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Subject[PATCH 4.12 144/196] MIPS: Send SIGILL for R6 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 a60b1a5bf88a250f1a77977c0224e502c901c77b upstream.

Fix:

* commit 8467ca0122e2 ("MIPS: Emulate the new MIPS R6 branch compact
(BC) instruction"),

* commit 84fef630127a ("MIPS: Emulate the new MIPS R6 BALC
instruction"),

* commit 69b9a2fd05a3 ("MIPS: Emulate the new MIPS R6 BEQZC and JIC
instructions"),

* commit 28d6f93d201d ("MIPS: Emulate the new MIPS R6 BNEZC and JIALC
instructions"),

* commit c893ce38b265 ("MIPS: Emulate the new MIPS R6 BOVC, BEQC and
BEQZALC instructions")

and send SIGILL rather than returning -SIGILL for R6 branch and jump
instructions. Returning -SIGILL is never correct as the API defines
this function's result upon error to be -EFAULT and a signal actually
issued.

Fixes: 8467ca0122e2 ("MIPS: Emulate the new MIPS R6 branch compact (BC) instruction")
Fixes: 84fef630127a ("MIPS: Emulate the new MIPS R6 BALC instruction")
Fixes: 69b9a2fd05a3 ("MIPS: Emulate the new MIPS R6 BEQZC and JIC instructions")
Fixes: 28d6f93d201d ("MIPS: Emulate the new MIPS R6 BNEZC and JIALC instructions")
Fixes: c893ce38b265 ("MIPS: Emulate the new MIPS R6 BOVC, BEQC and BEQZALC instructions")
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/16399/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/mips/kernel/branch.c | 35 +++++++++++++++--------------------
1 file changed, 15 insertions(+), 20 deletions(-)

--- a/arch/mips/kernel/branch.c
+++ b/arch/mips/kernel/branch.c
@@ -771,35 +771,27 @@ int __compute_return_epc_for_insn(struct
#else
case bc6_op:
/* Only valid for MIPS R6 */
- if (!cpu_has_mips_r6) {
- ret = -SIGILL;
- break;
- }
+ if (!cpu_has_mips_r6)
+ goto sigill_r6;
regs->cp0_epc += 8;
break;
case balc6_op:
- if (!cpu_has_mips_r6) {
- ret = -SIGILL;
- break;
- }
+ if (!cpu_has_mips_r6)
+ goto sigill_r6;
/* Compact branch: BALC */
regs->regs[31] = epc + 4;
epc += 4 + (insn.i_format.simmediate << 2);
regs->cp0_epc = epc;
break;
case pop66_op:
- if (!cpu_has_mips_r6) {
- ret = -SIGILL;
- break;
- }
+ if (!cpu_has_mips_r6)
+ goto sigill_r6;
/* Compact branch: BEQZC || JIC */
regs->cp0_epc += 8;
break;
case pop76_op:
- if (!cpu_has_mips_r6) {
- ret = -SIGILL;
- break;
- }
+ if (!cpu_has_mips_r6)
+ goto sigill_r6;
/* Compact branch: BNEZC || JIALC */
if (!insn.i_format.rs) {
/* JIALC: set $31/ra */
@@ -811,10 +803,8 @@ int __compute_return_epc_for_insn(struct
case pop10_op:
case pop30_op:
/* Only valid for MIPS R6 */
- if (!cpu_has_mips_r6) {
- ret = -SIGILL;
- break;
- }
+ if (!cpu_has_mips_r6)
+ goto sigill_r6;
/*
* Compact branches:
* bovc, beqc, beqzalc, bnvc, bnec, bnezlac
@@ -837,6 +827,11 @@ sigill_r2r6:
current->comm);
force_sig(SIGILL, current);
return -EFAULT;
+sigill_r6:
+ pr_info("%s: R6 branch but no MIPSr6 ISA support - sending SIGILL.\n",
+ current->comm);
+ force_sig(SIGILL, current);
+ return -EFAULT;
}
EXPORT_SYMBOL_GPL(__compute_return_epc_for_insn);


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