MIPS: kernel: branch: Do not emulate the branch likelies on MIPS R6

MIPS R6 removed the BLTZL, BGEZL, BLTZAL, BGEZAL, BEQL, BNEL, BLEZL,
BGTZL branch likely instructions so we must not try to emulate them on
MIPS R6 if the R2-to-R6 emulator is not present.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

arch/mips/kernel/branch.c

@@ -431,8 +431,10 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
 	 */
 	case bcond_op:
 		switch (insn.i_format.rt) {
-		case bltz_op:
 		case bltzl_op:
+			if (NO_R6EMU)
+				goto sigill_r6;
+		case bltz_op:
 			if ((long)regs->regs[insn.i_format.rs] < 0) {
 				epc = epc + 4 + (insn.i_format.simmediate << 2);
 				if (insn.i_format.rt == bltzl_op)
@@ -442,8 +444,10 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
 			regs->cp0_epc = epc;
 			break;
 
-		case bgez_op:
 		case bgezl_op:
+			if (NO_R6EMU)
+				goto sigill_r6;
+		case bgez_op:
 			if ((long)regs->regs[insn.i_format.rs] >= 0) {
 				epc = epc + 4 + (insn.i_format.simmediate << 2);
 				if (insn.i_format.rt == bgezl_op)
@@ -455,7 +459,29 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
 
 		case bltzal_op:
 		case bltzall_op:
+			if (NO_R6EMU && (insn.i_format.rs ||
+			    insn.i_format.rt == bltzall_op)) {
+				ret = -SIGILL;
+				break;
+			}
 			regs->regs[31] = epc + 8;
+			/*
+			 * OK we are here either because we hit a NAL
+			 * instruction or because we are emulating an
+			 * old bltzal{,l} one. Lets figure out what the
+			 * case really is.
+			 */
+			if (!insn.i_format.rs) {
+				/*
+				 * NAL or BLTZAL with rs == 0
+				 * Doesn't matter if we are R6 or not. The
+				 * result is the same
+				 */
+				regs->cp0_epc += 4 +
+					(insn.i_format.simmediate << 2);
+				break;
+			}
+			/* Now do the real thing for non-R6 BLTZAL{,L} */
 			if ((long)regs->regs[insn.i_format.rs] < 0) {
 				epc = epc + 4 + (insn.i_format.simmediate << 2);
 				if (insn.i_format.rt == bltzall_op)
@@ -467,7 +493,29 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
 
 		case bgezal_op:
 		case bgezall_op:
+			if (NO_R6EMU && (insn.i_format.rs ||
+			    insn.i_format.rt == bgezall_op)) {
+				ret = -SIGILL;
+				break;
+			}
 			regs->regs[31] = epc + 8;
+			/*
+			 * OK we are here either because we hit a BAL
+			 * instruction or because we are emulating an
+			 * old bgezal{,l} one. Lets figure out what the
+			 * case really is.
+			 */
+			if (!insn.i_format.rs) {
+				/*
+				 * BAL or BGEZAL with rs == 0
+				 * Doesn't matter if we are R6 or not. The
+				 * result is the same
+				 */
+				regs->cp0_epc += 4 +
+					(insn.i_format.simmediate << 2);
+				break;
+			}
+			/* Now do the real thing for non-R6 BGEZAL{,L} */
 			if ((long)regs->regs[insn.i_format.rs] >= 0) {
 				epc = epc + 4 + (insn.i_format.simmediate << 2);
 				if (insn.i_format.rt == bgezall_op)
@@ -510,8 +558,10 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
 	/*
 	 * These are conditional and in i_format.
 	 */
-	case beq_op:
 	case beql_op:
+		if (NO_R6EMU)
+			goto sigill_r6;
+	case beq_op:
 		if (regs->regs[insn.i_format.rs] ==
 		    regs->regs[insn.i_format.rt]) {
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
@@ -522,8 +572,10 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
 		regs->cp0_epc = epc;
 		break;
 
-	case bne_op:
 	case bnel_op:
+		if (NO_R6EMU)
+			goto sigill_r6;
+	case bne_op:
 		if (regs->regs[insn.i_format.rs] !=
 		    regs->regs[insn.i_format.rt]) {
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
@@ -534,8 +586,10 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
 		regs->cp0_epc = epc;
 		break;
 
-	case blez_op: /* not really i_format */
-	case blezl_op:
+	case blezl_op: /* not really i_format */
+		if (NO_R6EMU)
+			goto sigill_r6;
+	case blez_op:
 		/* rt field assumed to be zero */
 		if ((long)regs->regs[insn.i_format.rs] <= 0) {
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
@@ -546,8 +600,10 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
 		regs->cp0_epc = epc;
 		break;
 
-	case bgtz_op:
 	case bgtzl_op:
+		if (NO_R6EMU)
+			goto sigill_r6;
+	case bgtz_op:
 		/* rt field assumed to be zero */
 		if ((long)regs->regs[insn.i_format.rs] > 0) {
 			epc = epc + 4 + (insn.i_format.simmediate << 2);

arch/mips/math-emu/cp1emu.c

@@ -459,12 +459,18 @@ static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
 		switch (insn.i_format.rt) {
 		case bltzal_op:
 		case bltzall_op:
+			if (NO_R6EMU && (insn.i_format.rs ||
+			    insn.i_format.rt == bltzall_op))
+				break;
+
 			regs->regs[31] = regs->cp0_epc +
 				dec_insn.pc_inc +
 				dec_insn.next_pc_inc;
 			/* Fall through */
-		case bltz_op:
 		case bltzl_op:
+			if (NO_R6EMU)
+				break;
+		case bltz_op:
 			if ((long)regs->regs[insn.i_format.rs] < 0)
 				*contpc = regs->cp0_epc +
 					dec_insn.pc_inc +
@@ -476,12 +482,18 @@ static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
 			return 1;
 		case bgezal_op:
 		case bgezall_op:
+			if (NO_R6EMU && (insn.i_format.rs ||
+			    insn.i_format.rt == bgezall_op))
+				break;
+
 			regs->regs[31] = regs->cp0_epc +
 				dec_insn.pc_inc +
 				dec_insn.next_pc_inc;
 			/* Fall through */
-		case bgez_op:
 		case bgezl_op:
+			if (NO_R6EMU)
+				break;
+		case bgez_op:
 			if ((long)regs->regs[insn.i_format.rs] >= 0)
 				*contpc = regs->cp0_epc +
 					dec_insn.pc_inc +
@@ -508,8 +520,10 @@ static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
 		/* Set microMIPS mode bit: XOR for jalx. */
 		*contpc ^= bit;
 		return 1;
-	case beq_op:
 	case beql_op:
+		if (NO_R6EMU)
+			break;
+	case beq_op:
 		if (regs->regs[insn.i_format.rs] ==
 		    regs->regs[insn.i_format.rt])
 			*contpc = regs->cp0_epc +
@@ -520,8 +534,10 @@ static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
 				dec_insn.pc_inc +
 				dec_insn.next_pc_inc;
 		return 1;
-	case bne_op:
 	case bnel_op:
+		if (NO_R6EMU)
+			break;
+	case bne_op:
 		if (regs->regs[insn.i_format.rs] !=
 		    regs->regs[insn.i_format.rt])
 			*contpc = regs->cp0_epc +
@@ -532,8 +548,10 @@ static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
 				dec_insn.pc_inc +
 				dec_insn.next_pc_inc;
 		return 1;
-	case blez_op:
 	case blezl_op:
+		if (NO_R6EMU)
+			break;
+	case blez_op:
 		if ((long)regs->regs[insn.i_format.rs] <= 0)
 			*contpc = regs->cp0_epc +
 				dec_insn.pc_inc +
@@ -543,8 +561,10 @@ static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
 				dec_insn.pc_inc +
 				dec_insn.next_pc_inc;
 		return 1;
-	case bgtz_op:
 	case bgtzl_op:
+		if (NO_R6EMU)
+			break;
+	case bgtz_op:
 		if ((long)regs->regs[insn.i_format.rs] > 0)
 			*contpc = regs->cp0_epc +
 				dec_insn.pc_inc +