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_AARCH64
  39 #define EM_AARCH64      183
  40 #endif
  41
  42 static int fd_map;      /* File descriptor for file being modified. */
  43 static int mmap_failed; /* Boolean flag. */
  44 static void *ehdr_curr; /* current ElfXX_Ehdr *  for resource cleanup */
  45 static struct stat sb;  /* Remember .st_size, etc. */
  46 static jmp_buf jmpenv;  /* setjmp/longjmp per-file error escape */
  47
  48 /* setjmp() return values */
  49 enum {
  50         SJ_SETJMP = 0,  /* hardwired first return */
  51         SJ_FAIL,
  52         SJ_SUCCEED
  53 };
  54
  55 /* Per-file resource cleanup when multiple files. */
  56 static void
  57 cleanup(void)
  58 {
  59         if (!mmap_failed)
  60                 munmap(ehdr_curr, sb.st_size);
  61         close(fd_map);
  62 }
  63
  64 static void __attribute__((noreturn))
  65 fail_file(void)
  66 {
  67         cleanup();
  68         longjmp(jmpenv, SJ_FAIL);
  69 }
  70
  71 /*
  72  * Get the whole file as a programming convenience in order to avoid
  73  * malloc+lseek+read+free of many pieces.  If successful, then mmap
  74  * avoids copying unused pieces; else just read the whole file.
  75  * Open for both read and write.
  76  */
  77 static void *mmap_file(char const *fname)
  78 {
  79         void *addr;
  80
  81         fd_map = open(fname, O_RDWR);
  82         if (fd_map < 0 || fstat(fd_map, &sb) < 0) {
  83                 perror(fname);
  84                 fail_file();
  85         }
  86         if (!S_ISREG(sb.st_mode)) {
  87                 fprintf(stderr, "not a regular file: %s\n", fname);
  88                 fail_file();
  89         }
  90         addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_SHARED,
  91                     fd_map, 0);
  92         if (addr == MAP_FAILED) {
  93                 mmap_failed = 1;
  94                 fprintf(stderr, "Could not mmap file: %s\n", fname);
  95                 fail_file();
  96         }
  97         return addr;
  98 }
  99
 100 static uint64_t r8be(const uint64_t *x)
 101 {
 102         return get_unaligned_be64(x);
 103 }
 104 static uint32_t rbe(const uint32_t *x)
 105 {
 106         return get_unaligned_be32(x);
 107 }
 108 static uint16_t r2be(const uint16_t *x)
 109 {
 110         return get_unaligned_be16(x);
 111 }
 112 static uint64_t r8le(const uint64_t *x)
 113 {
 114         return get_unaligned_le64(x);
 115 }
 116 static uint32_t rle(const uint32_t *x)
 117 {
 118         return get_unaligned_le32(x);
 119 }
 120 static uint16_t r2le(const uint16_t *x)
 121 {
 122         return get_unaligned_le16(x);
 123 }
 124
 125 static void w8be(uint64_t val, uint64_t *x)
 126 {
 127         put_unaligned_be64(val, x);
 128 }
 129 static void wbe(uint32_t val, uint32_t *x)
 130 {
 131         put_unaligned_be32(val, x);
 132 }
 133 static void w2be(uint16_t val, uint16_t *x)
 134 {
 135         put_unaligned_be16(val, x);
 136 }
 137 static void w8le(uint64_t val, uint64_t *x)
 138 {
 139         put_unaligned_le64(val, x);
 140 }
 141 static void wle(uint32_t val, uint32_t *x)
 142 {
 143         put_unaligned_le32(val, x);
 144 }
 145 static void w2le(uint16_t val, uint16_t *x)
 146 {
 147         put_unaligned_le16(val, x);
 148 }
 149
 150 static uint64_t (*r8)(const uint64_t *);
 151 static uint32_t (*r)(const uint32_t *);
 152 static uint16_t (*r2)(const uint16_t *);
 153 static void (*w8)(uint64_t, uint64_t *);
 154 static void (*w)(uint32_t, uint32_t *);
 155 static void (*w2)(uint16_t, uint16_t *);
 156
 157 typedef void (*table_sort_t)(char *, int);
 158
 159 /*
 160  * Move reserved section indices SHN_LORESERVE..SHN_HIRESERVE out of
 161  * the way to -256..-1, to avoid conflicting with real section
 162  * indices.
 163  */
 164 #define SPECIAL(i) ((i) - (SHN_HIRESERVE + 1))
 165
 166 static inline int is_shndx_special(unsigned int i)
 167 {
 168         return i != SHN_XINDEX && i >= SHN_LORESERVE && i <= SHN_HIRESERVE;
 169 }
 170
 171 /* Accessor for sym->st_shndx, hides ugliness of "64k sections" */
 172 static inline unsigned int get_secindex(unsigned int shndx,
 173                                         unsigned int sym_offs,
 174                                         const Elf32_Word *symtab_shndx_start)
 175 {
 176         if (is_shndx_special(shndx))
 177                 return SPECIAL(shndx);
 178         if (shndx != SHN_XINDEX)
 179                 return shndx;
 180         return r(&symtab_shndx_start[sym_offs]);
 181 }
 182
 183 /* 32 bit and 64 bit are very similar */
 184 #include "sortextable.h"
 185 #define SORTEXTABLE_64
 186 #include "sortextable.h"
 187
 188 static int compare_relative_table(const void *a, const void *b)
 189 {
 190         int32_t av = (int32_t)r(a);
 191         int32_t bv = (int32_t)r(b);
 192
 193         if (av < bv)
 194                 return -1;
 195         if (av > bv)
 196                 return 1;
 197         return 0;
 198 }
 199
 200 static void sort_relative_table(char *extab_image, int image_size)
 201 {
 202         int i;
 203
 204         /*
 205          * Do the same thing the runtime sort does, first normalize to
 206          * being relative to the start of the section.
 207          */
 208         i = 0;
 209         while (i < image_size) {
 210                 uint32_t *loc = (uint32_t *)(extab_image + i);
 211                 w(r(loc) + i, loc);
 212                 i += 4;
 213         }
 214
 215         qsort(extab_image, image_size / 8, 8, compare_relative_table);
 216
 217         /* Now denormalize. */
 218         i = 0;
 219         while (i < image_size) {
 220                 uint32_t *loc = (uint32_t *)(extab_image + i);
 221                 w(r(loc) - i, loc);
 222                 i += 4;
 223         }
 224 }
 225
 226 static void
 227 do_file(char const *const fname)
 228 {
 229         table_sort_t custom_sort;
 230         Elf32_Ehdr *ehdr = mmap_file(fname);
 231
 232         ehdr_curr = ehdr;
 233         switch (ehdr->e_ident[EI_DATA]) {
 234         default:
 235                 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
 236                         ehdr->e_ident[EI_DATA], fname);
 237                 fail_file();
 238                 break;
 239         case ELFDATA2LSB:
 240                 r = rle;
 241                 r2 = r2le;
 242                 r8 = r8le;
 243                 w = wle;
 244                 w2 = w2le;
 245                 w8 = w8le;
 246                 break;
 247         case ELFDATA2MSB:
 248                 r = rbe;
 249                 r2 = r2be;
 250                 r8 = r8be;
 251                 w = wbe;
 252                 w2 = w2be;
 253                 w8 = w8be;
 254                 break;
 255         }  /* end switch */
 256         if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
 257         ||  r2(&ehdr->e_type) != ET_EXEC
 258         ||  ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
 259                 fprintf(stderr, "unrecognized ET_EXEC file %s\n", fname);
 260                 fail_file();
 261         }
 262
 263         custom_sort = NULL;
 264         switch (r2(&ehdr->e_machine)) {
 265         default:
 266                 fprintf(stderr, "unrecognized e_machine %d %s\n",
 267                         r2(&ehdr->e_machine), fname);
 268                 fail_file();
 269                 break;
 270         case EM_386:
 271         case EM_X86_64:
 272         case EM_S390:
 273                 custom_sort = sort_relative_table;
 274                 break;
 275         case EM_ARCOMPACT:
 276         case EM_ARM:
 277         case EM_AARCH64:
 278         case EM_MIPS:
 279                 break;
 280         }  /* end switch */
 281
 282         switch (ehdr->e_ident[EI_CLASS]) {
 283         default:
 284                 fprintf(stderr, "unrecognized ELF class %d %s\n",
 285                         ehdr->e_ident[EI_CLASS], fname);
 286                 fail_file();
 287                 break;
 288         case ELFCLASS32:
 289                 if (r2(&ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
 290                 ||  r2(&ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
 291                         fprintf(stderr,
 292                                 "unrecognized ET_EXEC file: %s\n", fname);
 293                         fail_file();
 294                 }
 295                 do32(ehdr, fname, custom_sort);
 296                 break;
 297         case ELFCLASS64: {
 298                 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
 299                 if (r2(&ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
 300                 ||  r2(&ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
 301                         fprintf(stderr,
 302                                 "unrecognized ET_EXEC file: %s\n", fname);
 303                         fail_file();
 304                 }
 305                 do64(ghdr, fname, custom_sort);
 306                 break;
 307         }
 308         }  /* end switch */
 309
 310         cleanup();
 311 }
 312
 313 int
 314 main(int argc, char *argv[])
 315 {
 316         int n_error = 0;  /* gcc-4.3.0 false positive complaint */
 317         int i;
 318
 319         if (argc < 2) {
 320                 fprintf(stderr, "usage: sortextable vmlinux...\n");
 321                 return 0;
 322         }
 323
 324         /* Process each file in turn, allowing deep failure. */
 325         for (i = 1; i < argc; i++) {
 326                 char *file = argv[i];
 327                 int const sjval = setjmp(jmpenv);
 328
 329                 switch (sjval) {
 330                 default:
 331                         fprintf(stderr, "internal error: %s\n", file);
 332                         exit(1);
 333                         break;
 334                 case SJ_SETJMP:    /* normal sequence */
 335                         /* Avoid problems if early cleanup() */
 336                         fd_map = -1;
 337                         ehdr_curr = NULL;
 338                         mmap_failed = 1;
 339                         do_file(file);
 340                         break;
 341                 case SJ_FAIL:    /* error in do_file or below */
 342                         ++n_error;
 343                         break;
 344                 case SJ_SUCCEED:    /* premature success */
 345                         /* do nothing */
 346                         break;
 347                 }  /* end switch */
 348         }
 349         return !!n_error;
 350 }