MIPS: Emulate the new MIPS R6 branch compact (BC) instruction

MIPS R6 uses the <R6 LWC2 opcode for the new BC instruction.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

3 files changed, 23 insertions, 1 deletions

diff --git a/arch/mips/include/uapi/asm/inst.h b/arch/mips/include/uapi/asm/inst.h
index 19d3bc1e6510..9ce5e34b9c64 100644
--- a/arch/mips/include/uapi/asm/inst.h
+++ b/arch/mips/include/uapi/asm/inst.h
@@ -31,7 +31,7 @@ enum major_op {
         lbu_op, lhu_op, lwr_op, lwu_op,
         sb_op, sh_op, swl_op, sw_op,
         sdl_op, sdr_op, swr_op, cache_op,
-        ll_op, lwc1_op, lwc2_op, pref_op,
+        ll_op, lwc1_op, lwc2_op, bc6_op = lwc2_op, pref_op,
         lld_op, ldc1_op, ldc2_op, ld_op,
         sc_op, swc1_op, swc2_op, major_3b_op,
         scd_op, sdc1_op, sdc2_op, sd_op
diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c
index cd880b91f092..1a0a30e16684 100644
--- a/arch/mips/kernel/branch.c
+++ b/arch/mips/kernel/branch.c
@@ -780,6 +780,15 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
                         epc += 8;
                 regs->cp0_epc = epc;
                 break;
+#else
+        case bc6_op:
+                /* Only valid for MIPS R6 */
+                if (!cpu_has_mips_r6) {
+                        ret = -SIGILL;
+                        break;
+                }
+                regs->cp0_epc += 8;
+                break;
 #endif
         }
 
diff --git a/arch/mips/math-emu/cp1emu.c b/arch/mips/math-emu/cp1emu.c
index d6d67e2a0434..7f373a2858b5 100644
--- a/arch/mips/math-emu/cp1emu.c
+++ b/arch/mips/math-emu/cp1emu.c
@@ -648,6 +648,19 @@ static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
                 else
                         *contpc = regs->cp0_epc + 8;
                 return 1;
+#else
+        case bc6_op:
+                /*
+                 * Only valid for MIPS R6 but we can still end up
+                 * here from a broken userland so just tell emulator
+                 * this is not a branch and let it break later on.
+                 */
+                if  (!cpu_has_mips_r6)
+                        break;
+                *contpc = regs->cp0_epc + dec_insn.pc_inc +
+                        dec_insn.next_pc_inc;
+
+                return 1;
 #endif
         case cop0_op:
         case cop1_op: