From 2297b8134bf79e45eabd9038fed230aacb3e1ec7 Mon Sep 17 00:00:00 2001
From: Michael Davidsaver <mdavidsaver@gmail.com>
Date: Fri, 2 Mar 2018 13:45:02 -0500
Subject: [PATCH] armv7m: honour CCR.STACKALIGN on exception entry

The CCR.STACKALIGN bit controls whether the CPU is supposed to force
8-alignment of the stack pointer on entry to the exception handler.

Backports commit dc858c6633a9af8b80c1509cf6f825e4390d3ad1 from qemu
---
 qemu/target/arm/helper.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/qemu/target/arm/helper.c b/qemu/target/arm/helper.c
index bd4dcaf6..a1ef6a96 100644
--- a/qemu/target/arm/helper.c
+++ b/qemu/target/arm/helper.c
@@ -5483,10 +5483,8 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
         return; /* Never happens.  Keep compiler happy.  */
     }
 
-    /* Align stack pointer.  */
-    /* ??? Should only do this if Configuration Control Register
-       STACKALIGN bit is set.  */
-    if (env->regs[13] & 4) {
+    /* Align stack pointer if the guest wants that */
+    if ((env->regs[13] & 4) && (env->v7m.ccr & R_V7M_CCR_STKALIGN_MASK)) {
         env->regs[13] -= 4;
         xpsr |= 0x200;
     }