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
  34static int fd_map;      /* File descriptor for file being modified. */
  35static int mmap_failed; /* Boolean flag. */
  36static void *ehdr_curr; /* current ElfXX_Ehdr *  for resource cleanup */
  37static struct stat sb;  /* Remember .st_size, etc. */
  38static jmp_buf jmpenv;  /* setjmp/longjmp per-file error escape */
  39
  40/* setjmp() return values */
  41enum {
  42        SJ_SETJMP = 0,  /* hardwired first return */
  43        SJ_FAIL,
  44        SJ_SUCCEED
  45};
  46
  47/* Per-file resource cleanup when multiple files. */
  48static void
  49cleanup(void)
  50{
  51        if (!mmap_failed)
  52                munmap(ehdr_curr, sb.st_size);
  53        close(fd_map);
  54}
  55
  56static void __attribute__((noreturn))
  57fail_file(void)
  58{
  59        cleanup();
  60        longjmp(jmpenv, SJ_FAIL);
  61}
  62
  63static void __attribute__((noreturn))
  64succeed_file(void)
  65{
  66        cleanup();
  67        longjmp(jmpenv, SJ_SUCCEED);
  68}
  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/* 32 bit and 64 bit are very similar */
 160#include "sortextable.h"
 161#define SORTEXTABLE_64
 162#include "sortextable.h"
 163
 164static int compare_relative_table(const void *a, const void *b)
 165{
 166        int32_t av = (int32_t)r(a);
 167        int32_t bv = (int32_t)r(b);
 168
 169        if (av < bv)
 170                return -1;
 171        if (av > bv)
 172                return 1;
 173        return 0;
 174}
 175
 176static void sort_relative_table(char *extab_image, int image_size)
 177{
 178        int i;
 179
 180        /*
 181         * Do the same thing the runtime sort does, first normalize to
 182         * being relative to the start of the section.
 183         */
 184        i = 0;
 185        while (i < image_size) {
 186                uint32_t *loc = (uint32_t *)(extab_image + i);
 187                w(r(loc) + i, loc);
 188                i += 4;
 189        }
 190
 191        qsort(extab_image, image_size / 8, 8, compare_relative_table);
 192
 193        /* Now denormalize. */
 194        i = 0;
 195        while (i < image_size) {
 196                uint32_t *loc = (uint32_t *)(extab_image + i);
 197                w(r(loc) - i, loc);
 198                i += 4;
 199        }
 200}
 201
 202static void
 203do_file(char const *const fname)
 204{
 205        table_sort_t custom_sort;
 206        Elf32_Ehdr *ehdr = mmap_file(fname);
 207
 208        ehdr_curr = ehdr;
 209        switch (ehdr->e_ident[EI_DATA]) {
 210        default:
 211                fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
 212                        ehdr->e_ident[EI_DATA], fname);
 213                fail_file();
 214                break;
 215        case ELFDATA2LSB:
 216                r = rle;
 217                r2 = r2le;
 218                r8 = r8le;
 219                w = wle;
 220                w2 = w2le;
 221                w8 = w8le;
 222                break;
 223        case ELFDATA2MSB:
 224                r = rbe;
 225                r2 = r2be;
 226                r8 = r8be;
 227                w = wbe;
 228                w2 = w2be;
 229                w8 = w8be;
 230                break;
 231        }  /* end switch */
 232        if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
 233        ||  r2(&ehdr->e_type) != ET_EXEC
 234        ||  ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
 235                fprintf(stderr, "unrecognized ET_EXEC file %s\n", fname);
 236                fail_file();
 237        }
 238
 239        custom_sort = NULL;
 240        switch (r2(&ehdr->e_machine)) {
 241        default:
 242                fprintf(stderr, "unrecognized e_machine %d %s\n",
 243                        r2(&ehdr->e_machine), fname);
 244                fail_file();
 245                break;
 246        case EM_386:
 247        case EM_X86_64:
 248        case EM_S390:
 249                custom_sort = sort_relative_table;
 250                break;
 251        case EM_MIPS:
 252                break;
 253        }  /* end switch */
 254
 255        switch (ehdr->e_ident[EI_CLASS]) {
 256        default:
 257                fprintf(stderr, "unrecognized ELF class %d %s\n",
 258                        ehdr->e_ident[EI_CLASS], fname);
 259                fail_file();
 260                break;
 261        case ELFCLASS32:
 262                if (r2(&ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
 263                ||  r2(&ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
 264                        fprintf(stderr,
 265                                "unrecognized ET_EXEC file: %s\n", fname);
 266                        fail_file();
 267                }
 268                do32(ehdr, fname, custom_sort);
 269                break;
 270        case ELFCLASS64: {
 271                Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
 272                if (r2(&ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
 273                ||  r2(&ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
 274                        fprintf(stderr,
 275                                "unrecognized ET_EXEC file: %s\n", fname);
 276                        fail_file();
 277                }
 278                do64(ghdr, fname, custom_sort);
 279                break;
 280        }
 281        }  /* end switch */
 282
 283        cleanup();
 284}
 285
 286int
 287main(int argc, char *argv[])
 288{
 289        int n_error = 0;  /* gcc-4.3.0 false positive complaint */
 290        int i;
 291
 292        if (argc < 2) {
 293                fprintf(stderr, "usage: sortextable vmlinux...\n");
 294                return 0;
 295        }
 296
 297        /* Process each file in turn, allowing deep failure. */
 298        for (i = 1; i < argc; i++) {
 299                char *file = argv[i];
 300                int const sjval = setjmp(jmpenv);
 301
 302                switch (sjval) {
 303                default:
 304                        fprintf(stderr, "internal error: %s\n", file);
 305                        exit(1);
 306                        break;
 307                case SJ_SETJMP:    /* normal sequence */
 308                        /* Avoid problems if early cleanup() */
 309                        fd_map = -1;
 310                        ehdr_curr = NULL;
 311                        mmap_failed = 1;
 312                        do_file(file);
 313                        break;
 314                case SJ_FAIL:    /* error in do_file or below */
 315                        ++n_error;
 316                        break;
 317                case SJ_SUCCEED:    /* premature success */
 318                        /* do nothing */
 319                        break;
 320                }  /* end switch */
 321        }
 322        return !!n_error;
 323}
 324
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