arch/mips/kernel/branch.c - linux - Git at Google

 /*
  * This file is subject to the terms and conditions of the GNU General Public
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  *
  * Copyright (C) 1996, 97, 2000, 2001 by Ralf Baechle
  * Copyright (C) 2001 MIPS Technologies, Inc.
  */
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/signal.h>
 #include <linux/module.h>
 #include <asm/branch.h>
 #include <asm/cpu.h>
 #include <asm/cpu-features.h>
 #include <asm/fpu.h>
 #include <asm/fpu_emulator.h>
 #include <asm/inst.h>
 #include <asm/mips-r2-to-r6-emul.h>
 #include <asm/ptrace.h>
 #include <asm/uaccess.h>

 /*
  * Calculate and return exception PC in case of branch delay slot
  * for microMIPS and MIPS16e. It does not clear the ISA mode bit.
  */
 int __isa_exception_epc(struct pt_regs *regs)
 {
 	unsigned short inst;
 	long epc = regs->cp0_epc;

 	/* Calculate exception PC in branch delay slot. */
 	if (__get_user(inst, (u16 __user *) msk_isa16_mode(epc))) {
 		/* This should never happen because delay slot was checked. */
 		force_sig(SIGSEGV, current);
 		return epc;
 	}
 	if (cpu_has_mips16) {
 		union mips16e_instruction inst_mips16e;

 		inst_mips16e.full = inst;
 		if (inst_mips16e.ri.opcode == MIPS16e_jal_op)
 			epc += 4;
 		else
 			epc += 2;
 	} else if (mm_insn_16bit(inst))
 		epc += 2;
 	else
 		epc += 4;

 	return epc;
 }

 /* (microMIPS) Convert 16-bit register encoding to 32-bit register encoding. */
 static const unsigned int reg16to32map[8] = {16, 17, 2, 3, 4, 5, 6, 7};

 int __mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
 		       unsigned long *contpc)
 {
 	union mips_instruction insn = (union mips_instruction)dec_insn.insn;
 	int bc_false = 0;
 	unsigned int fcr31;
 	unsigned int bit;

 	if (!cpu_has_mmips)
 		return 0;

 	switch (insn.mm_i_format.opcode) {
 	case mm_pool32a_op:
 		if ((insn.mm_i_format.simmediate & MM_POOL32A_MINOR_MASK) ==
 		    mm_pool32axf_op) {
 			switch (insn.mm_i_format.simmediate >>
 				MM_POOL32A_MINOR_SHIFT) {
 			case mm_jalr_op:
 			case mm_jalrhb_op:
 			case mm_jalrs_op:
 			case mm_jalrshb_op:
 				if (insn.mm_i_format.rt != 0)	/* Not mm_jr */
 					regs->regs[insn.mm_i_format.rt] =
 						regs->cp0_epc +
 						dec_insn.pc_inc +
 						dec_insn.next_pc_inc;
 				*contpc = regs->regs[insn.mm_i_format.rs];
 				return 1;
 			}
 		}
 		break;
 	case mm_pool32i_op:
 		switch (insn.mm_i_format.rt) {
 		case mm_bltzals_op:
 		case mm_bltzal_op:
 			regs->regs[31] = regs->cp0_epc +
 				dec_insn.pc_inc +
 				dec_insn.next_pc_inc;
 			/* Fall through */
 		case mm_bltz_op:
 			if ((long)regs->regs[insn.mm_i_format.rs] < 0)
 				*contpc = regs->cp0_epc +
 					dec_insn.pc_inc +
 					(insn.mm_i_format.simmediate << 1);
 			else
 				*contpc = regs->cp0_epc +
 					dec_insn.pc_inc +
 					dec_insn.next_pc_inc;
 			return 1;
 		case mm_bgezals_op:
 		case mm_bgezal_op:
 			regs->regs[31] = regs->cp0_epc +
 					dec_insn.pc_inc +
 					dec_insn.next_pc_inc;
 			/* Fall through */
 		case mm_bgez_op:
 			if ((long)regs->regs[insn.mm_i_format.rs] >= 0)
 				*contpc = regs->cp0_epc +
 					dec_insn.pc_inc +
 					(insn.mm_i_format.simmediate << 1);
 			else
 				*contpc = regs->cp0_epc +
 					dec_insn.pc_inc +
 					dec_insn.next_pc_inc;
 			return 1;
 		case mm_blez_op:
 			if ((long)regs->regs[insn.mm_i_format.rs] <= 0)
 				*contpc = regs->cp0_epc +
 					dec_insn.pc_inc +
 					(insn.mm_i_format.simmediate << 1);
 			else
 				*contpc = regs->cp0_epc +
 					dec_insn.pc_inc +
 					dec_insn.next_pc_inc;
 			return 1;
 		case mm_bgtz_op:
 			if ((long)regs->regs[insn.mm_i_format.rs] <= 0)
 				*contpc = regs->cp0_epc +
 					dec_insn.pc_inc +
 					(insn.mm_i_format.simmediate << 1);
 			else
 				*contpc = regs->cp0_epc +
 					dec_insn.pc_inc +
 					dec_insn.next_pc_inc;
 			return 1;
 		case mm_bc2f_op:
 		case mm_bc1f_op:
 			bc_false = 1;
 			/* Fall through */
 		case mm_bc2t_op:
 		case mm_bc1t_op:
 			preempt_disable();
 			if (is_fpu_owner())
 			        fcr31 = read_32bit_cp1_register(CP1_STATUS);
 			else
 				fcr31 = current->thread.fpu.fcr31;
 			preempt_enable();

 			if (bc_false)
 				fcr31 = ~fcr31;

 			bit = (insn.mm_i_format.rs >> 2);
 			bit += (bit != 0);
 			bit += 23;
 			if (fcr31 & (1 << bit))
 				*contpc = regs->cp0_epc +
 					dec_insn.pc_inc +
 					(insn.mm_i_format.simmediate << 1);
 			else
 				*contpc = regs->cp0_epc +
 					dec_insn.pc_inc + dec_insn.next_pc_inc;
 			return 1;
 		}
 		break;
 	case mm_pool16c_op:
 		switch (insn.mm_i_format.rt) {
 		case mm_jalr16_op:
 		case mm_jalrs16_op:
 			regs->regs[31] = regs->cp0_epc +
 				dec_insn.pc_inc + dec_insn.next_pc_inc;
 			/* Fall through */
 		case mm_jr16_op:
 			*contpc = regs->regs[insn.mm_i_format.rs];
 			return 1;
 		}
 		break;
 	case mm_beqz16_op:
 		if ((long)regs->regs[reg16to32map[insn.mm_b1_format.rs]] == 0)
 			*contpc = regs->cp0_epc +
 				dec_insn.pc_inc +
 				(insn.mm_b1_format.simmediate << 1);
 		else
 			*contpc = regs->cp0_epc +
 				dec_insn.pc_inc + dec_insn.next_pc_inc;
 		return 1;
 	case mm_bnez16_op:
 		if ((long)regs->regs[reg16to32map[insn.mm_b1_format.rs]] != 0)
 			*contpc = regs->cp0_epc +
 				dec_insn.pc_inc +
 				(insn.mm_b1_format.simmediate << 1);
 		else
 			*contpc = regs->cp0_epc +
 				dec_insn.pc_inc + dec_insn.next_pc_inc;
 		return 1;
 	case mm_b16_op:
 		*contpc = regs->cp0_epc + dec_insn.pc_inc +
 			 (insn.mm_b0_format.simmediate << 1);
 		return 1;
 	case mm_beq32_op:
 		if (regs->regs[insn.mm_i_format.rs] ==
 		    regs->regs[insn.mm_i_format.rt])
 			*contpc = regs->cp0_epc +
 				dec_insn.pc_inc +
 				(insn.mm_i_format.simmediate << 1);
 		else
 			*contpc = regs->cp0_epc +
 				dec_insn.pc_inc +
 				dec_insn.next_pc_inc;
 		return 1;
 	case mm_bne32_op:
 		if (regs->regs[insn.mm_i_format.rs] !=
 		    regs->regs[insn.mm_i_format.rt])
 			*contpc = regs->cp0_epc +
 				dec_insn.pc_inc +
 				(insn.mm_i_format.simmediate << 1);
 		else
 			*contpc = regs->cp0_epc +
 				dec_insn.pc_inc + dec_insn.next_pc_inc;
 		return 1;
 	case mm_jalx32_op:
 		regs->regs[31] = regs->cp0_epc +
 			dec_insn.pc_inc + dec_insn.next_pc_inc;
 		*contpc = regs->cp0_epc + dec_insn.pc_inc;
 		*contpc >>= 28;
 		*contpc <<= 28;
 		*contpc |= (insn.j_format.target << 2);
 		return 1;
 	case mm_jals32_op:
 	case mm_jal32_op:
 		regs->regs[31] = regs->cp0_epc +
 			dec_insn.pc_inc + dec_insn.next_pc_inc;
 		/* Fall through */
 	case mm_j32_op:
 		*contpc = regs->cp0_epc + dec_insn.pc_inc;
 		*contpc >>= 27;
 		*contpc <<= 27;
 		*contpc |= (insn.j_format.target << 1);
 		set_isa16_mode(*contpc);
 		return 1;
 	}
 	return 0;
 }

 /*
  * Compute return address and emulate branch in microMIPS mode after an
  * exception only. It does not handle compact branches/jumps and cannot
  * be used in interrupt context. (Compact branches/jumps do not cause
  * exceptions.)
  */
 int __microMIPS_compute_return_epc(struct pt_regs *regs)
 {
 	u16 __user *pc16;
 	u16 halfword;
 	unsigned int word;
 	unsigned long contpc;
 	struct mm_decoded_insn mminsn = { 0 };

 	mminsn.micro_mips_mode = 1;

 	/* This load never faults. */
 	pc16 = (unsigned short __user *)msk_isa16_mode(regs->cp0_epc);
 	__get_user(halfword, pc16);
 	pc16++;
 	contpc = regs->cp0_epc + 2;
 	word = ((unsigned int)halfword << 16);
 	mminsn.pc_inc = 2;

 	if (!mm_insn_16bit(halfword)) {
 		__get_user(halfword, pc16);
 		pc16++;
 		contpc = regs->cp0_epc + 4;
 		mminsn.pc_inc = 4;
 		word |= halfword;
 	}
 	mminsn.insn = word;

 	if (get_user(halfword, pc16))
 		goto sigsegv;
 	mminsn.next_pc_inc = 2;
 	word = ((unsigned int)halfword << 16);

 	if (!mm_insn_16bit(halfword)) {
 		pc16++;
 		if (get_user(halfword, pc16))
 			goto sigsegv;
 		mminsn.next_pc_inc = 4;
 		word |= halfword;
 	}
 	mminsn.next_insn = word;

 	mm_isBranchInstr(regs, mminsn, &contpc);

 	regs->cp0_epc = contpc;

 	return 0;

 sigsegv:
 	force_sig(SIGSEGV, current);
 	return -EFAULT;
 }

 /*
  * Compute return address and emulate branch in MIPS16e mode after an
  * exception only. It does not handle compact branches/jumps and cannot
  * be used in interrupt context. (Compact branches/jumps do not cause
  * exceptions.)
  */
 int __MIPS16e_compute_return_epc(struct pt_regs *regs)
 {
 	u16 __user *addr;
 	union mips16e_instruction inst;
 	u16 inst2;
 	u32 fullinst;
 	long epc;

 	epc = regs->cp0_epc;

 	/* Read the instruction. */
 	addr = (u16 __user *)msk_isa16_mode(epc);
 	if (__get_user(inst.full, addr)) {
 		force_sig(SIGSEGV, current);
 		return -EFAULT;
 	}

 	switch (inst.ri.opcode) {
 	case MIPS16e_extend_op:
 		regs->cp0_epc += 4;
 		return 0;

 		/*
 		 *  JAL and JALX in MIPS16e mode
 		 */
 	case MIPS16e_jal_op:
 		addr += 1;
 		if (__get_user(inst2, addr)) {
 			force_sig(SIGSEGV, current);
 			return -EFAULT;
 		}
 		fullinst = ((unsigned)inst.full << 16) | inst2;
 		regs->regs[31] = epc + 6;
 		epc += 4;
 		epc >>= 28;
 		epc <<= 28;
 		/*
 		 * JAL:5 X:1 TARGET[20-16]:5 TARGET[25:21]:5 TARGET[15:0]:16
 		 *
 		 * ......TARGET[15:0].................TARGET[20:16]...........
 		 * ......TARGET[25:21]
 		 */
 		epc |=
 		    ((fullinst & 0xffff) << 2) | ((fullinst & 0x3e00000) >> 3) |
 		    ((fullinst & 0x1f0000) << 7);
 		if (!inst.jal.x)
 			set_isa16_mode(epc);	/* Set ISA mode bit. */
 		regs->cp0_epc = epc;
 		return 0;

 		/*
 		 *  J(AL)R(C)
 		 */
 	case MIPS16e_rr_op:
 		if (inst.rr.func == MIPS16e_jr_func) {

 			if (inst.rr.ra)
 				regs->cp0_epc = regs->regs[31];
 			else
 				regs->cp0_epc =
 				    regs->regs[reg16to32[inst.rr.rx]];

 			if (inst.rr.l) {
 				if (inst.rr.nd)
 					regs->regs[31] = epc + 2;
 				else
 					regs->regs[31] = epc + 4;
 			}
 			return 0;
 		}
 		break;
 	}

 	/*
 	 * All other cases have no branch delay slot and are 16-bits.
 	 * Branches do not cause an exception.
 	 */
 	regs->cp0_epc += 2;

 	return 0;
 }

 /**
  * __compute_return_epc_for_insn - Computes the return address and do emulate
  *				    branch simulation, if required.
  *
  * @regs:	Pointer to pt_regs
  * @insn:	branch instruction to decode
  * @returns:	-EFAULT on error and forces SIGBUS, and on success
  *		returns 0 or BRANCH_LIKELY_TAKEN as appropriate after
  *		evaluating the branch.
  *
  * MIPS R6 Compact branches and forbidden slots:
  *	Compact branches do not throw exceptions because they do
  *	not have delay slots. The forbidden slot instruction ($PC+4)
  *	is only executed if the branch was not taken. Otherwise the
  *	forbidden slot is skipped entirely. This means that the
  *	only possible reason to be here because of a MIPS R6 compact
  *	branch instruction is that the forbidden slot has thrown one.
  *	In that case the branch was not taken, so the EPC can be safely
  *	set to EPC + 8.
  */
 int __compute_return_epc_for_insn(struct pt_regs *regs,
 				   union mips_instruction insn)
 {
 	unsigned int bit, fcr31, dspcontrol, reg;
 	long epc = regs->cp0_epc;
 	int ret = 0;

 	switch (insn.i_format.opcode) {
 	/*
 	 * jr and jalr are in r_format format.
 	 */
 	case spec_op:
 		switch (insn.r_format.func) {
 		case jalr_op:
 			regs->regs[insn.r_format.rd] = epc + 8;
 			/* Fall through */
 		case jr_op:
 			if (NO_R6EMU && insn.r_format.func == jr_op)
 				goto sigill_r6;
 			regs->cp0_epc = regs->regs[insn.r_format.rs];
 			break;
 		}
 		break;

 	/*
 	 * This group contains:
 	 * bltz_op, bgez_op, bltzl_op, bgezl_op,
 	 * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
 	 */
 	case bcond_op:
 		switch (insn.i_format.rt) {
 		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)
 					ret = BRANCH_LIKELY_TAKEN;
 			} else
 				epc += 8;
 			regs->cp0_epc = epc;
 			break;

 		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)
 					ret = BRANCH_LIKELY_TAKEN;
 			} else
 				epc += 8;
 			regs->cp0_epc = epc;
 			break;

 		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. Let's 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)
 					ret = BRANCH_LIKELY_TAKEN;
 			} else
 				epc += 8;
 			regs->cp0_epc = epc;
 			break;

 		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. Let's 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)
 					ret = BRANCH_LIKELY_TAKEN;
 			} else
 				epc += 8;
 			regs->cp0_epc = epc;
 			break;

 		case bposge32_op:
 			if (!cpu_has_dsp)
 				goto sigill_dsp;

 			dspcontrol = rddsp(0x01);

 			if (dspcontrol >= 32) {
 				epc = epc + 4 + (insn.i_format.simmediate << 2);
 			} else
 				epc += 8;
 			regs->cp0_epc = epc;
 			break;
 		}
 		break;

 	/*
 	 * These are unconditional and in j_format.
 	 */
 	case jal_op:
 		regs->regs[31] = regs->cp0_epc + 8;
 	case j_op:
 		epc += 4;
 		epc >>= 28;
 		epc <<= 28;
 		epc |= (insn.j_format.target << 2);
 		regs->cp0_epc = epc;
 		if (insn.i_format.opcode == jalx_op)
 			set_isa16_mode(regs->cp0_epc);
 		break;

 	/*
 	 * These are conditional and in i_format.
 	 */
 	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);
 			if (insn.i_format.opcode == beql_op)
 				ret = BRANCH_LIKELY_TAKEN;
 		} else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;

 	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);
 			if (insn.i_format.opcode == bnel_op)
 				ret = BRANCH_LIKELY_TAKEN;
 		} else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;

 	case blezl_op: /* not really i_format */
 		if (!insn.i_format.rt && NO_R6EMU)
 			goto sigill_r6;
 	case blez_op:
 		/*
 		 * Compact branches for R6 for the
 		 * blez and blezl opcodes.
 		 * BLEZ  | rs = 0 | rt != 0  == BLEZALC
 		 * BLEZ  | rs = rt != 0      == BGEZALC
 		 * BLEZ  | rs != 0 | rt != 0 == BGEUC
 		 * BLEZL | rs = 0 | rt != 0  == BLEZC
 		 * BLEZL | rs = rt != 0      == BGEZC
 		 * BLEZL | rs != 0 | rt != 0 == BGEC
 		 *
 		 * For real BLEZ{,L}, rt is always 0.
 		 */

 		if (cpu_has_mips_r6 && insn.i_format.rt) {
 			if ((insn.i_format.opcode == blez_op) &&
 			    ((!insn.i_format.rs && insn.i_format.rt) ||
 			     (insn.i_format.rs == insn.i_format.rt)))
 				regs->regs[31] = epc + 4;
 			regs->cp0_epc += 8;
 			break;
 		}
 		/* rt field assumed to be zero */
 		if ((long)regs->regs[insn.i_format.rs] <= 0) {
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 			if (insn.i_format.opcode == blezl_op)
 				ret = BRANCH_LIKELY_TAKEN;
 		} else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;

 	case bgtzl_op:
 		if (!insn.i_format.rt && NO_R6EMU)
 			goto sigill_r6;
 	case bgtz_op:
 		/*
 		 * Compact branches for R6 for the
 		 * bgtz and bgtzl opcodes.
 		 * BGTZ  | rs = 0 | rt != 0  == BGTZALC
 		 * BGTZ  | rs = rt != 0      == BLTZALC
 		 * BGTZ  | rs != 0 | rt != 0 == BLTUC
 		 * BGTZL | rs = 0 | rt != 0  == BGTZC
 		 * BGTZL | rs = rt != 0      == BLTZC
 		 * BGTZL | rs != 0 | rt != 0 == BLTC
 		 *
 		 * *ZALC varint for BGTZ &&& rt != 0
 		 * For real GTZ{,L}, rt is always 0.
 		 */
 		if (cpu_has_mips_r6 && insn.i_format.rt) {
 			if ((insn.i_format.opcode == blez_op) &&
 			    ((!insn.i_format.rs && insn.i_format.rt) ||
 			    (insn.i_format.rs == insn.i_format.rt)))
 				regs->regs[31] = epc + 4;
 			regs->cp0_epc += 8;
 			break;
 		}

 		/* rt field assumed to be zero */
 		if ((long)regs->regs[insn.i_format.rs] > 0) {
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 			if (insn.i_format.opcode == bgtzl_op)
 				ret = BRANCH_LIKELY_TAKEN;
 		} else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;

 	/*
 	 * And now the FPA/cp1 branch instructions.
 	 */
 	case cop1_op:
 		if (cpu_has_mips_r6 &&
 		    ((insn.i_format.rs == bc1eqz_op) ||
 		     (insn.i_format.rs == bc1nez_op))) {
 			if (!used_math()) { /* First time FPU user */
 				ret = init_fpu();
 				if (ret && NO_R6EMU) {
 					ret = -ret;
 					break;
 				}
 				ret = 0;
 				set_used_math();
 			}
 			lose_fpu(1);    /* Save FPU state for the emulator. */
 			reg = insn.i_format.rt;
 			bit = get_fpr32(&current->thread.fpu.fpr[reg], 0) & 0x1;
 			if (insn.i_format.rs == bc1eqz_op)
 				bit = !bit;
 			own_fpu(1);
 			if (bit)
 				epc = epc + 4 +
 					(insn.i_format.simmediate << 2);
 			else
 				epc += 8;
 			regs->cp0_epc = epc;

 			break;
 		} else {

 			preempt_disable();
 			if (is_fpu_owner())
 			        fcr31 = read_32bit_cp1_register(CP1_STATUS);
 			else
 				fcr31 = current->thread.fpu.fcr31;
 			preempt_enable();

 			bit = (insn.i_format.rt >> 2);
 			bit += (bit != 0);
 			bit += 23;
 			switch (insn.i_format.rt & 3) {
 			case 0: /* bc1f */
 			case 2: /* bc1fl */
 				if (~fcr31 & (1 << bit)) {
 					epc = epc + 4 +
 						(insn.i_format.simmediate << 2);
 					if (insn.i_format.rt == 2)
 						ret = BRANCH_LIKELY_TAKEN;
 				} else
 					epc += 8;
 				regs->cp0_epc = epc;
 				break;

 			case 1: /* bc1t */
 			case 3: /* bc1tl */
 				if (fcr31 & (1 << bit)) {
 					epc = epc + 4 +
 						(insn.i_format.simmediate << 2);
 					if (insn.i_format.rt == 3)
 						ret = BRANCH_LIKELY_TAKEN;
 				} else
 					epc += 8;
 				regs->cp0_epc = epc;
 				break;
 			}
 			break;
 		}
 #ifdef CONFIG_CPU_CAVIUM_OCTEON
 	case lwc2_op: /* This is bbit0 on Octeon */
 		if ((regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
 		     == 0)
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 		else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;
 	case ldc2_op: /* This is bbit032 on Octeon */
 		if ((regs->regs[insn.i_format.rs] &
 		    (1ull<<(insn.i_format.rt+32))) == 0)
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 		else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;
 	case swc2_op: /* This is bbit1 on Octeon */
 		if (regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 		else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;
 	case sdc2_op: /* This is bbit132 on Octeon */
 		if (regs->regs[insn.i_format.rs] &
 		    (1ull<<(insn.i_format.rt+32)))
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 		else
 			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;
 	case balc6_op:
 		if (!cpu_has_mips_r6) {
 			ret = -SIGILL;
 			break;
 		}
 		/* Compact branch: BALC */
 		regs->regs[31] = epc + 4;
 		epc += 4 + (insn.i_format.simmediate << 2);
 		regs->cp0_epc = epc;
 		break;
 	case beqzcjic_op:
 		if (!cpu_has_mips_r6) {
 			ret = -SIGILL;
 			break;
 		}
 		/* Compact branch: BEQZC || JIC */
 		regs->cp0_epc += 8;
 		break;
 	case bnezcjialc_op:
 		if (!cpu_has_mips_r6) {
 			ret = -SIGILL;
 			break;
 		}
 		/* Compact branch: BNEZC || JIALC */
 		if (insn.i_format.rs)
 			regs->regs[31] = epc + 4;
 		regs->cp0_epc += 8;
 		break;
 #endif
 	case cbcond0_op:
 	case cbcond1_op:
 		/* Only valid for MIPS R6 */
 		if (!cpu_has_mips_r6) {
 			ret = -SIGILL;
 			break;
 		}
 		/*
 		 * Compact branches:
 		 * bovc, beqc, beqzalc, bnvc, bnec, bnezlac
 		 */
 		if (insn.i_format.rt && !insn.i_format.rs)
 			regs->regs[31] = epc + 4;
 		regs->cp0_epc += 8;
 		break;
 	}

 	return ret;

 sigill_dsp:
 	printk("%s: DSP branch but not DSP ASE - sending SIGBUS.\n", current->comm);
 	force_sig(SIGBUS, current);
 	return -EFAULT;
 sigill_r6:
 	pr_info("%s: R2 branch but r2-to-r6 emulator is not preset - sending SIGILL.\n",
 		current->comm);
 	force_sig(SIGILL, current);
 	return -EFAULT;
 }
 EXPORT_SYMBOL_GPL(__compute_return_epc_for_insn);

 int __compute_return_epc(struct pt_regs *regs)
 {
 	unsigned int __user *addr;
 	long epc;
 	union mips_instruction insn;

 	epc = regs->cp0_epc;
 	if (epc & 3)
 		goto unaligned;

 	/*
 	 * Read the instruction
 	 */
 	addr = (unsigned int __user *) epc;
 	if (__get_user(insn.word, addr)) {
 		force_sig(SIGSEGV, current);
 		return -EFAULT;
 	}

 	return __compute_return_epc_for_insn(regs, insn);

 unaligned:
 	printk("%s: unaligned epc - sending SIGBUS.\n", current->comm);
 	force_sig(SIGBUS, current);
 	return -EFAULT;
 }
	/*
	* This file is subject to the terms and conditions of the GNU General Public
	* License. See the file "COPYING" in the main directory of this archive
	* for more details.
	*
	* Copyright (C) 1996, 97, 2000, 2001 by Ralf Baechle
	* Copyright (C) 2001 MIPS Technologies, Inc.
	*/
	#include <linux/kernel.h>
	#include <linux/sched.h>
	#include <linux/signal.h>
	#include <linux/module.h>
	#include <asm/branch.h>
	#include <asm/cpu.h>
	#include <asm/cpu-features.h>
	#include <asm/fpu.h>
	#include <asm/fpu_emulator.h>
	#include <asm/inst.h>
	#include <asm/mips-r2-to-r6-emul.h>
	#include <asm/ptrace.h>
	#include <asm/uaccess.h>

	/*
	* Calculate and return exception PC in case of branch delay slot
	* for microMIPS and MIPS16e. It does not clear the ISA mode bit.
	*/
	int __isa_exception_epc(struct pt_regs *regs)
	{
	unsigned short inst;
	long epc = regs->cp0_epc;

	/* Calculate exception PC in branch delay slot. */
	if (__get_user(inst, (u16 __user *) msk_isa16_mode(epc))) {
	/* This should never happen because delay slot was checked. */
	force_sig(SIGSEGV, current);
	return epc;
	}
	if (cpu_has_mips16) {
	union mips16e_instruction inst_mips16e;

	inst_mips16e.full = inst;
	if (inst_mips16e.ri.opcode == MIPS16e_jal_op)
	epc += 4;
	else
	epc += 2;
	} else if (mm_insn_16bit(inst))
	epc += 2;
	else
	epc += 4;

	return epc;
	}

	/* (microMIPS) Convert 16-bit register encoding to 32-bit register encoding. */
	static const unsigned int reg16to32map[8] = {16, 17, 2, 3, 4, 5, 6, 7};

	int __mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
	unsigned long *contpc)
	{
	union mips_instruction insn = (union mips_instruction)dec_insn.insn;
	int bc_false = 0;
	unsigned int fcr31;
	unsigned int bit;

	if (!cpu_has_mmips)
	return 0;

	switch (insn.mm_i_format.opcode) {
	case mm_pool32a_op:
	if ((insn.mm_i_format.simmediate & MM_POOL32A_MINOR_MASK) ==
	mm_pool32axf_op) {
	switch (insn.mm_i_format.simmediate >>
	MM_POOL32A_MINOR_SHIFT) {
	case mm_jalr_op:
	case mm_jalrhb_op:
	case mm_jalrs_op:
	case mm_jalrshb_op:
	if (insn.mm_i_format.rt != 0) /* Not mm_jr */
	regs->regs[insn.mm_i_format.rt] =
	regs->cp0_epc +
	dec_insn.pc_inc +
	dec_insn.next_pc_inc;
	*contpc = regs->regs[insn.mm_i_format.rs];
	return 1;
	}
	}
	break;
	case mm_pool32i_op:
	switch (insn.mm_i_format.rt) {
	case mm_bltzals_op:
	case mm_bltzal_op:
	regs->regs[31] = regs->cp0_epc +
	dec_insn.pc_inc +
	dec_insn.next_pc_inc;
	/* Fall through */
	case mm_bltz_op:
	if ((long)regs->regs[insn.mm_i_format.rs] < 0)
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	(insn.mm_i_format.simmediate << 1);
	else
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	dec_insn.next_pc_inc;
	return 1;
	case mm_bgezals_op:
	case mm_bgezal_op:
	regs->regs[31] = regs->cp0_epc +
	dec_insn.pc_inc +
	dec_insn.next_pc_inc;
	/* Fall through */
	case mm_bgez_op:
	if ((long)regs->regs[insn.mm_i_format.rs] >= 0)
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	(insn.mm_i_format.simmediate << 1);
	else
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	dec_insn.next_pc_inc;
	return 1;
	case mm_blez_op:
	if ((long)regs->regs[insn.mm_i_format.rs] <= 0)
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	(insn.mm_i_format.simmediate << 1);
	else
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	dec_insn.next_pc_inc;
	return 1;
	case mm_bgtz_op:
	if ((long)regs->regs[insn.mm_i_format.rs] <= 0)
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	(insn.mm_i_format.simmediate << 1);
	else
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	dec_insn.next_pc_inc;
	return 1;
	case mm_bc2f_op:
	case mm_bc1f_op:
	bc_false = 1;
	/* Fall through */
	case mm_bc2t_op:
	case mm_bc1t_op:
	preempt_disable();
	if (is_fpu_owner())
	fcr31 = read_32bit_cp1_register(CP1_STATUS);
	else
	fcr31 = current->thread.fpu.fcr31;
	preempt_enable();

	if (bc_false)
	fcr31 = ~fcr31;

	bit = (insn.mm_i_format.rs >> 2);
	bit += (bit != 0);
	bit += 23;
	if (fcr31 & (1 << bit))
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	(insn.mm_i_format.simmediate << 1);
	else
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc + dec_insn.next_pc_inc;
	return 1;
	}
	break;
	case mm_pool16c_op:
	switch (insn.mm_i_format.rt) {
	case mm_jalr16_op:
	case mm_jalrs16_op:
	regs->regs[31] = regs->cp0_epc +
	dec_insn.pc_inc + dec_insn.next_pc_inc;
	/* Fall through */
	case mm_jr16_op:
	*contpc = regs->regs[insn.mm_i_format.rs];
	return 1;
	}
	break;
	case mm_beqz16_op:
	if ((long)regs->regs[reg16to32map[insn.mm_b1_format.rs]] == 0)
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	(insn.mm_b1_format.simmediate << 1);
	else
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc + dec_insn.next_pc_inc;
	return 1;
	case mm_bnez16_op:
	if ((long)regs->regs[reg16to32map[insn.mm_b1_format.rs]] != 0)
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	(insn.mm_b1_format.simmediate << 1);
	else
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc + dec_insn.next_pc_inc;
	return 1;
	case mm_b16_op:
	*contpc = regs->cp0_epc + dec_insn.pc_inc +
	(insn.mm_b0_format.simmediate << 1);
	return 1;
	case mm_beq32_op:
	if (regs->regs[insn.mm_i_format.rs] ==
	regs->regs[insn.mm_i_format.rt])
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	(insn.mm_i_format.simmediate << 1);
	else
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	dec_insn.next_pc_inc;
	return 1;
	case mm_bne32_op:
	if (regs->regs[insn.mm_i_format.rs] !=
	regs->regs[insn.mm_i_format.rt])
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc +
	(insn.mm_i_format.simmediate << 1);
	else
	*contpc = regs->cp0_epc +
	dec_insn.pc_inc + dec_insn.next_pc_inc;
	return 1;
	case mm_jalx32_op:
	regs->regs[31] = regs->cp0_epc +
	dec_insn.pc_inc + dec_insn.next_pc_inc;
	*contpc = regs->cp0_epc + dec_insn.pc_inc;
	*contpc >>= 28;
	*contpc <<= 28;
	*contpc \|= (insn.j_format.target << 2);
	return 1;
	case mm_jals32_op:
	case mm_jal32_op:
	regs->regs[31] = regs->cp0_epc +
	dec_insn.pc_inc + dec_insn.next_pc_inc;
	/* Fall through */
	case mm_j32_op:
	*contpc = regs->cp0_epc + dec_insn.pc_inc;
	*contpc >>= 27;
	*contpc <<= 27;
	*contpc \|= (insn.j_format.target << 1);
	set_isa16_mode(*contpc);
	return 1;
	}
	return 0;
	}

	/*
	* Compute return address and emulate branch in microMIPS mode after an
	* exception only. It does not handle compact branches/jumps and cannot
	* be used in interrupt context. (Compact branches/jumps do not cause
	* exceptions.)
	*/
	int __microMIPS_compute_return_epc(struct pt_regs *regs)
	{
	u16 __user *pc16;
	u16 halfword;
	unsigned int word;
	unsigned long contpc;
	struct mm_decoded_insn mminsn = { 0 };

	mminsn.micro_mips_mode = 1;

	/* This load never faults. */
	pc16 = (unsigned short __user *)msk_isa16_mode(regs->cp0_epc);
	__get_user(halfword, pc16);
	pc16++;
	contpc = regs->cp0_epc + 2;
	word = ((unsigned int)halfword << 16);
	mminsn.pc_inc = 2;

	if (!mm_insn_16bit(halfword)) {
	__get_user(halfword, pc16);
	pc16++;
	contpc = regs->cp0_epc + 4;
	mminsn.pc_inc = 4;
	word \|= halfword;
	}
	mminsn.insn = word;

	if (get_user(halfword, pc16))
	goto sigsegv;
	mminsn.next_pc_inc = 2;
	word = ((unsigned int)halfword << 16);

	if (!mm_insn_16bit(halfword)) {
	pc16++;
	if (get_user(halfword, pc16))
	goto sigsegv;
	mminsn.next_pc_inc = 4;
	word \|= halfword;
	}
	mminsn.next_insn = word;

	mm_isBranchInstr(regs, mminsn, &contpc);

	regs->cp0_epc = contpc;

	return 0;

	sigsegv:
	force_sig(SIGSEGV, current);
	return -EFAULT;
	}

	/*
	* Compute return address and emulate branch in MIPS16e mode after an
	* exception only. It does not handle compact branches/jumps and cannot
	* be used in interrupt context. (Compact branches/jumps do not cause
	* exceptions.)
	*/
	int __MIPS16e_compute_return_epc(struct pt_regs *regs)
	{
	u16 __user *addr;
	union mips16e_instruction inst;
	u16 inst2;
	u32 fullinst;
	long epc;

	epc = regs->cp0_epc;

	/* Read the instruction. */
	addr = (u16 __user *)msk_isa16_mode(epc);
	if (__get_user(inst.full, addr)) {
	force_sig(SIGSEGV, current);
	return -EFAULT;
	}

	switch (inst.ri.opcode) {
	case MIPS16e_extend_op:
	regs->cp0_epc += 4;
	return 0;

	/*
	* JAL and JALX in MIPS16e mode
	*/
	case MIPS16e_jal_op:
	addr += 1;
	if (__get_user(inst2, addr)) {
	force_sig(SIGSEGV, current);
	return -EFAULT;
	}
	fullinst = ((unsigned)inst.full << 16) \| inst2;
	regs->regs[31] = epc + 6;
	epc += 4;
	epc >>= 28;
	epc <<= 28;
	/*
	* JAL:5 X:1 TARGET[20-16]:5 TARGET[25:21]:5 TARGET[15:0]:16
	*
	* ......TARGET[15:0].................TARGET[20:16]...........
	* ......TARGET[25:21]
	*/
	epc \|=
	((fullinst & 0xffff) << 2) \| ((fullinst & 0x3e00000) >> 3) \|
	((fullinst & 0x1f0000) << 7);
	if (!inst.jal.x)
	set_isa16_mode(epc); /* Set ISA mode bit. */
	regs->cp0_epc = epc;
	return 0;

	/*
	* J(AL)R(C)
	*/
	case MIPS16e_rr_op:
	if (inst.rr.func == MIPS16e_jr_func) {

	if (inst.rr.ra)
	regs->cp0_epc = regs->regs[31];
	else
	regs->cp0_epc =
	regs->regs[reg16to32[inst.rr.rx]];

	if (inst.rr.l) {
	if (inst.rr.nd)
	regs->regs[31] = epc + 2;
	else
	regs->regs[31] = epc + 4;
	}
	return 0;
	}
	break;
	}

	/*
	* All other cases have no branch delay slot and are 16-bits.
	* Branches do not cause an exception.
	*/
	regs->cp0_epc += 2;

	return 0;
	}

	/**
	* __compute_return_epc_for_insn - Computes the return address and do emulate
	* branch simulation, if required.
	*
	* @regs: Pointer to pt_regs
	* @insn: branch instruction to decode
	* @returns: -EFAULT on error and forces SIGBUS, and on success
	* returns 0 or BRANCH_LIKELY_TAKEN as appropriate after
	* evaluating the branch.
	*
	* MIPS R6 Compact branches and forbidden slots:
	* Compact branches do not throw exceptions because they do
	* not have delay slots. The forbidden slot instruction ($PC+4)
	* is only executed if the branch was not taken. Otherwise the
	* forbidden slot is skipped entirely. This means that the
	* only possible reason to be here because of a MIPS R6 compact
	* branch instruction is that the forbidden slot has thrown one.
	* In that case the branch was not taken, so the EPC can be safely
	* set to EPC + 8.
	*/
	int __compute_return_epc_for_insn(struct pt_regs *regs,
	union mips_instruction insn)
	{
	unsigned int bit, fcr31, dspcontrol, reg;
	long epc = regs->cp0_epc;
	int ret = 0;

	switch (insn.i_format.opcode) {
	/*
	* jr and jalr are in r_format format.
	*/
	case spec_op:
	switch (insn.r_format.func) {
	case jalr_op:
	regs->regs[insn.r_format.rd] = epc + 8;
	/* Fall through */
	case jr_op:
	if (NO_R6EMU && insn.r_format.func == jr_op)
	goto sigill_r6;
	regs->cp0_epc = regs->regs[insn.r_format.rs];
	break;
	}
	break;

	/*
	* This group contains:
	* bltz_op, bgez_op, bltzl_op, bgezl_op,
	* bltzal_op, bgezal_op, bltzall_op, bgezall_op.
	*/
	case bcond_op:
	switch (insn.i_format.rt) {
	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)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	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)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	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. Let's 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)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	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. Let's 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)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	case bposge32_op:
	if (!cpu_has_dsp)
	goto sigill_dsp;

	dspcontrol = rddsp(0x01);

	if (dspcontrol >= 32) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;
	}
	break;

	/*
	* These are unconditional and in j_format.
	*/
	case jal_op:
	regs->regs[31] = regs->cp0_epc + 8;
	case j_op:
	epc += 4;
	epc >>= 28;
	epc <<= 28;
	epc \|= (insn.j_format.target << 2);
	regs->cp0_epc = epc;
	if (insn.i_format.opcode == jalx_op)
	set_isa16_mode(regs->cp0_epc);
	break;

	/*
	* These are conditional and in i_format.
	*/
	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);
	if (insn.i_format.opcode == beql_op)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	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);
	if (insn.i_format.opcode == bnel_op)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	case blezl_op: /* not really i_format */
	if (!insn.i_format.rt && NO_R6EMU)
	goto sigill_r6;
	case blez_op:
	/*
	* Compact branches for R6 for the
	* blez and blezl opcodes.
	* BLEZ \| rs = 0 \| rt != 0 == BLEZALC
	* BLEZ \| rs = rt != 0 == BGEZALC
	* BLEZ \| rs != 0 \| rt != 0 == BGEUC
	* BLEZL \| rs = 0 \| rt != 0 == BLEZC
	* BLEZL \| rs = rt != 0 == BGEZC
	* BLEZL \| rs != 0 \| rt != 0 == BGEC
	*
	* For real BLEZ{,L}, rt is always 0.
	*/

	if (cpu_has_mips_r6 && insn.i_format.rt) {
	if ((insn.i_format.opcode == blez_op) &&
	((!insn.i_format.rs && insn.i_format.rt) \|\|
	(insn.i_format.rs == insn.i_format.rt)))
	regs->regs[31] = epc + 4;
	regs->cp0_epc += 8;
	break;
	}
	/* rt field assumed to be zero */
	if ((long)regs->regs[insn.i_format.rs] <= 0) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	if (insn.i_format.opcode == blezl_op)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	case bgtzl_op:
	if (!insn.i_format.rt && NO_R6EMU)
	goto sigill_r6;
	case bgtz_op:
	/*
	* Compact branches for R6 for the
	* bgtz and bgtzl opcodes.
	* BGTZ \| rs = 0 \| rt != 0 == BGTZALC
	* BGTZ \| rs = rt != 0 == BLTZALC
	* BGTZ \| rs != 0 \| rt != 0 == BLTUC
	* BGTZL \| rs = 0 \| rt != 0 == BGTZC
	* BGTZL \| rs = rt != 0 == BLTZC
	* BGTZL \| rs != 0 \| rt != 0 == BLTC
	*
	* *ZALC varint for BGTZ &&& rt != 0
	* For real GTZ{,L}, rt is always 0.
	*/
	if (cpu_has_mips_r6 && insn.i_format.rt) {
	if ((insn.i_format.opcode == blez_op) &&
	((!insn.i_format.rs && insn.i_format.rt) \|\|
	(insn.i_format.rs == insn.i_format.rt)))
	regs->regs[31] = epc + 4;
	regs->cp0_epc += 8;
	break;
	}

	/* rt field assumed to be zero */
	if ((long)regs->regs[insn.i_format.rs] > 0) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	if (insn.i_format.opcode == bgtzl_op)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	/*
	* And now the FPA/cp1 branch instructions.
	*/
	case cop1_op:
	if (cpu_has_mips_r6 &&
	((insn.i_format.rs == bc1eqz_op) \|\|
	(insn.i_format.rs == bc1nez_op))) {
	if (!used_math()) { /* First time FPU user */
	ret = init_fpu();
	if (ret && NO_R6EMU) {
	ret = -ret;
	break;
	}
	ret = 0;
	set_used_math();
	}
	lose_fpu(1); /* Save FPU state for the emulator. */
	reg = insn.i_format.rt;
	bit = get_fpr32(&current->thread.fpu.fpr[reg], 0) & 0x1;
	if (insn.i_format.rs == bc1eqz_op)
	bit = !bit;
	own_fpu(1);
	if (bit)
	epc = epc + 4 +
	(insn.i_format.simmediate << 2);
	else
	epc += 8;
	regs->cp0_epc = epc;

	break;
	} else {

	preempt_disable();
	if (is_fpu_owner())
	fcr31 = read_32bit_cp1_register(CP1_STATUS);
	else
	fcr31 = current->thread.fpu.fcr31;
	preempt_enable();

	bit = (insn.i_format.rt >> 2);
	bit += (bit != 0);
	bit += 23;
	switch (insn.i_format.rt & 3) {
	case 0: /* bc1f */
	case 2: /* bc1fl */
	if (~fcr31 & (1 << bit)) {
	epc = epc + 4 +
	(insn.i_format.simmediate << 2);
	if (insn.i_format.rt == 2)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	case 1: /* bc1t */
	case 3: /* bc1tl */
	if (fcr31 & (1 << bit)) {
	epc = epc + 4 +
	(insn.i_format.simmediate << 2);
	if (insn.i_format.rt == 3)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;
	}
	break;
	}
	#ifdef CONFIG_CPU_CAVIUM_OCTEON
	case lwc2_op: /* This is bbit0 on Octeon */
	if ((regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
	== 0)
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	else
	epc += 8;
	regs->cp0_epc = epc;
	break;
	case ldc2_op: /* This is bbit032 on Octeon */
	if ((regs->regs[insn.i_format.rs] &
	(1ull<<(insn.i_format.rt+32))) == 0)
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	else
	epc += 8;
	regs->cp0_epc = epc;
	break;
	case swc2_op: /* This is bbit1 on Octeon */
	if (regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	else
	epc += 8;
	regs->cp0_epc = epc;
	break;
	case sdc2_op: /* This is bbit132 on Octeon */
	if (regs->regs[insn.i_format.rs] &
	(1ull<<(insn.i_format.rt+32)))
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	else
	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;
	case balc6_op:
	if (!cpu_has_mips_r6) {
	ret = -SIGILL;
	break;
	}
	/* Compact branch: BALC */
	regs->regs[31] = epc + 4;
	epc += 4 + (insn.i_format.simmediate << 2);
	regs->cp0_epc = epc;
	break;
	case beqzcjic_op:
	if (!cpu_has_mips_r6) {
	ret = -SIGILL;
	break;
	}
	/* Compact branch: BEQZC \|\| JIC */
	regs->cp0_epc += 8;
	break;
	case bnezcjialc_op:
	if (!cpu_has_mips_r6) {
	ret = -SIGILL;
	break;
	}
	/* Compact branch: BNEZC \|\| JIALC */
	if (insn.i_format.rs)
	regs->regs[31] = epc + 4;
	regs->cp0_epc += 8;
	break;
	#endif
	case cbcond0_op:
	case cbcond1_op:
	/* Only valid for MIPS R6 */
	if (!cpu_has_mips_r6) {
	ret = -SIGILL;
	break;
	}
	/*
	* Compact branches:
	* bovc, beqc, beqzalc, bnvc, bnec, bnezlac
	*/
	if (insn.i_format.rt && !insn.i_format.rs)
	regs->regs[31] = epc + 4;
	regs->cp0_epc += 8;
	break;
	}

	return ret;

	sigill_dsp:
	printk("%s: DSP branch but not DSP ASE - sending SIGBUS.\n", current->comm);
	force_sig(SIGBUS, current);
	return -EFAULT;
	sigill_r6:
	pr_info("%s: R2 branch but r2-to-r6 emulator is not preset - sending SIGILL.\n",
	current->comm);
	force_sig(SIGILL, current);
	return -EFAULT;
	}
	EXPORT_SYMBOL_GPL(__compute_return_epc_for_insn);

	int __compute_return_epc(struct pt_regs *regs)
	{
	unsigned int __user *addr;
	long epc;
	union mips_instruction insn;

	epc = regs->cp0_epc;
	if (epc & 3)
	goto unaligned;

	/*
	* Read the instruction
	*/
	addr = (unsigned int __user *) epc;
	if (__get_user(insn.word, addr)) {
	force_sig(SIGSEGV, current);
	return -EFAULT;
	}

	return __compute_return_epc_for_insn(regs, insn);

	unaligned:
	printk("%s: unaligned epc - sending SIGBUS.\n", current->comm);
	force_sig(SIGBUS, current);
	return -EFAULT;
	}