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Subject[PATCH 4.12 143/196] MIPS: Send SIGILL for linked branches in `__compute_return_epc_for_insn
Date
4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Maciej W. Rozycki <macro@imgtec.com>

commit fef40be6da856afead4177aaa9d869a66fb3381f upstream.

Fix commit 319824eabc3f ("MIPS: kernel: branch: Do not emulate the
branch likelies on MIPS R6") and also send SIGILL rather than returning
-SIGILL for BLTZAL, BLTZALL, BGEZAL and BGEZALL instruction encodings no
longer supported in R6, except where emulated. Returning -SIGILL is
never correct as the API defines this function's result upon error to be
-EFAULT and a signal actually issued.

Fixes: 319824eabc3f ("MIPS: kernel: branch: Do not emulate the branch likelies on MIPS R6")
Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16398/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/mips/kernel/branch.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)

--- a/arch/mips/kernel/branch.c
+++ b/arch/mips/kernel/branch.c
@@ -473,10 +473,8 @@ int __compute_return_epc_for_insn(struct
case bltzal_op:
case bltzall_op:
if (NO_R6EMU && (insn.i_format.rs ||
- insn.i_format.rt == bltzall_op)) {
- ret = -SIGILL;
- break;
- }
+ insn.i_format.rt == bltzall_op))
+ goto sigill_r2r6;
regs->regs[31] = epc + 8;
/*
* OK we are here either because we hit a NAL
@@ -507,10 +505,8 @@ int __compute_return_epc_for_insn(struct
case bgezal_op:
case bgezall_op:
if (NO_R6EMU && (insn.i_format.rs ||
- insn.i_format.rt == bgezall_op)) {
- ret = -SIGILL;
- break;
- }
+ insn.i_format.rt == bgezall_op))
+ goto sigill_r2r6;
regs->regs[31] = epc + 8;
/*
* OK we are here either because we hit a BAL

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