1/*
2 * Copyright (c) 1997 Christopher G. Demetriou.  All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 * 3. All advertising materials mentioning features or use of this software
13 *    must display the following acknowledgement:
14 *      This product includes software developed by Christopher G. Demetriou
15 *	for the NetBSD Project.
16 * 4. The name of the author may not be used to endorse or promote products
17 *    derived from this software without specific prior written permission
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31#include <sys/cdefs.h>
32#ifndef lint
33#if 0
34__RCSID("$NetBSD: exec_elf32.c,v 1.6 1999/09/20 04:12:16 christos Exp $");
35#endif
36#endif
37__FBSDID("$FreeBSD$");
38
39#ifndef ELFSIZE
40#define ELFSIZE         32
41#endif
42
43#include <sys/types.h>
44#include <sys/endian.h>
45#include <sys/stat.h>
46
47#include <errno.h>
48#include <limits.h>
49#include <stdio.h>
50#include <stdlib.h>
51#include <string.h>
52#include <unistd.h>
53
54#include "extern.h"
55
56#if (defined(NLIST_ELF32) && (ELFSIZE == 32)) || \
57    (defined(NLIST_ELF64) && (ELFSIZE == 64))
58
59#define	__ELF_WORD_SIZE ELFSIZE
60#if (ELFSIZE == 32)
61#include <sys/elf32.h>
62#define	xewtoh(x)	((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
63#define	htoxew(x)	((data == ELFDATA2MSB) ? htobe32(x) : htole32(x))
64#define	wewtoh(x)	((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
65#define	htowew(x)	((data == ELFDATA2MSB) ? htobe32(x) : htole32(x))
66#elif (ELFSIZE == 64)
67#include <sys/elf64.h>
68#define	xewtoh(x)	((data == ELFDATA2MSB) ? be64toh(x) : le64toh(x))
69#define	htoxew(x)	((data == ELFDATA2MSB) ? htobe64(x) : htole64(x))
70/* elf64 Elf64_Word are 32 bits */
71#define	wewtoh(x)	((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
72#define	htowew(x)	((data == ELFDATA2MSB) ? htobe32(x) : htole32(x))
73#endif
74#include <sys/elf_generic.h>
75
76#define CONCAT(x,y)     __CONCAT(x,y)
77#define ELFNAME(x)      CONCAT(elf,CONCAT(ELFSIZE,CONCAT(_,x)))
78#define ELFNAME2(x,y)   CONCAT(x,CONCAT(_elf,CONCAT(ELFSIZE,CONCAT(_,y))))
79#define ELFNAMEEND(x)   CONCAT(x,CONCAT(_elf,ELFSIZE))
80#define ELFDEFNNAME(x)  CONCAT(ELF,CONCAT(ELFSIZE,CONCAT(_,x)))
81
82#define	xe16toh(x)	((data == ELFDATA2MSB) ? be16toh(x) : le16toh(x))
83#define	xe32toh(x)	((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
84#define	htoxe32(x)	((data == ELFDATA2MSB) ? htobe32(x) : htole32(x))
85
86struct shlayout {
87	Elf_Shdr *shdr;
88	void *bufp;
89};
90
91static ssize_t
92xreadatoff(int fd, void *buf, off_t off, size_t size, const char *fn)
93{
94	ssize_t rv;
95
96	if (lseek(fd, off, SEEK_SET) != off) {
97		perror(fn);
98		return -1;
99	}
100	if ((size_t)(rv = read(fd, buf, size)) != size) {
101		fprintf(stderr, "%s: read error: %s\n", fn,
102		    rv == -1 ? strerror(errno) : "short read");
103		return -1;
104	}
105	return size;
106}
107
108static ssize_t
109xwriteatoff(int fd, void *buf, off_t off, size_t size, const char *fn)
110{
111	ssize_t rv;
112
113	if (lseek(fd, off, SEEK_SET) != off) {
114		perror(fn);
115		return -1;
116	}
117	if ((size_t)(rv = write(fd, buf, size)) != size) {
118		fprintf(stderr, "%s: write error: %s\n", fn,
119		    rv == -1 ? strerror(errno) : "short write");
120		return -1;
121	}
122	return size;
123}
124
125static void *
126xmalloc(size_t size, const char *fn, const char *use)
127{
128	void *rv;
129
130	rv = malloc(size);
131	if (rv == NULL)
132		fprintf(stderr, "%s: out of memory (allocating for %s)\n",
133		    fn, use);
134	return (rv);
135}
136
137static void *
138xrealloc(void *ptr, size_t size, const char *fn, const char *use)
139{
140	void *rv;
141
142	rv = realloc(ptr, size);
143	if (rv == NULL) {
144		free(ptr);
145		fprintf(stderr, "%s: out of memory (reallocating for %s)\n",
146		    fn, use);
147	}
148	return (rv);
149}
150
151int
152ELFNAMEEND(check)(int fd, const char *fn)
153{
154	Elf_Ehdr eh;
155	struct stat sb;
156	unsigned char data;
157
158	/*
159	 * Check the header to maek sure it's an ELF file (of the
160	 * appropriate size).
161	 */
162	if (fstat(fd, &sb) == -1)
163		return 0;
164	if (sb.st_size < (off_t)(sizeof eh))
165		return 0;
166	if (read(fd, &eh, sizeof eh) != sizeof eh)
167		return 0;
168
169	if (IS_ELF(eh) == 0)
170                return 0;
171
172	data = eh.e_ident[EI_DATA];
173
174	switch (xe16toh(eh.e_machine)) {
175	case EM_386: break;
176	case EM_ALPHA: break;
177#ifndef EM_ARM
178#define EM_ARM		40
179#endif
180	case EM_ARM: break;
181#ifndef EM_MIPS
182#define EM_MIPS		8
183#endif
184#ifndef EM_MIPS_RS4_BE		/* same as EM_MIPS_RS3_LE */
185#define EM_MIPS_RS4_BE	10
186#endif
187	case EM_MIPS: break;
188	case /* EM_MIPS_RS3_LE */ EM_MIPS_RS4_BE: break;
189#ifndef EM_IA_64
190#define	EM_IA_64	50
191#endif
192	case EM_IA_64: break;
193#ifndef EM_PPC
194#define	EM_PPC		20
195#endif
196	case EM_PPC: break;
197#ifndef EM_PPC64
198#define	EM_PPC64	21
199#endif
200	case EM_PPC64: break;
201#ifndef EM_SPARCV9
202#define	EM_SPARCV9	43
203#endif
204	case EM_SPARCV9: break;
205#ifndef EM_X86_64
206#define	EM_X86_64	62
207#endif
208	case EM_X86_64: break;
209/*        ELFDEFNNAME(MACHDEP_ID_CASES) */
210
211        default:
212                return 0;
213        }
214
215	return 1;
216}
217
218/*
219 * This function 'hides' (some of) ELF executable file's symbols.
220 * It hides them by renaming them to "_$$hide$$ <filename> <symbolname>".
221 * Symbols in the global keep list, or which are marked as being undefined,
222 * are left alone.
223 *
224 * An old version of this code shuffled various tables around, turning
225 * global symbols to be hidden into local symbols.  That lost on the
226 * mips, because CALL16 relocs must reference global symbols, and, if
227 * those symbols were being hidden, they were no longer global.
228 *
229 * The new renaming behaviour doesn't take global symbols out of the
230 * namespace.  However, it's ... unlikely that there will ever be
231 * any collisions in practice because of the new method.
232 */
233int
234ELFNAMEEND(hide)(int fd, const char *fn)
235{
236	Elf_Ehdr ehdr;
237	struct shlayout *layoutp = NULL;
238	Elf_Shdr *shdrp = NULL, *symtabshdr, *strtabshdr, *shstrtabshdr;
239	Elf_Shdr shdrshdr;
240	Elf_Sym *symtabp = NULL;
241	char *shstrtabp = NULL, *strtabp = NULL;
242	Elf_Size nsyms, ewi;
243	Elf_Off off;
244	ssize_t shdrsize;
245	int rv, i, weird, l, m, r, strtabidx;
246	size_t nstrtab_size, nstrtab_nextoff, fn_size, size;
247	char *nstrtabp = NULL;
248	unsigned char data;
249	const char *weirdreason = NULL;
250	void *buf;
251	Elf_Half shnum;
252
253	rv = 0;
254	if (xreadatoff(fd, &ehdr, 0, sizeof ehdr, fn) != sizeof ehdr)
255		goto bad;
256
257	data = ehdr.e_ident[EI_DATA];
258	shnum = xe16toh(ehdr.e_shnum);
259
260	shdrsize = shnum * xe16toh(ehdr.e_shentsize);
261	if ((shdrp = xmalloc(shdrsize, fn, "section header table")) == NULL)
262		goto bad;
263	if (xreadatoff(fd, shdrp, xewtoh(ehdr.e_shoff), shdrsize, fn) !=
264	    shdrsize)
265		goto bad;
266
267	symtabshdr = strtabshdr = shstrtabshdr = NULL;
268	weird = 0;
269	for (i = 0; i < shnum; i++) {
270		switch (xe32toh(shdrp[i].sh_type)) {
271		case SHT_SYMTAB:
272			if (symtabshdr != NULL) {
273				weird = 1;
274				weirdreason = "multiple symbol tables";
275			}
276			symtabshdr = &shdrp[i];
277			strtabshdr = &shdrp[xe32toh(shdrp[i].sh_link)];
278			break;
279		case SHT_STRTAB:
280			if (i == xe16toh(ehdr.e_shstrndx))
281				shstrtabshdr = &shdrp[i];
282			break;
283		}
284	}
285	if (symtabshdr == NULL)
286		goto out;
287	if (strtabshdr == NULL) {
288		weird = 1;
289		weirdreason = "string table does not exist";
290	}
291	if (shstrtabshdr == NULL) {
292		weird = 1;
293		weirdreason = "section header string table does not exist";
294	}
295	if (weirdreason == NULL)
296		weirdreason = "unsupported";
297	if (weird) {
298		fprintf(stderr, "%s: weird executable (%s)\n", fn, weirdreason);
299		goto bad;
300	}
301
302	/*
303	 * sort section layout table by offset
304	 */
305	layoutp = xmalloc((shnum + 1) * sizeof(struct shlayout),
306	    fn, "layout table");
307	if (layoutp == NULL)
308		goto bad;
309
310	/* add a pseudo entry to represent the section header table */
311	shdrshdr.sh_offset = ehdr.e_shoff;
312	shdrshdr.sh_size = htoxew(shdrsize);
313	shdrshdr.sh_addralign = htoxew(ELFSIZE / 8);
314	layoutp[shnum].shdr = &shdrshdr;
315
316	/* insert and sort normal section headers */
317	for (i = shnum; i-- != 0;) {
318		l = i + 1;
319		r = shnum;
320		while (l <= r) {
321			m = ( l + r) / 2;
322			if (xewtoh(shdrp[i].sh_offset) >
323			    xewtoh(layoutp[m].shdr->sh_offset))
324				l = m + 1;
325			else
326				r = m - 1;
327		}
328
329		if (r != i) {
330			memmove(&layoutp[i], &layoutp[i + 1],
331			    sizeof(struct shlayout) * (r - i));
332		}
333
334		layoutp[r].shdr = &shdrp[i];
335		layoutp[r].bufp = NULL;
336	}
337	++shnum;
338
339	/*
340	 * load up everything we need
341	 */
342
343	/* load section string table for debug use */
344	if ((shstrtabp = xmalloc(xewtoh(shstrtabshdr->sh_size), fn,
345	    "section string table")) == NULL)
346		goto bad;
347	if ((size_t)xreadatoff(fd, shstrtabp, xewtoh(shstrtabshdr->sh_offset),
348	    xewtoh(shstrtabshdr->sh_size), fn) != xewtoh(shstrtabshdr->sh_size))
349		goto bad;
350
351	/* we need symtab, strtab, and everything behind strtab */
352	strtabidx = INT_MAX;
353	for (i = 0; i < shnum; i++) {
354		if (layoutp[i].shdr == &shdrshdr) {
355			/* not load section header again */
356			layoutp[i].bufp = shdrp;
357			continue;
358		}
359		if (layoutp[i].shdr == shstrtabshdr) {
360			/* not load section string table again */
361			layoutp[i].bufp = shstrtabp;
362			continue;
363		}
364
365		if (layoutp[i].shdr == strtabshdr)
366			strtabidx = i;
367		if (layoutp[i].shdr == symtabshdr || i >= strtabidx) {
368			off = xewtoh(layoutp[i].shdr->sh_offset);
369			size = xewtoh(layoutp[i].shdr->sh_size);
370			layoutp[i].bufp = xmalloc(size, fn,
371			    shstrtabp + xewtoh(layoutp[i].shdr->sh_name));
372			if (layoutp[i].bufp == NULL)
373				goto bad;
374			if ((size_t)xreadatoff(fd, layoutp[i].bufp, off, size, fn) !=
375			    size)
376				goto bad;
377
378			/* set symbol table and string table */
379			if (layoutp[i].shdr == symtabshdr)
380				symtabp = layoutp[i].bufp;
381			else if (layoutp[i].shdr == strtabshdr)
382				strtabp = layoutp[i].bufp;
383		}
384	}
385
386	nstrtab_size = 256;
387	nstrtabp = xmalloc(nstrtab_size, fn, "new string table");
388	if (nstrtabp == NULL)
389		goto bad;
390	nstrtab_nextoff = 0;
391
392	fn_size = strlen(fn);
393
394	/* Prepare data structures for symbol movement. */
395	nsyms = xewtoh(symtabshdr->sh_size) / xewtoh(symtabshdr->sh_entsize);
396
397	/* move symbols, making them local */
398	for (ewi = 0; ewi < nsyms; ewi++) {
399		Elf_Sym *sp = &symtabp[ewi];
400		const char *symname = strtabp + xe32toh(sp->st_name);
401		size_t newent_len;
402		/*
403		 * make sure there's size for the next entry, even if it's
404		 * as large as it can be.
405		 *
406		 * "_$$hide$$ <filename> <symname><NUL>" ->
407		 *    9 + 3 + sizes of fn and sym name
408		 */
409		while ((nstrtab_size - nstrtab_nextoff) <
410		    strlen(symname) + fn_size + 12) {
411			nstrtab_size *= 2;
412			nstrtabp = xrealloc(nstrtabp, nstrtab_size, fn,
413			    "new string table");
414			if (nstrtabp == NULL)
415				goto bad;
416		}
417
418		sp->st_name = htowew(nstrtab_nextoff);
419
420		/* if it's a keeper or is undefined, don't rename it. */
421		if (in_keep_list(symname) ||
422		    (xe16toh(sp->st_shndx) == SHN_UNDEF)) {
423			newent_len = sprintf(nstrtabp + nstrtab_nextoff,
424			    "%s", symname) + 1;
425		} else {
426			newent_len = sprintf(nstrtabp + nstrtab_nextoff,
427			    "_$$hide$$ %s %s", fn, symname) + 1;
428		}
429		nstrtab_nextoff += newent_len;
430	}
431	strtabshdr->sh_size = htoxew(nstrtab_nextoff);
432
433	/*
434	 * update section header table in ascending order of offset
435	 */
436	for (i = strtabidx + 1; i < shnum; i++) {
437		Elf_Off off, align;
438		off = xewtoh(layoutp[i - 1].shdr->sh_offset) +
439		    xewtoh(layoutp[i - 1].shdr->sh_size);
440		align = xewtoh(layoutp[i].shdr->sh_addralign);
441		off = (off + (align - 1)) & ~(align - 1);
442		layoutp[i].shdr->sh_offset = htoxew(off);
443	}
444
445	/*
446	 * write data to the file in descending order of offset
447	 */
448	for (i = shnum; i-- != 0;) {
449		if (layoutp[i].shdr == strtabshdr) {
450			/* new string table */
451			buf = nstrtabp;
452		} else
453			buf = layoutp[i].bufp;
454
455		if (layoutp[i].shdr == &shdrshdr ||
456		    layoutp[i].shdr == symtabshdr || i >= strtabidx) {
457			if (buf == NULL)
458				goto bad;
459
460			/*
461			 * update the offset of section header table in elf
462			 * header if needed.
463			 */
464			if (layoutp[i].shdr == &shdrshdr &&
465			    ehdr.e_shoff != shdrshdr.sh_offset) {
466				ehdr.e_shoff = shdrshdr.sh_offset;
467				off = (ELFSIZE == 32) ? 32 : 44;
468				size = sizeof(Elf_Off);
469				if ((size_t)xwriteatoff(fd, &ehdr.e_shoff, off, size,
470				    fn) != size)
471					goto bad;
472			}
473
474			off = xewtoh(layoutp[i].shdr->sh_offset);
475			size = xewtoh(layoutp[i].shdr->sh_size);
476			if ((size_t)xwriteatoff(fd, buf, off, size, fn) != size)
477				goto bad;
478		}
479	}
480
481out:
482	if (layoutp != NULL) {
483		for (i = 0; i < shnum; i++) {
484			if (layoutp[i].bufp != NULL)
485				free(layoutp[i].bufp);
486		}
487		free(layoutp);
488	}
489	free(nstrtabp);
490	return (rv);
491
492bad:
493	rv = 1;
494	goto out;
495}
496
497#endif /* include this size of ELF */
498