1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17/*
18 * Implementation of the user-space ashmem API for the simulator, which lacks
19 * an ashmem-enabled kernel. See ashmem-dev.c for the real ashmem-based version.
20 */
21
22#include <errno.h>
23#include <fcntl.h>
24#include <limits.h>
25#include <pthread.h>
26#include <stdbool.h>
27#include <stdio.h>
28#include <stdlib.h>
29#include <string.h>
30#include <sys/stat.h>
31#include <sys/types.h>
32#include <time.h>
33#include <unistd.h>
34
35#include <cutils/ashmem.h>
36
37#ifndef __unused
38#define __unused __attribute__((__unused__))
39#endif
40
41static pthread_once_t seed_initialized = PTHREAD_ONCE_INIT;
42static void initialize_random() {
43    srand(time(NULL) + getpid());
44}
45
46int ashmem_create_region(const char *ignored __unused, size_t size)
47{
48    static const char txt[] = "abcdefghijklmnopqrstuvwxyz"
49            "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
50    char name[64];
51    unsigned int retries = 0;
52    pid_t pid = getpid();
53    int fd;
54    if (pthread_once(&seed_initialized, &initialize_random) != 0) {
55        return -1;
56    }
57    do {
58        /* not beautiful, its just wolf-like loop unrolling */
59        snprintf(name, sizeof(name), "/tmp/android-ashmem-%d-%c%c%c%c%c%c%c%c",
60        pid,
61        txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
62        txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
63        txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
64        txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
65        txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
66        txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
67        txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
68        txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))]);
69
70        /* open O_EXCL & O_CREAT: we are either the sole owner or we fail */
71        fd = open(name, O_RDWR | O_CREAT | O_EXCL, 0600);
72        if (fd == -1) {
73            /* unlikely, but if we failed because `name' exists, retry */
74            if (errno != EEXIST || ++retries >= 6) {
75                return -1;
76            }
77        }
78    } while (fd == -1);
79    /* truncate the file to `len' bytes */
80    if (ftruncate(fd, size) != -1 && unlink(name) != -1) {
81        return fd;
82    }
83    close(fd);
84    return -1;
85}
86
87int ashmem_set_prot_region(int fd __unused, int prot __unused)
88{
89    return 0;
90}
91
92int ashmem_pin_region(int fd __unused, size_t offset __unused, size_t len __unused)
93{
94    return ASHMEM_NOT_PURGED;
95}
96
97int ashmem_unpin_region(int fd __unused, size_t offset __unused, size_t len __unused)
98{
99    return ASHMEM_IS_UNPINNED;
100}
101
102int ashmem_get_size_region(int fd)
103{
104    struct stat buf;
105    int result;
106
107    result = fstat(fd, &buf);
108    if (result == -1) {
109        return -1;
110    }
111
112    // Check if this is an "ashmem" region.
113    // TODO: This is very hacky, and can easily break. We need some reliable indicator.
114    if (!(buf.st_nlink == 0 && S_ISREG(buf.st_mode))) {
115        errno = ENOTTY;
116        return -1;
117    }
118
119    return (int)buf.st_size;    // TODO: care about overflow (> 2GB file)?
120}
121