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MIPS: Fix unaligned PC interpretation in `compute_return_epc'

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commit 11a3799dbeb620bf0400b1fda5cc2c6bea55f20a upstream.

Fix a regression introduced with commit fb6883e580 ("MIPS: microMIPS:
Support handling of delay slots.") and defer to `__compute_return_epc'
if the ISA bit is set in EPC with non-MIPS16, non-microMIPS hardware,
which will then arrange for a SIGBUS due to an unaligned instruction
reference.  Returning EPC here is never correct as the API defines this
function's result to be either a negative error code on failure or one
of 0 and BRANCH_LIKELY_TAKEN on success.

Fixes: fb6883e580 ("MIPS: microMIPS: Support handling of delay slots.")
Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16395/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Maciej W. Rozycki 2017-06-16 00:07:34 +01:00 • committed by Greg Kroah-Hartman
parent aebb79634f
commit 9dbca9e8a9
1 changed files with 1 additions and 4 deletions
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5
arch/mips/include/asm/branch.h
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@ -74,10 +74,7 @@ static inline int compute_return_epc(struct pt_regs *regs)
return __microMIPS_compute_return_epc(regs);
if (cpu_has_mips16)
return __MIPS16e_compute_return_epc(regs);
return regs->cp0_epc;
}
if (!delay_slot(regs)) {
} else if (!delay_slot(regs)) {
regs->cp0_epc += 4;
return 0;
}