gstreamer/ext/wayland/wlshmallocator.c
Emmanuel Gil Peyrot f97b718b4c waylandsink: Use memfd_create() when available
This (so-far) Linux- and FreeBSD-only API lets users create file
descriptors purely in memory, without any backing file on the filesystem
and the race condition which could ensue when unlink()ing it.

It also allows seals to be placed on the file, ensuring to every other
process that we won’t be allowed to shrink the contents, potentially
causing a SIGBUS when they try reading it.

This patch is best viewed with the -w option of git log -p.

It is an almost exact copy of Wayland commit
6908c8c85a2e33e5654f64a55cd4f847bf385cae, see
https://gitlab.freedesktop.org/wayland/wayland/merge_requests/4

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1577>
2020-09-15 19:17:12 +00:00

246 lines
6.9 KiB
C

/* GStreamer Wayland video sink
*
* Copyright (C) 2012 Intel Corporation
* Copyright (C) 2012 Sreerenj Balachandran <sreerenj.balachandran@intel.com>
* Copyright (C) 2014 Collabora Ltd.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
#include "wlshmallocator.h"
#include "wlvideoformat.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/types.h>
GST_DEBUG_CATEGORY_EXTERN (gstwayland_debug);
#define GST_CAT_DEFAULT gstwayland_debug
G_DEFINE_TYPE (GstWlShmAllocator, gst_wl_shm_allocator, GST_TYPE_FD_ALLOCATOR);
static GstMemory *
gst_wl_shm_allocator_alloc (GstAllocator * allocator, gsize size,
GstAllocationParams * params)
{
GstWlShmAllocator *self = GST_WL_SHM_ALLOCATOR (allocator);
char filename[1024];
static int init = 0;
int fd;
GstMemory *mem;
GstMapInfo info;
/* TODO: make use of the allocation params, if necessary */
#ifdef HAVE_MEMFD_CREATE
fd = memfd_create ("gst-wayland-shm", MFD_CLOEXEC | MFD_ALLOW_SEALING);
if (fd >= 0) {
/* We can add this seal before calling posix_fallocate(), as
* the file is currently zero-sized anyway.
*
* There is also no need to check for the return value, we
* couldn't do anything with it anyway.
*/
fcntl (fd, F_ADD_SEALS, F_SEAL_SHRINK);
} else
#endif
{
/* allocate shm pool */
snprintf (filename, 1024, "%s/%s-%d-%s", g_get_user_runtime_dir (),
"wayland-shm", init++, "XXXXXX");
fd = g_mkstemp (filename);
if (fd < 0) {
GST_ERROR_OBJECT (self, "opening temp file %s failed: %s", filename,
strerror (errno));
return NULL;
}
unlink (filename);
}
if (ftruncate (fd, size) < 0) {
GST_ERROR_OBJECT (self, "ftruncate failed: %s", strerror (errno));
close (fd);
return NULL;
}
mem = gst_fd_allocator_alloc (allocator, fd, size,
GST_FD_MEMORY_FLAG_KEEP_MAPPED);
if (G_UNLIKELY (!mem)) {
GST_ERROR_OBJECT (self, "GstFdMemory allocation failed");
close (fd);
return NULL;
}
/* we need to map the memory in order to unlink the file without losing it */
if (!gst_memory_map (mem, &info, GST_MAP_READWRITE)) {
GST_ERROR_OBJECT (self, "GstFdMemory map failed");
close (fd);
return NULL;
}
/* unmap will not really munmap(), we just
* need it to release the miniobject lock */
gst_memory_unmap (mem, &info);
return mem;
}
static void
gst_wl_shm_allocator_class_init (GstWlShmAllocatorClass * klass)
{
GstAllocatorClass *alloc_class = (GstAllocatorClass *) klass;
alloc_class->alloc = GST_DEBUG_FUNCPTR (gst_wl_shm_allocator_alloc);
}
static void
gst_wl_shm_allocator_init (GstWlShmAllocator * self)
{
GstAllocator *alloc = GST_ALLOCATOR_CAST (self);
alloc->mem_type = GST_ALLOCATOR_WL_SHM;
GST_OBJECT_FLAG_UNSET (self, GST_ALLOCATOR_FLAG_CUSTOM_ALLOC);
}
void
gst_wl_shm_allocator_register (void)
{
GstAllocator *alloc;
alloc = g_object_new (GST_TYPE_WL_SHM_ALLOCATOR, NULL);
gst_object_ref_sink (alloc);
gst_allocator_register (GST_ALLOCATOR_WL_SHM, alloc);
}
GstAllocator *
gst_wl_shm_allocator_get (void)
{
return gst_allocator_find (GST_ALLOCATOR_WL_SHM);
}
gboolean
gst_is_wl_shm_memory (GstMemory * mem)
{
return gst_memory_is_type (mem, GST_ALLOCATOR_WL_SHM);
}
/* Copied from gst_v4l2_object_extrapolate_stride() */
static gint
gst_wl_shm_extrapolate_stride (const GstVideoFormatInfo * finfo, gint plane,
gint stride)
{
gint estride;
switch (finfo->format) {
case GST_VIDEO_FORMAT_NV12:
case GST_VIDEO_FORMAT_NV12_64Z32:
case GST_VIDEO_FORMAT_NV21:
case GST_VIDEO_FORMAT_NV16:
case GST_VIDEO_FORMAT_NV61:
case GST_VIDEO_FORMAT_NV24:
estride = (plane == 0 ? 1 : 2) *
GST_VIDEO_FORMAT_INFO_SCALE_WIDTH (finfo, plane, stride);
break;
default:
estride = GST_VIDEO_FORMAT_INFO_SCALE_WIDTH (finfo, plane, stride);
break;
}
return estride;
}
static gboolean
gst_wl_shm_validate_video_info (const GstVideoInfo * vinfo)
{
gint height = GST_VIDEO_INFO_HEIGHT (vinfo);
gint base_stride = GST_VIDEO_INFO_PLANE_STRIDE (vinfo, 0);
gsize base_offs = GST_VIDEO_INFO_PLANE_OFFSET (vinfo, 0);
gint i;
gsize offs = 0;
for (i = 0; i < GST_VIDEO_INFO_N_PLANES (vinfo); i++) {
guint32 estride;
/* Overwrite the video info's stride and offset using the pitch calculcated
* by the kms driver. */
estride = gst_wl_shm_extrapolate_stride (vinfo->finfo, i, base_stride);
if (estride != GST_VIDEO_INFO_PLANE_STRIDE (vinfo, i))
return FALSE;
if (GST_VIDEO_INFO_PLANE_OFFSET (vinfo, i) - base_offs != offs)
return FALSE;
/* Note that we cannot negotiate special padding betweem each planes,
* hence using the display height here. */
offs +=
estride * GST_VIDEO_FORMAT_INFO_SCALE_HEIGHT (vinfo->finfo, i, height);
}
if (vinfo->size < offs)
return FALSE;
return TRUE;
}
struct wl_buffer *
gst_wl_shm_memory_construct_wl_buffer (GstMemory * mem, GstWlDisplay * display,
const GstVideoInfo * info)
{
gint width, height, stride;
gsize offset, size, memsize, maxsize;
enum wl_shm_format format;
struct wl_shm_pool *wl_pool;
struct wl_buffer *wbuffer;
if (!gst_wl_shm_validate_video_info (info)) {
GST_DEBUG_OBJECT (display, "Unsupported strides and offsets.");
return NULL;
}
width = GST_VIDEO_INFO_WIDTH (info);
height = GST_VIDEO_INFO_HEIGHT (info);
stride = GST_VIDEO_INFO_PLANE_STRIDE (info, 0);
size = GST_VIDEO_INFO_SIZE (info);
format = gst_video_format_to_wl_shm_format (GST_VIDEO_INFO_FORMAT (info));
memsize = gst_memory_get_sizes (mem, &offset, &maxsize);
offset += GST_VIDEO_INFO_PLANE_OFFSET (info, 0);
g_return_val_if_fail (gst_is_fd_memory (mem), NULL);
g_return_val_if_fail (size <= memsize, NULL);
g_return_val_if_fail (gst_wl_display_check_format_for_shm (display,
GST_VIDEO_INFO_FORMAT (info)), NULL);
GST_DEBUG_OBJECT (display, "Creating wl_buffer from SHM of size %"
G_GSSIZE_FORMAT " (%d x %d, stride %d), format %s", size, width, height,
stride, gst_wl_shm_format_to_string (format));
wl_pool = wl_shm_create_pool (display->shm, gst_fd_memory_get_fd (mem),
memsize);
wbuffer = wl_shm_pool_create_buffer (wl_pool, offset, width, height, stride,
format);
wl_shm_pool_destroy (wl_pool);
return wbuffer;
}