diff options
| -rw-r--r-- | scripts/recordmcount.c | 40 | ||||
| -rw-r--r-- | scripts/recordmcount.h | 82 |
2 files changed, 116 insertions, 6 deletions
diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c index 37c5965..78054a4 100644 --- a/scripts/recordmcount.c +++ b/scripts/recordmcount.c @@ -118,6 +118,34 @@ umalloc(size_t size) return addr; } +static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 }; +static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 }; +static unsigned char *ideal_nop; + +static char rel_type_nop; + +static int (*make_nop)(void *map, size_t const offset); + +static int make_nop_x86(void *map, size_t const offset) +{ + uint32_t *ptr; + unsigned char *op; + + /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */ + ptr = map + offset; + if (*ptr != 0) + return -1; + + op = map + offset - 1; + if (*op != 0xe8) + return -1; + + /* convert to nop */ + ulseek(fd_map, offset - 1, SEEK_SET); + uwrite(fd_map, ideal_nop, 5); + return 0; +} + /* * Get the whole file as a programming convenience in order to avoid * malloc+lseek+read+free of many pieces. If successful, then mmap @@ -301,7 +329,11 @@ do_file(char const *const fname) w2(ehdr->e_machine), fname); fail_file(); break; - case EM_386: reltype = R_386_32; break; + case EM_386: + reltype = R_386_32; + make_nop = make_nop_x86; + ideal_nop = ideal_nop5_x86_32; + break; case EM_ARM: reltype = R_ARM_ABS32; altmcount = "__gnu_mcount_nc"; break; @@ -312,7 +344,11 @@ do_file(char const *const fname) case EM_S390: /* reltype: e_class */ gpfx = '_'; break; case EM_SH: reltype = R_SH_DIR32; break; case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break; - case EM_X86_64: reltype = R_X86_64_64; break; + case EM_X86_64: + make_nop = make_nop_x86; + ideal_nop = ideal_nop5_x86_64; + reltype = R_X86_64_64; + break; } /* end switch */ switch (ehdr->e_ident[EI_CLASS]) { diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h index 7f8d5c4..657dbed 100644 --- a/scripts/recordmcount.h +++ b/scripts/recordmcount.h @@ -23,6 +23,7 @@ #undef fn_is_fake_mcount #undef MIPS_is_fake_mcount #undef sift_rel_mcount +#undef nop_mcount #undef find_secsym_ndx #undef __has_rel_mcount #undef has_rel_mcount @@ -49,6 +50,7 @@ #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 @@ -77,6 +79,7 @@ #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 @@ -304,6 +307,70 @@ static uint_t *sift_rel_mcount(uint_t *mlocp, 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 void nop_mcount(Elf_Shdr const *const relhdr, + Elf_Ehdr const *const ehdr) +{ + 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_Sym const *const sym0 = (Elf_Sym const *)(_w(symsec->sh_offset) + + (void *)ehdr); + + Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)]; + char const *const str0 = (char const *)(_w(strsec->sh_offset) + + (void *)ehdr); + + Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset) + + (void *)ehdr); + unsigned rel_entsize = _w(relhdr->sh_entsize); + unsigned const nrel = _w(relhdr->sh_size) / rel_entsize; + Elf_Rel const *relp = rel0; + + Elf_Shdr const *const shdr = &shdr0[w(relhdr->sh_info)]; + + unsigned mcountsym = 0; + unsigned t; + + for (t = nrel; t; --t) { + int ret = -1; + + if (!mcountsym) { + Elf_Sym const *const symp = + &sym0[Elf_r_sym(relp)]; + char const *symname = &str0[w(symp->st_name)]; + char const *mcount = gpfx == '_' ? "_mcount" : "mcount"; + + if (symname[0] == '.') + ++symname; /* ppc64 hack */ + if (strcmp(mcount, symname) == 0 || + (altmcount && strcmp(altmcount, symname) == 0)) + mcountsym = Elf_r_sym(relp); + } + + if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) + ret = make_nop((void *)ehdr, shdr->sh_offset + relp->r_offset); + + /* + * 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); + } +} + /* * Find a symbol in the given section, to be used as the base for relocating @@ -360,8 +427,7 @@ __has_rel_mcount(Elf_Shdr const *const relhdr, /* is SHT_REL or SHT_RELA */ succeed_file(); } if (w(txthdr->sh_type) != SHT_PROGBITS || - !(w(txthdr->sh_flags) & SHF_EXECINSTR) || - !is_mcounted_section_name(txtname)) + !(w(txthdr->sh_flags) & SHF_EXECINSTR)) return NULL; return txtname; } @@ -384,9 +450,11 @@ static unsigned tot_relsize(Elf_Shdr const *const shdr0, { unsigned totrelsz = 0; Elf_Shdr const *shdrp = shdr0; + char const *txtname; for (; nhdr; --nhdr, ++shdrp) { - if (has_rel_mcount(shdrp, shdr0, shstrtab, fname)) + txtname = has_rel_mcount(shdrp, shdr0, shstrtab, fname); + if (txtname && is_mcounted_section_name(txtname)) totrelsz += _w(shdrp->sh_size); } return totrelsz; @@ -422,7 +490,7 @@ do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype) for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) { char const *const txtname = has_rel_mcount(relhdr, shdr0, shstrtab, fname); - if (txtname) { + if (txtname && is_mcounted_section_name(txtname)) { uint_t recval = 0; unsigned const recsym = find_secsym_ndx( w(relhdr->sh_info), txtname, &recval, @@ -433,6 +501,12 @@ do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype) mlocp = sift_rel_mcount(mlocp, (void *)mlocp - (void *)mloc0, &mrelp, relhdr, ehdr, recsym, recval, reltype); + } else if (make_nop && txtname) { + /* + * This section is ignored by ftrace, but still + * has mcount calls. Convert them to nops now. + */ + nop_mcount(relhdr, ehdr); } } if (mloc0 != mlocp) { |
