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Linux/scripts/sortextable.c

  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 
 50 #ifndef EM_ARCV2
 51 #define EM_ARCV2        195
 52 #endif
 53 
 54 static int fd_map;      /* File descriptor for file being modified. */
 55 static int mmap_failed; /* Boolean flag. */
 56 static void *ehdr_curr; /* current ElfXX_Ehdr *  for resource cleanup */
 57 static struct stat sb;  /* Remember .st_size, etc. */
 58 static jmp_buf jmpenv;  /* setjmp/longjmp per-file error escape */
 59 
 60 /* setjmp() return values */
 61 enum {
 62         SJ_SETJMP = 0,  /* hardwired first return */
 63         SJ_FAIL,
 64         SJ_SUCCEED
 65 };
 66 
 67 /* Per-file resource cleanup when multiple files. */
 68 static void
 69 cleanup(void)
 70 {
 71         if (!mmap_failed)
 72                 munmap(ehdr_curr, sb.st_size);
 73         close(fd_map);
 74 }
 75 
 76 static void __attribute__((noreturn))
 77 fail_file(void)
 78 {
 79         cleanup();
 80         longjmp(jmpenv, SJ_FAIL);
 81 }
 82 
 83 /*
 84  * Get the whole file as a programming convenience in order to avoid
 85  * malloc+lseek+read+free of many pieces.  If successful, then mmap
 86  * avoids copying unused pieces; else just read the whole file.
 87  * Open for both read and write.
 88  */
 89 static void *mmap_file(char const *fname)
 90 {
 91         void *addr;
 92 
 93         fd_map = open(fname, O_RDWR);
 94         if (fd_map < 0 || fstat(fd_map, &sb) < 0) {
 95                 perror(fname);
 96                 fail_file();
 97         }
 98         if (!S_ISREG(sb.st_mode)) {
 99                 fprintf(stderr, "not a regular file: %s\n", fname);
100                 fail_file();
101         }
102         addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_SHARED,
103                     fd_map, 0);
104         if (addr == MAP_FAILED) {
105                 mmap_failed = 1;
106                 fprintf(stderr, "Could not mmap file: %s\n", fname);
107                 fail_file();
108         }
109         return addr;
110 }
111 
112 static uint64_t r8be(const uint64_t *x)
113 {
114         return get_unaligned_be64(x);
115 }
116 static uint32_t rbe(const uint32_t *x)
117 {
118         return get_unaligned_be32(x);
119 }
120 static uint16_t r2be(const uint16_t *x)
121 {
122         return get_unaligned_be16(x);
123 }
124 static uint64_t r8le(const uint64_t *x)
125 {
126         return get_unaligned_le64(x);
127 }
128 static uint32_t rle(const uint32_t *x)
129 {
130         return get_unaligned_le32(x);
131 }
132 static uint16_t r2le(const uint16_t *x)
133 {
134         return get_unaligned_le16(x);
135 }
136 
137 static void w8be(uint64_t val, uint64_t *x)
138 {
139         put_unaligned_be64(val, x);
140 }
141 static void wbe(uint32_t val, uint32_t *x)
142 {
143         put_unaligned_be32(val, x);
144 }
145 static void w2be(uint16_t val, uint16_t *x)
146 {
147         put_unaligned_be16(val, x);
148 }
149 static void w8le(uint64_t val, uint64_t *x)
150 {
151         put_unaligned_le64(val, x);
152 }
153 static void wle(uint32_t val, uint32_t *x)
154 {
155         put_unaligned_le32(val, x);
156 }
157 static void w2le(uint16_t val, uint16_t *x)
158 {
159         put_unaligned_le16(val, x);
160 }
161 
162 static uint64_t (*r8)(const uint64_t *);
163 static uint32_t (*r)(const uint32_t *);
164 static uint16_t (*r2)(const uint16_t *);
165 static void (*w8)(uint64_t, uint64_t *);
166 static void (*w)(uint32_t, uint32_t *);
167 static void (*w2)(uint16_t, uint16_t *);
168 
169 typedef void (*table_sort_t)(char *, int);
170 
171 /*
172  * Move reserved section indices SHN_LORESERVE..SHN_HIRESERVE out of
173  * the way to -256..-1, to avoid conflicting with real section
174  * indices.
175  */
176 #define SPECIAL(i) ((i) - (SHN_HIRESERVE + 1))
177 
178 static inline int is_shndx_special(unsigned int i)
179 {
180         return i != SHN_XINDEX && i >= SHN_LORESERVE && i <= SHN_HIRESERVE;
181 }
182 
183 /* Accessor for sym->st_shndx, hides ugliness of "64k sections" */
184 static inline unsigned int get_secindex(unsigned int shndx,
185                                         unsigned int sym_offs,
186                                         const Elf32_Word *symtab_shndx_start)
187 {
188         if (is_shndx_special(shndx))
189                 return SPECIAL(shndx);
190         if (shndx != SHN_XINDEX)
191                 return shndx;
192         return r(&symtab_shndx_start[sym_offs]);
193 }
194 
195 /* 32 bit and 64 bit are very similar */
196 #include "sortextable.h"
197 #define SORTEXTABLE_64
198 #include "sortextable.h"
199 
200 static int compare_relative_table(const void *a, const void *b)
201 {
202         int32_t av = (int32_t)r(a);
203         int32_t bv = (int32_t)r(b);
204 
205         if (av < bv)
206                 return -1;
207         if (av > bv)
208                 return 1;
209         return 0;
210 }
211 
212 static void x86_sort_relative_table(char *extab_image, int image_size)
213 {
214         int i;
215 
216         i = 0;
217         while (i < image_size) {
218                 uint32_t *loc = (uint32_t *)(extab_image + i);
219 
220                 w(r(loc) + i, loc);
221                 w(r(loc + 1) + i + 4, loc + 1);
222                 w(r(loc + 2) + i + 8, loc + 2);
223 
224                 i += sizeof(uint32_t) * 3;
225         }
226 
227         qsort(extab_image, image_size / 12, 12, compare_relative_table);
228 
229         i = 0;
230         while (i < image_size) {
231                 uint32_t *loc = (uint32_t *)(extab_image + i);
232 
233                 w(r(loc) - i, loc);
234                 w(r(loc + 1) - (i + 4), loc + 1);
235                 w(r(loc + 2) - (i + 8), loc + 2);
236 
237                 i += sizeof(uint32_t) * 3;
238         }
239 }
240 
241 static void sort_relative_table(char *extab_image, int image_size)
242 {
243         int i;
244 
245         /*
246          * Do the same thing the runtime sort does, first normalize to
247          * being relative to the start of the section.
248          */
249         i = 0;
250         while (i < image_size) {
251                 uint32_t *loc = (uint32_t *)(extab_image + i);
252                 w(r(loc) + i, loc);
253                 i += 4;
254         }
255 
256         qsort(extab_image, image_size / 8, 8, compare_relative_table);
257 
258         /* Now denormalize. */
259         i = 0;
260         while (i < image_size) {
261                 uint32_t *loc = (uint32_t *)(extab_image + i);
262                 w(r(loc) - i, loc);
263                 i += 4;
264         }
265 }
266 
267 static void
268 do_file(char const *const fname)
269 {
270         table_sort_t custom_sort;
271         Elf32_Ehdr *ehdr = mmap_file(fname);
272 
273         ehdr_curr = ehdr;
274         switch (ehdr->e_ident[EI_DATA]) {
275         default:
276                 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
277                         ehdr->e_ident[EI_DATA], fname);
278                 fail_file();
279                 break;
280         case ELFDATA2LSB:
281                 r = rle;
282                 r2 = r2le;
283                 r8 = r8le;
284                 w = wle;
285                 w2 = w2le;
286                 w8 = w8le;
287                 break;
288         case ELFDATA2MSB:
289                 r = rbe;
290                 r2 = r2be;
291                 r8 = r8be;
292                 w = wbe;
293                 w2 = w2be;
294                 w8 = w8be;
295                 break;
296         }  /* end switch */
297         if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
298         ||  (r2(&ehdr->e_type) != ET_EXEC && r2(&ehdr->e_type) != ET_DYN)
299         ||  ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
300                 fprintf(stderr, "unrecognized ET_EXEC/ET_DYN file %s\n", fname);
301                 fail_file();
302         }
303 
304         custom_sort = NULL;
305         switch (r2(&ehdr->e_machine)) {
306         default:
307                 fprintf(stderr, "unrecognized e_machine %d %s\n",
308                         r2(&ehdr->e_machine), fname);
309                 fail_file();
310                 break;
311         case EM_386:
312         case EM_X86_64:
313                 custom_sort = x86_sort_relative_table;
314                 break;
315 
316         case EM_S390:
317         case EM_AARCH64:
318         case EM_PARISC:
319         case EM_PPC:
320         case EM_PPC64:
321                 custom_sort = sort_relative_table;
322                 break;
323         case EM_ARCOMPACT:
324         case EM_ARCV2:
325         case EM_ARM:
326         case EM_MICROBLAZE:
327         case EM_MIPS:
328         case EM_XTENSA:
329                 break;
330         }  /* end switch */
331 
332         switch (ehdr->e_ident[EI_CLASS]) {
333         default:
334                 fprintf(stderr, "unrecognized ELF class %d %s\n",
335                         ehdr->e_ident[EI_CLASS], fname);
336                 fail_file();
337                 break;
338         case ELFCLASS32:
339                 if (r2(&ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
340                 ||  r2(&ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
341                         fprintf(stderr,
342                                 "unrecognized ET_EXEC/ET_DYN file: %s\n", fname);
343                         fail_file();
344                 }
345                 do32(ehdr, fname, custom_sort);
346                 break;
347         case ELFCLASS64: {
348                 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
349                 if (r2(&ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
350                 ||  r2(&ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
351                         fprintf(stderr,
352                                 "unrecognized ET_EXEC/ET_DYN file: %s\n", fname);
353                         fail_file();
354                 }
355                 do64(ghdr, fname, custom_sort);
356                 break;
357         }
358         }  /* end switch */
359 
360         cleanup();
361 }
362 
363 int
364 main(int argc, char *argv[])
365 {
366         int n_error = 0;  /* gcc-4.3.0 false positive complaint */
367         int i;
368 
369         if (argc < 2) {
370                 fprintf(stderr, "usage: sortextable vmlinux...\n");
371                 return 0;
372         }
373 
374         /* Process each file in turn, allowing deep failure. */
375         for (i = 1; i < argc; i++) {
376                 char *file = argv[i];
377                 int const sjval = setjmp(jmpenv);
378 
379                 switch (sjval) {
380                 default:
381                         fprintf(stderr, "internal error: %s\n", file);
382                         exit(1);
383                         break;
384                 case SJ_SETJMP:    /* normal sequence */
385                         /* Avoid problems if early cleanup() */
386                         fd_map = -1;
387                         ehdr_curr = NULL;
388                         mmap_failed = 1;
389                         do_file(file);
390                         break;
391                 case SJ_FAIL:    /* error in do_file or below */
392                         ++n_error;
393                         break;
394                 case SJ_SUCCEED:    /* premature success */
395                         /* do nothing */
396                         break;
397                 }  /* end switch */
398         }
399         return !!n_error;
400 }
401 

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