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am 03b87b49: Merge "Make host ashmem_create_region seed only once."

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* commit '03b87b49fae82a6304ab69b10426701c4f82c7e9':
  Make host ashmem_create_region seed only once.
This commit is contained in:
Mathieu Chartier 2014-06-03 20:48:37 +00:00 • committed by Android Git Automerger
commit b85c2494df
1 changed files with 59 additions and 57 deletions
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116
libcutils/ashmem-host.c
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@ -22,6 +22,8 @@
#include <errno.h> #include <errno.h>
#include <fcntl.h> #include <fcntl.h>
#include <limits.h> #include <limits.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h> #include <stdio.h>
#include <stdlib.h> #include <stdlib.h>
#include <string.h> #include <string.h>
@ -36,83 +38,83 @@
#define __unused __attribute__((__unused__)) #define __unused __attribute__((__unused__))
#endif #endif
static pthread_once_t seed_initialized = PTHREAD_ONCE_INIT;
static void initialize_random() {
srand(time(NULL) + getpid());
}
int ashmem_create_region(const char *ignored __unused, size_t size) int ashmem_create_region(const char *ignored __unused, size_t size)
{ {
static const char txt[] = "abcdefghijklmnopqrstuvwxyz" static const char txt[] = "abcdefghijklmnopqrstuvwxyz"
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"; "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char name[64]; char name[64];
unsigned int retries = 0; unsigned int retries = 0;
pid_t pid = getpid(); pid_t pid = getpid();
int fd; int fd;
if (pthread_once(&seed_initialized, &initialize_random) != 0) {
return -1;
}
do {
/* not beautiful, its just wolf-like loop unrolling */
snprintf(name, sizeof(name), "/tmp/android-ashmem-%d-%c%c%c%c%c%c%c%c",
pid,
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))]);
srand(time(NULL) + pid); /* open O_EXCL & O_CREAT: we are either the sole owner or we fail */
fd = open(name, O_RDWR | O_CREAT | O_EXCL, 0600);
retry: if (fd == -1) {
/* not beautiful, its just wolf-like loop unrolling */ /* unlikely, but if we failed because `name' exists, retry */
snprintf(name, sizeof(name), "/tmp/android-ashmem-%d-%c%c%c%c%c%c%c%c", if (errno != EEXIST || ++retries >= 6) {
pid, return -1;
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))], }
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))], }
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))], } while (fd == -1);
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))], /* truncate the file to `len' bytes */
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))], if (ftruncate(fd, size) != -1 && unlink(name) != -1) {
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))], return fd;
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))], }
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))]); close(fd);
return -1;
/* open O_EXCL & O_CREAT: we are either the sole owner or we fail */
fd = open(name, O_RDWR | O_CREAT | O_EXCL, 0600);
if (fd == -1) {
/* unlikely, but if we failed because `name' exists, retry */
if (errno == EEXIST && ++retries < 6)
goto retry;
return -1;
}
/* truncate the file to `len' bytes */
if (ftruncate(fd, size) == -1)
goto error;
if (unlink(name) == -1)
goto error;
return fd;
error:
close(fd);
return -1;
} }
int ashmem_set_prot_region(int fd __unused, int prot __unused) int ashmem_set_prot_region(int fd __unused, int prot __unused)
{ {
return 0; return 0;
} }
int ashmem_pin_region(int fd __unused, size_t offset __unused, size_t len __unused) int ashmem_pin_region(int fd __unused, size_t offset __unused, size_t len __unused)
{ {
return ASHMEM_NOT_PURGED; return ASHMEM_NOT_PURGED;
} }
int ashmem_unpin_region(int fd __unused, size_t offset __unused, size_t len __unused) int ashmem_unpin_region(int fd __unused, size_t offset __unused, size_t len __unused)
{ {
return ASHMEM_IS_UNPINNED; return ASHMEM_IS_UNPINNED;
} }
int ashmem_get_size_region(int fd) int ashmem_get_size_region(int fd)
{ {
struct stat buf; struct stat buf;
int result; int result;
result = fstat(fd, &buf); result = fstat(fd, &buf);
if (result == -1) { if (result == -1) {
return -1; return -1;
} }
// Check if this is an "ashmem" region. // Check if this is an "ashmem" region.
// TODO: This is very hacky, and can easily break. We need some reliable indicator. // TODO: This is very hacky, and can easily break. We need some reliable indicator.
if (!(buf.st_nlink == 0 && S_ISREG(buf.st_mode))) { if (!(buf.st_nlink == 0 && S_ISREG(buf.st_mode))) {
errno = ENOTTY; errno = ENOTTY;
return -1; return -1;
} }
return (int)buf.st_size; // TODO: care about overflow (> 2GB file)? return (int)buf.st_size; // TODO: care about overflow (> 2GB file)?
} }