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recordmcount.h
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/* SPDX-License-Identifier: GPL-2.0-only */ /* * 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. */ #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 find_symtab #undef get_shnum #undef set_shnum #undef get_shstrndx #undef get_symindex #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 find_symtab find_symtab64 # define get_shnum get_shnum64 # define set_shnum set_shnum64 # define get_shstrndx get_shstrndx64 # define get_symindex get_symindex64 # 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 find_symtab find_symtab32 # define get_shnum get_shnum32 # define set_shnum set_shnum32 # define get_shstrndx get_shstrndx32 # define get_symindex get_symindex32 # 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; } 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)); } 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)); } 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; } static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab, Elf32_Word const *symtab_shndx) { unsigned long offset; unsigned short shndx = w2(sym->st_shndx); int index; if (shndx > SHN_UNDEF && shndx < SHN_LORESERVE) return shndx; if (shndx == SHN_XINDEX) { offset = (unsigned long)sym - (unsigned long)symtab; index = offset / sizeof(*sym); return w(symtab_shndx[index]); } return 0; } static unsigned int get_shnum(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0) { if (shdr0 && !ehdr->e_shnum) return w(shdr0->sh_size); return w2(ehdr->e_shnum); } static void set_shnum(Elf_Ehdr *ehdr, Elf_Shdr *shdr0, unsigned int new_shnum) { if (new_shnum >= SHN_LORESERVE) { ehdr->e_shnum = 0; shdr0->sh_size = w(new_shnum); } else ehdr->e_shnum = w2(new_shnum); } static int get_shstrndx(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0) { if (ehdr->e_shstrndx != SHN_XINDEX) return w2(ehdr->e_shstrndx); return w(shdr0->sh_link); } static void find_symtab(Elf_Ehdr *const ehdr, Elf_Shdr const *shdr0, unsigned const nhdr, Elf32_Word **symtab, Elf32_Word **symtab_shndx) { Elf_Shdr const *relhdr; unsigned k; *symtab = NULL; *symtab_shndx = NULL; for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) { if (relhdr->sh_type == SHT_SYMTAB) *symtab = (void *)ehdr + relhdr->sh_offset; else if (relhdr->sh_type == SHT_SYMTAB_SHNDX) *symtab_shndx = (void *)ehdr + relhdr->sh_offset; if (*symtab && *symtab_shndx) break; } } /* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */ static int 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"; 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); Elf_Shdr *const shdr0 = (Elf_Shdr *)(old_shoff + (void *)ehdr); unsigned int const old_shnum = get_shnum(ehdr, shdr0); unsigned int const new_shnum = 2 + old_shnum; /* {.rel,}__mcount_loc */ 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; set_shnum(ehdr, shdr0, new_shnum); /* body for new shstrtab */ if (ulseek(sb.st_size, SEEK_SET) < 0) return -1; if (uwrite(old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size) < 0) return -1; if (uwrite(mc_name, 1 + strlen(mc_name)) < 0) return -1; /* old(modified) Elf_Shdr table, word-byte aligned */ if (ulseek(t, SEEK_SET) < 0) return -1; t += sizeof(Elf_Shdr) * old_shnum; if (uwrite(old_shoff + (void *)ehdr, sizeof(Elf_Shdr) * old_shnum) < 0) return -1; /* 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); if (uwrite(&mcsec, sizeof(mcsec)) < 0) return -1; 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); if (uwrite(&mcsec, sizeof(mcsec)) < 0) return -1; if (uwrite(mloc0, (void *)mlocp - (void *)mloc0) < 0) return -1; if (uwrite(mrel0, (void *)mrelp - (void *)mrel0) < 0) return -1; ehdr->e_shoff = _w(new_e_shoff); if (ulseek(0, SEEK_SET) < 0) return -1; if (uwrite(ehdr, sizeof(*ehdr)) < 0) return -1; return 0; } 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; } 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; } /* * 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 && 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; } /* * 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 int 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 0; } } /* * 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); if (ulseek((void *)relp - (void *)ehdr, SEEK_SET) < 0) return -1; if (uwrite(&rel, sizeof(rel)) < 0) return -1; } relp = (Elf_Rel const *)(rel_entsize + (void *)relp); } return 0; } /* * 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 int find_secsym_ndx(unsigned const txtndx, char const *const txtname, uint_t *const recvalp, unsigned int *sym_index, Elf_Shdr const *const symhdr, Elf32_Word const *symtab, Elf32_Word const *symtab_shndx, 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 == get_symindex(symp, symtab, symtab_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); *sym_index = symp - sym0; return 0; } } fprintf(stderr, "Cannot find symbol for section %u: %s.\n", txtndx, txtname); return -1; } /* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */ static char const * __has_rel_mcount(Elf_Shdr const *const relhdr, /* reltype */ 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); return already_has_rel_mcount; } if (w(txthdr->sh_type) != SHT_PROGBITS || !(_w(txthdr->sh_flags) & SHF_EXECINSTR)) return NULL; return txtname; } 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); } 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 == already_has_rel_mcount) { totrelsz = 0; break; } if (txtname && is_mcounted_section_name(txtname)) totrelsz += _w(shdrp->sh_size); } return totrelsz; } /* Overall supervision for Elf32 ET_REL file. */ static int 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 = get_shnum(ehdr, shdr0); Elf_Shdr *const shstr = &shdr0[get_shstrndx(ehdr, shdr0)]; char const *const shstrtab = (char const *)(_w(shstr->sh_offset) + (void *)ehdr); Elf_Shdr const *relhdr; unsigned k; Elf32_Word *symtab; Elf32_Word *symtab_shndx; /* Upper bound on space: assume all relevant relocs are for mcount. */ unsigned totrelsz; Elf_Rel * mrel0; Elf_Rel * mrelp; uint_t * mloc0; uint_t * mlocp; unsigned rel_entsize = 0; unsigned symsec_sh_link = 0; int result = 0; totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname); if (totrelsz == 0) return 0; mrel0 = umalloc(totrelsz); mrelp = mrel0; if (!mrel0) return -1; /* 2*sizeof(address) <= sizeof(Elf_Rel) */ mloc0 = umalloc(totrelsz>>1); mlocp = mloc0; if (!mloc0) { free(mrel0); return -1; } find_symtab(ehdr, shdr0, nhdr, &symtab, &symtab_shndx); for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) { char const *const txtname = has_rel_mcount(relhdr, shdr0, shstrtab, fname); if (txtname == already_has_rel_mcount) { result = 0; file_updated = 0; goto out; /* Nothing to be done; don't append! */ } if (txtname && is_mcounted_section_name(txtname)) { unsigned int recsym; uint_t recval = 0; symsec_sh_link = w(relhdr->sh_link); result = find_secsym_ndx(w(relhdr->sh_info), txtname, &recval, &recsym, &shdr0[symsec_sh_link], symtab, symtab_shndx, ehdr); if (result) goto out; rel_entsize = _w(relhdr->sh_entsize); mlocp = sift_rel_mcount(mlocp, (void *)mlocp - (void *)mloc0, &mrelp, relhdr, ehdr, recsym, recval, reltype); } else if (txtname && (warn_on_notrace_sect || make_nop)) { /* * This section is ignored by ftrace, but still * has mcount calls. Convert them to nops now. */ if (nop_mcount(relhdr, ehdr, txtname) < 0) { result = -1; goto out; } } } if (!result && mloc0 != mlocp) result = append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp, rel_entsize, symsec_sh_link); out: free(mrel0); free(mloc0); return result; }