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

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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>
This commit is contained in:
Vineet Gupta 2017-01-27 10:45:27 -08:00
parent 78f824d431
commit 9aed02feae
1 changed files with 2 additions and 1 deletions
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3
arch/arc/kernel/unaligned.c
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@ -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;