| 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 |
| @@ -445,9 +445,11 @@ 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: |
| /* For R6, JR already emulated in jalr_op */ |
