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

commit 9aed02feae57bf7a40cb04ea0e3017cb7a998db4 upstream.

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

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/arch/arc/kernel/unaligned.c b/arch/arc/kernel/unaligned.c
index 7ff5b5c183bb026716295c13f7b123de1d67a96f..dbde997d16c6cc75956e75c9ef912e4b2e35c5f0 100644 (file)
--- a/arch/arc/kernel/unaligned.c
+++ b/arch/arc/kernel/unaligned.c
@@ -240,8 +240,9 @@ 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;