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1/*
2 * recordmcount.h
3 *
4 * This code was taken out of recordmcount.c written by
5 * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved.
6 *
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
14 * it defined.
15 *
16 * This conversion to macros was done by:
17 * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
18 *
19 * Licensed under the GNU General Public License, version 2 (GPLv2).
20 */
21#undef append_func
22#undef is_fake_mcount
23#undef fn_is_fake_mcount
24#undef MIPS_is_fake_mcount
25#undef mcount_adjust
26#undef sift_rel_mcount
27#undef nop_mcount
28#undef find_secsym_ndx
29#undef __has_rel_mcount
30#undef has_rel_mcount
31#undef tot_relsize
32#undef get_mcountsym
33#undef get_sym_str_and_relp
34#undef do_func
35#undef Elf_Addr
36#undef Elf_Ehdr
37#undef Elf_Shdr
38#undef Elf_Rel
39#undef Elf_Rela
40#undef Elf_Sym
41#undef ELF_R_SYM
42#undef Elf_r_sym
43#undef ELF_R_INFO
44#undef Elf_r_info
45#undef ELF_ST_BIND
46#undef ELF_ST_TYPE
47#undef fn_ELF_R_SYM
48#undef fn_ELF_R_INFO
49#undef uint_t
50#undef _w
51#undef _align
52#undef _size
53
54#ifdef RECORD_MCOUNT_64
55# define append_func append64
56# define sift_rel_mcount sift64_rel_mcount
57# define nop_mcount nop_mcount_64
58# define find_secsym_ndx find64_secsym_ndx
59# define __has_rel_mcount __has64_rel_mcount
60# define has_rel_mcount has64_rel_mcount
61# define tot_relsize tot64_relsize
62# define get_sym_str_and_relp get_sym_str_and_relp_64
63# define do_func do64
64# define get_mcountsym get_mcountsym_64
65# define is_fake_mcount is_fake_mcount64
66# define fn_is_fake_mcount fn_is_fake_mcount64
67# define MIPS_is_fake_mcount MIPS64_is_fake_mcount
68# define mcount_adjust mcount_adjust_64
69# define Elf_Addr Elf64_Addr
70# define Elf_Ehdr Elf64_Ehdr
71# define Elf_Shdr Elf64_Shdr
72# define Elf_Rel Elf64_Rel
73# define Elf_Rela Elf64_Rela
74# define Elf_Sym Elf64_Sym
75# define ELF_R_SYM ELF64_R_SYM
76# define Elf_r_sym Elf64_r_sym
77# define ELF_R_INFO ELF64_R_INFO
78# define Elf_r_info Elf64_r_info
79# define ELF_ST_BIND ELF64_ST_BIND
80# define ELF_ST_TYPE ELF64_ST_TYPE
81# define fn_ELF_R_SYM fn_ELF64_R_SYM
82# define fn_ELF_R_INFO fn_ELF64_R_INFO
83# define uint_t uint64_t
84# define _w w8
85# define _align 7u
86# define _size 8
87#else
88# define append_func append32
89# define sift_rel_mcount sift32_rel_mcount
90# define nop_mcount nop_mcount_32
91# define find_secsym_ndx find32_secsym_ndx
92# define __has_rel_mcount __has32_rel_mcount
93# define has_rel_mcount has32_rel_mcount
94# define tot_relsize tot32_relsize
95# define get_sym_str_and_relp get_sym_str_and_relp_32
96# define do_func do32
97# define get_mcountsym get_mcountsym_32
98# define is_fake_mcount is_fake_mcount32
99# define fn_is_fake_mcount fn_is_fake_mcount32
100# define MIPS_is_fake_mcount MIPS32_is_fake_mcount
101# define mcount_adjust mcount_adjust_32
102# define Elf_Addr Elf32_Addr
103# define Elf_Ehdr Elf32_Ehdr
104# define Elf_Shdr Elf32_Shdr
105# define Elf_Rel Elf32_Rel
106# define Elf_Rela Elf32_Rela
107# define Elf_Sym Elf32_Sym
108# define ELF_R_SYM ELF32_R_SYM
109# define Elf_r_sym Elf32_r_sym
110# define ELF_R_INFO ELF32_R_INFO
111# define Elf_r_info Elf32_r_info
112# define ELF_ST_BIND ELF32_ST_BIND
113# define ELF_ST_TYPE ELF32_ST_TYPE
114# define fn_ELF_R_SYM fn_ELF32_R_SYM
115# define fn_ELF_R_INFO fn_ELF32_R_INFO
116# define uint_t uint32_t
117# define _w w
118# define _align 3u
119# define _size 4
120#endif
121
122/* Functions and pointers that do_file() may override for specific e_machine. */
123static int fn_is_fake_mcount(Elf_Rel const *rp)
124{
125 return 0;
126}
127static int (*is_fake_mcount)(Elf_Rel const *rp) = fn_is_fake_mcount;
128
129static uint_t fn_ELF_R_SYM(Elf_Rel const *rp)
130{
131 return ELF_R_SYM(_w(rp->r_info));
132}
133static uint_t (*Elf_r_sym)(Elf_Rel const *rp) = fn_ELF_R_SYM;
134
135static void fn_ELF_R_INFO(Elf_Rel *const rp, unsigned sym, unsigned type)
136{
137 rp->r_info = _w(ELF_R_INFO(sym, type));
138}
139static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO;
140
141static int mcount_adjust = 0;
142
143/*
144 * MIPS mcount long call has 2 _mcount symbols, only the position of the 1st
145 * _mcount symbol is needed for dynamic function tracer, with it, to disable
146 * tracing(ftrace_make_nop), the instruction in the position is replaced with
147 * the "b label" instruction, to enable tracing(ftrace_make_call), replace the
148 * instruction back. So, here, we set the 2nd one as fake and filter it.
149 *
150 * c: 3c030000 lui v1,0x0 <--> b label
151 * c: R_MIPS_HI16 _mcount
152 * c: R_MIPS_NONE *ABS*
153 * c: R_MIPS_NONE *ABS*
154 * 10: 64630000 daddiu v1,v1,0
155 * 10: R_MIPS_LO16 _mcount
156 * 10: R_MIPS_NONE *ABS*
157 * 10: R_MIPS_NONE *ABS*
158 * 14: 03e0082d move at,ra
159 * 18: 0060f809 jalr v1
160 * label:
161 */
162#define MIPS_FAKEMCOUNT_OFFSET 4
163
164static int MIPS_is_fake_mcount(Elf_Rel const *rp)
165{
166 static Elf_Addr old_r_offset;
167 Elf_Addr current_r_offset = _w(rp->r_offset);
168 int is_fake;
169
170 is_fake = old_r_offset &&
171 (current_r_offset - old_r_offset == MIPS_FAKEMCOUNT_OFFSET);
172 old_r_offset = current_r_offset;
173
174 return is_fake;
175}
176
177/* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */
178static void append_func(Elf_Ehdr *const ehdr,
179 Elf_Shdr *const shstr,
180 uint_t const *const mloc0,
181 uint_t const *const mlocp,
182 Elf_Rel const *const mrel0,
183 Elf_Rel const *const mrelp,
184 unsigned int const rel_entsize,
185 unsigned int const symsec_sh_link)
186{
187 /* Begin constructing output file */
188 Elf_Shdr mcsec;
189 char const *mc_name = (sizeof(Elf_Rela) == rel_entsize)
190 ? ".rela__mcount_loc"
191 : ".rel__mcount_loc";
192 unsigned const old_shnum = w2(ehdr->e_shnum);
193 uint_t const old_shoff = _w(ehdr->e_shoff);
194 uint_t const old_shstr_sh_size = _w(shstr->sh_size);
195 uint_t const old_shstr_sh_offset = _w(shstr->sh_offset);
196 uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size);
197 uint_t new_e_shoff;
198
199 shstr->sh_size = _w(t);
200 shstr->sh_offset = _w(sb.st_size);
201 t += sb.st_size;
202 t += (_align & -t); /* word-byte align */
203 new_e_shoff = t;
204
205 /* body for new shstrtab */
206 ulseek(fd_map, sb.st_size, SEEK_SET);
207 uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size);
208 uwrite(fd_map, mc_name, 1 + strlen(mc_name));
209
210 /* old(modified) Elf_Shdr table, word-byte aligned */
211 ulseek(fd_map, t, SEEK_SET);
212 t += sizeof(Elf_Shdr) * old_shnum;
213 uwrite(fd_map, old_shoff + (void *)ehdr,
214 sizeof(Elf_Shdr) * old_shnum);
215
216 /* new sections __mcount_loc and .rel__mcount_loc */
217 t += 2*sizeof(mcsec);
218 mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel")
219 + old_shstr_sh_size);
220 mcsec.sh_type = w(SHT_PROGBITS);
221 mcsec.sh_flags = _w(SHF_ALLOC);
222 mcsec.sh_addr = 0;
223 mcsec.sh_offset = _w(t);
224 mcsec.sh_size = _w((void *)mlocp - (void *)mloc0);
225 mcsec.sh_link = 0;
226 mcsec.sh_info = 0;
227 mcsec.sh_addralign = _w(_size);
228 mcsec.sh_entsize = _w(_size);
229 uwrite(fd_map, &mcsec, sizeof(mcsec));
230
231 mcsec.sh_name = w(old_shstr_sh_size);
232 mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize)
233 ? w(SHT_RELA)
234 : w(SHT_REL);
235 mcsec.sh_flags = 0;
236 mcsec.sh_addr = 0;
237 mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t);
238 mcsec.sh_size = _w((void *)mrelp - (void *)mrel0);
239 mcsec.sh_link = w(symsec_sh_link);
240 mcsec.sh_info = w(old_shnum);
241 mcsec.sh_addralign = _w(_size);
242 mcsec.sh_entsize = _w(rel_entsize);
243 uwrite(fd_map, &mcsec, sizeof(mcsec));
244
245 uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0);
246 uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0);
247
248 ehdr->e_shoff = _w(new_e_shoff);
249 ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum)); /* {.rel,}__mcount_loc */
250 ulseek(fd_map, 0, SEEK_SET);
251 uwrite(fd_map, ehdr, sizeof(*ehdr));
252}
253
254static unsigned get_mcountsym(Elf_Sym const *const sym0,
255 Elf_Rel const *relp,
256 char const *const str0)
257{
258 unsigned mcountsym = 0;
259
260 Elf_Sym const *const symp =
261 &sym0[Elf_r_sym(relp)];
262 char const *symname = &str0[w(symp->st_name)];
263 char const *mcount = gpfx == '_' ? "_mcount" : "mcount";
264
265 if (symname[0] == '.')
266 ++symname; /* ppc64 hack */
267 if (strcmp(mcount, symname) == 0 ||
268 (altmcount && strcmp(altmcount, symname) == 0))
269 mcountsym = Elf_r_sym(relp);
270
271 return mcountsym;
272}
273
274static void get_sym_str_and_relp(Elf_Shdr const *const relhdr,
275 Elf_Ehdr const *const ehdr,
276 Elf_Sym const **sym0,
277 char const **str0,
278 Elf_Rel const **relp)
279{
280 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
281 + (void *)ehdr);
282 unsigned const symsec_sh_link = w(relhdr->sh_link);
283 Elf_Shdr const *const symsec = &shdr0[symsec_sh_link];
284 Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)];
285 Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset)
286 + (void *)ehdr);
287
288 *sym0 = (Elf_Sym const *)(_w(symsec->sh_offset)
289 + (void *)ehdr);
290
291 *str0 = (char const *)(_w(strsec->sh_offset)
292 + (void *)ehdr);
293
294 *relp = rel0;
295}
296
297/*
298 * Look at the relocations in order to find the calls to mcount.
299 * Accumulate the section offsets that are found, and their relocation info,
300 * onto the end of the existing arrays.
301 */
302static uint_t *sift_rel_mcount(uint_t *mlocp,
303 unsigned const offbase,
304 Elf_Rel **const mrelpp,
305 Elf_Shdr const *const relhdr,
306 Elf_Ehdr const *const ehdr,
307 unsigned const recsym,
308 uint_t const recval,
309 unsigned const reltype)
310{
311 uint_t *const mloc0 = mlocp;
312 Elf_Rel *mrelp = *mrelpp;
313 Elf_Sym const *sym0;
314 char const *str0;
315 Elf_Rel const *relp;
316 unsigned rel_entsize = _w(relhdr->sh_entsize);
317 unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
318 unsigned mcountsym = 0;
319 unsigned t;
320
321 get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp);
322
323 for (t = nrel; t; --t) {
324 if (!mcountsym)
325 mcountsym = get_mcountsym(sym0, relp, str0);
326
327 if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
328 uint_t const addend =
329 _w(_w(relp->r_offset) - recval + mcount_adjust);
330 mrelp->r_offset = _w(offbase
331 + ((void *)mlocp - (void *)mloc0));
332 Elf_r_info(mrelp, recsym, reltype);
333 if (rel_entsize == sizeof(Elf_Rela)) {
334 ((Elf_Rela *)mrelp)->r_addend = addend;
335 *mlocp++ = 0;
336 } else
337 *mlocp++ = addend;
338
339 mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp);
340 }
341 relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
342 }
343 *mrelpp = mrelp;
344 return mlocp;
345}
346
347/*
348 * Read the relocation table again, but this time its called on sections
349 * that are not going to be traced. The mcount calls here will be converted
350 * into nops.
351 */
352static void nop_mcount(Elf_Shdr const *const relhdr,
353 Elf_Ehdr const *const ehdr,
354 const char *const txtname)
355{
356 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
357 + (void *)ehdr);
358 Elf_Sym const *sym0;
359 char const *str0;
360 Elf_Rel const *relp;
361 Elf_Shdr const *const shdr = &shdr0[w(relhdr->sh_info)];
362 unsigned rel_entsize = _w(relhdr->sh_entsize);
363 unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
364 unsigned mcountsym = 0;
365 unsigned t;
366 int once = 0;
367
368 get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp);
369
370 for (t = nrel; t; --t) {
371 int ret = -1;
372
373 if (!mcountsym)
374 mcountsym = get_mcountsym(sym0, relp, str0);
375
376 if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
377 if (make_nop)
378 ret = make_nop((void *)ehdr, shdr->sh_offset + relp->r_offset);
379 if (warn_on_notrace_sect && !once) {
380 printf("Section %s has mcount callers being ignored\n",
381 txtname);
382 once = 1;
383 /* just warn? */
384 if (!make_nop)
385 return;
386 }
387 }
388
389 /*
390 * If we successfully removed the mcount, mark the relocation
391 * as a nop (don't do anything with it).
392 */
393 if (!ret) {
394 Elf_Rel rel;
395 rel = *(Elf_Rel *)relp;
396 Elf_r_info(&rel, Elf_r_sym(relp), rel_type_nop);
397 ulseek(fd_map, (void *)relp - (void *)ehdr, SEEK_SET);
398 uwrite(fd_map, &rel, sizeof(rel));
399 }
400 relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
401 }
402}
403
404
405/*
406 * Find a symbol in the given section, to be used as the base for relocating
407 * the table of offsets of calls to mcount. A local or global symbol suffices,
408 * but avoid a Weak symbol because it may be overridden; the change in value
409 * would invalidate the relocations of the offsets of the calls to mcount.
410 * Often the found symbol will be the unnamed local symbol generated by
411 * GNU 'as' for the start of each section. For example:
412 * Num: Value Size Type Bind Vis Ndx Name
413 * 2: 00000000 0 SECTION LOCAL DEFAULT 1
414 */
415static unsigned find_secsym_ndx(unsigned const txtndx,
416 char const *const txtname,
417 uint_t *const recvalp,
418 Elf_Shdr const *const symhdr,
419 Elf_Ehdr const *const ehdr)
420{
421 Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset)
422 + (void *)ehdr);
423 unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize);
424 Elf_Sym const *symp;
425 unsigned t;
426
427 for (symp = sym0, t = nsym; t; --t, ++symp) {
428 unsigned int const st_bind = ELF_ST_BIND(symp->st_info);
429
430 if (txtndx == w2(symp->st_shndx)
431 /* avoid STB_WEAK */
432 && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) {
433 /* function symbols on ARM have quirks, avoid them */
434 if (w2(ehdr->e_machine) == EM_ARM
435 && ELF_ST_TYPE(symp->st_info) == STT_FUNC)
436 continue;
437
438 *recvalp = _w(symp->st_value);
439 return symp - sym0;
440 }
441 }
442 fprintf(stderr, "Cannot find symbol for section %d: %s.\n",
443 txtndx, txtname);
444 fail_file();
445}
446
447
448/* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */
449static char const *
450__has_rel_mcount(Elf_Shdr const *const relhdr, /* is SHT_REL or SHT_RELA */
451 Elf_Shdr const *const shdr0,
452 char const *const shstrtab,
453 char const *const fname)
454{
455 /* .sh_info depends on .sh_type == SHT_REL[,A] */
456 Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)];
457 char const *const txtname = &shstrtab[w(txthdr->sh_name)];
458
459 if (strcmp("__mcount_loc", txtname) == 0) {
460 fprintf(stderr, "warning: __mcount_loc already exists: %s\n",
461 fname);
462 succeed_file();
463 }
464 if (w(txthdr->sh_type) != SHT_PROGBITS ||
465 !(_w(txthdr->sh_flags) & SHF_EXECINSTR))
466 return NULL;
467 return txtname;
468}
469
470static char const *has_rel_mcount(Elf_Shdr const *const relhdr,
471 Elf_Shdr const *const shdr0,
472 char const *const shstrtab,
473 char const *const fname)
474{
475 if (w(relhdr->sh_type) != SHT_REL && w(relhdr->sh_type) != SHT_RELA)
476 return NULL;
477 return __has_rel_mcount(relhdr, shdr0, shstrtab, fname);
478}
479
480
481static unsigned tot_relsize(Elf_Shdr const *const shdr0,
482 unsigned nhdr,
483 const char *const shstrtab,
484 const char *const fname)
485{
486 unsigned totrelsz = 0;
487 Elf_Shdr const *shdrp = shdr0;
488 char const *txtname;
489
490 for (; nhdr; --nhdr, ++shdrp) {
491 txtname = has_rel_mcount(shdrp, shdr0, shstrtab, fname);
492 if (txtname && is_mcounted_section_name(txtname))
493 totrelsz += _w(shdrp->sh_size);
494 }
495 return totrelsz;
496}
497
498
499/* Overall supervision for Elf32 ET_REL file. */
500static void
501do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype)
502{
503 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
504 + (void *)ehdr);
505 unsigned const nhdr = w2(ehdr->e_shnum);
506 Elf_Shdr *const shstr = &shdr0[w2(ehdr->e_shstrndx)];
507 char const *const shstrtab = (char const *)(_w(shstr->sh_offset)
508 + (void *)ehdr);
509
510 Elf_Shdr const *relhdr;
511 unsigned k;
512
513 /* Upper bound on space: assume all relevant relocs are for mcount. */
514 unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname);
515 Elf_Rel *const mrel0 = umalloc(totrelsz);
516 Elf_Rel * mrelp = mrel0;
517
518 /* 2*sizeof(address) <= sizeof(Elf_Rel) */
519 uint_t *const mloc0 = umalloc(totrelsz>>1);
520 uint_t * mlocp = mloc0;
521
522 unsigned rel_entsize = 0;
523 unsigned symsec_sh_link = 0;
524
525 for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {
526 char const *const txtname = has_rel_mcount(relhdr, shdr0,
527 shstrtab, fname);
528 if (txtname && is_mcounted_section_name(txtname)) {
529 uint_t recval = 0;
530 unsigned const recsym = find_secsym_ndx(
531 w(relhdr->sh_info), txtname, &recval,
532 &shdr0[symsec_sh_link = w(relhdr->sh_link)],
533 ehdr);
534
535 rel_entsize = _w(relhdr->sh_entsize);
536 mlocp = sift_rel_mcount(mlocp,
537 (void *)mlocp - (void *)mloc0, &mrelp,
538 relhdr, ehdr, recsym, recval, reltype);
539 } else if (txtname && (warn_on_notrace_sect || make_nop)) {
540 /*
541 * This section is ignored by ftrace, but still
542 * has mcount calls. Convert them to nops now.
543 */
544 nop_mcount(relhdr, ehdr, txtname);
545 }
546 }
547 if (mloc0 != mlocp) {
548 append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp,
549 rel_entsize, symsec_sh_link);
550 }
551 free(mrel0);
552 free(mloc0);
553}