util: use shm_open for in-memory files

shm_open is a POSIX function creating an in-memory file. Using it simplifies
the code and removes the dependency on XDG_RUNTIME_DIR. The only downside is
that we need to generate a random name for the shm file.
This commit is contained in:
emersion 2018-10-26 18:38:23 +02:00
parent f668e49fae
commit 346ec21c4c
No known key found for this signature in database
GPG Key ID: 0FDE7BE0E88F5E48
8 changed files with 80 additions and 164 deletions

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@ -30,4 +30,3 @@ generic
* *WAYLAND_DISPLAY*, *_WAYLAND_DISPLAY*, *WAYLAND_SOCKET*: if set probe Wayland * *WAYLAND_DISPLAY*, *_WAYLAND_DISPLAY*, *WAYLAND_SOCKET*: if set probe Wayland
backend in *wlr_backend_autocreate* backend in *wlr_backend_autocreate*
* *XCURSOR_PATH*: directory where xcursors are located * *XCURSOR_PATH*: directory where xcursors are located
* *XDG_RUNTIME_DIR*: used to store non persistent temporary files

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@ -1,9 +0,0 @@
#ifndef UTIL_OS_COMPATIBILITY_H
#define UTIL_OS_COMPATIBILITY_H
int os_fd_set_cloexec(int fd);
int set_cloexec_or_close(int fd);
int create_tmpfile_cloexec(char *tmpname);
int os_create_anonymous_file(off_t size);
#endif

7
include/util/shm.h Normal file
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@ -0,0 +1,7 @@
#ifndef UTIL_SHM_H
#define UTIL_SHM_H
int create_shm_file(void);
int allocate_shm_file(size_t size);
#endif

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@ -56,7 +56,8 @@ udev = dependency('libudev')
pixman = dependency('pixman-1') pixman = dependency('pixman-1')
libcap = dependency('libcap', required: get_option('libcap')) libcap = dependency('libcap', required: get_option('libcap'))
logind = dependency('lib' + get_option('logind-provider'), required: get_option('logind'), version: '>=237') logind = dependency('lib' + get_option('logind-provider'), required: get_option('logind'), version: '>=237')
math = cc.find_library('m', required: false) math = cc.find_library('m')
rt = cc.find_library('rt')
wlr_parts = [] wlr_parts = []
wlr_deps = [] wlr_deps = []

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@ -12,7 +12,7 @@
#include <wlr/util/log.h> #include <wlr/util/log.h>
#include "types/wlr_seat.h" #include "types/wlr_seat.h"
#include "util/signal.h" #include "util/signal.h"
#include "util/os-compatibility.h" #include "util/shm.h"
static void default_keyboard_enter(struct wlr_seat_keyboard_grab *grab, static void default_keyboard_enter(struct wlr_seat_keyboard_grab *grab,
struct wlr_surface *surface, uint32_t keycodes[], size_t num_keycodes, struct wlr_surface *surface, uint32_t keycodes[], size_t num_keycodes,
@ -341,7 +341,7 @@ static void seat_client_send_keymap(struct wlr_seat_client *client,
continue; continue;
} }
int keymap_fd = os_create_anonymous_file(keyboard->keymap_size); int keymap_fd = allocate_shm_file(keyboard->keymap_size);
if (keymap_fd < 0) { if (keymap_fd < 0) {
wlr_log(WLR_ERROR, "creating a keymap file for %zu bytes failed", keyboard->keymap_size); wlr_log(WLR_ERROR, "creating a keymap file for %zu bytes failed", keyboard->keymap_size);
continue; continue;

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@ -3,10 +3,10 @@ lib_wlr_util = static_library(
files( files(
'array.c', 'array.c',
'log.c', 'log.c',
'os-compatibility.c',
'region.c', 'region.c',
'shm.c',
'signal.c', 'signal.c',
), ),
include_directories: wlr_inc, include_directories: wlr_inc,
dependencies: [wayland_server, pixman], dependencies: [wayland_server, pixman, rt],
) )

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@ -1,149 +0,0 @@
/*
* Copyright © 2012 Collabora, Ltd.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice (including the
* next paragraph) shall be included in all copies or substantial
* portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#define _POSIX_C_SOURCE 200809L
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <wlr/config.h>
#include "util/os-compatibility.h"
int os_fd_set_cloexec(int fd) {
if (fd == -1) {
return -1;
}
long flags = fcntl(fd, F_GETFD);
if (flags == -1) {
return -1;
}
if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1) {
return -1;
}
return 0;
}
int set_cloexec_or_close(int fd) {
if (os_fd_set_cloexec(fd) != 0) {
close(fd);
return -1;
}
return fd;
}
int create_tmpfile_cloexec(char *tmpname) {
int fd;
mode_t prev_umask = umask(0066);
#ifdef HAVE_MKOSTEMP
fd = mkostemp(tmpname, O_CLOEXEC);
if (fd >= 0) {
unlink(tmpname);
}
#else
fd = mkstemp(tmpname);
if (fd >= 0) {
fd = set_cloexec_or_close(fd);
unlink(tmpname);
}
#endif
umask(prev_umask);
return fd;
}
/*
* Create a new, unique, anonymous file of the given size, and
* return the file descriptor for it. The file descriptor is set
* CLOEXEC. The file is immediately suitable for mmap()'ing
* the given size at offset zero.
*
* The file should not have a permanent backing store like a disk,
* but may have if XDG_RUNTIME_DIR is not properly implemented in OS.
*
* The file name is deleted from the file system.
*
* The file is suitable for buffer sharing between processes by
* transmitting the file descriptor over Unix sockets using the
* SCM_RIGHTS methods.
*
* If the C library implements posix_fallocate(), it is used to
* guarantee that disk space is available for the file at the
* given size. If disk space is insufficient, errno is set to ENOSPC.
* If posix_fallocate() is not supported, program may receive
* SIGBUS on accessing mmap()'ed file contents instead.
*/
int os_create_anonymous_file(off_t size) {
static const char template[] = "/wlroots-shared-XXXXXX";
const char *path = getenv("XDG_RUNTIME_DIR");
if (!path) {
errno = ENOENT;
return -1;
}
char *name = malloc(strlen(path) + sizeof(template));
if (!name) {
return -1;
}
strcpy(name, path);
strcat(name, template);
int fd = create_tmpfile_cloexec(name);
free(name);
if (fd < 0) {
return -1;
}
#ifdef WLR_HAS_POSIX_FALLOCATE
int ret;
do {
ret = posix_fallocate(fd, 0, size);
} while (ret == EINTR);
if (ret != 0) {
close(fd);
errno = ret;
return -1;
}
#else
int ret;
do {
ret = ftruncate(fd, size);
} while (ret < 0 && errno == EINTR);
if (ret < 0) {
close(fd);
return -1;
}
#endif
return fd;
}

67
util/shm.c Normal file
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@ -0,0 +1,67 @@
#define _POSIX_C_SOURCE 200112L
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <sys/mman.h>
#include <time.h>
#include <unistd.h>
#include <wlr/config.h>
#include "util/shm.h"
static void randname(char *buf) {
struct timespec ts;
clock_gettime(CLOCK_REALTIME, &ts);
long r = ts.tv_nsec;
for (int i = 0; i < 6; ++i) {
buf[i] = 'A'+(r&15)+(r&16)*2;
r >>= 5;
}
}
int create_shm_file(void) {
int retries = 100;
do {
char name[] = "/wlroots-XXXXXX";
randname(name + strlen(name) - 6);
--retries;
// CLOEXEC is guaranteed to be set by shm_open
int fd = shm_open(name, O_RDWR | O_CREAT | O_EXCL, 0600);
if (fd >= 0) {
shm_unlink(name);
return fd;
}
} while (retries > 0 && errno == EEXIST);
return -1;
}
int allocate_shm_file(size_t size) {
int fd = create_shm_file();
if (fd < 0) {
return -1;
}
#ifdef WLR_HAS_POSIX_FALLOCATE
int ret;
do {
ret = posix_fallocate(fd, 0, size);
} while (ret == EINTR);
if (ret != 0) {
close(fd);
errno = ret;
return -1;
}
#else
int ret;
do {
ret = ftruncate(fd, size);
} while (ret < 0 && errno == EINTR);
if (ret < 0) {
close(fd);
return -1;
}
#endif
return fd;
}