ARC: [arcompact] handle unaligned access delay slot corner case

After emulating an unaligned access in delay slot of a branch, we
pretend as the delay slot never happened - so return back to actual
branch target (or next PC if branch was not taken).

Curently we did this by handling STATUS32.DE, we also need to clear the
BTA.T bit, which is disregarded when returning from original misaligned
exception, but could cause weirdness if it took the interrupt return
path (in case interrupt was acive too)

One ARC700 customer ran into this when enabling unaligned access fixup
for kernel mode accesses as well

Cc: stable@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

diff --git a/arch/arc/kernel/unaligned.c b/arch/arc/kernel/unaligned.c
index abd961f3e7639f13fb7954da68885ed0215f432c..91ebe382147f6d915a58f94027fa748ca8319f30 100644 (file)
--- a/arch/arc/kernel/unaligned.c
+++ b/arch/arc/kernel/unaligned.c
@@ -241,8 +241,9 @@ int misaligned_fixup(unsigned long address, struct pt_regs *regs,
        if (state.fault)
                goto fault;
 
+       /* clear any remanants of delay slot */
        if (delay_mode(regs)) {
-               regs->ret = regs->bta;
+               regs->ret = regs->bta ~1U;
                regs->status32 &= ~STATUS_DE_MASK;
        } else {
                regs->ret += state.instr_len;