diff options
| author | Paul Burton <paul.burton@imgtec.com> | 2016-04-21 14:04:55 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-06-07 18:18:45 -0700 |
| commit | 555e302e907fe98a2600d25031a9a05b3b5907d3 (patch) | |
| tree | 3fee27f5a91c753cdacf0df7dfa232cefb335fe2 /arch | |
| parent | 3cef3b3d25da5e828e25ba5ea9638a0d775cbe63 (diff) | |
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -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 cdfd44ffa51c..41d3e0e7defa 100644 --- a/arch/mips/math-emu/cp1emu.c +++ b/arch/mips/math-emu/cp1emu.c @@ -445,9 +445,11 @@ 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: /* For R6, JR already emulated in jalr_op */ |