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| author | Paul Burton <paul.burton@imgtec.com> | 2016-04-21 14:04:55 +0100 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2016-08-22 22:37:58 +0100 |
| commit | 193f0270474b3cfe9309d1986645f95631b9e415 (patch) | |
| tree | 67f51ef8ad29a205a35d3c5e3d8555e897832eec /arch/mips/math-emu | |
| parent | f93675ec914d29fdaefb7f6d6bda82359937239d (diff) | |
| download | linux-stable-193f0270474b3cfe9309d1986645f95631b9e415.tar.gz linux-stable-193f0270474b3cfe9309d1986645f95631b9e415.tar.bz2 linux-stable-193f0270474b3cfe9309d1986645f95631b9e415.zip | |
MIPS: math-emu: Fix jalr emulation when rd == $0
commit ab4a92e66741b35ca12f8497896bafbe579c28a1 upstream.
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
Patchwork: https://patchwork.linux-mips.org/patch/13160/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch/mips/math-emu')
| -rw-r--r-- | arch/mips/math-emu/cp1emu.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/arch/mips/math-emu/cp1emu.c b/arch/mips/math-emu/cp1emu.c index 51a0fde4bec1..bc5ab0dbdf91 100644 --- a/arch/mips/math-emu/cp1emu.c +++ b/arch/mips/math-emu/cp1emu.c @@ -443,9 +443,11 @@ static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn, case spec_op: switch (insn.r_format.func) { case jalr_op: - regs->regs[insn.r_format.rd] = - regs->cp0_epc + dec_insn.pc_inc + - dec_insn.next_pc_inc; + if (insn.r_format.rd != 0) { + regs->regs[insn.r_format.rd] = + regs->cp0_epc + dec_insn.pc_inc + + dec_insn.next_pc_inc; + } /* Fall through */ case jr_op: *contpc = regs->regs[insn.r_format.rs]; |