1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
2 | /* |
3 | * recordmcount.h |
4 | * |
5 | * This code was taken out of recordmcount.c written by |
6 | * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved. |
7 | * |
8 | * The original code had the same algorithms for both 32bit |
9 | * and 64bit ELF files, but the code was duplicated to support |
10 | * the difference in structures that were used. This |
11 | * file creates a macro of everything that is different between |
12 | * the 64 and 32 bit code, such that by including this header |
13 | * twice we can create both sets of functions by including this |
14 | * header once with RECORD_MCOUNT_64 undefined, and again with |
15 | * it defined. |
16 | * |
17 | * This conversion to macros was done by: |
18 | * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc. |
19 | */ |
20 | #undef append_func |
21 | #undef is_fake_mcount |
22 | #undef fn_is_fake_mcount |
23 | #undef MIPS_is_fake_mcount |
24 | #undef mcount_adjust |
25 | #undef sift_rel_mcount |
26 | #undef nop_mcount |
27 | #undef find_secsym_ndx |
28 | #undef __has_rel_mcount |
29 | #undef has_rel_mcount |
30 | #undef tot_relsize |
31 | #undef get_mcountsym |
32 | #undef find_symtab |
33 | #undef get_shnum |
34 | #undef set_shnum |
35 | #undef get_shstrndx |
36 | #undef get_symindex |
37 | #undef get_sym_str_and_relp |
38 | #undef do_func |
39 | #undef Elf_Addr |
40 | #undef Elf_Ehdr |
41 | #undef Elf_Shdr |
42 | #undef Elf_Rel |
43 | #undef Elf_Rela |
44 | #undef Elf_Sym |
45 | #undef ELF_R_SYM |
46 | #undef Elf_r_sym |
47 | #undef ELF_R_INFO |
48 | #undef Elf_r_info |
49 | #undef ELF_ST_BIND |
50 | #undef ELF_ST_TYPE |
51 | #undef fn_ELF_R_SYM |
52 | #undef fn_ELF_R_INFO |
53 | #undef uint_t |
54 | #undef _w |
55 | #undef _align |
56 | #undef _size |
57 | |
58 | #ifdef RECORD_MCOUNT_64 |
59 | # define append_func append64 |
60 | # define sift_rel_mcount sift64_rel_mcount |
61 | # define nop_mcount nop_mcount_64 |
62 | # define find_secsym_ndx find64_secsym_ndx |
63 | # define __has_rel_mcount __has64_rel_mcount |
64 | # define has_rel_mcount has64_rel_mcount |
65 | # define tot_relsize tot64_relsize |
66 | # define find_symtab find_symtab64 |
67 | # define get_shnum get_shnum64 |
68 | # define set_shnum set_shnum64 |
69 | # define get_shstrndx get_shstrndx64 |
70 | # define get_symindex get_symindex64 |
71 | # define get_sym_str_and_relp get_sym_str_and_relp_64 |
72 | # define do_func do64 |
73 | # define get_mcountsym get_mcountsym_64 |
74 | # define is_fake_mcount is_fake_mcount64 |
75 | # define fn_is_fake_mcount fn_is_fake_mcount64 |
76 | # define MIPS_is_fake_mcount MIPS64_is_fake_mcount |
77 | # define mcount_adjust mcount_adjust_64 |
78 | # define Elf_Addr Elf64_Addr |
79 | # define Elf_Ehdr Elf64_Ehdr |
80 | # define Elf_Shdr Elf64_Shdr |
81 | # define Elf_Rel Elf64_Rel |
82 | # define Elf_Rela Elf64_Rela |
83 | # define Elf_Sym Elf64_Sym |
84 | # define ELF_R_SYM ELF64_R_SYM |
85 | # define Elf_r_sym Elf64_r_sym |
86 | # define ELF_R_INFO ELF64_R_INFO |
87 | # define Elf_r_info Elf64_r_info |
88 | # define ELF_ST_BIND ELF64_ST_BIND |
89 | # define ELF_ST_TYPE ELF64_ST_TYPE |
90 | # define fn_ELF_R_SYM fn_ELF64_R_SYM |
91 | # define fn_ELF_R_INFO fn_ELF64_R_INFO |
92 | # define uint_t uint64_t |
93 | # define _w w8 |
94 | # define _align 7u |
95 | # define _size 8 |
96 | #else |
97 | # define append_func append32 |
98 | # define sift_rel_mcount sift32_rel_mcount |
99 | # define nop_mcount nop_mcount_32 |
100 | # define find_secsym_ndx find32_secsym_ndx |
101 | # define __has_rel_mcount __has32_rel_mcount |
102 | # define has_rel_mcount has32_rel_mcount |
103 | # define tot_relsize tot32_relsize |
104 | # define find_symtab find_symtab32 |
105 | # define get_shnum get_shnum32 |
106 | # define set_shnum set_shnum32 |
107 | # define get_shstrndx get_shstrndx32 |
108 | # define get_symindex get_symindex32 |
109 | # define get_sym_str_and_relp get_sym_str_and_relp_32 |
110 | # define do_func do32 |
111 | # define get_mcountsym get_mcountsym_32 |
112 | # define is_fake_mcount is_fake_mcount32 |
113 | # define fn_is_fake_mcount fn_is_fake_mcount32 |
114 | # define MIPS_is_fake_mcount MIPS32_is_fake_mcount |
115 | # define mcount_adjust mcount_adjust_32 |
116 | # define Elf_Addr Elf32_Addr |
117 | # define Elf_Ehdr Elf32_Ehdr |
118 | # define Elf_Shdr Elf32_Shdr |
119 | # define Elf_Rel Elf32_Rel |
120 | # define Elf_Rela Elf32_Rela |
121 | # define Elf_Sym Elf32_Sym |
122 | # define ELF_R_SYM ELF32_R_SYM |
123 | # define Elf_r_sym Elf32_r_sym |
124 | # define ELF_R_INFO ELF32_R_INFO |
125 | # define Elf_r_info Elf32_r_info |
126 | # define ELF_ST_BIND ELF32_ST_BIND |
127 | # define ELF_ST_TYPE ELF32_ST_TYPE |
128 | # define fn_ELF_R_SYM fn_ELF32_R_SYM |
129 | # define fn_ELF_R_INFO fn_ELF32_R_INFO |
130 | # define uint_t uint32_t |
131 | # define _w w |
132 | # define _align 3u |
133 | # define _size 4 |
134 | #endif |
135 | |
136 | /* Functions and pointers that do_file() may override for specific e_machine. */ |
137 | static int fn_is_fake_mcount(Elf_Rel const *rp) |
138 | { |
139 | return 0; |
140 | } |
141 | static int (*is_fake_mcount)(Elf_Rel const *rp) = fn_is_fake_mcount; |
142 | |
143 | static uint_t fn_ELF_R_SYM(Elf_Rel const *rp) |
144 | { |
145 | return ELF_R_SYM(_w(rp->r_info)); |
146 | } |
147 | static uint_t (*Elf_r_sym)(Elf_Rel const *rp) = fn_ELF_R_SYM; |
148 | |
149 | static void fn_ELF_R_INFO(Elf_Rel *const rp, unsigned sym, unsigned type) |
150 | { |
151 | rp->r_info = _w(ELF_R_INFO(sym, type)); |
152 | } |
153 | static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO; |
154 | |
155 | static int mcount_adjust = 0; |
156 | |
157 | /* |
158 | * MIPS mcount long call has 2 _mcount symbols, only the position of the 1st |
159 | * _mcount symbol is needed for dynamic function tracer, with it, to disable |
160 | * tracing(ftrace_make_nop), the instruction in the position is replaced with |
161 | * the "b label" instruction, to enable tracing(ftrace_make_call), replace the |
162 | * instruction back. So, here, we set the 2nd one as fake and filter it. |
163 | * |
164 | * c: 3c030000 lui v1,0x0 <--> b label |
165 | * c: R_MIPS_HI16 _mcount |
166 | * c: R_MIPS_NONE *ABS* |
167 | * c: R_MIPS_NONE *ABS* |
168 | * 10: 64630000 daddiu v1,v1,0 |
169 | * 10: R_MIPS_LO16 _mcount |
170 | * 10: R_MIPS_NONE *ABS* |
171 | * 10: R_MIPS_NONE *ABS* |
172 | * 14: 03e0082d move at,ra |
173 | * 18: 0060f809 jalr v1 |
174 | * label: |
175 | */ |
176 | #define MIPS_FAKEMCOUNT_OFFSET 4 |
177 | |
178 | static int MIPS_is_fake_mcount(Elf_Rel const *rp) |
179 | { |
180 | static Elf_Addr old_r_offset = ~(Elf_Addr)0; |
181 | Elf_Addr current_r_offset = _w(rp->r_offset); |
182 | int is_fake; |
183 | |
184 | is_fake = (old_r_offset != ~(Elf_Addr)0) && |
185 | (current_r_offset - old_r_offset == MIPS_FAKEMCOUNT_OFFSET); |
186 | old_r_offset = current_r_offset; |
187 | |
188 | return is_fake; |
189 | } |
190 | |
191 | static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab, |
192 | Elf32_Word const *symtab_shndx) |
193 | { |
194 | unsigned long offset; |
195 | unsigned short shndx = w2(sym->st_shndx); |
196 | int index; |
197 | |
198 | if (shndx > SHN_UNDEF && shndx < SHN_LORESERVE) |
199 | return shndx; |
200 | |
201 | if (shndx == SHN_XINDEX) { |
202 | offset = (unsigned long)sym - (unsigned long)symtab; |
203 | index = offset / sizeof(*sym); |
204 | |
205 | return w(symtab_shndx[index]); |
206 | } |
207 | |
208 | return 0; |
209 | } |
210 | |
211 | static unsigned int get_shnum(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0) |
212 | { |
213 | if (shdr0 && !ehdr->e_shnum) |
214 | return w(shdr0->sh_size); |
215 | |
216 | return w2(ehdr->e_shnum); |
217 | } |
218 | |
219 | static void set_shnum(Elf_Ehdr *ehdr, Elf_Shdr *shdr0, unsigned int new_shnum) |
220 | { |
221 | if (new_shnum >= SHN_LORESERVE) { |
222 | ehdr->e_shnum = 0; |
223 | shdr0->sh_size = w(new_shnum); |
224 | } else |
225 | ehdr->e_shnum = w2(new_shnum); |
226 | } |
227 | |
228 | static int get_shstrndx(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0) |
229 | { |
230 | if (ehdr->e_shstrndx != SHN_XINDEX) |
231 | return w2(ehdr->e_shstrndx); |
232 | |
233 | return w(shdr0->sh_link); |
234 | } |
235 | |
236 | static void find_symtab(Elf_Ehdr *const ehdr, Elf_Shdr const *shdr0, |
237 | unsigned const nhdr, Elf32_Word **symtab, |
238 | Elf32_Word **symtab_shndx) |
239 | { |
240 | Elf_Shdr const *relhdr; |
241 | unsigned k; |
242 | |
243 | *symtab = NULL; |
244 | *symtab_shndx = NULL; |
245 | |
246 | for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) { |
247 | if (relhdr->sh_type == SHT_SYMTAB) |
248 | *symtab = (void *)ehdr + relhdr->sh_offset; |
249 | else if (relhdr->sh_type == SHT_SYMTAB_SHNDX) |
250 | *symtab_shndx = (void *)ehdr + relhdr->sh_offset; |
251 | |
252 | if (*symtab && *symtab_shndx) |
253 | break; |
254 | } |
255 | } |
256 | |
257 | /* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */ |
258 | static int append_func(Elf_Ehdr *const ehdr, |
259 | Elf_Shdr *const shstr, |
260 | uint_t const *const mloc0, |
261 | uint_t const *const mlocp, |
262 | Elf_Rel const *const mrel0, |
263 | Elf_Rel const *const mrelp, |
264 | unsigned int const rel_entsize, |
265 | unsigned int const symsec_sh_link) |
266 | { |
267 | /* Begin constructing output file */ |
268 | Elf_Shdr mcsec; |
269 | char const *mc_name = (sizeof(Elf_Rela) == rel_entsize) |
270 | ? ".rela__mcount_loc" |
271 | : ".rel__mcount_loc" ; |
272 | uint_t const old_shoff = _w(ehdr->e_shoff); |
273 | uint_t const old_shstr_sh_size = _w(shstr->sh_size); |
274 | uint_t const old_shstr_sh_offset = _w(shstr->sh_offset); |
275 | Elf_Shdr *const shdr0 = (Elf_Shdr *)(old_shoff + (void *)ehdr); |
276 | unsigned int const old_shnum = get_shnum(ehdr, shdr0); |
277 | unsigned int const new_shnum = 2 + old_shnum; /* {.rel,}__mcount_loc */ |
278 | uint_t t = 1 + strlen(s: mc_name) + _w(shstr->sh_size); |
279 | uint_t new_e_shoff; |
280 | |
281 | shstr->sh_size = _w(t); |
282 | shstr->sh_offset = _w(sb.st_size); |
283 | t += sb.st_size; |
284 | t += (_align & -t); /* word-byte align */ |
285 | new_e_shoff = t; |
286 | |
287 | set_shnum(ehdr, shdr0, new_shnum); |
288 | |
289 | /* body for new shstrtab */ |
290 | if (ulseek(offset: sb.st_size, SEEK_SET) < 0) |
291 | return -1; |
292 | if (uwrite(buf: old_shstr_sh_offset + (void *)ehdr, count: old_shstr_sh_size) < 0) |
293 | return -1; |
294 | if (uwrite(buf: mc_name, count: 1 + strlen(s: mc_name)) < 0) |
295 | return -1; |
296 | |
297 | /* old(modified) Elf_Shdr table, word-byte aligned */ |
298 | if (ulseek(offset: t, SEEK_SET) < 0) |
299 | return -1; |
300 | t += sizeof(Elf_Shdr) * old_shnum; |
301 | if (uwrite(buf: old_shoff + (void *)ehdr, |
302 | count: sizeof(Elf_Shdr) * old_shnum) < 0) |
303 | return -1; |
304 | |
305 | /* new sections __mcount_loc and .rel__mcount_loc */ |
306 | t += 2*sizeof(mcsec); |
307 | mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(s: ".rel" ) |
308 | + old_shstr_sh_size); |
309 | mcsec.sh_type = w(SHT_PROGBITS); |
310 | mcsec.sh_flags = _w(SHF_ALLOC); |
311 | mcsec.sh_addr = 0; |
312 | mcsec.sh_offset = _w(t); |
313 | mcsec.sh_size = _w((void *)mlocp - (void *)mloc0); |
314 | mcsec.sh_link = 0; |
315 | mcsec.sh_info = 0; |
316 | mcsec.sh_addralign = _w(_size); |
317 | mcsec.sh_entsize = _w(_size); |
318 | if (uwrite(buf: &mcsec, count: sizeof(mcsec)) < 0) |
319 | return -1; |
320 | |
321 | mcsec.sh_name = w(old_shstr_sh_size); |
322 | mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize) |
323 | ? w(SHT_RELA) |
324 | : w(SHT_REL); |
325 | mcsec.sh_flags = 0; |
326 | mcsec.sh_addr = 0; |
327 | mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t); |
328 | mcsec.sh_size = _w((void *)mrelp - (void *)mrel0); |
329 | mcsec.sh_link = w(symsec_sh_link); |
330 | mcsec.sh_info = w(old_shnum); |
331 | mcsec.sh_addralign = _w(_size); |
332 | mcsec.sh_entsize = _w(rel_entsize); |
333 | |
334 | if (uwrite(buf: &mcsec, count: sizeof(mcsec)) < 0) |
335 | return -1; |
336 | |
337 | if (uwrite(buf: mloc0, count: (void *)mlocp - (void *)mloc0) < 0) |
338 | return -1; |
339 | if (uwrite(buf: mrel0, count: (void *)mrelp - (void *)mrel0) < 0) |
340 | return -1; |
341 | |
342 | ehdr->e_shoff = _w(new_e_shoff); |
343 | if (ulseek(offset: 0, SEEK_SET) < 0) |
344 | return -1; |
345 | if (uwrite(buf: ehdr, count: sizeof(*ehdr)) < 0) |
346 | return -1; |
347 | return 0; |
348 | } |
349 | |
350 | static unsigned get_mcountsym(Elf_Sym const *const sym0, |
351 | Elf_Rel const *relp, |
352 | char const *const str0) |
353 | { |
354 | unsigned mcountsym = 0; |
355 | |
356 | Elf_Sym const *const symp = |
357 | &sym0[Elf_r_sym(relp)]; |
358 | char const *symname = &str0[w(symp->st_name)]; |
359 | char const *mcount = gpfx == '_' ? "_mcount" : "mcount" ; |
360 | char const *fentry = "__fentry__" ; |
361 | |
362 | if (symname[0] == '.') |
363 | ++symname; /* ppc64 hack */ |
364 | if (strcmp(s1: mcount, s2: symname) == 0 || |
365 | (altmcount && strcmp(s1: altmcount, s2: symname) == 0) || |
366 | (strcmp(s1: fentry, s2: symname) == 0)) |
367 | mcountsym = Elf_r_sym(relp); |
368 | |
369 | return mcountsym; |
370 | } |
371 | |
372 | static void get_sym_str_and_relp(Elf_Shdr const *const relhdr, |
373 | Elf_Ehdr const *const ehdr, |
374 | Elf_Sym const **sym0, |
375 | char const **str0, |
376 | Elf_Rel const **relp) |
377 | { |
378 | Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) |
379 | + (void *)ehdr); |
380 | unsigned const symsec_sh_link = w(relhdr->sh_link); |
381 | Elf_Shdr const *const symsec = &shdr0[symsec_sh_link]; |
382 | Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)]; |
383 | Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset) |
384 | + (void *)ehdr); |
385 | |
386 | *sym0 = (Elf_Sym const *)(_w(symsec->sh_offset) |
387 | + (void *)ehdr); |
388 | |
389 | *str0 = (char const *)(_w(strsec->sh_offset) |
390 | + (void *)ehdr); |
391 | |
392 | *relp = rel0; |
393 | } |
394 | |
395 | /* |
396 | * Look at the relocations in order to find the calls to mcount. |
397 | * Accumulate the section offsets that are found, and their relocation info, |
398 | * onto the end of the existing arrays. |
399 | */ |
400 | static uint_t *sift_rel_mcount(uint_t *mlocp, |
401 | unsigned const offbase, |
402 | Elf_Rel **const mrelpp, |
403 | Elf_Shdr const *const relhdr, |
404 | Elf_Ehdr const *const ehdr, |
405 | unsigned const recsym, |
406 | uint_t const recval, |
407 | unsigned const reltype) |
408 | { |
409 | uint_t *const mloc0 = mlocp; |
410 | Elf_Rel *mrelp = *mrelpp; |
411 | Elf_Sym const *sym0; |
412 | char const *str0; |
413 | Elf_Rel const *relp; |
414 | unsigned rel_entsize = _w(relhdr->sh_entsize); |
415 | unsigned const nrel = _w(relhdr->sh_size) / rel_entsize; |
416 | unsigned mcountsym = 0; |
417 | unsigned t; |
418 | |
419 | get_sym_str_and_relp(relhdr, ehdr, sym0: &sym0, str0: &str0, relp: &relp); |
420 | |
421 | for (t = nrel; t; --t) { |
422 | if (!mcountsym) |
423 | mcountsym = get_mcountsym(sym0, relp, str0); |
424 | |
425 | if (mcountsym && mcountsym == Elf_r_sym(relp) && |
426 | !is_fake_mcount(relp)) { |
427 | uint_t const addend = |
428 | _w(_w(relp->r_offset) - recval + mcount_adjust); |
429 | mrelp->r_offset = _w(offbase |
430 | + ((void *)mlocp - (void *)mloc0)); |
431 | Elf_r_info(mrelp, recsym, reltype); |
432 | if (rel_entsize == sizeof(Elf_Rela)) { |
433 | ((Elf_Rela *)mrelp)->r_addend = addend; |
434 | *mlocp++ = 0; |
435 | } else |
436 | *mlocp++ = addend; |
437 | |
438 | mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp); |
439 | } |
440 | relp = (Elf_Rel const *)(rel_entsize + (void *)relp); |
441 | } |
442 | *mrelpp = mrelp; |
443 | return mlocp; |
444 | } |
445 | |
446 | /* |
447 | * Read the relocation table again, but this time its called on sections |
448 | * that are not going to be traced. The mcount calls here will be converted |
449 | * into nops. |
450 | */ |
451 | static int nop_mcount(Elf_Shdr const *const relhdr, |
452 | Elf_Ehdr const *const ehdr, |
453 | const char *const txtname) |
454 | { |
455 | Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) |
456 | + (void *)ehdr); |
457 | Elf_Sym const *sym0; |
458 | char const *str0; |
459 | Elf_Rel const *relp; |
460 | Elf_Shdr const *const shdr = &shdr0[w(relhdr->sh_info)]; |
461 | unsigned rel_entsize = _w(relhdr->sh_entsize); |
462 | unsigned const nrel = _w(relhdr->sh_size) / rel_entsize; |
463 | unsigned mcountsym = 0; |
464 | unsigned t; |
465 | int once = 0; |
466 | |
467 | get_sym_str_and_relp(relhdr, ehdr, sym0: &sym0, str0: &str0, relp: &relp); |
468 | |
469 | for (t = nrel; t; --t) { |
470 | int ret = -1; |
471 | |
472 | if (!mcountsym) |
473 | mcountsym = get_mcountsym(sym0, relp, str0); |
474 | |
475 | if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) { |
476 | if (make_nop) |
477 | ret = make_nop((void *)ehdr, _w(shdr->sh_offset) + _w(relp->r_offset)); |
478 | if (warn_on_notrace_sect && !once) { |
479 | printf(format: "Section %s has mcount callers being ignored\n" , |
480 | txtname); |
481 | once = 1; |
482 | /* just warn? */ |
483 | if (!make_nop) |
484 | return 0; |
485 | } |
486 | } |
487 | |
488 | /* |
489 | * If we successfully removed the mcount, mark the relocation |
490 | * as a nop (don't do anything with it). |
491 | */ |
492 | if (!ret) { |
493 | Elf_Rel rel; |
494 | rel = *(Elf_Rel *)relp; |
495 | Elf_r_info(&rel, Elf_r_sym(relp), rel_type_nop); |
496 | if (ulseek(offset: (void *)relp - (void *)ehdr, SEEK_SET) < 0) |
497 | return -1; |
498 | if (uwrite(buf: &rel, count: sizeof(rel)) < 0) |
499 | return -1; |
500 | } |
501 | relp = (Elf_Rel const *)(rel_entsize + (void *)relp); |
502 | } |
503 | return 0; |
504 | } |
505 | |
506 | /* |
507 | * Find a symbol in the given section, to be used as the base for relocating |
508 | * the table of offsets of calls to mcount. A local or global symbol suffices, |
509 | * but avoid a Weak symbol because it may be overridden; the change in value |
510 | * would invalidate the relocations of the offsets of the calls to mcount. |
511 | * Often the found symbol will be the unnamed local symbol generated by |
512 | * GNU 'as' for the start of each section. For example: |
513 | * Num: Value Size Type Bind Vis Ndx Name |
514 | * 2: 00000000 0 SECTION LOCAL DEFAULT 1 |
515 | */ |
516 | static int find_secsym_ndx(unsigned const txtndx, |
517 | char const *const txtname, |
518 | uint_t *const recvalp, |
519 | unsigned int *sym_index, |
520 | Elf_Shdr const *const symhdr, |
521 | Elf32_Word const *symtab, |
522 | Elf32_Word const *symtab_shndx, |
523 | Elf_Ehdr const *const ehdr) |
524 | { |
525 | Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset) |
526 | + (void *)ehdr); |
527 | unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize); |
528 | Elf_Sym const *symp; |
529 | unsigned t; |
530 | |
531 | for (symp = sym0, t = nsym; t; --t, ++symp) { |
532 | unsigned int const st_bind = ELF_ST_BIND(symp->st_info); |
533 | |
534 | if (txtndx == get_symindex(sym: symp, symtab, symtab_shndx) |
535 | /* avoid STB_WEAK */ |
536 | && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) { |
537 | /* function symbols on ARM have quirks, avoid them */ |
538 | if (w2(ehdr->e_machine) == EM_ARM |
539 | && ELF_ST_TYPE(symp->st_info) == STT_FUNC) |
540 | continue; |
541 | |
542 | *recvalp = _w(symp->st_value); |
543 | *sym_index = symp - sym0; |
544 | return 0; |
545 | } |
546 | } |
547 | fprintf(stderr, format: "Cannot find symbol for section %u: %s.\n" , |
548 | txtndx, txtname); |
549 | return -1; |
550 | } |
551 | |
552 | /* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */ |
553 | static char const * __has_rel_mcount(Elf_Shdr const *const relhdr, /* reltype */ |
554 | Elf_Shdr const *const shdr0, |
555 | char const *const shstrtab, |
556 | char const *const fname) |
557 | { |
558 | /* .sh_info depends on .sh_type == SHT_REL[,A] */ |
559 | Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)]; |
560 | char const *const txtname = &shstrtab[w(txthdr->sh_name)]; |
561 | |
562 | if (strcmp(s1: "__mcount_loc" , s2: txtname) == 0) { |
563 | fprintf(stderr, format: "warning: __mcount_loc already exists: %s\n" , |
564 | fname); |
565 | return already_has_rel_mcount; |
566 | } |
567 | if (w(txthdr->sh_type) != SHT_PROGBITS || |
568 | !(_w(txthdr->sh_flags) & SHF_EXECINSTR)) |
569 | return NULL; |
570 | return txtname; |
571 | } |
572 | |
573 | static char const *has_rel_mcount(Elf_Shdr const *const relhdr, |
574 | Elf_Shdr const *const shdr0, |
575 | char const *const shstrtab, |
576 | char const *const fname) |
577 | { |
578 | if (w(relhdr->sh_type) != SHT_REL && w(relhdr->sh_type) != SHT_RELA) |
579 | return NULL; |
580 | return __has_rel_mcount(relhdr, shdr0, shstrtab, fname); |
581 | } |
582 | |
583 | |
584 | static unsigned tot_relsize(Elf_Shdr const *const shdr0, |
585 | unsigned nhdr, |
586 | const char *const shstrtab, |
587 | const char *const fname) |
588 | { |
589 | unsigned totrelsz = 0; |
590 | Elf_Shdr const *shdrp = shdr0; |
591 | char const *txtname; |
592 | |
593 | for (; nhdr; --nhdr, ++shdrp) { |
594 | txtname = has_rel_mcount(relhdr: shdrp, shdr0, shstrtab, fname); |
595 | if (txtname == already_has_rel_mcount) { |
596 | totrelsz = 0; |
597 | break; |
598 | } |
599 | if (txtname && is_mcounted_section_name(txtname)) |
600 | totrelsz += _w(shdrp->sh_size); |
601 | } |
602 | return totrelsz; |
603 | } |
604 | |
605 | /* Overall supervision for Elf32 ET_REL file. */ |
606 | static int do_func(Elf_Ehdr *const ehdr, char const *const fname, |
607 | unsigned const reltype) |
608 | { |
609 | Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) |
610 | + (void *)ehdr); |
611 | unsigned const nhdr = get_shnum(ehdr, shdr0); |
612 | Elf_Shdr *const shstr = &shdr0[get_shstrndx(ehdr, shdr0)]; |
613 | char const *const shstrtab = (char const *)(_w(shstr->sh_offset) |
614 | + (void *)ehdr); |
615 | |
616 | Elf_Shdr const *relhdr; |
617 | unsigned k; |
618 | |
619 | Elf32_Word *symtab; |
620 | Elf32_Word *symtab_shndx; |
621 | |
622 | /* Upper bound on space: assume all relevant relocs are for mcount. */ |
623 | unsigned totrelsz; |
624 | |
625 | Elf_Rel * mrel0; |
626 | Elf_Rel * mrelp; |
627 | |
628 | uint_t * mloc0; |
629 | uint_t * mlocp; |
630 | |
631 | unsigned rel_entsize = 0; |
632 | unsigned symsec_sh_link = 0; |
633 | |
634 | int result = 0; |
635 | |
636 | totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname); |
637 | if (totrelsz == 0) |
638 | return 0; |
639 | mrel0 = umalloc(size: totrelsz); |
640 | mrelp = mrel0; |
641 | if (!mrel0) |
642 | return -1; |
643 | |
644 | /* 2*sizeof(address) <= sizeof(Elf_Rel) */ |
645 | mloc0 = umalloc(size: totrelsz>>1); |
646 | mlocp = mloc0; |
647 | if (!mloc0) { |
648 | free(ptr: mrel0); |
649 | return -1; |
650 | } |
651 | |
652 | find_symtab(ehdr, shdr0, nhdr, symtab: &symtab, symtab_shndx: &symtab_shndx); |
653 | |
654 | for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) { |
655 | char const *const txtname = has_rel_mcount(relhdr, shdr0, |
656 | shstrtab, fname); |
657 | if (txtname == already_has_rel_mcount) { |
658 | result = 0; |
659 | file_updated = 0; |
660 | goto out; /* Nothing to be done; don't append! */ |
661 | } |
662 | if (txtname && is_mcounted_section_name(txtname)) { |
663 | unsigned int recsym; |
664 | uint_t recval = 0; |
665 | |
666 | symsec_sh_link = w(relhdr->sh_link); |
667 | result = find_secsym_ndx(txtndx: w(relhdr->sh_info), txtname, |
668 | recvalp: &recval, sym_index: &recsym, |
669 | symhdr: &shdr0[symsec_sh_link], |
670 | symtab, symtab_shndx, |
671 | ehdr); |
672 | if (result) |
673 | goto out; |
674 | |
675 | rel_entsize = _w(relhdr->sh_entsize); |
676 | mlocp = sift_rel_mcount(mlocp, |
677 | offbase: (void *)mlocp - (void *)mloc0, mrelpp: &mrelp, |
678 | relhdr, ehdr, recsym, recval, reltype); |
679 | } else if (txtname && (warn_on_notrace_sect || make_nop)) { |
680 | /* |
681 | * This section is ignored by ftrace, but still |
682 | * has mcount calls. Convert them to nops now. |
683 | */ |
684 | if (nop_mcount(relhdr, ehdr, txtname) < 0) { |
685 | result = -1; |
686 | goto out; |
687 | } |
688 | } |
689 | } |
690 | if (!result && mloc0 != mlocp) |
691 | result = append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp, |
692 | rel_entsize, symsec_sh_link); |
693 | out: |
694 | free(ptr: mrel0); |
695 | free(ptr: mloc0); |
696 | return result; |
697 | } |
698 | |