90 lines
1.6 KiB
C
90 lines
1.6 KiB
C
#define _POSIX_C_SOURCE 200112L
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#include <errno.h>
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#include <fcntl.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <time.h>
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#include <unistd.h>
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#include <wlr/config.h>
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#include "util/shm.h"
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#define RANDNAME_PATTERN "/wlroots-XXXXXX"
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static void randname(char *buf) {
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struct timespec ts;
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clock_gettime(CLOCK_REALTIME, &ts);
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long r = ts.tv_nsec;
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for (int i = 0; i < 6; ++i) {
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buf[i] = 'A'+(r&15)+(r&16)*2;
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r >>= 5;
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}
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}
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static int excl_shm_open(char *name) {
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int retries = 100;
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do {
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randname(name + strlen(RANDNAME_PATTERN) - 6);
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--retries;
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// CLOEXEC is guaranteed to be set by shm_open
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int fd = shm_open(name, O_RDWR | O_CREAT | O_EXCL, 0600);
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if (fd >= 0) {
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return fd;
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}
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} while (retries > 0 && errno == EEXIST);
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return -1;
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}
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int allocate_shm_file(size_t size) {
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char name[] = RANDNAME_PATTERN;
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int fd = excl_shm_open(name);
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if (fd < 0) {
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return -1;
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}
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shm_unlink(name);
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int ret;
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do {
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ret = ftruncate(fd, size);
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} while (ret < 0 && errno == EINTR);
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if (ret < 0) {
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close(fd);
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return -1;
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}
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return fd;
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}
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bool allocate_shm_file_pair(size_t size, int *rw_fd_ptr, int *ro_fd_ptr) {
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char name[] = RANDNAME_PATTERN;
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int rw_fd = excl_shm_open(name);
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if (rw_fd < 0) {
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return false;
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}
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// CLOEXEC is guaranteed to be set by shm_open
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int ro_fd = shm_open(name, O_RDONLY, 0);
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if (ro_fd < 0) {
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shm_unlink(name);
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close(rw_fd);
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return false;
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}
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shm_unlink(name);
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int ret;
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do {
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ret = ftruncate(rw_fd, size);
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} while (ret < 0 && errno == EINTR);
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if (ret < 0) {
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close(rw_fd);
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close(ro_fd);
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return false;
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}
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*rw_fd_ptr = rw_fd;
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*ro_fd_ptr = ro_fd;
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return true;
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}
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