gallium/rtasm: handle mmap failures appropriately

For a variety of reasons mmap (selinux and pax to name
a few) and can fail and with current code. This will
result in a crash in the driver, if not worse.

This has been the case since the inception of the
gallium copy of rtasm.

Cc: 9.1 9.2 10.0 <mesa-stable@lists.freedesktop.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=73473
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>

src/gallium/auxiliary/rtasm/rtasm_execmem.c

@@ -69,7 +69,7 @@ static struct mem_block *exec_heap = NULL;
 static unsigned char *exec_mem = NULL;
 
 
-static void
+static int
 init_heap(void)
 {
    if (!exec_heap)
@@ -79,6 +79,8 @@ init_heap(void)
       exec_mem = (unsigned char *) mmap(0, EXEC_HEAP_SIZE, 
 					PROT_EXEC | PROT_READ | PROT_WRITE, 
 					MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+   return (exec_mem != MAP_FAILED);
 }
 
 
@@ -90,7 +92,8 @@ rtasm_exec_malloc(size_t size)
 
    pipe_mutex_lock(exec_mutex);
 
-   init_heap();
+   if (!init_heap())
+      goto bail;
 
    if (exec_heap) {
       size = (size + 31) & ~31;  /* next multiple of 32 bytes */
@@ -101,7 +104,8 @@ rtasm_exec_malloc(size_t size)
       addr = exec_mem + block->ofs;
    else 
       debug_printf("rtasm_exec_malloc failed\n");
-   
+
+bail:
    pipe_mutex_unlock(exec_mutex);
    
    return addr;