boot: Fall back to using image load address for stack guard

If we cannot get random data from the RNG protocol we can still use our
load address to make the stack guard a little less static.

diff --git a/src/boot/efi/log.c b/src/boot/efi/log.c
index 93631aca942ca6eb61857d8b8f068800c5f65cf9..dd651bf18e83c1c2248717935489c2fa771fbb0f 100644 (file)
--- a/src/boot/efi/log.c
+++ b/src/boot/efi/log.c
@@ -79,6 +79,9 @@ void __stack_chk_guard_init(void) {
         EFI_RNG_PROTOCOL *rng;
         if (BS->LocateProtocol(MAKE_GUID_PTR(EFI_RNG_PROTOCOL), NULL, (void **) &rng) == EFI_SUCCESS)
                 (void) rng->GetRNG(rng, NULL, sizeof(__stack_chk_guard), (void *) &__stack_chk_guard);
+        else
+                /* Better than no extra entropy. */
+                __stack_chk_guard ^= (intptr_t) &__ImageBase;
 }
 #endif