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GCC Code Coverage Report

Directory:	./		Exec	Total	Coverage
File:	usr.bin/ctfdump/elf.c	Lines:	63	118	53.4 %
Date:	2017-11-07	Branches:	41	102	40.2 %


/*	$OpenBSD: elf.c,v 1.3 2017/08/29 21:10:20 deraadt Exp $ */

/*
 * Copyright (c) 2016 Martin Pieuchot <mpi@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>
#include <sys/exec_elf.h>

#include <machine/reloc.h>

#include <assert.h>
#include <err.h>
#include <string.h>

static int	elf_reloc_size(unsigned long);
static void	elf_reloc_apply(const char *, const char *, size_t, ssize_t,
		    char *, size_t);

int
iself(const char *p, size_t filesize)
{
	Elf_Ehdr		*eh = (Elf_Ehdr *)p;

	if (filesize < (off_t)sizeof(Elf_Ehdr)) {
		warnx("file too small to be ELF");
		return 0;
	}

	if (eh->e_ehsize < sizeof(Elf_Ehdr) || !IS_ELF(*eh))
		return 0;

	if (eh->e_ident[EI_CLASS] != ELFCLASS) {
		warnx("unexpected word size %u", eh->e_ident[EI_CLASS]);
		return 0;
	}
	if (eh->e_ident[EI_VERSION] != ELF_TARG_VER) {
		warnx("unexpected version %u", eh->e_ident[EI_VERSION]);
		return 0;
	}
	if (eh->e_ident[EI_DATA] >= ELFDATANUM) {
		warnx("unexpected data format %u", eh->e_ident[EI_DATA]);
		return 0;
	}
	if (eh->e_shoff > filesize) {
		warnx("bogus section table offset 0x%llx", (off_t)eh->e_shoff);
		return 0;
	}
	if (eh->e_shentsize < sizeof(Elf_Shdr)) {
		warnx("bogus section header size %u", eh->e_shentsize);
		return 0;
	}
	if (eh->e_shnum > (filesize - eh->e_shoff) / eh->e_shentsize) {
		warnx("bogus section header count %u", eh->e_shnum);
		return 0;
	}
	if (eh->e_shstrndx >= eh->e_shnum) {
		warnx("bogus string table index %u", eh->e_shstrndx);
		return 0;
	}

	return 1;
}

int
elf_getshstab(const char *p, size_t filesize, const char **shstab,
    size_t *shstabsize)
{
	Elf_Ehdr		*eh = (Elf_Ehdr *)p;
	Elf_Shdr		*sh;

	sh = (Elf_Shdr *)(p + eh->e_shoff + eh->e_shstrndx * eh->e_shentsize);
	if (sh->sh_type != SHT_STRTAB) {
		warnx("unexpected string table type");
		return -1;
	}
	if (sh->sh_offset > filesize) {
		warnx("bogus string table offset");
		return -1;
	}
	if (sh->sh_size > filesize - sh->sh_offset) {
		warnx("bogus string table size");
		return -1;
	}
	if (shstab != NULL)
		*shstab = p + sh->sh_offset;
	if (shstabsize != NULL)
		*shstabsize = sh->sh_size;

	return 0;
}

ssize_t
elf_getsymtab(const char *p, const char *shstab, size_t shstabsz,
    const Elf_Sym **symtab, size_t *nsymb)
{
	Elf_Ehdr	*eh = (Elf_Ehdr *)p;
	Elf_Shdr	*sh;
	size_t		 snlen;
	ssize_t		 i;

	snlen = strlen(ELF_SYMTAB);

	for (i = 0; i < eh->e_shnum; i++) {
		sh = (Elf_Shdr *)(p + eh->e_shoff + i * eh->e_shentsize);

		if (sh->sh_type != SHT_SYMTAB)
			continue;

		if ((sh->sh_link >= eh->e_shnum) || (sh->sh_name >= shstabsz))
			continue;

		if (strncmp(shstab + sh->sh_name, ELF_SYMTAB, snlen) == 0) {
			if (symtab != NULL)
				*symtab = (Elf_Sym *)(p + sh->sh_offset);
			if (nsymb != NULL)
				*nsymb = (sh->sh_size / sh->sh_entsize);

			return i;
		}
	}

	return -1;
}

ssize_t
elf_getsection(char *p, const char *sname, const char *shstab,
    size_t shstabsz, const char **psdata, size_t *pssz)
{
	Elf_Ehdr	*eh = (Elf_Ehdr *)p;
	Elf_Shdr	*sh;
	char		*sdata = NULL;
	size_t		 snlen, ssz = 0;
	ssize_t		 sidx, i;

	snlen = strlen(sname);
	if (snlen == 0)
		return -1;

	/* Find the given section. */
	for (i = 0; i < eh->e_shnum; i++) {
		sh = (Elf_Shdr *)(p + eh->e_shoff + i * eh->e_shentsize);

		if ((sh->sh_link >= eh->e_shnum) || (sh->sh_name >= shstabsz))
			continue;

		if (strncmp(shstab + sh->sh_name, sname, snlen) == 0) {
			sidx = i;
			sdata = p + sh->sh_offset;
			ssz = sh->sh_size;
			elf_reloc_apply(p, shstab, shstabsz, sidx, sdata, ssz);
			break;
		}
	}

	if (sdata == NULL)
		return -1;

	if (psdata != NULL)
		*psdata = sdata;
	if (pssz != NULL)
		*pssz = ssz;

	return sidx;
}

static int
elf_reloc_size(unsigned long type)
{
	switch (type) {
#ifdef R_X86_64_64
	case R_X86_64_64:
		return sizeof(uint64_t);
#endif
#ifdef R_X86_64_32
	case R_X86_64_32:
		return sizeof(uint32_t);
#endif
#ifdef RELOC_32
	case RELOC_32:
		return sizeof(uint32_t);
#endif
	default:
		break;
	}

	return -1;
}

#define ELF_WRITE_RELOC(buf, val, rsize)				\
do {									\
	if (rsize == 4) {						\
		uint32_t v32 = val;					\
		memcpy(buf, &v32, sizeof(v32));				\
	} else {							\
		uint64_t v64 = val;					\
		memcpy(buf, &v64, sizeof(v64));				\
	}								\
} while (0)

static void
elf_reloc_apply(const char *p, const char *shstab, size_t shstabsz,
    ssize_t sidx, char *sdata, size_t ssz)
{
	Elf_Ehdr	*eh = (Elf_Ehdr *)p;
	Elf_Shdr	*sh;
	Elf_Rel		*rel = NULL;
	Elf_RelA	*rela = NULL;
	const Elf_Sym	*symtab, *sym;
	ssize_t		 symtabidx;
	size_t		 nsymb, rsym, rtyp, roff;
	size_t		 i, j;
	uint64_t	 value;
	int		 rsize;

	/* Find symbol table location and number of symbols. */
	symtabidx = elf_getsymtab(p, shstab, shstabsz, &symtab, &nsymb);
	if (symtabidx == -1) {
		warnx("symbol table not found");
		return;
	}

	/* Apply possible relocation. */
	for (i = 0; i < eh->e_shnum; i++) {
		sh = (Elf_Shdr *)(p + eh->e_shoff + i * eh->e_shentsize);

		if (sh->sh_size == 0)
			continue;

		if ((sh->sh_info != sidx) || (sh->sh_link != symtabidx))
			continue;

		switch (sh->sh_type) {
		case SHT_RELA:
			rela = (Elf_RelA *)(p + sh->sh_offset);
			for (j = 0; j < (sh->sh_size / sizeof(Elf_RelA)); j++) {
				rsym = ELF_R_SYM(rela[j].r_info);
				rtyp = ELF_R_TYPE(rela[j].r_info);
				roff = rela[j].r_offset;
				if (rsym >= nsymb)
					continue;
				sym = &symtab[rsym];
				value = sym->st_value + rela[j].r_addend;

				rsize = elf_reloc_size(rtyp);
				if (rsize == -1 || roff + rsize >= ssz)
					continue;

				ELF_WRITE_RELOC(sdata + roff, value, rsize);
			}
			break;
		case SHT_REL:
			rel = (Elf_Rel *)(p + sh->sh_offset);
			for (j = 0; j < (sh->sh_size / sizeof(Elf_Rel)); j++) {
				rsym = ELF_R_SYM(rel[j].r_info);
				rtyp = ELF_R_TYPE(rel[j].r_info);
				roff = rel[j].r_offset;
				if (rsym >= nsymb)
					continue;
				sym = &symtab[rsym];
				value = sym->st_value;

				rsize = elf_reloc_size(rtyp);
				if (rsize == -1 || roff + rsize >= ssz)
					continue;

				ELF_WRITE_RELOC(sdata + roff, value, rsize);
			}
			break;
		default:
			continue;
		}
	}
}


Generated by: GCOVR (Version 3.3)

Line	Branch	Exec	Source
1			/* $OpenBSD: elf.c,v 1.3 2017/08/29 21:10:20 deraadt Exp $ */
2
3			/*
4			* Copyright (c) 2016 Martin Pieuchot <mpi@openbsd.org>
5			*
6			* Permission to use, copy, modify, and distribute this software for any
7			* purpose with or without fee is hereby granted, provided that the above
8			* copyright notice and this permission notice appear in all copies.
9			*
10			* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11			* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12			* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13			* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14			* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15			* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16			* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17			*/
18
19			#include <sys/types.h>
20			#include <sys/exec_elf.h>
21
22			#include <machine/reloc.h>
23
24			#include <assert.h>
25			#include <err.h>
26			#include <string.h>
27
28			static int elf_reloc_size(unsigned long);
29			static void elf_reloc_apply(const char , const char , size_t, ssize_t,
30			char *, size_t);
31
32			int
33			iself(const char *p, size_t filesize)
34			{
35		4	Elf_Ehdr eh = (Elf_Ehdr )p;
36
37	✗✓	2	if (filesize < (off_t)sizeof(Elf_Ehdr)) {
38			warnx("file too small to be ELF");
39			return 0;
40			}
41
42	✓✗✓✗ ✓✗✓✗ ✗✓	10	if (eh->e_ehsize < sizeof(Elf_Ehdr) \|\| !IS_ELF(*eh))
43			return 0;
44
45	✗✓	2	if (eh->e_ident[EI_CLASS] != ELFCLASS) {
46			warnx("unexpected word size %u", eh->e_ident[EI_CLASS]);
47			return 0;
48			}
49	✗✓	2	if (eh->e_ident[EI_VERSION] != ELF_TARG_VER) {
50			warnx("unexpected version %u", eh->e_ident[EI_VERSION]);
51			return 0;
52			}
53	✗✓	2	if (eh->e_ident[EI_DATA] >= ELFDATANUM) {
54			warnx("unexpected data format %u", eh->e_ident[EI_DATA]);
55			return 0;
56			}
57	✗✓	2	if (eh->e_shoff > filesize) {
58			warnx("bogus section table offset 0x%llx", (off_t)eh->e_shoff);
59			return 0;
60			}
61	✗✓	2	if (eh->e_shentsize < sizeof(Elf_Shdr)) {
62			warnx("bogus section header size %u", eh->e_shentsize);
63			return 0;
64			}
65	✗✓	2	if (eh->e_shnum > (filesize - eh->e_shoff) / eh->e_shentsize) {
66			warnx("bogus section header count %u", eh->e_shnum);
67			return 0;
68			}
69	✗✓	2	if (eh->e_shstrndx >= eh->e_shnum) {
70			warnx("bogus string table index %u", eh->e_shstrndx);
71			return 0;
72			}
73
74		2	return 1;
75		2	}
76
77			int
78			elf_getshstab(const char p, size_t filesize, const char *shstab,
79			size_t *shstabsize)
80			{
81		4	Elf_Ehdr eh = (Elf_Ehdr )p;
82			Elf_Shdr *sh;
83
84		2	sh = (Elf_Shdr )(p + eh->e_shoff + eh->e_shstrndx eh->e_shentsize);
85	✗✓	2	if (sh->sh_type != SHT_STRTAB) {
86			warnx("unexpected string table type");
87			return -1;
88			}
89	✗✓	2	if (sh->sh_offset > filesize) {
90			warnx("bogus string table offset");
91			return -1;
92			}
93	✗✓	2	if (sh->sh_size > filesize - sh->sh_offset) {
94			warnx("bogus string table size");
95			return -1;
96			}
97	✓✗	2	if (shstab != NULL)
98		2	*shstab = p + sh->sh_offset;
99	✓✗	2	if (shstabsize != NULL)
100		2	*shstabsize = sh->sh_size;
101
102		2	return 0;
103		2	}
104
105			ssize_t
106			elf_getsymtab(const char p, const char shstab, size_t shstabsz,
107			const Elf_Sym *symtab, size_t nsymb)
108			{
109		8	Elf_Ehdr eh = (Elf_Ehdr )p;
110			Elf_Shdr *sh;
111			size_t snlen;
112			ssize_t i;
113
114			snlen = strlen(ELF_SYMTAB);
115
116	✓✗	256	for (i = 0; i < eh->e_shnum; i++) {
117		128	sh = (Elf_Shdr )(p + eh->e_shoff + i eh->e_shentsize);
118
119	✓✓	128	if (sh->sh_type != SHT_SYMTAB)
120			continue;
121
122	✓✗✓✗	8	if ((sh->sh_link >= eh->e_shnum) \|\| (sh->sh_name >= shstabsz))
123			continue;
124
125	✓✗	4	if (strncmp(shstab + sh->sh_name, ELF_SYMTAB, snlen) == 0) {
126	✓✗	4	if (symtab != NULL)
127		4	symtab = (Elf_Sym )(p + sh->sh_offset);
128	✓✗	4	if (nsymb != NULL)
129		4	*nsymb = (sh->sh_size / sh->sh_entsize);
130
131		4	return i;
132			}
133			}
134
135			return -1;
136		4	}
137
138			ssize_t
139			elf_getsection(char p, const char sname, const char *shstab,
140			size_t shstabsz, const char *psdata, size_t pssz)
141			{
142		4	Elf_Ehdr eh = (Elf_Ehdr )p;
143			Elf_Shdr *sh;
144			char *sdata = NULL;
145			size_t snlen, ssz = 0;
146			ssize_t sidx, i;
147
148		2	snlen = strlen(sname);
149	✗✓	2	if (snlen == 0)
150			return -1;
151
152			/* Find the given section. */
153	✓✗	132	for (i = 0; i < eh->e_shnum; i++) {
154		66	sh = (Elf_Shdr )(p + eh->e_shoff + i eh->e_shentsize);
155
156	✓✗✓✗	132	if ((sh->sh_link >= eh->e_shnum) \|\| (sh->sh_name >= shstabsz))
157			continue;
158
159	✓✓	66	if (strncmp(shstab + sh->sh_name, sname, snlen) == 0) {
160			sidx = i;
161		2	sdata = p + sh->sh_offset;
162		2	ssz = sh->sh_size;
163		2	elf_reloc_apply(p, shstab, shstabsz, sidx, sdata, ssz);
164		2	break;
165			}
166			}
167
168	✗✓	2	if (sdata == NULL)
169			return -1;
170
171	✓✗	2	if (psdata != NULL)
172		2	*psdata = sdata;
173	✓✗	2	if (pssz != NULL)
174		2	*pssz = ssz;
175
176		2	return sidx;
177		2	}
178
179			static int
180			elf_reloc_size(unsigned long type)
181			{
182			switch (type) {
183			#ifdef R_X86_64_64
184			case R_X86_64_64:
185			return sizeof(uint64_t);
186			#endif
187			#ifdef R_X86_64_32
188			case R_X86_64_32:
189			return sizeof(uint32_t);
190			#endif
191			#ifdef RELOC_32
192			case RELOC_32:
193			return sizeof(uint32_t);
194			#endif
195			default:
196			break;
197			}
198
199			return -1;
200			}
201
202			#define ELF_WRITE_RELOC(buf, val, rsize) \
203			do { \
204			if (rsize == 4) { \
205			uint32_t v32 = val; \
206			memcpy(buf, &v32, sizeof(v32)); \
207			} else { \
208			uint64_t v64 = val; \
209			memcpy(buf, &v64, sizeof(v64)); \
210			} \
211			} while (0)
212
213			static void
214			elf_reloc_apply(const char p, const char shstab, size_t shstabsz,
215			ssize_t sidx, char *sdata, size_t ssz)
216			{
217		4	Elf_Ehdr eh = (Elf_Ehdr )p;
218			Elf_Shdr *sh;
219			Elf_Rel *rel = NULL;
220			Elf_RelA *rela = NULL;
221		2	const Elf_Sym symtab, sym;
222			ssize_t symtabidx;
223		2	size_t nsymb, rsym, rtyp, roff;
224			size_t i, j;
225			uint64_t value;
226			int rsize;
227
228			/* Find symbol table location and number of symbols. */
229		2	symtabidx = elf_getsymtab(p, shstab, shstabsz, &symtab, &nsymb);
230	✗✓	2	if (symtabidx == -1) {
231			warnx("symbol table not found");
232			return;
233			}
234
235			/* Apply possible relocation. */
236	✓✓	136	for (i = 0; i < eh->e_shnum; i++) {
237		66	sh = (Elf_Shdr )(p + eh->e_shoff + i eh->e_shentsize);
238
239	✓✓	66	if (sh->sh_size == 0)
240			continue;
241
242	✗✓✗✗	64	if ((sh->sh_info != sidx) \|\| (sh->sh_link != symtabidx))
243			continue;
244
245			switch (sh->sh_type) {
246			case SHT_RELA:
247			rela = (Elf_RelA *)(p + sh->sh_offset);
248			for (j = 0; j < (sh->sh_size / sizeof(Elf_RelA)); j++) {
249			rsym = ELF_R_SYM(rela[j].r_info);
250			rtyp = ELF_R_TYPE(rela[j].r_info);
251			roff = rela[j].r_offset;
252			if (rsym >= nsymb)
253			continue;
254			sym = &symtab[rsym];
255			value = sym->st_value + rela[j].r_addend;
256
257			rsize = elf_reloc_size(rtyp);
258			if (rsize == -1 \|\| roff + rsize >= ssz)
259			continue;
260
261			ELF_WRITE_RELOC(sdata + roff, value, rsize);
262			}
263			break;
264			case SHT_REL:
265			rel = (Elf_Rel *)(p + sh->sh_offset);
266			for (j = 0; j < (sh->sh_size / sizeof(Elf_Rel)); j++) {
267			rsym = ELF_R_SYM(rel[j].r_info);
268			rtyp = ELF_R_TYPE(rel[j].r_info);
269			roff = rel[j].r_offset;
270			if (rsym >= nsymb)
271			continue;
272			sym = &symtab[rsym];
273			value = sym->st_value;
274
275			rsize = elf_reloc_size(rtyp);
276			if (rsize == -1 \|\| roff + rsize >= ssz)
277			continue;
278
279			ELF_WRITE_RELOC(sdata + roff, value, rsize);
280			}
281			break;
282			default:
283			continue;
284			}
285			}
286		4	}