target-arm: raise exception on misaligned LDREX operands

Qemu does not generally perform alignment checks. However, the ARM ARM
requires implementation of alignment exceptions for a number of cases
including LDREX, and Windows-on-ARM relies on this.

This change adds plumbing to enable alignment checks on loads using
MO_ALIGN, a do_unaligned_access hook to raise the exception (data
abort), and uses the new aligned loads in LDREX (for all but
single-byte loads).

Signed-off-by: Andrew Baumann <Andrew.Baumann@microsoft.com>
Message-id: 1449167808-5656-1-git-send-email-Andrew.Baumann@microsoft.com
[PMM: set WnR bits in syndrome and FSR as appropriate]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/target-arm/helper.c b/target-arm/helper.c
index afc4163342..59d5a41b58 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -5996,6 +5996,14 @@ static inline bool regime_using_lpae_format(CPUARMState *env,
     return false;
 }
 
+/* Returns true if the translation regime is using LPAE format page tables.
+ * Used when raising alignment exceptions, whose FSR changes depending on
+ * whether the long or short descriptor format is in use. */
+bool arm_regime_using_lpae_format(CPUARMState *env, ARMMMUIdx mmu_idx)
+{
+    return regime_using_lpae_format(env, mmu_idx);
+}
+
 static inline bool regime_is_user(CPUARMState *env, ARMMMUIdx mmu_idx)
 {
     switch (mmu_idx) {