sna: Catch SIGBUS to prevent X death

We know that when we access either a CPU or GTT mmap we are vulernable
to receiving a SIGBUS. In fact, we can catch these and abort the
operation preventing X and all of its clients from randomly dieing.

This helps for instance if you try and use a 1GiB frontbuffer on a 2GiB
machine...

For complete protection, we also need to catch signals for all GTT maps,
such as VBO and staging buffers. (TBD)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/sna/sna.h b/src/sna/sna.h
index d3890267..f7c5315c 100644
--- a/src/sna/sna.h
+++ b/src/sna/sna.h
@@ -69,6 +69,9 @@ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include <libudev.h>
 #endif
 
+#include <signal.h>
+#include <setjmp.h>
+
 #include "compiler.h"
 
 #if HAS_DEBUG_FULL
@@ -973,4 +976,16 @@ void sna_image_composite(pixman_op_t        op,
 			 uint16_t           width,
 			 uint16_t           height);
 
+extern jmp_buf sigjmp;
+extern volatile sig_atomic_t sigtrap;
+
+#define sigtrap_assert() assert(sigtrap == 0)
+#define sigtrap_get() sigsetjmp(sigjmp, ++sigtrap)
+
+static inline void sigtrap_put(void)
+{
+	--sigtrap;
+	sigtrap_assert();
+}
+
 #endif /* _SNA_H */