linux/scripts/sortextable.c
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   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
  42static int fd_map;      /* File descriptor for file being modified. */
  43static int mmap_failed; /* Boolean flag. */
  44static void *ehdr_curr; /* current ElfXX_Ehdr *  for resource cleanup */
  45static struct stat sb;  /* Remember .st_size, etc. */
  46static jmp_buf jmpenv;  /* setjmp/longjmp per-file error escape */
  47
  48/* setjmp() return values */
  49enum {
  50        SJ_SETJMP = 0,  /* hardwired first return */
  51        SJ_FAIL,
  52        SJ_SUCCEED
  53};
  54
  55/* Per-file resource cleanup when multiple files. */
  56static void
  57cleanup(void)
  58{
  59        if (!mmap_failed)
  60                munmap(ehdr_curr, sb.st_size);
  61        close(fd_map);
  62}
  63
  64static void __attribute__((noreturn))
  65fail_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 */
  77static 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
 100static uint64_t r8be(const uint64_t *x)
 101{
 102        return get_unaligned_be64(x);
 103}
 104static uint32_t rbe(const uint32_t *x)
 105{
 106        return get_unaligned_be32(x);
 107}
 108static uint16_t r2be(const uint16_t *x)
 109{
 110        return get_unaligned_be16(x);
 111}
 112static uint64_t r8le(const uint64_t *x)
 113{
 114        return get_unaligned_le64(x);
 115}
 116static uint32_t rle(const uint32_t *x)
 117{
 118        return get_unaligned_le32(x);
 119}
 120static uint16_t r2le(const uint16_t *x)
 121{
 122        return get_unaligned_le16(x);
 123}
 124
 125static void w8be(uint64_t val, uint64_t *x)
 126{
 127        put_unaligned_be64(val, x);
 128}
 129static void wbe(uint32_t val, uint32_t *x)
 130{
 131        put_unaligned_be32(val, x);
 132}
 133static void w2be(uint16_t val, uint16_t *x)
 134{
 135        put_unaligned_be16(val, x);
 136}
 137static void w8le(uint64_t val, uint64_t *x)
 138{
 139        put_unaligned_le64(val, x);
 140}
 141static void wle(uint32_t val, uint32_t *x)
 142{
 143        put_unaligned_le32(val, x);
 144}
 145static void w2le(uint16_t val, uint16_t *x)
 146{
 147        put_unaligned_le16(val, x);
 148}
 149
 150static uint64_t (*r8)(const uint64_t *);
 151static uint32_t (*r)(const uint32_t *);
 152static uint16_t (*r2)(const uint16_t *);
 153static void (*w8)(uint64_t, uint64_t *);
 154static void (*w)(uint32_t, uint32_t *);
 155static void (*w2)(uint16_t, uint16_t *);
 156
 157typedef 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
 166static 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" */
 172static 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
 188static 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
 200static 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
 226static void
 227do_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
 313int
 314main(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}
 351
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