MIPS: Send SIGILL for R6 branches in `__compute_return_epc_for_insn'

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
Cc: stable@vger.kernel.org # 3.19+
Patchwork: https://patchwork.linux-mips.org/patch/16399/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c
index 64c8360..6d536e5 100644 (file)
--- a/arch/mips/kernel/branch.c
+++ b/arch/mips/kernel/branch.c
@@ -771,35 +771,27 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
 #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 pt_regs *regs,
        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);