1/*
2 * sortextable.c: Sort the kernel's exception table
3 *
4 * Copyright 2011 - 2012 Cavium, Inc.
5 *
6 * Based on code taken from recortmcount.c which is:
7 *
8 * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>.  All rights reserved.
9 * Licensed under the GNU General Public License, version 2 (GPLv2).
10 *
11 * Restructured to fit Linux format, as well as other updates:
12 *  Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
13 */
14
15/*
16 * Strategy: alter the vmlinux file in-place.
17 */
18
19#include <sys/types.h>
20#include <sys/mman.h>
21#include <sys/stat.h>
22#include <getopt.h>
23#include <elf.h>
24#include <fcntl.h>
25#include <setjmp.h>
26#include <stdio.h>
27#include <stdlib.h>
28#include <string.h>
29#include <unistd.h>
30
31#include <tools/be_byteshift.h>
32#include <tools/le_byteshift.h>
33
34#ifndef EM_ARCOMPACT
35#define EM_ARCOMPACT	93
36#endif
37
38#ifndef EM_XTENSA
39#define EM_XTENSA	94
40#endif
41
42#ifndef EM_AARCH64
43#define EM_AARCH64	183
44#endif
45
46#ifndef EM_MICROBLAZE
47#define EM_MICROBLAZE	189
48#endif
49
50static int fd_map;	/* File descriptor for file being modified. */
51static int mmap_failed; /* Boolean flag. */
52static void *ehdr_curr; /* current ElfXX_Ehdr *  for resource cleanup */
53static struct stat sb;	/* Remember .st_size, etc. */
54static jmp_buf jmpenv;	/* setjmp/longjmp per-file error escape */
55
56/* setjmp() return values */
57enum {
58	SJ_SETJMP = 0,  /* hardwired first return */
59	SJ_FAIL,
60	SJ_SUCCEED
61};
62
63/* Per-file resource cleanup when multiple files. */
64static void
65cleanup(void)
66{
67	if (!mmap_failed)
68		munmap(ehdr_curr, sb.st_size);
69	close(fd_map);
70}
71
72static void __attribute__((noreturn))
73fail_file(void)
74{
75	cleanup();
76	longjmp(jmpenv, SJ_FAIL);
77}
78
79/*
80 * Get the whole file as a programming convenience in order to avoid
81 * malloc+lseek+read+free of many pieces.  If successful, then mmap
82 * avoids copying unused pieces; else just read the whole file.
83 * Open for both read and write.
84 */
85static void *mmap_file(char const *fname)
86{
87	void *addr;
88
89	fd_map = open(fname, O_RDWR);
90	if (fd_map < 0 || fstat(fd_map, &sb) < 0) {
91		perror(fname);
92		fail_file();
93	}
94	if (!S_ISREG(sb.st_mode)) {
95		fprintf(stderr, "not a regular file: %s\n", fname);
96		fail_file();
97	}
98	addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_SHARED,
99		    fd_map, 0);
100	if (addr == MAP_FAILED) {
101		mmap_failed = 1;
102		fprintf(stderr, "Could not mmap file: %s\n", fname);
103		fail_file();
104	}
105	return addr;
106}
107
108static uint64_t r8be(const uint64_t *x)
109{
110	return get_unaligned_be64(x);
111}
112static uint32_t rbe(const uint32_t *x)
113{
114	return get_unaligned_be32(x);
115}
116static uint16_t r2be(const uint16_t *x)
117{
118	return get_unaligned_be16(x);
119}
120static uint64_t r8le(const uint64_t *x)
121{
122	return get_unaligned_le64(x);
123}
124static uint32_t rle(const uint32_t *x)
125{
126	return get_unaligned_le32(x);
127}
128static uint16_t r2le(const uint16_t *x)
129{
130	return get_unaligned_le16(x);
131}
132
133static void w8be(uint64_t val, uint64_t *x)
134{
135	put_unaligned_be64(val, x);
136}
137static void wbe(uint32_t val, uint32_t *x)
138{
139	put_unaligned_be32(val, x);
140}
141static void w2be(uint16_t val, uint16_t *x)
142{
143	put_unaligned_be16(val, x);
144}
145static void w8le(uint64_t val, uint64_t *x)
146{
147	put_unaligned_le64(val, x);
148}
149static void wle(uint32_t val, uint32_t *x)
150{
151	put_unaligned_le32(val, x);
152}
153static void w2le(uint16_t val, uint16_t *x)
154{
155	put_unaligned_le16(val, x);
156}
157
158static uint64_t (*r8)(const uint64_t *);
159static uint32_t (*r)(const uint32_t *);
160static uint16_t (*r2)(const uint16_t *);
161static void (*w8)(uint64_t, uint64_t *);
162static void (*w)(uint32_t, uint32_t *);
163static void (*w2)(uint16_t, uint16_t *);
164
165typedef void (*table_sort_t)(char *, int);
166
167/*
168 * Move reserved section indices SHN_LORESERVE..SHN_HIRESERVE out of
169 * the way to -256..-1, to avoid conflicting with real section
170 * indices.
171 */
172#define SPECIAL(i) ((i) - (SHN_HIRESERVE + 1))
173
174static inline int is_shndx_special(unsigned int i)
175{
176	return i != SHN_XINDEX && i >= SHN_LORESERVE && i <= SHN_HIRESERVE;
177}
178
179/* Accessor for sym->st_shndx, hides ugliness of "64k sections" */
180static inline unsigned int get_secindex(unsigned int shndx,
181					unsigned int sym_offs,
182					const Elf32_Word *symtab_shndx_start)
183{
184	if (is_shndx_special(shndx))
185		return SPECIAL(shndx);
186	if (shndx != SHN_XINDEX)
187		return shndx;
188	return r(&symtab_shndx_start[sym_offs]);
189}
190
191/* 32 bit and 64 bit are very similar */
192#include "sortextable.h"
193#define SORTEXTABLE_64
194#include "sortextable.h"
195
196static int compare_relative_table(const void *a, const void *b)
197{
198	int32_t av = (int32_t)r(a);
199	int32_t bv = (int32_t)r(b);
200
201	if (av < bv)
202		return -1;
203	if (av > bv)
204		return 1;
205	return 0;
206}
207
208static void sort_relative_table(char *extab_image, int image_size)
209{
210	int i;
211
212	/*
213	 * Do the same thing the runtime sort does, first normalize to
214	 * being relative to the start of the section.
215	 */
216	i = 0;
217	while (i < image_size) {
218		uint32_t *loc = (uint32_t *)(extab_image + i);
219		w(r(loc) + i, loc);
220		i += 4;
221	}
222
223	qsort(extab_image, image_size / 8, 8, compare_relative_table);
224
225	/* Now denormalize. */
226	i = 0;
227	while (i < image_size) {
228		uint32_t *loc = (uint32_t *)(extab_image + i);
229		w(r(loc) - i, loc);
230		i += 4;
231	}
232}
233
234static void
235do_file(char const *const fname)
236{
237	table_sort_t custom_sort;
238	Elf32_Ehdr *ehdr = mmap_file(fname);
239
240	ehdr_curr = ehdr;
241	switch (ehdr->e_ident[EI_DATA]) {
242	default:
243		fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
244			ehdr->e_ident[EI_DATA], fname);
245		fail_file();
246		break;
247	case ELFDATA2LSB:
248		r = rle;
249		r2 = r2le;
250		r8 = r8le;
251		w = wle;
252		w2 = w2le;
253		w8 = w8le;
254		break;
255	case ELFDATA2MSB:
256		r = rbe;
257		r2 = r2be;
258		r8 = r8be;
259		w = wbe;
260		w2 = w2be;
261		w8 = w8be;
262		break;
263	}  /* end switch */
264	if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
265	||  r2(&ehdr->e_type) != ET_EXEC
266	||  ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
267		fprintf(stderr, "unrecognized ET_EXEC file %s\n", fname);
268		fail_file();
269	}
270
271	custom_sort = NULL;
272	switch (r2(&ehdr->e_machine)) {
273	default:
274		fprintf(stderr, "unrecognized e_machine %d %s\n",
275			r2(&ehdr->e_machine), fname);
276		fail_file();
277		break;
278	case EM_386:
279	case EM_X86_64:
280	case EM_S390:
281		custom_sort = sort_relative_table;
282		break;
283	case EM_ARCOMPACT:
284	case EM_ARM:
285	case EM_AARCH64:
286	case EM_MICROBLAZE:
287	case EM_MIPS:
288	case EM_XTENSA:
289		break;
290	}  /* end switch */
291
292	switch (ehdr->e_ident[EI_CLASS]) {
293	default:
294		fprintf(stderr, "unrecognized ELF class %d %s\n",
295			ehdr->e_ident[EI_CLASS], fname);
296		fail_file();
297		break;
298	case ELFCLASS32:
299		if (r2(&ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
300		||  r2(&ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
301			fprintf(stderr,
302				"unrecognized ET_EXEC file: %s\n", fname);
303			fail_file();
304		}
305		do32(ehdr, fname, custom_sort);
306		break;
307	case ELFCLASS64: {
308		Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
309		if (r2(&ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
310		||  r2(&ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
311			fprintf(stderr,
312				"unrecognized ET_EXEC file: %s\n", fname);
313			fail_file();
314		}
315		do64(ghdr, fname, custom_sort);
316		break;
317	}
318	}  /* end switch */
319
320	cleanup();
321}
322
323int
324main(int argc, char *argv[])
325{
326	int n_error = 0;  /* gcc-4.3.0 false positive complaint */
327	int i;
328
329	if (argc < 2) {
330		fprintf(stderr, "usage: sortextable vmlinux...\n");
331		return 0;
332	}
333
334	/* Process each file in turn, allowing deep failure. */
335	for (i = 1; i < argc; i++) {
336		char *file = argv[i];
337		int const sjval = setjmp(jmpenv);
338
339		switch (sjval) {
340		default:
341			fprintf(stderr, "internal error: %s\n", file);
342			exit(1);
343			break;
344		case SJ_SETJMP:    /* normal sequence */
345			/* Avoid problems if early cleanup() */
346			fd_map = -1;
347			ehdr_curr = NULL;
348			mmap_failed = 1;
349			do_file(file);
350			break;
351		case SJ_FAIL:    /* error in do_file or below */
352			++n_error;
353			break;
354		case SJ_SUCCEED:    /* premature success */
355			/* do nothing */
356			break;
357		}  /* end switch */
358	}
359	return !!n_error;
360}
361