balloon: Don't balloon roms
[qemu.git] / 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
35 unsigned 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. */
44 typedef struct {
45 unsigned long a_type;
46 unsigned long a_val;
47 } ElfW_auxv_t;
48
49 static const ElfW_auxv_t *auxv;
50
51 static 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
85 unsigned 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
104 unsigned long qemu_getauxval(unsigned long type)
105 {
106 return 0;
107 }
108
109 #endif