM_ARG1 "; call __alt_reloc_selftest;", X86_FEATURE_ALWAYS) : /* output */ : [mem] "m" (__alt_reloc_selftest_addr) : _ASM_ARG1 ); } void __init alternative_instructions(void) { int3_selftest(); /* * The patching is not fully atomic, so try to avoid local * interruptions that might execute the to be patched code. * Other CPUs are not running. */ stop_nmi(); /* * Don't stop machine check exceptions while patching. * MCEs only happen when something got corrupted and in this * case we must do something about the corruption. * Ignoring it is worse than an unlikely patching race. * Also machine checks tend to be broadcast and if one CPU * goes into machine check the others follow quickly, so we don't * expect a machine check to cause undue problems during to code * patching. */ /* * Paravirt patching and alternative patching can be combined to * replace a function call with a short direct code sequence (e.g. * by setting a constant return value instead of doing that in an * external function). * In order to make this work the following sequence is required: * 1. set (artificial) features depending on used paravirt * functions which can later influence alternative patching * 2. apply paravirt patching (generally replacing an indirect * function call with a direct one) * 3. apply alternative patching (e.g. replacing a direct function * call with a custom code sequence) * Doing paravirt patching after alternative patching would clobber * the optimization of the custom code with a function call again. */ paravirt_set_cap(); /* * First patch paravirt functions, such that we overwrite the indirect * call with the direct call. */ apply_paravirt(__parainstructions, __parainstructions_end); __apply_fineibt(__retpoline_sites, __retpoline_sites_end, __cfi_sites, __cfi_sites_end, true); /* * Rewrite the retpolines, must be done before alternatives since * those can rewrite the retpoline thunks. */ apply_retpolines(__retpoline_sites, __retpoline_sites_end); apply_returns(__return_sites, __return_sites_end); /* * Then patch alternatives, such that those paravirt calls that are in * alternatives can be overwritten by their immediate fragments. */ apply_alternatives(__alt_instructions, __alt_instructions_end); /* * Now all calls are established. Apply the call thunks if * required. */ callthunks_patch_builtin_calls(); /* * Seal all functions that do not have their address taken. */ apply_seal_endbr(__ibt_endbr_seal, __ibt_endbr_seal_end); #ifdef CONFIG_SMP /* Patch to UP if other cpus not imminent. */ if (!noreplace_smp && (num_present_cpus() == 1 || setup_max_cpus <= 1)) { uniproc_patched = true; alternatives_smp_module_add(NULL, "core kernel", __smp_locks, __smp_locks_end, _text, _etext); } if (!uniproc_patched || num_possible_cpus() == 1) { free_init_pages("SMP alternatives", (unsigned long)__smp_locks, (unsigned long)__smp_locks_end); } #endif restart_nmi(); alternatives_patched = 1; alt_reloc_selftest(); } /** * text_poke_early - Update instructions on a live kernel at boot time * @addr: address to modify * @opcode: source of the copy * @len: length to copy * * When you use this code to patch more than one byte of an instruction * you need to make sure that other CPUs cannot execute this code in parallel. * Also no thread must be currently preempted in the middle of these * instructions. And on the local CPU you need to be protected against NMI or * MCE handlers seeing an inconsistent instruction while you patch. */ void __init_or_module text_poke_early(void *addr, const void *opcode, size_t len) { unsigned long flags; if (boot_cpu_has(X86_FEATURE_NX) && is_module_text_address((unsigned long)addr)) { /* * Modules text is marked initially as non-executable, so the * code cannot be running and speculative code-fetches are * prevented. Just change the code. */ memcpy(addr, opcode, len); } else { local_irq_save(flags); memcpy(addr, opcode, len); sync_core(); local_irq_restore(flags); /* * Could also do a CLFLUSH here to speed up CPU recovery; but * that causes hangs on some VIA CPUs. */ } } typedef struct { struct mm_struct *mm; } temp_mm_state_t; /* * Using a temporary mm allows to set temporary mappings that are not accessible * by other CPUs. Such mappings are needed to perform sensitive memory writes * that override the kernel memory protections (e.g., W^X), without exposing the * temporary page-table mappings that are required for these write operations to * other CPUs. Using a temporary mm also allows to avoid TLB shootdowns when the * mapping is torn down. * * Context: The temporary mm needs to be used exclusively by a single core. To * harden security IRQs must be disabled while the temporary mm is * loaded, thereby preventing interrupt handler bugs from overriding * the kernel memory protection. */ static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm) { temp_mm_state_t temp_state; lockdep_assert_irqs_disabled(); /* * Make sure not to be in TLB lazy mode, as otherwise we'll end up * with a stale address space WITHOUT being in lazy mode after * restoring the previous mm. */ if (this_cpu_read(cpu_tlbstate_shared.is_lazy)) leave_mm(smp_processor_id()); temp_state.mm = this_cpu_read(cpu_tlbstate.loaded_mm); switch_mm_irqs_off(NULL, mm, current); /* * If breakpoints are enabled, disable them while the temporary mm is * used. Userspace might set up watchpoints on addresses that are used * in the temporary mm, which would lead to wrong signals being sent or * crashes. * * Note that breakpoints are not disabled selectively, which also causes * kernel breakpoints (e.g., perf's) to be disabled. This might be * undesirable, but still seems reasonable as the code that runs in the * temporary mm should be short. */ if (hw_breakpoint_active()) hw_breakpoint_disable(); return temp_state; } static inline void unuse_temporary_mm(temp_mm_state_t prev_state) { lockdep_assert_irqs_disabled(); switch_mm_irqs_off(NULL, prev_state.mm, current); /* * Restore the breakpoints if they were disabled before the temporary mm * was loaded. */ if (hw_breakpoint_active()) hw_breakpoint_restore(); } __ro_after_init struct mm_struct *poking_mm; __ro_after_init unsigned long poking_addr; static void text_poke_memcpy(void *dst, const void *src, size_t len) { memcpy(dst, src, len); } static void text_poke_memset(void *dst, const void *src, size_t len) { int c = *(const int *)src; memset(dst, c, len); } typedef void text_poke_f(void *dst, const void *src, size_t len); static void *__text_poke(text_poke_f func, void *addr, const void *src, size_t len) { bool cross_page_boundary = offset_in_page(addr) + len > PAGE_SIZE; struct page *pages[2] = {NULL}; temp_mm_state_t prev; unsigned long flags; pte_t pte, *ptep; spinlock_t *ptl; pgprot_t pgprot; /* * While boot memory allocator is running we cannot use struct pages as * they are not yet initialized. There is no way to recover. */ BUG_ON(!after_bootmem); if (!core_kernel_text((unsigned long)addr)) { pages[0] = vmalloc_to_page(addr); if (cross_page_boundary) pages[1] = vmalloc_to_page(addr + PAGE_SIZE); } else { pages[0] = virt_to_page(addr); WARN_ON(!PageReserved(pages[0])); if (cross_page_boundary) pages[1] = virt_to_page(addr + PAGE_SIZE); } /* * If something went wrong, crash and burn since recovery paths are not * implemented. */ BUG_ON(!pages[0] || (cross_page_boundary && !pages[1])); /* * Map the page without the global bit, as TLB flushing is done with * flush_tlb_mm_range(), which is intended for non-global PTEs. */ pgprot = __pgprot(pgprot_val(PAGE_KERNEL) & ~_PAGE_GLOBAL); /* * The lock is not really needed, but this allows to avoid open-coding. */ ptep = get_locked_pte(poking_mm, poking_addr, &ptl); /* * This must not fail; preallocated in poking_init(). */ VM_BUG_ON(!ptep); local_irq_save(flags); pte = mk_pte(pages[0], pgprot); set_pte_at(poking_mm, poking_addr, ptep, pte); if (cross_page_boundary) { pte = mk_pte(pages[1], pgprot); set_pte_at(poking_mm, poking_addr + PAGE_SIZE, ptep + 1, pte); } /* * Loading the temporary mm behaves as a compiler barrier, which * guarantees that the PTE will be set at the time memcpy() is done. */ prev = use_temporary_mm(poking_mm); kasan_disable_current(); func((u8 *)poking_addr + offset_in_page(addr), src, len); kasan_enable_current(); /* * Ensure that the PTE is only cleared after the instructions of memcpy * were issued by using a compiler barrier. */ barrier(); pte_clear(poking_mm, poking_addr, ptep); if (cross_page_boundary) pte_clear(poking_mm, poking_addr + PAGE_SIZE, ptep + 1); /* * Loading the previous page-table hierarchy requires a serializing * instruction that already allows the core to see the updated version. * Xen-PV is assumed to serialize execution in a similar manner. */ unuse_temporary_mm(prev); /* * Flushing the TLB might involve IPIs, which would require enabled * IRQs, but not if the mm is not used, as it is in this point. */ flush_tlb_mm_range(poking_mm, poking_addr, poking_addr + (cross_page_boundary ? 2 : 1) * PAGE_SIZE, PAGE_SHIFT, false); if (func == text_poke_memcpy) { /* * If the text does not match what we just wrote then something is * fundamentally screwy; there's nothing we can really do about that. */ BUG_ON(memcmp(addr, src, len)); } local_irq_restore(flags); pte_unmap_unlock(ptep, ptl); return addr; } /** * text_poke - Update instructions on a live kernel * @addr: address to modify * @opcode: source of the copy * @len: length to copy * * Only atomic text poke/set should be allowed when not doing early patching. * It means the size must be writable atomically and the address must be aligned * in a way that permits an atomic write. It also makes sure we fit on a single * page. * * Note that the caller must ensure that if the modified code is part of a * module, the module would not be removed during poking. This can be achieved * by registering a module notifier, and ordering module removal and patching * trough a mutex. */ void *text_poke(void *addr, const void *opcode, size_t len) { lockdep_assert_held(&text_mutex); return __text_poke(text_poke_memcpy, addr, opcode, len); } /** * text_poke_kgdb - Update instructions on a live kernel by kgdb * @addr: address to modify * @opcode: source of the copy * @len: length to copy * * Only atomic text poke/set should be allowed when not doing early patching. * It means the size must be writable atomically and the address must be aligned * in a way that permits an atomic write. It also makes sure we fit on a single * page. * * Context: should only be used by kgdb, which ensures no other core is running, * despite the fact it does not hold the text_mutex. */ void *text_poke_kgdb(void *addr, const void *opcode, size_t len) { return __text_poke(text_poke_memcpy, addr, opcode, len); } void *text_poke_copy_locked(void *addr, const void *opcode, size_t len, bool core_ok) { unsigned long start = (unsigned long)addr; size_t patched = 0; if (WARN_ON_ONCE(!core_ok && core_kernel_text(start))) return NULL; while (patched < len) { unsigned long ptr = start + patched; size_t s; s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched); __text_poke(text_poke_memcpy, (void *)ptr, opcode + patched, s); patched += s; } return addr; } /** * text_poke_copy - Copy instructions into (an unused part of) RX memory * @addr: address to modify * @opcode: source of the copy * @len: length to copy, could be more than 2x PAGE_SIZE * * Not safe against concurrent execution; useful for JITs to dump * new code blocks into unused regions of RX memory. Can be used in * conjunction with synchronize_rcu_tasks() to wait for existing * execution to quiesce after having made sure no existing functions * pointers are live. */ void *text_poke_copy(void *addr, const void *opcode, size_t len) { mutex_lock(&text_mutex); addr = text_poke_copy_locked(addr, opcode, len, false); mutex_unlock(&text_mutex); return addr; } /** * text_poke_set - memset into (an unused part of) RX memory * @addr: address to modify * @c: the byte to fill the area with * @len: length to copy, could be more than 2x PAGE_SIZE * * This is useful to overwrite unused regions of RX memory with illegal * instructions. */ void *text_poke_set(void *addr, int c, size_t len) { unsigned long start = (unsigned long)addr; size_t patched = 0; if (WARN_ON_ONCE(core_kernel_text(start))) return NULL; mutex_lock(&text_mutex); while (patched < len) { unsigned long ptr = start + patched; size_t s; s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched); __text_poke(text_poke_memset, (void *)ptr, (void *)&c, s); patched += s; } mutex_unlock(&text_mutex); return addr; } static void do_sync_core(void *info) { sync_core(); } void text_poke_sync(void) { on_each_cpu(do_sync_core, NULL, 1); } /* * NOTE: crazy scheme to allow patching Jcc.d32 but not increase the size of * this thing. When len == 6 everything is prefixed with 0x0f and we map * opcode to Jcc.d8, using len to distinguish. */ struct text_poke_loc { /* addr := _stext + rel_addr */ s32 rel_addr; s32 disp; u8 len; u8 opcode; const u8 text[POKE_MAX_OPCODE_SIZE]; /* see text_poke_bp_batch() */ u8 old; }; struct bp_patching_desc { struct text_poke_loc *vec; int nr_entries; atomic_t refs; }; static struct bp_patching_desc bp_desc; static __always_inline struct bp_patching_desc *try_get_desc(void) { struct bp_patching_desc *desc = &bp_desc; if (!raw_atomic_inc_not_zero(&desc->refs)) return NULL; return desc; } static __always_inline void put_desc(void) { struct bp_patching_desc *desc = &bp_desc; smp_mb__before_atomic(); raw_atomic_dec(&desc->refs); } static __always_inline void *text_poke_addr(struct text_poke_loc *tp) { return _stext + tp->rel_addr; } static __always_inline int patch_cmp(const void *key, const void *elt) { struct text_poke_loc *tp = (struct text_poke_loc *) elt; if (key < text_poke_addr(tp)) return -1; if (key > text_poke_addr(tp)) return 1; return 0; } noinstr int poke_int3_handler(struct pt_regs *regs) { struct bp_patching_desc *desc; struct text_poke_loc *tp; int ret = 0; void *ip; if (user_mode(regs)) return 0; /* * Having observed our INT3 instruction, we now must observe * bp_desc with non-zero refcount: * * bp_desc.refs = 1 INT3 * WMB RMB * write INT3 if (bp_desc.refs != 0) */ smp_rmb(); desc = try_get_desc(); if (!desc) return 0; /* * Discount the INT3. See text_poke_bp_batch(). */ ip = (void *) regs->ip - INT3_INSN_SIZE; /* * Skip the binary search if there is a single member in the vector. */ if (unlikely(desc->nr_entries > 1)) { tp = __inline_bsearch(ip, desc->vec, desc->nr_entries, sizeof(struct text_poke_loc), patch_cmp); if (!tp) goto out_put; } else { tp = desc->vec; if (text_poke_addr(tp) != ip) goto out_put; } ip += tp->len; switch (tp->opcode) { case INT3_INSN_OPCODE: /* * Someone poked an explicit INT3, they'll want to handle it, * do not consume. */ goto out_put; case RET_INSN_OPCODE: int3_emulate_ret(regs); break; case CALL_INSN_OPCODE: int3_emulate_call(regs, (long)ip + tp->disp); break; case JMP32_INSN_OPCODE: case JMP8_INSN_OPCODE: int3_emulate_jmp(regs, (long)ip + tp->disp); break; case 0x70 ... 0x7f: /* Jcc */ int3_emulate_jcc(regs, tp->opcode & 0xf, (long)ip, tp->disp); break; default: BUG(); } ret = 1; out_put: put_desc(); return ret; } #define TP_VEC_MAX (PAGE_SIZE / sizeof(struct text_poke_loc)) static struct text_poke_loc tp_vec[TP_VEC_MAX]; static int tp_vec_nr; /** * text_poke_bp_batch() -- update instructions on live kernel on SMP * @tp: vector of instructions to patch * @nr_entries: number of entries in the vector * * Modify multi-byte instruction by using int3 breakpoint on SMP. * We completely avoid stop_machine() here, and achieve the * synchronization using int3 breakpoint. * * The way it is done: * - For each entry in the vector: * - add a int3 trap to the address that will be patched * - sync cores * - For each entry in the vector: * - update all but the first byte of the patched range * - sync cores * - For each entry in the vector: * - replace the first byte (int3) by the first byte of * replacing opcode * - sync cores */ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries) { unsigned char int3 = INT3_INSN_OPCODE; unsigned int i; int do_sync; lockdep_assert_held(&text_mutex); bp_desc.vec = tp; bp_desc.nr_entries = nr_entries; /* * Corresponds to the implicit memory barrier in try_get_desc() to * ensure reading a non-zero refcount provides up to date bp_desc data. */ atomic_set_release(&bp_desc.refs, 1); /* * Function tracing can enable thousands of places that need to be * updated. This can take quite some time, and with full kernel debugging * enabled, this could cause the softlockup watchdog to trigger. * This function gets called every 256 entries added to be patched. * Call cond_resched() here to make sure that other tasks can get scheduled * while processing all the functions being patched. */ cond_resched(); /* * Corresponding read barrier in int3 notifier for making sure the * nr_entries and handler are correctly ordered wrt. patching. */ smp_wmb(); /* * First step: add a int3 trap to the address that will be patched. */ for (i = 0; i < nr_entries; i++) { tp[i].old = *(u8 *)text_poke_addr(&tp[i]); text_poke(text_poke_addr(&tp[i]), &int3, INT3_INSN_SIZE); } text_poke_sync(); /* * Second step: update all but the first byte of the patched range. */ for (do_sync = 0, i = 0; i < nr_entries; i++) { u8 old[POKE_MAX_OPCODE_SIZE+1] = { tp[i].old, }; u8 _new[POKE_MAX_OPCODE_SIZE+1]; const u8 *new = tp[i].text; int len = tp[i].len; if (len - INT3_INSN_SIZE > 0) { memcpy(old + INT3_INSN_SIZE, text_poke_addr(&tp[i]) + INT3_INSN_SIZE, len - INT3_INSN_SIZE); if (len == 6) { _new[0] = 0x0f; memcpy(_new + 1, new, 5); new = _new; } text_poke(text_poke_addr(&tp[i]) + INT3_INSN_SIZE, new + INT3_INSN_SIZE, len - INT3_INSN_SIZE); do_sync++; } /* * Emit a perf event to record the text poke, primarily to * support Intel PT decoding which must walk the executable code * to reconstruct the trace. The flow up to here is: * - write INT3 byte * - IPI-SYNC * - write instruction tail * At this point the actual control flow will be through the * INT3 and handler and not hit the old or new instruction. * Intel PT outputs FUP/TIP packets for the INT3, so the flow * can still be decoded. Subsequently: * - emit RECORD_TEXT_POKE with the new instruction * - IPI-SYNC * - write first byte * - IPI-SYNC * So before the text poke event timestamp, the decoder will see * either the old instruction flow or FUP/TIP of INT3. After the * text poke event timestamp, the decoder will see either the * new instruction flow or FUP/TIP of INT3. Thus decoders can * use the timestamp as the point at which to modify the * executable code. * The old instruction is recorded so that the event can be * processed forwards or backwards. */ perf_event_text_poke(text_poke_addr(&tp[i]), old, len, new, len); } if (do_sync) { /* * According to Intel, this core syncing is very likely * not necessary and we'd be safe even without it. But * better safe than sorry (plus there's not only Intel). */ text_poke_sync(); } /* * Third step: replace the first byte (int3) by the first byte of * replacing opcode. */ for (do_sync = 0, i = 0; i < nr_entries; i++) { u8 byte = tp[i].text[0]; if (tp[i].len == 6) byte = 0x0f; if (byte == INT3_INSN_OPCODE) continue; text_poke(text_poke_addr(&tp[i]), &byte, INT3_INSN_SIZE); do_sync++; } if (do_sync) text_poke_sync(); /* * Remove and wait for refs to be zero. */ if (!atomic_dec_and_test(&bp_desc.refs)) atomic_cond_read_acquire(&bp_desc.refs, !VAL); } static void text_poke_loc_init(struct text_poke_loc *tp, void *addr, const void *opcode, size_t len, const void *emulate) { struct insn insn; int ret, i = 0; if (len == 6) i = 1; memcpy((void *)tp->text, opcode+i, len-i); if (!emulate) emulate = opcode; ret = insn_decode_kernel(&insn, emulate); BUG_ON(ret < 0); tp->rel_addr = addr - (void *)_stext; tp->len = len; tp->opcode = insn.opcode.bytes[0]; if (is_jcc32(&insn)) { /* * Map Jcc.d32 onto Jcc.d8 and use len to distinguish. */ tp->opcode = insn.opcode.bytes[1] - 0x10; } switch (tp->opcode) { case RET_INSN_OPCODE: case JMP32_INSN_OPCODE: case JMP8_INSN_OPCODE: /* * Control flow instructions without implied execution of the * next instruction can be padded with INT3. */ for (i = insn.length; i < len; i++) BUG_ON(tp->text[i] != INT3_INSN_OPCODE); break; default: BUG_ON(len != insn.length); } switch (tp->opcode) { case INT3_INSN_OPCODE: case RET_INSN_OPCODE: break; case CALL_INSN_OPCODE: case JMP32_INSN_OPCODE: case JMP8_INSN_OPCODE: case 0x70 ... 0x7f: /* Jcc */ tp->disp = insn.immediate.value; break; default: /* assume NOP */ switch (len) { case 2: /* NOP2 -- emulate as JMP8+0 */ BUG_ON(memcmp(emulate, x86_nops[len], len)); tp->opcode = JMP8_INSN_OPCODE; tp->disp = 0; break; case 5: /* NOP5 -- emulate as JMP32+0 */ BUG_ON(memcmp(emulate, x86_nops[len], len)); tp->opcode = JMP32_INSN_OPCODE; tp->disp = 0; break; default: /* unknown instruction */ BUG(); } break; } } /* * We hard rely on the tp_vec being ordered; ensure this is so by flushing * early if needed. */ static bool tp_order_fail(void *addr) { struct text_poke_loc *tp; if (!tp_vec_nr) return false; if (!addr) /* force */ return true; tp = &tp_vec[tp_vec_nr - 1]; if ((unsigned long)text_poke_addr(tp) > (unsigned long)addr) return true; return false; } static void text_poke_flush(void *addr) { if (tp_vec_nr == TP_VEC_MAX || tp_order_fail(addr)) { text_poke_bp_batch(tp_vec, tp_vec_nr); tp_vec_nr = 0; } } void text_poke_finish(void) { text_poke_flush(NULL); } void __ref text_poke_queue(void *addr, const void *opcode, size_t len, const void *emulate) { struct text_poke_loc *tp; text_poke_flush(addr); tp = &tp_vec[tp_vec_nr++]; text_poke_loc_init(tp, addr, opcode, len, emulate); } /** * text_poke_bp() -- update instructions on live kernel on SMP * @addr: address to patch * @opcode: opcode of new instruction * @len: length to copy * @emulate: instruction to be emulated * * Update a single instruction with the vector in the stack, avoiding * dynamically allocated memory. This function should be used when it is * not possible to allocate memory. */ void __ref text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate) { struct text_poke_loc tp; text_poke_loc_init(&tp, addr, opcode, len, emulate); text_poke_bp_batch(&tp, 1); }
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