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c28d5077 SR |
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 sift_rel_mcount | |
23 | #undef find_secsym_ndx | |
24 | #undef __has_rel_mcount | |
25 | #undef has_rel_mcount | |
26 | #undef tot_relsize | |
27 | #undef do_func | |
28 | #undef Elf_Ehdr | |
29 | #undef Elf_Shdr | |
30 | #undef Elf_Rel | |
31 | #undef Elf_Rela | |
32 | #undef Elf_Sym | |
33 | #undef ELF_R_SYM | |
34 | #undef ELF_R_INFO | |
35 | #undef ELF_ST_BIND | |
36 | #undef uint_t | |
37 | #undef _w | |
38 | #undef _align | |
39 | #undef _size | |
40 | ||
41 | #ifdef RECORD_MCOUNT_64 | |
42 | # define append_func append64 | |
43 | # define sift_rel_mcount sift64_rel_mcount | |
44 | # define find_secsym_ndx find64_secsym_ndx | |
45 | # define __has_rel_mcount __has64_rel_mcount | |
46 | # define has_rel_mcount has64_rel_mcount | |
47 | # define tot_relsize tot64_relsize | |
48 | # define do_func do64 | |
49 | # define Elf_Ehdr Elf64_Ehdr | |
50 | # define Elf_Shdr Elf64_Shdr | |
51 | # define Elf_Rel Elf64_Rel | |
52 | # define Elf_Rela Elf64_Rela | |
53 | # define Elf_Sym Elf64_Sym | |
54 | # define ELF_R_SYM ELF64_R_SYM | |
55 | # define ELF_R_INFO ELF64_R_INFO | |
56 | # define ELF_ST_BIND ELF64_ST_BIND | |
57 | # define uint_t uint64_t | |
58 | # define _w w8 | |
59 | # define _align 7u | |
60 | # define _size 8 | |
61 | #else | |
62 | # define append_func append32 | |
63 | # define sift_rel_mcount sift32_rel_mcount | |
64 | # define find_secsym_ndx find32_secsym_ndx | |
65 | # define __has_rel_mcount __has32_rel_mcount | |
66 | # define has_rel_mcount has32_rel_mcount | |
67 | # define tot_relsize tot32_relsize | |
68 | # define do_func do32 | |
69 | # define Elf_Ehdr Elf32_Ehdr | |
70 | # define Elf_Shdr Elf32_Shdr | |
71 | # define Elf_Rel Elf32_Rel | |
72 | # define Elf_Rela Elf32_Rela | |
73 | # define Elf_Sym Elf32_Sym | |
74 | # define ELF_R_SYM ELF32_R_SYM | |
75 | # define ELF_R_INFO ELF32_R_INFO | |
76 | # define ELF_ST_BIND ELF32_ST_BIND | |
77 | # define uint_t uint32_t | |
78 | # define _w w | |
79 | # define _align 3u | |
80 | # define _size 4 | |
81 | #endif | |
82 | ||
83 | /* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */ | |
84 | static void append_func(Elf_Ehdr *const ehdr, | |
85 | Elf_Shdr *const shstr, | |
86 | uint_t const *const mloc0, | |
87 | uint_t const *const mlocp, | |
88 | Elf_Rel const *const mrel0, | |
89 | Elf_Rel const *const mrelp, | |
90 | unsigned int const rel_entsize, | |
91 | unsigned int const symsec_sh_link) | |
92 | { | |
93 | /* Begin constructing output file */ | |
94 | Elf_Shdr mcsec; | |
95 | char const *mc_name = (sizeof(Elf_Rela) == rel_entsize) | |
96 | ? ".rela__mcount_loc" | |
97 | : ".rel__mcount_loc"; | |
98 | unsigned const old_shnum = w2(ehdr->e_shnum); | |
99 | uint_t const old_shoff = _w(ehdr->e_shoff); | |
100 | uint_t const old_shstr_sh_size = _w(shstr->sh_size); | |
101 | uint_t const old_shstr_sh_offset = _w(shstr->sh_offset); | |
102 | uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size); | |
103 | uint_t new_e_shoff; | |
104 | ||
105 | shstr->sh_size = _w(t); | |
106 | shstr->sh_offset = _w(sb.st_size); | |
107 | t += sb.st_size; | |
108 | t += (_align & -t); /* word-byte align */ | |
109 | new_e_shoff = t; | |
110 | ||
111 | /* body for new shstrtab */ | |
112 | ulseek(fd_map, sb.st_size, SEEK_SET); | |
113 | uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size); | |
114 | uwrite(fd_map, mc_name, 1 + strlen(mc_name)); | |
115 | ||
116 | /* old(modified) Elf_Shdr table, word-byte aligned */ | |
117 | ulseek(fd_map, t, SEEK_SET); | |
118 | t += sizeof(Elf_Shdr) * old_shnum; | |
119 | uwrite(fd_map, old_shoff + (void *)ehdr, | |
120 | sizeof(Elf_Shdr) * old_shnum); | |
121 | ||
122 | /* new sections __mcount_loc and .rel__mcount_loc */ | |
123 | t += 2*sizeof(mcsec); | |
124 | mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel") | |
125 | + old_shstr_sh_size); | |
126 | mcsec.sh_type = w(SHT_PROGBITS); | |
127 | mcsec.sh_flags = _w(SHF_ALLOC); | |
128 | mcsec.sh_addr = 0; | |
129 | mcsec.sh_offset = _w(t); | |
130 | mcsec.sh_size = _w((void *)mlocp - (void *)mloc0); | |
131 | mcsec.sh_link = 0; | |
132 | mcsec.sh_info = 0; | |
133 | mcsec.sh_addralign = _w(_size); | |
134 | mcsec.sh_entsize = _w(_size); | |
135 | uwrite(fd_map, &mcsec, sizeof(mcsec)); | |
136 | ||
137 | mcsec.sh_name = w(old_shstr_sh_size); | |
138 | mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize) | |
139 | ? w(SHT_RELA) | |
140 | : w(SHT_REL); | |
141 | mcsec.sh_flags = 0; | |
142 | mcsec.sh_addr = 0; | |
143 | mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t); | |
144 | mcsec.sh_size = _w((void *)mrelp - (void *)mrel0); | |
145 | mcsec.sh_link = w(symsec_sh_link); | |
146 | mcsec.sh_info = w(old_shnum); | |
147 | mcsec.sh_addralign = _w(_size); | |
148 | mcsec.sh_entsize = _w(rel_entsize); | |
149 | uwrite(fd_map, &mcsec, sizeof(mcsec)); | |
150 | ||
151 | uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0); | |
152 | uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0); | |
153 | ||
154 | ehdr->e_shoff = _w(new_e_shoff); | |
155 | ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum)); /* {.rel,}__mcount_loc */ | |
156 | ulseek(fd_map, 0, SEEK_SET); | |
157 | uwrite(fd_map, ehdr, sizeof(*ehdr)); | |
158 | } | |
159 | ||
160 | ||
161 | /* | |
162 | * Look at the relocations in order to find the calls to mcount. | |
163 | * Accumulate the section offsets that are found, and their relocation info, | |
164 | * onto the end of the existing arrays. | |
165 | */ | |
166 | static uint_t *sift_rel_mcount(uint_t *mlocp, | |
167 | unsigned const offbase, | |
168 | Elf_Rel **const mrelpp, | |
169 | Elf_Shdr const *const relhdr, | |
170 | Elf_Ehdr const *const ehdr, | |
171 | unsigned const recsym, | |
172 | uint_t const recval, | |
173 | unsigned const reltype) | |
174 | { | |
175 | uint_t *const mloc0 = mlocp; | |
176 | Elf_Rel *mrelp = *mrelpp; | |
177 | Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) | |
178 | + (void *)ehdr); | |
179 | unsigned const symsec_sh_link = w(relhdr->sh_link); | |
180 | Elf_Shdr const *const symsec = &shdr0[symsec_sh_link]; | |
181 | Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symsec->sh_offset) | |
182 | + (void *)ehdr); | |
183 | ||
184 | Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)]; | |
185 | char const *const str0 = (char const *)(_w(strsec->sh_offset) | |
186 | + (void *)ehdr); | |
187 | ||
188 | Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset) | |
189 | + (void *)ehdr); | |
190 | unsigned rel_entsize = _w(relhdr->sh_entsize); | |
191 | unsigned const nrel = _w(relhdr->sh_size) / rel_entsize; | |
192 | Elf_Rel const *relp = rel0; | |
193 | ||
194 | unsigned mcountsym = 0; | |
195 | unsigned t; | |
196 | ||
197 | for (t = nrel; t; --t) { | |
198 | if (!mcountsym) { | |
199 | Elf_Sym const *const symp = | |
200 | &sym0[ELF_R_SYM(_w(relp->r_info))]; | |
201 | char const *symname = &str0[w(symp->st_name)]; | |
202 | ||
203 | if ('.' == symname[0]) | |
204 | ++symname; /* ppc64 hack */ | |
205 | if (0 == strcmp((('_' == gpfx) ? "_mcount" : "mcount"), | |
206 | symname)) | |
207 | mcountsym = ELF_R_SYM(_w(relp->r_info)); | |
208 | } | |
209 | ||
210 | if (mcountsym == ELF_R_SYM(_w(relp->r_info))) { | |
211 | uint_t const addend = _w(_w(relp->r_offset) - recval); | |
212 | ||
213 | mrelp->r_offset = _w(offbase | |
214 | + ((void *)mlocp - (void *)mloc0)); | |
215 | mrelp->r_info = _w(ELF_R_INFO(recsym, reltype)); | |
216 | if (sizeof(Elf_Rela) == rel_entsize) { | |
217 | ((Elf_Rela *)mrelp)->r_addend = addend; | |
218 | *mlocp++ = 0; | |
219 | } else | |
220 | *mlocp++ = addend; | |
221 | ||
222 | mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp); | |
223 | } | |
224 | relp = (Elf_Rel const *)(rel_entsize + (void *)relp); | |
225 | } | |
226 | *mrelpp = mrelp; | |
227 | return mlocp; | |
228 | } | |
229 | ||
230 | ||
231 | /* | |
232 | * Find a symbol in the given section, to be used as the base for relocating | |
233 | * the table of offsets of calls to mcount. A local or global symbol suffices, | |
234 | * but avoid a Weak symbol because it may be overridden; the change in value | |
235 | * would invalidate the relocations of the offsets of the calls to mcount. | |
236 | * Often the found symbol will be the unnamed local symbol generated by | |
237 | * GNU 'as' for the start of each section. For example: | |
238 | * Num: Value Size Type Bind Vis Ndx Name | |
239 | * 2: 00000000 0 SECTION LOCAL DEFAULT 1 | |
240 | */ | |
241 | static unsigned find_secsym_ndx(unsigned const txtndx, | |
242 | char const *const txtname, | |
243 | uint_t *const recvalp, | |
244 | Elf_Shdr const *const symhdr, | |
245 | Elf_Ehdr const *const ehdr) | |
246 | { | |
247 | Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset) | |
248 | + (void *)ehdr); | |
249 | unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize); | |
250 | Elf_Sym const *symp; | |
251 | unsigned t; | |
252 | ||
253 | for (symp = sym0, t = nsym; t; --t, ++symp) { | |
254 | unsigned int const st_bind = ELF_ST_BIND(symp->st_info); | |
255 | ||
256 | if (txtndx == w2(symp->st_shndx) | |
257 | /* avoid STB_WEAK */ | |
258 | && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) { | |
259 | *recvalp = _w(symp->st_value); | |
260 | return symp - sym0; | |
261 | } | |
262 | } | |
263 | fprintf(stderr, "Cannot find symbol for section %d: %s.\n", | |
264 | txtndx, txtname); | |
265 | fail_file(); | |
266 | } | |
267 | ||
268 | ||
269 | /* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */ | |
270 | static char const * | |
271 | __has_rel_mcount(Elf_Shdr const *const relhdr, /* is SHT_REL or SHT_RELA */ | |
272 | Elf_Shdr const *const shdr0, | |
273 | char const *const shstrtab, | |
274 | char const *const fname) | |
275 | { | |
276 | /* .sh_info depends on .sh_type == SHT_REL[,A] */ | |
277 | Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)]; | |
278 | char const *const txtname = &shstrtab[w(txthdr->sh_name)]; | |
279 | ||
280 | if (0 == strcmp("__mcount_loc", txtname)) { | |
281 | fprintf(stderr, "warning: __mcount_loc already exists: %s\n", | |
282 | fname); | |
283 | succeed_file(); | |
284 | } | |
285 | if (SHT_PROGBITS != w(txthdr->sh_type) || | |
286 | !is_mcounted_section_name(txtname)) | |
287 | return NULL; | |
288 | return txtname; | |
289 | } | |
290 | ||
291 | static char const *has_rel_mcount(Elf_Shdr const *const relhdr, | |
292 | Elf_Shdr const *const shdr0, | |
293 | char const *const shstrtab, | |
294 | char const *const fname) | |
295 | { | |
296 | if (SHT_REL != w(relhdr->sh_type) && SHT_RELA != w(relhdr->sh_type)) | |
297 | return NULL; | |
298 | return __has_rel_mcount(relhdr, shdr0, shstrtab, fname); | |
299 | } | |
300 | ||
301 | ||
302 | static unsigned tot_relsize(Elf_Shdr const *const shdr0, | |
303 | unsigned nhdr, | |
304 | const char *const shstrtab, | |
305 | const char *const fname) | |
306 | { | |
307 | unsigned totrelsz = 0; | |
308 | Elf_Shdr const *shdrp = shdr0; | |
309 | ||
310 | for (; nhdr; --nhdr, ++shdrp) { | |
311 | if (has_rel_mcount(shdrp, shdr0, shstrtab, fname)) | |
312 | totrelsz += _w(shdrp->sh_size); | |
313 | } | |
314 | return totrelsz; | |
315 | } | |
316 | ||
317 | ||
318 | /* Overall supervision for Elf32 ET_REL file. */ | |
319 | static void | |
320 | do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype) | |
321 | { | |
322 | Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) | |
323 | + (void *)ehdr); | |
324 | unsigned const nhdr = w2(ehdr->e_shnum); | |
325 | Elf_Shdr *const shstr = &shdr0[w2(ehdr->e_shstrndx)]; | |
326 | char const *const shstrtab = (char const *)(_w(shstr->sh_offset) | |
327 | + (void *)ehdr); | |
328 | ||
329 | Elf_Shdr const *relhdr; | |
330 | unsigned k; | |
331 | ||
332 | /* Upper bound on space: assume all relevant relocs are for mcount. */ | |
333 | unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname); | |
334 | Elf_Rel *const mrel0 = umalloc(totrelsz); | |
335 | Elf_Rel * mrelp = mrel0; | |
336 | ||
337 | /* 2*sizeof(address) <= sizeof(Elf_Rel) */ | |
338 | uint_t *const mloc0 = umalloc(totrelsz>>1); | |
339 | uint_t * mlocp = mloc0; | |
340 | ||
341 | unsigned rel_entsize = 0; | |
342 | unsigned symsec_sh_link = 0; | |
343 | ||
344 | for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) { | |
345 | char const *const txtname = has_rel_mcount(relhdr, shdr0, | |
346 | shstrtab, fname); | |
347 | if (txtname) { | |
348 | uint_t recval = 0; | |
349 | unsigned const recsym = find_secsym_ndx( | |
350 | w(relhdr->sh_info), txtname, &recval, | |
351 | &shdr0[symsec_sh_link = w(relhdr->sh_link)], | |
352 | ehdr); | |
353 | ||
354 | rel_entsize = _w(relhdr->sh_entsize); | |
355 | mlocp = sift_rel_mcount(mlocp, | |
356 | (void *)mlocp - (void *)mloc0, &mrelp, | |
357 | relhdr, ehdr, recsym, recval, reltype); | |
358 | } | |
359 | } | |
360 | if (mloc0 != mlocp) { | |
361 | append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp, | |
362 | rel_entsize, symsec_sh_link); | |
363 | } | |
364 | free(mrel0); | |
365 | free(mloc0); | |
366 | } |