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Re: [Qemu-devel] [Qemu-arm] [PATCH 07/20] target/arm: Warn about restori


From: Philippe Mathieu-Daudé
Subject: Re: [Qemu-devel] [Qemu-arm] [PATCH 07/20] target/arm: Warn about restoring to unaligned stack
Date: Fri, 29 Sep 2017 18:05:25 -0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0

On 09/22/2017 11:59 AM, Peter Maydell wrote:
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 <address@hidden>

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

---
  target/arm/helper.c | 7 +++++++
  1 file changed, 7 insertions(+)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index a2e46fb..979129e 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6403,6 +6403,13 @@ 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.




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