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authorPaul Burton <paul.burton@imgtec.com>2016-04-21 14:04:55 +0100
committerRalf Baechle <ralf@linux-mips.org>2016-05-13 14:02:24 +0200
commitab4a92e66741b35ca12f8497896bafbe579c28a1 (patch)
treebb02af859ec986423ab97adfef216a67fd65a3db /arch/mips/math-emu
parentdb57f29d50683afd75c7f8b9908af7669837c3a9 (diff)
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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>
Diffstat (limited to 'arch/mips/math-emu')
-rw-r--r--arch/mips/math-emu/cp1emu.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/arch/mips/math-emu/cp1emu.c b/arch/mips/math-emu/cp1emu.c
index 85dd17497151..d96e912b9d44 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 */