From 2aea283c4f4c3b430a2a92cea3397685b9cf9a26 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Mon, 5 Mar 2018 01:40:37 -0500 Subject: [PATCH] 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.) Backports commit cb484f9a6e790205e69d9a444c3e353a3a1cfd84 from qemu --- qemu/target/arm/helper.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/qemu/target/arm/helper.c b/qemu/target/arm/helper.c index d710ad2a..e7b3fe7b 100644 --- a/qemu/target/arm/helper.c +++ b/qemu/target/arm/helper.c @@ -5677,6 +5677,13 @@ 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.