egl/surfaceless: Allow DRMless fallback.

Allow platform_surfaceless to use swrast even if DRM is not available.
To be used to allow a fuzzer for virgl to be run on a jailed VM without
hardware GL or DRM support.

Reviewed-by: Eric Engestrom <[email protected]>
Reviewed-by: Chad Versace <[email protected]>
Signed-off-by: David Riley <[email protected]>

1 files changed, 19 insertions, 0 deletions

diff --git a/src/egl/drivers/dri2/platform_surfaceless.c b/src/egl/drivers/dri2/platform_surfaceless.c
index 54bafaee0ef..bfc8fb99eab 100644
--- a/src/egl/drivers/dri2/platform_surfaceless.c
+++ b/src/egl/drivers/dri2/platform_surfaceless.c
@@ -293,6 +293,7 @@ surfaceless_probe_device(_EGLDisplay *dpy, bool swrast)
    int fd;
    int i;
 
+   /* Attempt to find DRM device. */
    for (i = 0; i < limit; ++i) {
       char *card_path;
       if (asprintf(&card_path, DRM_RENDER_DEV_NAME, DRM_DIR_NAME, base + i) < 0)
@@ -326,6 +327,24 @@ surfaceless_probe_device(_EGLDisplay *dpy, bool swrast)
       dri2_dpy->loader_extensions = NULL;
    }
 
+   /* No DRM device, so attempt to fall back to software path w/o DRM. */
+   if (swrast) {
+      _eglLog(_EGL_DEBUG, "Falling back to surfaceless swrast without DRM.");
+      dri2_dpy->fd = -1;
+      dri2_dpy->driver_name = strdup("swrast");
+      if (!dri2_dpy->driver_name) {
+         return false;
+      }
+
+      if (dri2_load_driver_swrast(dpy)) {
+         dri2_dpy->loader_extensions = swrast_loader_extensions;
+         return true;
+      }
+
+      free(dri2_dpy->driver_name);
+      dri2_dpy->driver_name = NULL;
+   }
+
    return false;
 }