--- /dev/null
+From ab4a92e66741b35ca12f8497896bafbe579c28a1 Mon Sep 17 00:00:00 2001
+From: Paul Burton <paul.burton@imgtec.com>
+Date: Thu, 21 Apr 2016 14:04:55 +0100
+Subject: MIPS: math-emu: Fix jalr emulation when rd == $0
+
+From: Paul Burton <paul.burton@imgtec.com>
+
+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>
+
+---
+ arch/mips/math-emu/cp1emu.c | 8 +++++---
+ 1 file changed, 5 insertions(+), 3 deletions(-)
+
+--- a/arch/mips/math-emu/cp1emu.c
++++ b/arch/mips/math-emu/cp1emu.c
+@@ -676,9 +676,11 @@ static int isBranchInstr(struct pt_regs
+ 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];