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_AARCH64
  35 #define EM_AARCH64      183
  36 #endif
  37
  38 static int fd_map;      /* File descriptor for file being modified. */
  39 static int mmap_failed; /* Boolean flag. */
  40 static void *ehdr_curr; /* current ElfXX_Ehdr *  for resource cleanup */
  41 static struct stat sb;  /* Remember .st_size, etc. */
  42 static jmp_buf jmpenv;  /* setjmp/longjmp per-file error escape */
  43
  44 /* setjmp() return values */
  45 enum {
  46         SJ_SETJMP = 0,  /* hardwired first return */
  47         SJ_FAIL,
  48         SJ_SUCCEED
  49 };
  50
  51 /* Per-file resource cleanup when multiple files. */
  52 static void
  53 cleanup(void)
  54 {
  55         if (!mmap_failed)
  56                 munmap(ehdr_curr, sb.st_size);
  57         close(fd_map);
  58 }
  59
  60 static void __attribute__((noreturn))
  61 fail_file(void)
  62 {
  63         cleanup();
  64         longjmp(jmpenv, SJ_FAIL);
  65 }
  66
  67 /*
  68  * Get the whole file as a programming convenience in order to avoid
  69  * malloc+lseek+read+free of many pieces.  If successful, then mmap
  70  * avoids copying unused pieces; else just read the whole file.
  71  * Open for both read and write.
  72  */
  73 static void *mmap_file(char const *fname)
  74 {
  75         void *addr;
  76
  77         fd_map = open(fname, O_RDWR);
  78         if (fd_map < 0 || fstat(fd_map, &sb) < 0) {
  79                 perror(fname);
  80                 fail_file();
  81         }
  82         if (!S_ISREG(sb.st_mode)) {
  83                 fprintf(stderr, "not a regular file: %s\n", fname);
  84                 fail_file();
  85         }
  86         addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_SHARED,
  87                     fd_map, 0);
  88         if (addr == MAP_FAILED) {
  89                 mmap_failed = 1;
  90                 fprintf(stderr, "Could not mmap file: %s\n", fname);
  91                 fail_file();
  92         }
  93         return addr;
  94 }
  95
  96 static uint64_t r8be(const uint64_t *x)
  97 {
  98         return get_unaligned_be64(x);
  99 }
 100 static uint32_t rbe(const uint32_t *x)
 101 {
 102         return get_unaligned_be32(x);
 103 }
 104 static uint16_t r2be(const uint16_t *x)
 105 {
 106         return get_unaligned_be16(x);
 107 }
 108 static uint64_t r8le(const uint64_t *x)
 109 {
 110         return get_unaligned_le64(x);
 111 }
 112 static uint32_t rle(const uint32_t *x)
 113 {
 114         return get_unaligned_le32(x);
 115 }
 116 static uint16_t r2le(const uint16_t *x)
 117 {
 118         return get_unaligned_le16(x);
 119 }
 120
 121 static void w8be(uint64_t val, uint64_t *x)
 122 {
 123         put_unaligned_be64(val, x);
 124 }
 125 static void wbe(uint32_t val, uint32_t *x)
 126 {
 127         put_unaligned_be32(val, x);
 128 }
 129 static void w2be(uint16_t val, uint16_t *x)
 130 {
 131         put_unaligned_be16(val, x);
 132 }
 133 static void w8le(uint64_t val, uint64_t *x)
 134 {
 135         put_unaligned_le64(val, x);
 136 }
 137 static void wle(uint32_t val, uint32_t *x)
 138 {
 139         put_unaligned_le32(val, x);
 140 }
 141 static void w2le(uint16_t val, uint16_t *x)
 142 {
 143         put_unaligned_le16(val, x);
 144 }
 145
 146 static uint64_t (*r8)(const uint64_t *);
 147 static uint32_t (*r)(const uint32_t *);
 148 static uint16_t (*r2)(const uint16_t *);
 149 static void (*w8)(uint64_t, uint64_t *);
 150 static void (*w)(uint32_t, uint32_t *);
 151 static void (*w2)(uint16_t, uint16_t *);
 152
 153 typedef void (*table_sort_t)(char *, int);
 154
 155 /*
 156  * Move reserved section indices SHN_LORESERVE..SHN_HIRESERVE out of
 157  * the way to -256..-1, to avoid conflicting with real section
 158  * indices.
 159  */
 160 #define SPECIAL(i) ((i) - (SHN_HIRESERVE + 1))
 161
 162 static inline int is_shndx_special(unsigned int i)
 163 {
 164         return i != SHN_XINDEX && i >= SHN_LORESERVE && i <= SHN_HIRESERVE;
 165 }
 166
 167 /* Accessor for sym->st_shndx, hides ugliness of "64k sections" */
 168 static inline unsigned int get_secindex(unsigned int shndx,
 169                                         unsigned int sym_offs,
 170                                         const Elf32_Word *symtab_shndx_start)
 171 {
 172         if (is_shndx_special(shndx))
 173                 return SPECIAL(shndx);
 174         if (shndx != SHN_XINDEX)
 175                 return shndx;
 176         return r(&symtab_shndx_start[sym_offs]);
 177 }
 178
 179 /* 32 bit and 64 bit are very similar */
 180 #include "sortextable.h"
 181 #define SORTEXTABLE_64
 182 #include "sortextable.h"
 183
 184 static int compare_relative_table(const void *a, const void *b)
 185 {
 186         int32_t av = (int32_t)r(a);
 187         int32_t bv = (int32_t)r(b);
 188
 189         if (av < bv)
 190                 return -1;
 191         if (av > bv)
 192                 return 1;
 193         return 0;
 194 }
 195
 196 static void sort_relative_table(char *extab_image, int image_size)
 197 {
 198         int i;
 199
 200         /*
 201          * Do the same thing the runtime sort does, first normalize to
 202          * being relative to the start of the section.
 203          */
 204         i = 0;
 205         while (i < image_size) {
 206                 uint32_t *loc = (uint32_t *)(extab_image + i);
 207                 w(r(loc) + i, loc);
 208                 i += 4;
 209         }
 210
 211         qsort(extab_image, image_size / 8, 8, compare_relative_table);
 212
 213         /* Now denormalize. */
 214         i = 0;
 215         while (i < image_size) {
 216                 uint32_t *loc = (uint32_t *)(extab_image + i);
 217                 w(r(loc) - i, loc);
 218                 i += 4;
 219         }
 220 }
 221
 222 static void
 223 do_file(char const *const fname)
 224 {
 225         table_sort_t custom_sort;
 226         Elf32_Ehdr *ehdr = mmap_file(fname);
 227
 228         ehdr_curr = ehdr;
 229         switch (ehdr->e_ident[EI_DATA]) {
 230         default:
 231                 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
 232                         ehdr->e_ident[EI_DATA], fname);
 233                 fail_file();
 234                 break;
 235         case ELFDATA2LSB:
 236                 r = rle;
 237                 r2 = r2le;
 238                 r8 = r8le;
 239                 w = wle;
 240                 w2 = w2le;
 241                 w8 = w8le;
 242                 break;
 243         case ELFDATA2MSB:
 244                 r = rbe;
 245                 r2 = r2be;
 246                 r8 = r8be;
 247                 w = wbe;
 248                 w2 = w2be;
 249                 w8 = w8be;
 250                 break;
 251         }  /* end switch */
 252         if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
 253         ||  r2(&ehdr->e_type) != ET_EXEC
 254         ||  ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
 255                 fprintf(stderr, "unrecognized ET_EXEC file %s\n", fname);
 256                 fail_file();
 257         }
 258
 259         custom_sort = NULL;
 260         switch (r2(&ehdr->e_machine)) {
 261         default:
 262                 fprintf(stderr, "unrecognized e_machine %d %s\n",
 263                         r2(&ehdr->e_machine), fname);
 264                 fail_file();
 265                 break;
 266         case EM_386:
 267         case EM_X86_64:
 268         case EM_S390:
 269                 custom_sort = sort_relative_table;
 270                 break;
 271         case EM_ARM:
 272         case EM_AARCH64:
 273         case EM_MIPS:
 274                 break;
 275         }  /* end switch */
 276
 277         switch (ehdr->e_ident[EI_CLASS]) {
 278         default:
 279                 fprintf(stderr, "unrecognized ELF class %d %s\n",
 280                         ehdr->e_ident[EI_CLASS], fname);
 281                 fail_file();
 282                 break;
 283         case ELFCLASS32:
 284                 if (r2(&ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
 285                 ||  r2(&ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
 286                         fprintf(stderr,
 287                                 "unrecognized ET_EXEC file: %s\n", fname);
 288                         fail_file();
 289                 }
 290                 do32(ehdr, fname, custom_sort);
 291                 break;
 292         case ELFCLASS64: {
 293                 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
 294                 if (r2(&ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
 295                 ||  r2(&ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
 296                         fprintf(stderr,
 297                                 "unrecognized ET_EXEC file: %s\n", fname);
 298                         fail_file();
 299                 }
 300                 do64(ghdr, fname, custom_sort);
 301                 break;
 302         }
 303         }  /* end switch */
 304
 305         cleanup();
 306 }
 307
 308 int
 309 main(int argc, char *argv[])
 310 {
 311         int n_error = 0;  /* gcc-4.3.0 false positive complaint */
 312         int i;
 313
 314         if (argc < 2) {
 315                 fprintf(stderr, "usage: sortextable vmlinux...\n");
 316                 return 0;
 317         }
 318
 319         /* Process each file in turn, allowing deep failure. */
 320         for (i = 1; i < argc; i++) {
 321                 char *file = argv[i];
 322                 int const sjval = setjmp(jmpenv);
 323
 324                 switch (sjval) {
 325                 default:
 326                         fprintf(stderr, "internal error: %s\n", file);
 327                         exit(1);
 328                         break;
 329                 case SJ_SETJMP:    /* normal sequence */
 330                         /* Avoid problems if early cleanup() */
 331                         fd_map = -1;
 332                         ehdr_curr = NULL;
 333                         mmap_failed = 1;
 334                         do_file(file);
 335                         break;
 336                 case SJ_FAIL:    /* error in do_file or below */
 337                         ++n_error;
 338                         break;
 339                 case SJ_SUCCEED:    /* premature success */
 340                         /* do nothing */
 341                         break;
 342                 }  /* end switch */
 343         }
 344         return !!n_error;
 345 }