target/arm: Warn about restoring to unaligned stack

Attempting to do an exception return with an exception frame that is not 8-aligned is UNPREDICTABLE in v8M; warn about this. (It is not UNPREDICTABLE in v7M, and our implementation can handle the merely-4-aligned case fine, so we don't need to do anything except warn.) Signed-off-by: Peter Maydell <[email protected]> Reviewed-by: Philippe Mathieu-Daudé <[email protected]> Reviewed-by: Richard Henderson <[email protected]> Message-id: [email protected]
0x3h · Oct 6, 2017 · cb484f9 · cb484f9
1 parent 224e0c3
commit cb484f9
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/target/arm/helper.c b/target/arm/helper.c
@@ -6413,6 +6413,13 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
                                               return_to_sp_process);
         uint32_t frameptr = *frame_sp_p;
 
+        if (!QEMU_IS_ALIGNED(frameptr, 8) &&
+            arm_feature(env, ARM_FEATURE_V8)) {
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "M profile exception return with non-8-aligned SP "
+                          "for destination state is UNPREDICTABLE\n");
+        }
+
         /* Pop registers. TODO: make these accesses use the correct
          * attributes and address space (S/NS, priv/unpriv) and handle
          * memory transaction failures.