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MIPS: math-emu: Correct delay-slot exception propagation

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Restore EPC at the branch whose delay slot is emulated if the delay-slot
instruction signals.  This is so that code in `fpu_emulator_cop1Handler'
does not see EPC having advanced and mistakenly successfully resume
userland execution from the location at the branch target in that case.
Restoring EPC guarantees an immediate exit from the emulation loop and
if EPC hasn't advanced at all since entering the loop, also issuing the
signal reported by the delay-slot instruction.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9701/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Maciej W. Rozycki
2015-04-03 23:26:56 +01:00
committed by Ralf Baechle
parent 2d83fea786
commit 9ab4471c9f
2 changed files with 30 additions and 6 deletions
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2
arch/mips/math-emu/dsemul.c
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@@ -96,7 +96,7 @@ int mips_dsemul(struct pt_regs *regs, mips_instruction ir, unsigned long cpc)
flush_cache_sigtramp((unsigned long)&fr->emul);
return SIGILL; /* force out of emulation loop */
return 0;
}
int do_dsemulret(struct pt_regs *xcp)