[PATCH for-5.0] hw/ppc/e500.c: Handle qemu_find_file() failure

[Peter Maydell]

If qemu_find_file() doesn't find the BIOS it returns NULL; we were
passing that unchecked through to load_elf(), which assumes a non-NULL
pointer and may misbehave. In practice it fails with a weird message:

  $ qemu-system-ppc -M ppce500 -display none -kernel nonesuch
  Bad address
  qemu-system-ppc: could not load firmware '(null)'

Handle the failure case better:

  $ qemu-system-ppc -M ppce500 -display none -kernel nonesuch
  qemu-system-ppc: could not find firmware/kernel file 'nonesuch'

Spotted by Coverity (CID 1238954).

Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
---
 hw/ppc/e500.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/ppc/e500.c b/hw/ppc/e500.c
index 854cd3ac465..0d1f41197cf 100644
--- a/hw/ppc/e500.c
+++ b/hw/ppc/e500.c
@@ -1047,6 +1047,10 @@ void ppce500_init(MachineState *machine)
     }
 
     filename = qemu_find_file(QEMU_FILE_TYPE_BIOS, payload_name);
+    if (!filename) {
+        error_report("could not find firmware/kernel file '%s'", payload_name);
+        exit(1);
+    }
 
     payload_size = load_elf(filename, NULL, NULL, NULL,
                             &bios_entry, &loadaddr, NULL, NULL,
-- 
2.20.1