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
  27#ifdef CONFIG_GETAUXVAL
  28/* Don't inline this in qemu/osdep.h, because pulling in <sys/auxv.h> for
  29   the system declaration of getauxval pulls in the system <elf.h>, which
  30   conflicts with qemu's version.  */
  31
  32#include <sys/auxv.h>
  33
  34unsigned long qemu_getauxval(unsigned long key)
  35{
  36    return getauxval(key);
  37}
  38#elif defined(__linux__)
  39#include "elf.h"
  40
  41/* Our elf.h doesn't contain Elf32_auxv_t and Elf64_auxv_t, which is ok because
  42   that just makes it easier to define it properly for the host here.  */
  43typedef struct {
  44    unsigned long a_type;
  45    unsigned long a_val;
  46} ElfW_auxv_t;
  47
  48static const ElfW_auxv_t *auxv;
  49
  50static const ElfW_auxv_t *qemu_init_auxval(void)
  51{
  52    ElfW_auxv_t *a;
  53    ssize_t size = 512, r, ofs;
  54    int fd;
  55
  56    /* Allocate some initial storage.  Make sure the first entry is set
  57       to end-of-list, so that we've got a valid list in case of error.  */
  58    auxv = a = g_malloc(size);
  59    a[0].a_type = 0;
  60    a[0].a_val = 0;
  61
  62    fd = open("/proc/self/auxv", O_RDONLY);
  63    if (fd < 0) {
  64        return a;
  65    }
  66
  67    /* Read the first SIZE bytes.  Hopefully, this covers everything.  */
  68    r = read(fd, a, size);
  69
  70    if (r == size) {
  71        /* Continue to expand until we do get a partial read.  */
  72        do {
  73            ofs = size;
  74            size *= 2;
  75            auxv = a = g_realloc(a, size);
  76            r = read(fd, (char *)a + ofs, ofs);
  77        } while (r == ofs);
  78    }
  79
  80    close(fd);
  81    return a;
  82}
  83
  84unsigned long qemu_getauxval(unsigned long type)
  85{
  86    const ElfW_auxv_t *a = auxv;
  87
  88    if (unlikely(a == NULL)) {
  89        a = qemu_init_auxval();
  90    }
  91
  92    for (; a->a_type != 0; a++) {
  93        if (a->a_type == type) {
  94            return a->a_val;
  95        }
  96    }
  97
  98    return 0;
  99}
 100
 101#elif defined(__FreeBSD__)
 102#include <sys/auxv.h>
 103
 104unsigned long qemu_getauxval(unsigned long type)
 105{
 106    unsigned long aux = 0;
 107    elf_aux_info(type, &aux, sizeof(aux));
 108    return aux;
 109}
 110
 111#else
 112
 113unsigned long qemu_getauxval(unsigned long type)
 114{
 115    return 0;
 116}
 117
 118#endif
 119