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#include "shm.h"
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <linux/memfd.h>
#include <tllist.h>
#define LOG_MODULE "shm"
#include "log.h"
#include "stride.h"
#if !defined(MAP_UNINITIALIZED)
#define MAP_UNINITIALIZED 0
#endif
static void
buffer_destroy(struct buffer *buf)
{
pixman_image_unref(buf->pix);
wl_buffer_destroy(buf->wl_buf);
munmap(buf->mmapped, buf->size);
free(buf);
}
static void
buffer_release(void *data, struct wl_buffer *wl_buffer)
{
struct buffer *buffer = data;
buffer_destroy(buffer);
}
static const struct wl_buffer_listener buffer_listener = {
.release = &buffer_release,
};
struct buffer *
shm_get_buffer(struct wl_shm *shm, int width, int height, unsigned long cookie)
{
/*
* 1. open a memory backed "file" with memfd_create()
* 2. mmap() the memory file, to be used by the pixman image
* 3. create a wayland shm buffer for the same memory file
*
* The pixman image and the wayland buffer are now sharing memory.
*/
int pool_fd = -1;
void *mmapped = NULL;
size_t size = 0;
struct wl_shm_pool *pool = NULL;
struct wl_buffer *buf = NULL;
pixman_image_t *pix = NULL;
/* Backing memory for SHM */
/*
* Older kernels reject MFD_NOEXEC_SEAL with EINVAL. Try first
* *with* it, and if that fails, try again *without* it.
*/
errno = 0;
pool_fd = memfd_create(
"wbg-wayland-shm-buffer-pool",
MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_NOEXEC_SEAL);
if (pool_fd < 0 && errno == EINVAL) {
pool_fd = memfd_create(
"wbg-wayland-shm-buffer-pool", MFD_CLOEXEC | MFD_ALLOW_SEALING);
}
if (pool_fd == -1) {
LOG_ERRNO("failed to create SHM backing memory file");
goto err;
}
/* Total size */
const uint32_t stride = stride_for_format_and_width(PIXMAN_x8r8g8b8, width);
size = stride * height;
if (ftruncate(pool_fd, size) == -1) {
LOG_ERRNO("failed to truncate SHM pool");
goto err;
}
mmapped = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, pool_fd, 0);
if (mmapped == MAP_FAILED) {
LOG_ERR("failed to mmap SHM backing memory file");
goto err;
}
/* Seal file - we no longer allow any kind of resizing */
/* TODO: wayland mmaps(PROT_WRITE), for some unknown reason, hence we cannot use F_SEAL_FUTURE_WRITE */
if (fcntl(pool_fd, F_ADD_SEALS,
F_SEAL_GROW | F_SEAL_SHRINK | /*F_SEAL_FUTURE_WRITE |*/ F_SEAL_SEAL) < 0)
{
LOG_ERRNO("failed to seal SHM backing memory file");
/* This is not a fatal error */
}
pool = wl_shm_create_pool(shm, pool_fd, size);
if (pool == NULL) {
LOG_ERR("failed to create SHM pool");
goto err;
}
buf = wl_shm_pool_create_buffer(
pool, 0, width, height, stride, WL_SHM_FORMAT_XRGB8888);
if (buf == NULL) {
LOG_ERR("failed to create SHM buffer");
goto err;
}
/* We use the entire pool for our single buffer */
wl_shm_pool_destroy(pool); pool = NULL;
close(pool_fd); pool_fd = -1;
pix = pixman_image_create_bits_no_clear(
PIXMAN_x8r8g8b8, width, height, mmapped, stride);
if (pix == NULL) {
LOG_ERR("failed to create pixman image");
goto err;
}
struct buffer *buffer = malloc(sizeof(*buffer));
*buffer = (struct buffer){
.width = width,
.height = height,
.stride = stride,
.cookie = cookie,
.busy = true,
.size = size,
.mmapped = mmapped,
.wl_buf = buf,
.pix = pix,
};
wl_buffer_add_listener(buffer->wl_buf, &buffer_listener, buffer);
return buffer;
err:
if (pix != NULL)
pixman_image_unref(pix);
if (buf != NULL)
wl_buffer_destroy(buf);
if (pool != NULL)
wl_shm_pool_destroy(pool);
if (pool_fd != -1)
close(pool_fd);
if (mmapped != NULL)
munmap(mmapped, size);
return NULL;
}
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