LXR qemu/util/getauxval.c

   1/*
   2 * QEMU access to the auxiliary vector
   3 *
   4 * Copyright (C) 2013 Red Hat, Inc
   5 *
   6 * Permission is hereby granted, free of charge, to any person obtaining a copy
   7 * of this software and associated documentation files (the "Software"), to deal
   8 * in the Software without restriction, including without limitation the rights
   9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10 * copies of the Software, and to permit persons to whom the Software is
  11 * furnished to do so, subject to the following conditions:
  12 *
  13 * The above copyright notice and this permission notice shall be included in
  14 * all copies or substantial portions of the Software.
  15 *
  16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22 * THE SOFTWARE.
  23 */
  24
  25#include "qemu/osdep.h"
  26#include "qemu-common.h"
  27
  28#ifdef CONFIG_GETAUXVAL
  29/* Don't inline this in qemu/osdep.h, because pulling in <sys/auxv.h> for
  30   the system declaration of getauxval pulls in the system <elf.h>, which
  31   conflicts with qemu's version.  */
  32
  33#include <sys/auxv.h>
  34
  35unsigned long qemu_getauxval(unsigned long key)
  36{
  37    return getauxval(key);
  38}
  39#elif defined(__linux__)
  40#include "elf.h"
  41
  42/* Our elf.h doesn't contain Elf32_auxv_t and Elf64_auxv_t, which is ok because
  43   that just makes it easier to define it properly for the host here.  */
  44typedef struct {
  45    unsigned long a_type;
  46    unsigned long a_val;
  47} ElfW_auxv_t;
  48
  49static const ElfW_auxv_t *auxv;
  50
  51static const ElfW_auxv_t *qemu_init_auxval(void)
  52{
  53    ElfW_auxv_t *a;
  54    ssize_t size = 512, r, ofs;
  55    int fd;
  56
  57    /* Allocate some initial storage.  Make sure the first entry is set
  58       to end-of-list, so that we've got a valid list in case of error.  */
  59    auxv = a = g_malloc(size);
  60    a[0].a_type = 0;
  61    a[0].a_val = 0;
  62
  63    fd = open("/proc/self/auxv", O_RDONLY);
  64    if (fd < 0) {
  65        return a;
  66    }
  67
  68    /* Read the first SIZE bytes.  Hopefully, this covers everything.  */
  69    r = read(fd, a, size);
  70
  71    if (r == size) {
  72        /* Continue to expand until we do get a partial read.  */
  73        do {
  74            ofs = size;
  75            size *= 2;
  76            auxv = a = g_realloc(a, size);
  77            r = read(fd, (char *)a + ofs, ofs);
  78        } while (r == ofs);
  79    }
  80
  81    close(fd);
  82    return a;
  83}
  84
  85unsigned long qemu_getauxval(unsigned long type)
  86{
  87    const ElfW_auxv_t *a = auxv;
  88
  89    if (unlikely(a == NULL)) {
  90        a = qemu_init_auxval();
  91    }
  92
  93    for (; a->a_type != 0; a++) {
  94        if (a->a_type == type) {
  95            return a->a_val;
  96        }
  97    }
  98
  99    return 0;
 100}
 101
 102#else
 103
 104unsigned long qemu_getauxval(unsigned long type)
 105{
 106    return 0;
 107}
 108
 109#endif
 110