MIPS: math-emu: Fix jalr emulation when rd == $0
authorPaul Burton <paul.burton@imgtec.com>
Thu, 21 Apr 2016 13:04:55 +0000 (14:04 +0100)
committerRalf Baechle <ralf@linux-mips.org>
Fri, 13 May 2016 12:02:24 +0000 (14:02 +0200)
commitab4a92e66741b35ca12f8497896bafbe579c28a1
treebb02af859ec986423ab97adfef216a67fd65a3db
parentdb57f29d50683afd75c7f8b9908af7669837c3a9
MIPS: math-emu: Fix jalr emulation when rd == $0

When emulating a jalr instruction with rd == $0, the code in
isBranchInstr was incorrectly writing to GPR $0 which should actually
always remain zeroed. This would lead to any further instructions
emulated which use $0 operating on a bogus value until the task is next
context switched, at which point the value of $0 in the task context
would be restored to the correct zero by a store in SAVE_SOME. Fix this
by not writing to rd if it is $0.

Fixes: 102cedc32a6e ("MIPS: microMIPS: Floating point support.")
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Maciej W. Rozycki <macro@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: stable <stable@vger.kernel.org> # v3.10
Patchwork: https://patchwork.linux-mips.org/patch/13160/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
arch/mips/math-emu/cp1emu.c