aboutsummaryrefslogtreecommitdiffstats
path: root/scripts/recordmcount.h
blob: 7f39d0943d2d93099068114605da1f1508eafedc (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
/*
 * recordmcount.h
 *
 * This code was taken out of recordmcount.c written by
 * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>.  All rights reserved.
 *
 * The original code had the same algorithms for both 32bit
 * and 64bit ELF files, but the code was duplicated to support
 * the difference in structures that were used. This
 * file creates a macro of everything that is different between
 * the 64 and 32 bit code, such that by including this header
 * twice we can create both sets of functions by including this
 * header once with RECORD_MCOUNT_64 undefined, and again with
 * it defined.
 *
 * This conversion to macros was done by:
 * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
 *
 * Licensed under the GNU General Public License, version 2 (GPLv2).
 */
#undef append_func
#undef sift_rel_mcount
#undef find_secsym_ndx
#undef __has_rel_mcount
#undef has_rel_mcount
#undef tot_relsize
#undef do_func
#undef Elf_Ehdr
#undef Elf_Shdr
#undef Elf_Rel
#undef Elf_Rela
#undef Elf_Sym
#undef ELF_R_SYM
#undef ELF_R_INFO
#undef ELF_ST_BIND
#undef uint_t
#undef _w
#undef _align
#undef _size

#ifdef RECORD_MCOUNT_64
# define append_func		append64
# define sift_rel_mcount	sift64_rel_mcount
# define find_secsym_ndx	find64_secsym_ndx
# define __has_rel_mcount	__has64_rel_mcount
# define has_rel_mcount		has64_rel_mcount
# define tot_relsize		tot64_relsize
# define do_func		do64
# define Elf_Ehdr		Elf64_Ehdr
# define Elf_Shdr		Elf64_Shdr
# define Elf_Rel		Elf64_Rel
# define Elf_Rela		Elf64_Rela
# define Elf_Sym		Elf64_Sym
# define ELF_R_SYM		ELF64_R_SYM
# define ELF_R_INFO		ELF64_R_INFO
# define ELF_ST_BIND		ELF64_ST_BIND
# define uint_t			uint64_t
# define _w			w8
# define _align			7u
# define _size			8
#else
# define append_func		append32
# define sift_rel_mcount	sift32_rel_mcount
# define find_secsym_ndx	find32_secsym_ndx
# define __has_rel_mcount	__has32_rel_mcount
# define has_rel_mcount		has32_rel_mcount
# define tot_relsize		tot32_relsize
# define do_func		do32
# define Elf_Ehdr		Elf32_Ehdr
# define Elf_Shdr		Elf32_Shdr
# define Elf_Rel		Elf32_Rel
# define Elf_Rela		Elf32_Rela
# define Elf_Sym		Elf32_Sym
# define ELF_R_SYM		ELF32_R_SYM
# define ELF_R_INFO		ELF32_R_INFO
# define ELF_ST_BIND		ELF32_ST_BIND
# define uint_t			uint32_t
# define _w			w
# define _align			3u
# define _size			4
#endif

/* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */
static void append_func(Elf_Ehdr *const ehdr,
			Elf_Shdr *const shstr,
			uint_t const *const mloc0,
			uint_t const *const mlocp,
			Elf_Rel const *const mrel0,
			Elf_Rel const *const mrelp,
			unsigned int const rel_entsize,
			unsigned int const symsec_sh_link)
{
	/* Begin constructing output file */
	Elf_Shdr mcsec;
	char const *mc_name = (sizeof(Elf_Rela) == rel_entsize)
		? ".rela__mcount_loc"
		:  ".rel__mcount_loc";
	unsigned const old_shnum = w2(ehdr->e_shnum);
	uint_t const old_shoff = _w(ehdr->e_shoff);
	uint_t const old_shstr_sh_size   = _w(shstr->sh_size);
	uint_t const old_shstr_sh_offset = _w(shstr->sh_offset);
	uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size);
	uint_t new_e_shoff;

	shstr->sh_size = _w(t);
	shstr->sh_offset = _w(sb.st_size);
	t += sb.st_size;
	t += (_align & -t);  /* word-byte align */
	new_e_shoff = t;

	/* body for new shstrtab */
	ulseek(fd_map, sb.st_size, SEEK_SET);
	uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size);
	uwrite(fd_map, mc_name, 1 + strlen(mc_name));

	/* old(modified) Elf_Shdr table, word-byte aligned */
	ulseek(fd_map, t, SEEK_SET);
	t += sizeof(Elf_Shdr) * old_shnum;
	uwrite(fd_map, old_shoff + (void *)ehdr,
	       sizeof(Elf_Shdr) * old_shnum);

	/* new sections __mcount_loc and .rel__mcount_loc */
	t += 2*sizeof(mcsec);
	mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel")
		+ old_shstr_sh_size);
	mcsec.sh_type = w(SHT_PROGBITS);
	mcsec.sh_flags = _w(SHF_ALLOC);
	mcsec.sh_addr = 0;
	mcsec.sh_offset = _w(t);
	mcsec.sh_size = _w((void *)mlocp - (void *)mloc0);
	mcsec.sh_link = 0;
	mcsec.sh_info = 0;
	mcsec.sh_addralign = _w(_size);
	mcsec.sh_entsize = _w(_size);
	uwrite(fd_map, &mcsec, sizeof(mcsec));

	mcsec.sh_name = w(old_shstr_sh_size);
	mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize)
		? w(SHT_RELA)
		: w(SHT_REL);
	mcsec.sh_flags = 0;
	mcsec.sh_addr = 0;
	mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t);
	mcsec.sh_size   = _w((void *)mrelp - (void *)mrel0);
	mcsec.sh_link = w(symsec_sh_link);
	mcsec.sh_info = w(old_shnum);
	mcsec.sh_addralign = _w(_size);
	mcsec.sh_entsize = _w(rel_entsize);
	uwrite(fd_map, &mcsec, sizeof(mcsec));

	uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0);
	uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0);

	ehdr->e_shoff = _w(new_e_shoff);
	ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum));  /* {.rel,}__mcount_loc */
	ulseek(fd_map, 0, SEEK_SET);
	uwrite(fd_map, ehdr, sizeof(*ehdr));
}


/*
 * Look at the relocations in order to find the calls to mcount.
 * Accumulate the section offsets that are found, and their relocation info,
 * onto the end of the existing arrays.
 */
static uint_t *sift_rel_mcount(uint_t *mlocp,
			       unsigned const offbase,
			       Elf_Rel **const mrelpp,
			       Elf_Shdr const *const relhdr,
			       Elf_Ehdr const *const ehdr,
			       unsigned const recsym,
			       uint_t const recval,
			       unsigned const reltype)
{
	uint_t *const mloc0 = mlocp;
	Elf_Rel *mrelp = *mrelpp;
	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;

	unsigned mcountsym = 0;
	unsigned t;

	for (t = nrel; t; --t) {
		if (!mcountsym) {
			Elf_Sym const *const symp =
				&sym0[ELF_R_SYM(_w(relp->r_info))];
			char const *symname = &str0[w(symp->st_name)];

			if ('.' == symname[0])
				++symname;  /* ppc64 hack */
			if (0 == strcmp((('_' == gpfx) ? "_mcount" : "mcount"),
					symname))
				mcountsym = ELF_R_SYM(_w(relp->r_info));
		}

		if (mcountsym == ELF_R_SYM(_w(relp->r_info))) {
			uint_t const addend = _w(_w(relp->r_offset) - recval);

			mrelp->r_offset = _w(offbase
				+ ((void *)mlocp - (void *)mloc0));
			mrelp->r_info = _w(ELF_R_INFO(recsym, reltype));
			if (sizeof(Elf_Rela) == rel_entsize) {
				((Elf_Rela *)mrelp)->r_addend = addend;
				*mlocp++ = 0;
			} else
				*mlocp++ = addend;

			mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp);
		}
		relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
	}
	*mrelpp = mrelp;
	return mlocp;
}


/*
 * Find a symbol in the given section, to be used as the base for relocating
 * the table of offsets of calls to mcount.  A local or global symbol suffices,
 * but avoid a Weak symbol because it may be overridden; the change in value
 * would invalidate the relocations of the offsets of the calls to mcount.
 * Often the found symbol will be the unnamed local symbol generated by
 * GNU 'as' for the start of each section.  For example:
 *    Num:    Value  Size Type    Bind   Vis      Ndx Name
 *      2: 00000000     0 SECTION LOCAL  DEFAULT    1
 */
static unsigned find_secsym_ndx(unsigned const txtndx,
				char const *const txtname,
				uint_t *const recvalp,
				Elf_Shdr const *const symhdr,
				Elf_Ehdr const *const ehdr)
{
	Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset)
		+ (void *)ehdr);
	unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize);
	Elf_Sym const *symp;
	unsigned t;

	for (symp = sym0, t = nsym; t; --t, ++symp) {
		unsigned int const st_bind = ELF_ST_BIND(symp->st_info);

		if (txtndx == w2(symp->st_shndx)
			/* avoid STB_WEAK */
		    && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) {
			*recvalp = _w(symp->st_value);
			return symp - sym0;
		}
	}
	fprintf(stderr, "Cannot find symbol for section %d: %s.\n",
		txtndx, txtname);
	fail_file();
}


/* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */
static char const *
__has_rel_mcount(Elf_Shdr const *const relhdr,  /* is SHT_REL or SHT_RELA */
		 Elf_Shdr const *const shdr0,
		 char const *const shstrtab,
		 char const *const fname)
{
	/* .sh_info depends on .sh_type == SHT_REL[,A] */
	Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)];
	char const *const txtname = &shstrtab[w(txthdr->sh_name)];

	if (0 == strcmp("__mcount_loc", txtname)) {
		fprintf(stderr, "warning: __mcount_loc already exists: %s\n",
			fname);
		succeed_file();
	}
	if (SHT_PROGBITS != w(txthdr->sh_type) ||
	    !is_mcounted_section_name(txtname))
		return NULL;
	return txtname;
}

static char const *has_rel_mcount(Elf_Shdr const *const relhdr,
				  Elf_Shdr const *const shdr0,
				  char const *const shstrtab,
				  char const *const fname)
{
	if (SHT_REL  != w(relhdr->sh_type) && SHT_RELA != w(relhdr->sh_type))
		return NULL;
	return __has_rel_mcount(relhdr, shdr0, shstrtab, fname);
}


static unsigned tot_relsize(Elf_Shdr const *const shdr0,
			    unsigned nhdr,
			    const char *const shstrtab,
			    const char *const fname)
{
	unsigned totrelsz = 0;
	Elf_Shdr const *shdrp = shdr0;

	for (; nhdr; --nhdr, ++shdrp) {
		if (has_rel_mcount(shdrp, shdr0, shstrtab, fname))
			totrelsz += _w(shdrp->sh_size);
	}
	return totrelsz;
}


/* Overall supervision for Elf32 ET_REL file. */
static void
do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype)
{
	Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
		+ (void *)ehdr);
	unsigned const nhdr = w2(ehdr->e_shnum);
	Elf_Shdr *const shstr = &shdr0[w2(ehdr->e_shstrndx)];
	char const *const shstrtab = (char const *)(_w(shstr->sh_offset)
		+ (void *)ehdr);

	Elf_Shdr const *relhdr;
	unsigned k;

	/* Upper bound on space: assume all relevant relocs are for mcount. */
	unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname);
	Elf_Rel *const mrel0 = umalloc(totrelsz);
	Elf_Rel *      mrelp = mrel0;

	/* 2*sizeof(address) <= sizeof(Elf_Rel) */
	uint_t *const mloc0 = umalloc(totrelsz>>1);
	uint_t *      mlocp = mloc0;

	unsigned rel_entsize = 0;
	unsigned symsec_sh_link = 0;

	for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {
		char const *const txtname = has_rel_mcount(relhdr, shdr0,
			shstrtab, fname);
		if (txtname) {
			uint_t recval = 0;
			unsigned const recsym = find_secsym_ndx(
				w(relhdr->sh_info), txtname, &recval,
				&shdr0[symsec_sh_link = w(relhdr->sh_link)],
				ehdr);

			rel_entsize = _w(relhdr->sh_entsize);
			mlocp = sift_rel_mcount(mlocp,
				(void *)mlocp - (void *)mloc0, &mrelp,
				relhdr, ehdr, recsym, recval, reltype);
		}
	}
	if (mloc0 != mlocp) {
		append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp,
			    rel_entsize, symsec_sh_link);
	}
	free(mrel0);
	free(mloc0);
}