cregit-Linux how code gets into the kernel

Release 4.17 scripts/recordmcount.h

Directory: scripts
/*
 * recordmcount.h
 *
 * This code was taken out of recordmcount.c written by
 * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>.  All rights reserved.
 *
 * The original code had the same algorithms for both 32bit
 * and 64bit ELF files, but the code was duplicated to support
 * the difference in structures that were used. This
 * file creates a macro of everything that is different between
 * the 64 and 32 bit code, such that by including this header
 * twice we can create both sets of functions by including this
 * header once with RECORD_MCOUNT_64 undefined, and again with
 * it defined.
 *
 * This conversion to macros was done by:
 * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
 *
 * Licensed under the GNU General Public License, version 2 (GPLv2).
 */
#undef append_func
#undef is_fake_mcount
#undef fn_is_fake_mcount
#undef MIPS_is_fake_mcount
#undef mcount_adjust
#undef sift_rel_mcount
#undef nop_mcount
#undef find_secsym_ndx
#undef __has_rel_mcount
#undef has_rel_mcount
#undef tot_relsize
#undef get_mcountsym
#undef get_sym_str_and_relp
#undef do_func
#undef Elf_Addr
#undef Elf_Ehdr
#undef Elf_Shdr
#undef Elf_Rel
#undef Elf_Rela
#undef Elf_Sym
#undef ELF_R_SYM
#undef Elf_r_sym
#undef ELF_R_INFO
#undef Elf_r_info
#undef ELF_ST_BIND
#undef ELF_ST_TYPE
#undef fn_ELF_R_SYM
#undef fn_ELF_R_INFO
#undef uint_t
#undef _w
#undef _align
#undef _size

#ifdef RECORD_MCOUNT_64

# define append_func		append64

# define sift_rel_mcount	sift64_rel_mcount

# define nop_mcount		nop_mcount_64

# define find_secsym_ndx	find64_secsym_ndx

# define __has_rel_mcount	__has64_rel_mcount

# define has_rel_mcount		has64_rel_mcount

# define tot_relsize		tot64_relsize

# define get_sym_str_and_relp	get_sym_str_and_relp_64

# define do_func		do64

# define get_mcountsym		get_mcountsym_64

# define is_fake_mcount		is_fake_mcount64

# define fn_is_fake_mcount	fn_is_fake_mcount64

# define MIPS_is_fake_mcount	MIPS64_is_fake_mcount

# define mcount_adjust		mcount_adjust_64

# define Elf_Addr		Elf64_Addr

# define Elf_Ehdr		Elf64_Ehdr

# define Elf_Shdr		Elf64_Shdr

# define Elf_Rel		Elf64_Rel

# define Elf_Rela		Elf64_Rela

# define Elf_Sym		Elf64_Sym

# define ELF_R_SYM		ELF64_R_SYM

# define Elf_r_sym		Elf64_r_sym

# define ELF_R_INFO		ELF64_R_INFO

# define Elf_r_info		Elf64_r_info

# define ELF_ST_BIND		ELF64_ST_BIND

# define ELF_ST_TYPE		ELF64_ST_TYPE

# define fn_ELF_R_SYM		fn_ELF64_R_SYM

# define fn_ELF_R_INFO		fn_ELF64_R_INFO

# define uint_t			uint64_t

# define _w			w8

# define _align			7u

# define _size			8
#else

# define append_func		append32

# define sift_rel_mcount	sift32_rel_mcount

# define nop_mcount		nop_mcount_32

# define find_secsym_ndx	find32_secsym_ndx

# define __has_rel_mcount	__has32_rel_mcount

# define has_rel_mcount		has32_rel_mcount

# define tot_relsize		tot32_relsize

# define get_sym_str_and_relp	get_sym_str_and_relp_32

# define do_func		do32

# define get_mcountsym		get_mcountsym_32

# define is_fake_mcount		is_fake_mcount32

# define fn_is_fake_mcount	fn_is_fake_mcount32

# define MIPS_is_fake_mcount	MIPS32_is_fake_mcount

# define mcount_adjust		mcount_adjust_32

# define Elf_Addr		Elf32_Addr

# define Elf_Ehdr		Elf32_Ehdr

# define Elf_Shdr		Elf32_Shdr

# define Elf_Rel		Elf32_Rel

# define Elf_Rela		Elf32_Rela

# define Elf_Sym		Elf32_Sym

# define ELF_R_SYM		ELF32_R_SYM

# define Elf_r_sym		Elf32_r_sym

# define ELF_R_INFO		ELF32_R_INFO

# define Elf_r_info		Elf32_r_info

# define ELF_ST_BIND		ELF32_ST_BIND

# define ELF_ST_TYPE		ELF32_ST_TYPE

# define fn_ELF_R_SYM		fn_ELF32_R_SYM

# define fn_ELF_R_INFO		fn_ELF32_R_INFO

# define uint_t			uint32_t

# define _w			w

# define _align			3u

# define _size			4
#endif

/* Functions and pointers that do_file() may override for specific e_machine. */

static int fn_is_fake_mcount(Elf_Rel const *rp) { return 0; }

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static int (*is_fake_mcount)(Elf_Rel const *rp) = fn_is_fake_mcount;
static uint_t fn_ELF_R_SYM(Elf_Rel const *rp) { return ELF_R_SYM(_w(rp->r_info)); }

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static uint_t (*Elf_r_sym)(Elf_Rel const *rp) = fn_ELF_R_SYM;
static void fn_ELF_R_INFO(Elf_Rel *const rp, unsigned sym, unsigned type) { rp->r_info = _w(ELF_R_INFO(sym, type)); }

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static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO; static int mcount_adjust = 0; /* * MIPS mcount long call has 2 _mcount symbols, only the position of the 1st * _mcount symbol is needed for dynamic function tracer, with it, to disable * tracing(ftrace_make_nop), the instruction in the position is replaced with * the "b label" instruction, to enable tracing(ftrace_make_call), replace the * instruction back. So, here, we set the 2nd one as fake and filter it. * * c: 3c030000 lui v1,0x0 <--> b label * c: R_MIPS_HI16 _mcount * c: R_MIPS_NONE *ABS* * c: R_MIPS_NONE *ABS* * 10: 64630000 daddiu v1,v1,0 * 10: R_MIPS_LO16 _mcount * 10: R_MIPS_NONE *ABS* * 10: R_MIPS_NONE *ABS* * 14: 03e0082d move at,ra * 18: 0060f809 jalr v1 * label: */ #define MIPS_FAKEMCOUNT_OFFSET 4
static int MIPS_is_fake_mcount(Elf_Rel const *rp) { static Elf_Addr old_r_offset = ~(Elf_Addr)0; Elf_Addr current_r_offset = _w(rp->r_offset); int is_fake; is_fake = (old_r_offset != ~(Elf_Addr)0) && (current_r_offset - old_r_offset == MIPS_FAKEMCOUNT_OFFSET); old_r_offset = current_r_offset; return is_fake; }

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/* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */
static void append_func(Elf_Ehdr *const ehdr, Elf_Shdr *const shstr, uint_t const *const mloc0, uint_t const *const mlocp, Elf_Rel const *const mrel0, Elf_Rel const *const mrelp, unsigned int const rel_entsize, unsigned int const symsec_sh_link) { /* Begin constructing output file */ Elf_Shdr mcsec; char const *mc_name = (sizeof(Elf_Rela) == rel_entsize) ? ".rela__mcount_loc" : ".rel__mcount_loc"; unsigned const old_shnum = w2(ehdr->e_shnum); uint_t const old_shoff = _w(ehdr->e_shoff); uint_t const old_shstr_sh_size = _w(shstr->sh_size); uint_t const old_shstr_sh_offset = _w(shstr->sh_offset); uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size); uint_t new_e_shoff; shstr->sh_size = _w(t); shstr->sh_offset = _w(sb.st_size); t += sb.st_size; t += (_align & -t); /* word-byte align */ new_e_shoff = t; /* body for new shstrtab */ ulseek(fd_map, sb.st_size, SEEK_SET); uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size); uwrite(fd_map, mc_name, 1 + strlen(mc_name)); /* old(modified) Elf_Shdr table, word-byte aligned */ ulseek(fd_map, t, SEEK_SET); t += sizeof(Elf_Shdr) * old_shnum; uwrite(fd_map, old_shoff + (void *)ehdr, sizeof(Elf_Shdr) * old_shnum); /* new sections __mcount_loc and .rel__mcount_loc */ t += 2*sizeof(mcsec); mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel") + old_shstr_sh_size); mcsec.sh_type = w(SHT_PROGBITS); mcsec.sh_flags = _w(SHF_ALLOC); mcsec.sh_addr = 0; mcsec.sh_offset = _w(t); mcsec.sh_size = _w((void *)mlocp - (void *)mloc0); mcsec.sh_link = 0; mcsec.sh_info = 0; mcsec.sh_addralign = _w(_size); mcsec.sh_entsize = _w(_size); uwrite(fd_map, &mcsec, sizeof(mcsec)); mcsec.sh_name = w(old_shstr_sh_size); mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize) ? w(SHT_RELA) : w(SHT_REL); mcsec.sh_flags = 0; mcsec.sh_addr = 0; mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t); mcsec.sh_size = _w((void *)mrelp - (void *)mrel0); mcsec.sh_link = w(symsec_sh_link); mcsec.sh_info = w(old_shnum); mcsec.sh_addralign = _w(_size); mcsec.sh_entsize = _w(rel_entsize); uwrite(fd_map, &mcsec, sizeof(mcsec)); uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0); uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0); ehdr->e_shoff = _w(new_e_shoff); ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum)); /* {.rel,}__mcount_loc */ ulseek(fd_map, 0, SEEK_SET); uwrite(fd_map, ehdr, sizeof(*ehdr)); }

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static unsigned get_mcountsym(Elf_Sym const *const sym0, Elf_Rel const *relp, char const *const str0) { unsigned mcountsym = 0; Elf_Sym const *const symp = &sym0[Elf_r_sym(relp)]; char const *symname = &str0[w(symp->st_name)]; char const *mcount = gpfx == '_' ? "_mcount" : "mcount"; char const *fentry = "__fentry__"; if (symname[0] == '.') ++symname; /* ppc64 hack */ if (strcmp(mcount, symname) == 0 || (altmcount && strcmp(altmcount, symname) == 0) || (strcmp(fentry, symname) == 0)) mcountsym = Elf_r_sym(relp); return mcountsym; }

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static void get_sym_str_and_relp(Elf_Shdr const *const relhdr, Elf_Ehdr const *const ehdr, Elf_Sym const **sym0, char const **str0, Elf_Rel const **relp) { Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) + (void *)ehdr); unsigned const symsec_sh_link = w(relhdr->sh_link); Elf_Shdr const *const symsec = &shdr0[symsec_sh_link]; Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)]; Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset) + (void *)ehdr); *sym0 = (Elf_Sym const *)(_w(symsec->sh_offset) + (void *)ehdr); *str0 = (char const *)(_w(strsec->sh_offset) + (void *)ehdr); *relp = rel0; }

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/* * Look at the relocations in order to find the calls to mcount. * Accumulate the section offsets that are found, and their relocation info, * onto the end of the existing arrays. */
static uint_t *sift_rel_mcount(uint_t *mlocp, unsigned const offbase, Elf_Rel **const mrelpp, Elf_Shdr const *const relhdr, Elf_Ehdr const *const ehdr, unsigned const recsym, uint_t const recval, unsigned const reltype) { uint_t *const mloc0 = mlocp; Elf_Rel *mrelp = *mrelpp; Elf_Sym const *sym0; char const *str0; Elf_Rel const *relp; unsigned rel_entsize = _w(relhdr->sh_entsize); unsigned const nrel = _w(relhdr->sh_size) / rel_entsize; unsigned mcountsym = 0; unsigned t; get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp); for (t = nrel; t; --t) { if (!mcountsym) mcountsym = get_mcountsym(sym0, relp, str0); if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) { uint_t const addend = _w(_w(relp->r_offset) - recval + mcount_adjust); mrelp->r_offset = _w(offbase + ((void *)mlocp - (void *)mloc0)); Elf_r_info(mrelp, recsym, reltype); if (rel_entsize == sizeof(Elf_Rela)) { ((Elf_Rela *)mrelp)->r_addend = addend; *mlocp++ = 0; } else *mlocp++ = addend; mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp); } relp = (Elf_Rel const *)(rel_entsize + (void *)relp); } *mrelpp = mrelp; return mlocp; }

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/* * Read the relocation table again, but this time its called on sections * that are not going to be traced. The mcount calls here will be converted * into nops. */
static void nop_mcount(Elf_Shdr const *const relhdr, Elf_Ehdr const *const ehdr, const char *const txtname) { Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) + (void *)ehdr); Elf_Sym const *sym0; char const *str0; Elf_Rel const *relp; Elf_Shdr const *const shdr = &shdr0[w(relhdr->sh_info)]; unsigned rel_entsize = _w(relhdr->sh_entsize); unsigned const nrel = _w(relhdr->sh_size) / rel_entsize; unsigned mcountsym = 0; unsigned t; int once = 0; get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp); for (t = nrel; t; --t) { int ret = -1; if (!mcountsym) mcountsym = get_mcountsym(sym0, relp, str0); if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) { if (make_nop) ret = make_nop((void *)ehdr, _w(shdr->sh_offset) + _w(relp->r_offset)); if (warn_on_notrace_sect && !once) { printf("Section %s has mcount callers being ignored\n", txtname); once = 1; /* just warn? */ if (!make_nop) return; } } /* * If we successfully removed the mcount, mark the relocation * as a nop (don't do anything with it). */ if (!ret) { Elf_Rel rel; rel = *(Elf_Rel *)relp; Elf_r_info(&rel, Elf_r_sym(relp), rel_type_nop); ulseek(fd_map, (void *)relp - (void *)ehdr, SEEK_SET); uwrite(fd_map, &rel, sizeof(rel)); } relp = (Elf_Rel const *)(rel_entsize + (void *)relp); } }

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/* * Find a symbol in the given section, to be used as the base for relocating * the table of offsets of calls to mcount. A local or global symbol suffices, * but avoid a Weak symbol because it may be overridden; the change in value * would invalidate the relocations of the offsets of the calls to mcount. * Often the found symbol will be the unnamed local symbol generated by * GNU 'as' for the start of each section. For example: * Num: Value Size Type Bind Vis Ndx Name * 2: 00000000 0 SECTION LOCAL DEFAULT 1 */
static unsigned find_secsym_ndx(unsigned const txtndx, char const *const txtname, uint_t *const recvalp, Elf_Shdr const *const symhdr, Elf_Ehdr const *const ehdr) { Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset) + (void *)ehdr); unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize); Elf_Sym const *symp; unsigned t; for (symp = sym0, t = nsym; t; --t, ++symp) { unsigned int const st_bind = ELF_ST_BIND(symp->st_info); if (txtndx == w2(symp->st_shndx) /* avoid STB_WEAK */ && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) { /* function symbols on ARM have quirks, avoid them */ if (w2(ehdr->e_machine) == EM_ARM && ELF_ST_TYPE(symp->st_info) == STT_FUNC) continue; *recvalp = _w(symp->st_value); return symp - sym0; } } fprintf(stderr, "Cannot find symbol for section %d: %s.\n", txtndx, txtname); fail_file(); }

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/* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */
static char const * __has_rel_mcount(Elf_Shdr const *const relhdr, /* is SHT_REL or SHT_RELA */ Elf_Shdr const *const shdr0, char const *const shstrtab, char const *const fname) { /* .sh_info depends on .sh_type == SHT_REL[,A] */ Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)]; char const *const txtname = &shstrtab[w(txthdr->sh_name)]; if (strcmp("__mcount_loc", txtname) == 0) { fprintf(stderr, "warning: __mcount_loc already exists: %s\n", fname); succeed_file(); } if (w(txthdr->sh_type) != SHT_PROGBITS || !(_w(txthdr->sh_flags) & SHF_EXECINSTR)) return NULL; return txtname; }

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static char const *has_rel_mcount(Elf_Shdr const *const relhdr, Elf_Shdr const *const shdr0, char const *const shstrtab, char const *const fname) { if (w(relhdr->sh_type) != SHT_REL && w(relhdr->sh_type) != SHT_RELA) return NULL; return __has_rel_mcount(relhdr, shdr0, shstrtab, fname); }

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static unsigned tot_relsize(Elf_Shdr const *const shdr0, unsigned nhdr, const char *const shstrtab, const char *const fname) { unsigned totrelsz = 0; Elf_Shdr const *shdrp = shdr0; char const *txtname; for (; nhdr; --nhdr, ++shdrp) { txtname = has_rel_mcount(shdrp, shdr0, shstrtab, fname); if (txtname && is_mcounted_section_name(txtname)) totrelsz += _w(shdrp->sh_size); } return totrelsz; }

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/* Overall supervision for Elf32 ET_REL file. */
static void do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype) { Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) + (void *)ehdr); unsigned const nhdr = w2(ehdr->e_shnum); Elf_Shdr *const shstr = &shdr0[w2(ehdr->e_shstrndx)]; char const *const shstrtab = (char const *)(_w(