4 * This code was taken out of recordmcount.c written by
5 * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved.
7 * The original code had the same algorithms for both 32bit
8 * and 64bit ELF files, but the code was duplicated to support
9 * the difference in structures that were used. This
10 * file creates a macro of everything that is different between
11 * the 64 and 32 bit code, such that by including this header
12 * twice we can create both sets of functions by including this
13 * header once with RECORD_MCOUNT_64 undefined, and again with
16 * This conversion to macros was done by:
17 * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
19 * Licensed under the GNU General Public License, version 2 (GPLv2).
23 #undef fn_is_fake_mcount
24 #undef MIPS_is_fake_mcount
25 #undef sift_rel_mcount
27 #undef find_secsym_ndx
28 #undef __has_rel_mcount
32 #undef get_sym_str_and_relp
52 #ifdef RECORD_MCOUNT_64
53 # define append_func append64
54 # define sift_rel_mcount sift64_rel_mcount
55 # define nop_mcount nop_mcount_64
56 # define find_secsym_ndx find64_secsym_ndx
57 # define __has_rel_mcount __has64_rel_mcount
58 # define has_rel_mcount has64_rel_mcount
59 # define tot_relsize tot64_relsize
60 # define get_sym_str_and_relp get_sym_str_and_relp_64
62 # define get_mcountsym get_mcountsym_64
63 # define is_fake_mcount is_fake_mcount64
64 # define fn_is_fake_mcount fn_is_fake_mcount64
65 # define MIPS_is_fake_mcount MIPS64_is_fake_mcount
66 # define Elf_Addr Elf64_Addr
67 # define Elf_Ehdr Elf64_Ehdr
68 # define Elf_Shdr Elf64_Shdr
69 # define Elf_Rel Elf64_Rel
70 # define Elf_Rela Elf64_Rela
71 # define Elf_Sym Elf64_Sym
72 # define ELF_R_SYM ELF64_R_SYM
73 # define Elf_r_sym Elf64_r_sym
74 # define ELF_R_INFO ELF64_R_INFO
75 # define Elf_r_info Elf64_r_info
76 # define ELF_ST_BIND ELF64_ST_BIND
77 # define fn_ELF_R_SYM fn_ELF64_R_SYM
78 # define fn_ELF_R_INFO fn_ELF64_R_INFO
79 # define uint_t uint64_t
84 # define append_func append32
85 # define sift_rel_mcount sift32_rel_mcount
86 # define nop_mcount nop_mcount_32
87 # define find_secsym_ndx find32_secsym_ndx
88 # define __has_rel_mcount __has32_rel_mcount
89 # define has_rel_mcount has32_rel_mcount
90 # define tot_relsize tot32_relsize
91 # define get_sym_str_and_relp get_sym_str_and_relp_32
93 # define get_mcountsym get_mcountsym_32
94 # define is_fake_mcount is_fake_mcount32
95 # define fn_is_fake_mcount fn_is_fake_mcount32
96 # define MIPS_is_fake_mcount MIPS32_is_fake_mcount
97 # define Elf_Addr Elf32_Addr
98 # define Elf_Ehdr Elf32_Ehdr
99 # define Elf_Shdr Elf32_Shdr
100 # define Elf_Rel Elf32_Rel
101 # define Elf_Rela Elf32_Rela
102 # define Elf_Sym Elf32_Sym
103 # define ELF_R_SYM ELF32_R_SYM
104 # define Elf_r_sym Elf32_r_sym
105 # define ELF_R_INFO ELF32_R_INFO
106 # define Elf_r_info Elf32_r_info
107 # define ELF_ST_BIND ELF32_ST_BIND
108 # define fn_ELF_R_SYM fn_ELF32_R_SYM
109 # define fn_ELF_R_INFO fn_ELF32_R_INFO
110 # define uint_t uint32_t
116 /* Functions and pointers that do_file() may override for specific e_machine. */
117 static int fn_is_fake_mcount(Elf_Rel const *rp)
121 static int (*is_fake_mcount)(Elf_Rel const *rp) = fn_is_fake_mcount;
123 static uint_t fn_ELF_R_SYM(Elf_Rel const *rp)
125 return ELF_R_SYM(_w(rp->r_info));
127 static uint_t (*Elf_r_sym)(Elf_Rel const *rp) = fn_ELF_R_SYM;
129 static void fn_ELF_R_INFO(Elf_Rel *const rp, unsigned sym, unsigned type)
131 rp->r_info = _w(ELF_R_INFO(sym, type));
133 static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO;
136 * MIPS mcount long call has 2 _mcount symbols, only the position of the 1st
137 * _mcount symbol is needed for dynamic function tracer, with it, to disable
138 * tracing(ftrace_make_nop), the instruction in the position is replaced with
139 * the "b label" instruction, to enable tracing(ftrace_make_call), replace the
140 * instruction back. So, here, we set the 2nd one as fake and filter it.
142 * c: 3c030000 lui v1,0x0 <--> b label
143 * c: R_MIPS_HI16 _mcount
144 * c: R_MIPS_NONE *ABS*
145 * c: R_MIPS_NONE *ABS*
146 * 10: 64630000 daddiu v1,v1,0
147 * 10: R_MIPS_LO16 _mcount
148 * 10: R_MIPS_NONE *ABS*
149 * 10: R_MIPS_NONE *ABS*
150 * 14: 03e0082d move at,ra
151 * 18: 0060f809 jalr v1
154 #define MIPS_FAKEMCOUNT_OFFSET 4
156 static int MIPS_is_fake_mcount(Elf_Rel const *rp)
158 static Elf_Addr old_r_offset;
159 Elf_Addr current_r_offset = _w(rp->r_offset);
162 is_fake = old_r_offset &&
163 (current_r_offset - old_r_offset == MIPS_FAKEMCOUNT_OFFSET);
164 old_r_offset = current_r_offset;
169 /* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */
170 static void append_func(Elf_Ehdr *const ehdr,
171 Elf_Shdr *const shstr,
172 uint_t const *const mloc0,
173 uint_t const *const mlocp,
174 Elf_Rel const *const mrel0,
175 Elf_Rel const *const mrelp,
176 unsigned int const rel_entsize,
177 unsigned int const symsec_sh_link)
179 /* Begin constructing output file */
181 char const *mc_name = (sizeof(Elf_Rela) == rel_entsize)
182 ? ".rela__mcount_loc"
183 : ".rel__mcount_loc";
184 unsigned const old_shnum = w2(ehdr->e_shnum);
185 uint_t const old_shoff = _w(ehdr->e_shoff);
186 uint_t const old_shstr_sh_size = _w(shstr->sh_size);
187 uint_t const old_shstr_sh_offset = _w(shstr->sh_offset);
188 uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size);
191 shstr->sh_size = _w(t);
192 shstr->sh_offset = _w(sb.st_size);
194 t += (_align & -t); /* word-byte align */
197 /* body for new shstrtab */
198 ulseek(fd_map, sb.st_size, SEEK_SET);
199 uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size);
200 uwrite(fd_map, mc_name, 1 + strlen(mc_name));
202 /* old(modified) Elf_Shdr table, word-byte aligned */
203 ulseek(fd_map, t, SEEK_SET);
204 t += sizeof(Elf_Shdr) * old_shnum;
205 uwrite(fd_map, old_shoff + (void *)ehdr,
206 sizeof(Elf_Shdr) * old_shnum);
208 /* new sections __mcount_loc and .rel__mcount_loc */
209 t += 2*sizeof(mcsec);
210 mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel")
211 + old_shstr_sh_size);
212 mcsec.sh_type = w(SHT_PROGBITS);
213 mcsec.sh_flags = _w(SHF_ALLOC);
215 mcsec.sh_offset = _w(t);
216 mcsec.sh_size = _w((void *)mlocp - (void *)mloc0);
219 mcsec.sh_addralign = _w(_size);
220 mcsec.sh_entsize = _w(_size);
221 uwrite(fd_map, &mcsec, sizeof(mcsec));
223 mcsec.sh_name = w(old_shstr_sh_size);
224 mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize)
229 mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t);
230 mcsec.sh_size = _w((void *)mrelp - (void *)mrel0);
231 mcsec.sh_link = w(symsec_sh_link);
232 mcsec.sh_info = w(old_shnum);
233 mcsec.sh_addralign = _w(_size);
234 mcsec.sh_entsize = _w(rel_entsize);
235 uwrite(fd_map, &mcsec, sizeof(mcsec));
237 uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0);
238 uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0);
240 ehdr->e_shoff = _w(new_e_shoff);
241 ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum)); /* {.rel,}__mcount_loc */
242 ulseek(fd_map, 0, SEEK_SET);
243 uwrite(fd_map, ehdr, sizeof(*ehdr));
246 static unsigned get_mcountsym(Elf_Sym const *const sym0,
248 char const *const str0)
250 unsigned mcountsym = 0;
252 Elf_Sym const *const symp =
253 &sym0[Elf_r_sym(relp)];
254 char const *symname = &str0[w(symp->st_name)];
255 char const *mcount = gpfx == '_' ? "_mcount" : "mcount";
257 if (symname[0] == '.')
258 ++symname; /* ppc64 hack */
259 if (strcmp(mcount, symname) == 0 ||
260 (altmcount && strcmp(altmcount, symname) == 0))
261 mcountsym = Elf_r_sym(relp);
266 static void get_sym_str_and_relp(Elf_Shdr const *const relhdr,
267 Elf_Ehdr const *const ehdr,
268 Elf_Sym const **sym0,
270 Elf_Rel const **relp)
272 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
274 unsigned const symsec_sh_link = w(relhdr->sh_link);
275 Elf_Shdr const *const symsec = &shdr0[symsec_sh_link];
276 Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)];
277 Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset)
280 *sym0 = (Elf_Sym const *)(_w(symsec->sh_offset)
283 *str0 = (char const *)(_w(strsec->sh_offset)
290 * Look at the relocations in order to find the calls to mcount.
291 * Accumulate the section offsets that are found, and their relocation info,
292 * onto the end of the existing arrays.
294 static uint_t *sift_rel_mcount(uint_t *mlocp,
295 unsigned const offbase,
296 Elf_Rel **const mrelpp,
297 Elf_Shdr const *const relhdr,
298 Elf_Ehdr const *const ehdr,
299 unsigned const recsym,
301 unsigned const reltype)
303 uint_t *const mloc0 = mlocp;
304 Elf_Rel *mrelp = *mrelpp;
308 unsigned rel_entsize = _w(relhdr->sh_entsize);
309 unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
310 unsigned mcountsym = 0;
313 get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp);
315 for (t = nrel; t; --t) {
317 mcountsym = get_mcountsym(sym0, relp, str0);
319 if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
320 uint_t const addend = _w(_w(relp->r_offset) - recval);
322 mrelp->r_offset = _w(offbase
323 + ((void *)mlocp - (void *)mloc0));
324 Elf_r_info(mrelp, recsym, reltype);
325 if (rel_entsize == sizeof(Elf_Rela)) {
326 ((Elf_Rela *)mrelp)->r_addend = addend;
331 mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp);
333 relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
340 * Read the relocation table again, but this time its called on sections
341 * that are not going to be traced. The mcount calls here will be converted
344 static void nop_mcount(Elf_Shdr const *const relhdr,
345 Elf_Ehdr const *const ehdr,
346 const char *const txtname)
348 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
353 Elf_Shdr const *const shdr = &shdr0[w(relhdr->sh_info)];
354 unsigned rel_entsize = _w(relhdr->sh_entsize);
355 unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
356 unsigned mcountsym = 0;
360 get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp);
362 for (t = nrel; t; --t) {
366 mcountsym = get_mcountsym(sym0, relp, str0);
368 if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
370 ret = make_nop((void *)ehdr, shdr->sh_offset + relp->r_offset);
371 if (warn_on_notrace_sect && !once) {
372 printf("Section %s has mcount callers being ignored\n",
382 * If we successfully removed the mcount, mark the relocation
383 * as a nop (don't do anything with it).
387 rel = *(Elf_Rel *)relp;
388 Elf_r_info(&rel, Elf_r_sym(relp), rel_type_nop);
389 ulseek(fd_map, (void *)relp - (void *)ehdr, SEEK_SET);
390 uwrite(fd_map, &rel, sizeof(rel));
392 relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
398 * Find a symbol in the given section, to be used as the base for relocating
399 * the table of offsets of calls to mcount. A local or global symbol suffices,
400 * but avoid a Weak symbol because it may be overridden; the change in value
401 * would invalidate the relocations of the offsets of the calls to mcount.
402 * Often the found symbol will be the unnamed local symbol generated by
403 * GNU 'as' for the start of each section. For example:
404 * Num: Value Size Type Bind Vis Ndx Name
405 * 2: 00000000 0 SECTION LOCAL DEFAULT 1
407 static unsigned find_secsym_ndx(unsigned const txtndx,
408 char const *const txtname,
409 uint_t *const recvalp,
410 Elf_Shdr const *const symhdr,
411 Elf_Ehdr const *const ehdr)
413 Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset)
415 unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize);
419 for (symp = sym0, t = nsym; t; --t, ++symp) {
420 unsigned int const st_bind = ELF_ST_BIND(symp->st_info);
422 if (txtndx == w2(symp->st_shndx)
424 && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) {
425 *recvalp = _w(symp->st_value);
429 fprintf(stderr, "Cannot find symbol for section %d: %s.\n",
435 /* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */
437 __has_rel_mcount(Elf_Shdr const *const relhdr, /* is SHT_REL or SHT_RELA */
438 Elf_Shdr const *const shdr0,
439 char const *const shstrtab,
440 char const *const fname)
442 /* .sh_info depends on .sh_type == SHT_REL[,A] */
443 Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)];
444 char const *const txtname = &shstrtab[w(txthdr->sh_name)];
446 if (strcmp("__mcount_loc", txtname) == 0) {
447 fprintf(stderr, "warning: __mcount_loc already exists: %s\n",
451 if (w(txthdr->sh_type) != SHT_PROGBITS ||
452 !(w(txthdr->sh_flags) & SHF_EXECINSTR))
457 static char const *has_rel_mcount(Elf_Shdr const *const relhdr,
458 Elf_Shdr const *const shdr0,
459 char const *const shstrtab,
460 char const *const fname)
462 if (w(relhdr->sh_type) != SHT_REL && w(relhdr->sh_type) != SHT_RELA)
464 return __has_rel_mcount(relhdr, shdr0, shstrtab, fname);
468 static unsigned tot_relsize(Elf_Shdr const *const shdr0,
470 const char *const shstrtab,
471 const char *const fname)
473 unsigned totrelsz = 0;
474 Elf_Shdr const *shdrp = shdr0;
477 for (; nhdr; --nhdr, ++shdrp) {
478 txtname = has_rel_mcount(shdrp, shdr0, shstrtab, fname);
479 if (txtname && is_mcounted_section_name(txtname))
480 totrelsz += _w(shdrp->sh_size);
486 /* Overall supervision for Elf32 ET_REL file. */
488 do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype)
490 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
492 unsigned const nhdr = w2(ehdr->e_shnum);
493 Elf_Shdr *const shstr = &shdr0[w2(ehdr->e_shstrndx)];
494 char const *const shstrtab = (char const *)(_w(shstr->sh_offset)
497 Elf_Shdr const *relhdr;
500 /* Upper bound on space: assume all relevant relocs are for mcount. */
501 unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname);
502 Elf_Rel *const mrel0 = umalloc(totrelsz);
503 Elf_Rel * mrelp = mrel0;
505 /* 2*sizeof(address) <= sizeof(Elf_Rel) */
506 uint_t *const mloc0 = umalloc(totrelsz>>1);
507 uint_t * mlocp = mloc0;
509 unsigned rel_entsize = 0;
510 unsigned symsec_sh_link = 0;
512 for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {
513 char const *const txtname = has_rel_mcount(relhdr, shdr0,
515 if (txtname && is_mcounted_section_name(txtname)) {
517 unsigned const recsym = find_secsym_ndx(
518 w(relhdr->sh_info), txtname, &recval,
519 &shdr0[symsec_sh_link = w(relhdr->sh_link)],
522 rel_entsize = _w(relhdr->sh_entsize);
523 mlocp = sift_rel_mcount(mlocp,
524 (void *)mlocp - (void *)mloc0, &mrelp,
525 relhdr, ehdr, recsym, recval, reltype);
526 } else if (txtname && (warn_on_notrace_sect || make_nop)) {
528 * This section is ignored by ftrace, but still
529 * has mcount calls. Convert them to nops now.
531 nop_mcount(relhdr, ehdr, txtname);
534 if (mloc0 != mlocp) {
535 append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp,
536 rel_entsize, symsec_sh_link);