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

 /*
  * Handle unaligned accesses by emulation.
  *
  * 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, 1998, 1999, 2002 by Ralf Baechle
  * Copyright (C) 1999 Silicon Graphics, Inc.
  *
  * This file contains exception handler for address error exception with the
  * special capability to execute faulting instructions in software.  The
  * handler does not try to handle the case when the program counter points
  * to an address not aligned to a word boundary.
  *
  * Putting data to unaligned addresses is a bad practice even on Intel where
  * only the performance is affected.  Much worse is that such code is non-
  * portable.  Due to several programs that die on MIPS due to alignment
  * problems I decided to implement this handler anyway though I originally
  * didn't intend to do this at all for user code.
  *
  * For now I enable fixing of address errors by default to make life easier.
  * I however intend to disable this somewhen in the future when the alignment
  * problems with user programs have been fixed.  For programmers this is the
  * right way to go.
  *
  * Fixing address errors is a per process option.  The option is inherited
  * across fork(2) and execve(2) calls.  If you really want to use the
  * option in your user programs - I discourage the use of the software
  * emulation strongly - use the following code in your userland stuff:
  *
  * #include <sys/sysmips.h>
  *
  * ...
  * sysmips(MIPS_FIXADE, x);
  * ...
  *
  * The argument x is 0 for disabling software emulation, enabled otherwise.
  *
  * Below a little program to play around with this feature.
  *
  * #include <stdio.h>
  * #include <sys/sysmips.h>
  *
  * struct foo {
  *         unsigned char bar[8];
  * };
  *
  * main(int argc, char *argv[])
  * {
  *         struct foo x = {0, 1, 2, 3, 4, 5, 6, 7};
  *         unsigned int *p = (unsigned int *) (x.bar + 3);
  *         int i;
  *
  *         if (argc > 1)
  *                 sysmips(MIPS_FIXADE, atoi(argv[1]));
  *
  *         printf("*p = %08lx\n", *p);
  *
  *         *p = 0xdeadface;
  *
  *         for(i = 0; i <= 7; i++)
  *         printf("%02x ", x.bar[i]);
  *         printf("\n");
  * }
  *
  * Coprocessor loads are not supported; I think this case is unimportant
  * in the practice.
  *
  * TODO: Handle ndc (attempted store to doubleword in uncached memory)
  *       exception for the R6000.
  *       A store crossing a page boundary might be executed only partially.
  *       Undo the partial store in this case.
  */
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/signal.h>
 #include <linux/smp.h>
 #include <linux/sched.h>
 #include <linux/debugfs.h>
 #include <asm/asm.h>
 #include <asm/branch.h>
 #include <asm/byteorder.h>
 #include <asm/inst.h>
 #include <asm/uaccess.h>
 #include <asm/system.h>

 #define STR(x)  __STR(x)
 #define __STR(x)  #x

 enum {
 	UNALIGNED_ACTION_QUIET,
 	UNALIGNED_ACTION_SIGNAL,
 	UNALIGNED_ACTION_SHOW,
 };
 #ifdef CONFIG_DEBUG_FS
 static u32 unaligned_instructions;
 static u32 unaligned_action;
 #else
 #define unaligned_action UNALIGNED_ACTION_QUIET
 #endif
 extern void show_registers(struct pt_regs *regs);

 static void emulate_load_store_insn(struct pt_regs *regs,
 	void __user *addr, unsigned int __user *pc)
 {
 	union mips_instruction insn;
 	unsigned long value;
 	unsigned int res;

 	regs->regs[0] = 0;

 	/*
 	 * This load never faults.
 	 */
 	__get_user(insn.word, pc);

 	switch (insn.i_format.opcode) {
 	/*
 	 * These are instructions that a compiler doesn't generate.  We
 	 * can assume therefore that the code is MIPS-aware and
 	 * really buggy.  Emulating these instructions would break the
 	 * semantics anyway.
 	 */
 	case ll_op:
 	case lld_op:
 	case sc_op:
 	case scd_op:

 	/*
 	 * For these instructions the only way to create an address
 	 * error is an attempted access to kernel/supervisor address
 	 * space.
 	 */
 	case ldl_op:
 	case ldr_op:
 	case lwl_op:
 	case lwr_op:
 	case sdl_op:
 	case sdr_op:
 	case swl_op:
 	case swr_op:
 	case lb_op:
 	case lbu_op:
 	case sb_op:
 		goto sigbus;

 	/*
 	 * The remaining opcodes are the ones that are really of interest.
 	 */
 	case lh_op:
 		if (!access_ok(VERIFY_READ, addr, 2))
 			goto sigbus;

 		__asm__ __volatile__ (".set\tnoat\n"
 #ifdef __BIG_ENDIAN
 			"1:\tlb\t%0, 0(%2)\n"
 			"2:\tlbu\t$1, 1(%2)\n\t"
 #endif
 #ifdef __LITTLE_ENDIAN
 			"1:\tlb\t%0, 1(%2)\n"
 			"2:\tlbu\t$1, 0(%2)\n\t"
 #endif
 			"sll\t%0, 0x8\n\t"
 			"or\t%0, $1\n\t"
 			"li\t%1, 0\n"
 			"3:\t.set\tat\n\t"
 			".section\t.fixup,\"ax\"\n\t"
 			"4:\tli\t%1, %3\n\t"
 			"j\t3b\n\t"
 			".previous\n\t"
 			".section\t__ex_table,\"a\"\n\t"
 			STR(PTR)"\t1b, 4b\n\t"
 			STR(PTR)"\t2b, 4b\n\t"
 			".previous"
 			: "=&r" (value), "=r" (res)
 			: "r" (addr), "i" (-EFAULT));
 		if (res)
 			goto fault;
 		compute_return_epc(regs);
 		regs->regs[insn.i_format.rt] = value;
 		break;

 	case lw_op:
 		if (!access_ok(VERIFY_READ, addr, 4))
 			goto sigbus;

 		__asm__ __volatile__ (
 #ifdef __BIG_ENDIAN
 			"1:\tlwl\t%0, (%2)\n"
 			"2:\tlwr\t%0, 3(%2)\n\t"
 #endif
 #ifdef __LITTLE_ENDIAN
 			"1:\tlwl\t%0, 3(%2)\n"
 			"2:\tlwr\t%0, (%2)\n\t"
 #endif
 			"li\t%1, 0\n"
 			"3:\t.section\t.fixup,\"ax\"\n\t"
 			"4:\tli\t%1, %3\n\t"
 			"j\t3b\n\t"
 			".previous\n\t"
 			".section\t__ex_table,\"a\"\n\t"
 			STR(PTR)"\t1b, 4b\n\t"
 			STR(PTR)"\t2b, 4b\n\t"
 			".previous"
 			: "=&r" (value), "=r" (res)
 			: "r" (addr), "i" (-EFAULT));
 		if (res)
 			goto fault;
 		compute_return_epc(regs);
 		regs->regs[insn.i_format.rt] = value;
 		break;

 	case lhu_op:
 		if (!access_ok(VERIFY_READ, addr, 2))
 			goto sigbus;

 		__asm__ __volatile__ (
 			".set\tnoat\n"
 #ifdef __BIG_ENDIAN
 			"1:\tlbu\t%0, 0(%2)\n"
 			"2:\tlbu\t$1, 1(%2)\n\t"
 #endif
 #ifdef __LITTLE_ENDIAN
 			"1:\tlbu\t%0, 1(%2)\n"
 			"2:\tlbu\t$1, 0(%2)\n\t"
 #endif
 			"sll\t%0, 0x8\n\t"
 			"or\t%0, $1\n\t"
 			"li\t%1, 0\n"
 			"3:\t.set\tat\n\t"
 			".section\t.fixup,\"ax\"\n\t"
 			"4:\tli\t%1, %3\n\t"
 			"j\t3b\n\t"
 			".previous\n\t"
 			".section\t__ex_table,\"a\"\n\t"
 			STR(PTR)"\t1b, 4b\n\t"
 			STR(PTR)"\t2b, 4b\n\t"
 			".previous"
 			: "=&r" (value), "=r" (res)
 			: "r" (addr), "i" (-EFAULT));
 		if (res)
 			goto fault;
 		compute_return_epc(regs);
 		regs->regs[insn.i_format.rt] = value;
 		break;

 	case lwu_op:
 #ifdef CONFIG_64BIT
 		/*
 		 * A 32-bit kernel might be running on a 64-bit processor.  But
 		 * if we're on a 32-bit processor and an i-cache incoherency
 		 * or race makes us see a 64-bit instruction here the sdl/sdr
 		 * would blow up, so for now we don't handle unaligned 64-bit
 		 * instructions on 32-bit kernels.
 		 */
 		if (!access_ok(VERIFY_READ, addr, 4))
 			goto sigbus;

 		__asm__ __volatile__ (
 #ifdef __BIG_ENDIAN
 			"1:\tlwl\t%0, (%2)\n"
 			"2:\tlwr\t%0, 3(%2)\n\t"
 #endif
 #ifdef __LITTLE_ENDIAN
 			"1:\tlwl\t%0, 3(%2)\n"
 			"2:\tlwr\t%0, (%2)\n\t"
 #endif
 			"dsll\t%0, %0, 32\n\t"
 			"dsrl\t%0, %0, 32\n\t"
 			"li\t%1, 0\n"
 			"3:\t.section\t.fixup,\"ax\"\n\t"
 			"4:\tli\t%1, %3\n\t"
 			"j\t3b\n\t"
 			".previous\n\t"
 			".section\t__ex_table,\"a\"\n\t"
 			STR(PTR)"\t1b, 4b\n\t"
 			STR(PTR)"\t2b, 4b\n\t"
 			".previous"
 			: "=&r" (value), "=r" (res)
 			: "r" (addr), "i" (-EFAULT));
 		if (res)
 			goto fault;
 		compute_return_epc(regs);
 		regs->regs[insn.i_format.rt] = value;
 		break;
 #endif /* CONFIG_64BIT */

 		/* Cannot handle 64-bit instructions in 32-bit kernel */
 		goto sigill;

 	case ld_op:
 #ifdef CONFIG_64BIT
 		/*
 		 * A 32-bit kernel might be running on a 64-bit processor.  But
 		 * if we're on a 32-bit processor and an i-cache incoherency
 		 * or race makes us see a 64-bit instruction here the sdl/sdr
 		 * would blow up, so for now we don't handle unaligned 64-bit
 		 * instructions on 32-bit kernels.
 		 */
 		if (!access_ok(VERIFY_READ, addr, 8))
 			goto sigbus;

 		__asm__ __volatile__ (
 #ifdef __BIG_ENDIAN
 			"1:\tldl\t%0, (%2)\n"
 			"2:\tldr\t%0, 7(%2)\n\t"
 #endif
 #ifdef __LITTLE_ENDIAN
 			"1:\tldl\t%0, 7(%2)\n"
 			"2:\tldr\t%0, (%2)\n\t"
 #endif
 			"li\t%1, 0\n"
 			"3:\t.section\t.fixup,\"ax\"\n\t"
 			"4:\tli\t%1, %3\n\t"
 			"j\t3b\n\t"
 			".previous\n\t"
 			".section\t__ex_table,\"a\"\n\t"
 			STR(PTR)"\t1b, 4b\n\t"
 			STR(PTR)"\t2b, 4b\n\t"
 			".previous"
 			: "=&r" (value), "=r" (res)
 			: "r" (addr), "i" (-EFAULT));
 		if (res)
 			goto fault;
 		compute_return_epc(regs);
 		regs->regs[insn.i_format.rt] = value;
 		break;
 #endif /* CONFIG_64BIT */

 		/* Cannot handle 64-bit instructions in 32-bit kernel */
 		goto sigill;

 	case sh_op:
 		if (!access_ok(VERIFY_WRITE, addr, 2))
 			goto sigbus;

 		value = regs->regs[insn.i_format.rt];
 		__asm__ __volatile__ (
 #ifdef __BIG_ENDIAN
 			".set\tnoat\n"
 			"1:\tsb\t%1, 1(%2)\n\t"
 			"srl\t$1, %1, 0x8\n"
 			"2:\tsb\t$1, 0(%2)\n\t"
 			".set\tat\n\t"
 #endif
 #ifdef __LITTLE_ENDIAN
 			".set\tnoat\n"
 			"1:\tsb\t%1, 0(%2)\n\t"
 			"srl\t$1,%1, 0x8\n"
 			"2:\tsb\t$1, 1(%2)\n\t"
 			".set\tat\n\t"
 #endif
 			"li\t%0, 0\n"
 			"3:\n\t"
 			".section\t.fixup,\"ax\"\n\t"
 			"4:\tli\t%0, %3\n\t"
 			"j\t3b\n\t"
 			".previous\n\t"
 			".section\t__ex_table,\"a\"\n\t"
 			STR(PTR)"\t1b, 4b\n\t"
 			STR(PTR)"\t2b, 4b\n\t"
 			".previous"
 			: "=r" (res)
 			: "r" (value), "r" (addr), "i" (-EFAULT));
 		if (res)
 			goto fault;
 		compute_return_epc(regs);
 		break;

 	case sw_op:
 		if (!access_ok(VERIFY_WRITE, addr, 4))
 			goto sigbus;

 		value = regs->regs[insn.i_format.rt];
 		__asm__ __volatile__ (
 #ifdef __BIG_ENDIAN
 			"1:\tswl\t%1,(%2)\n"
 			"2:\tswr\t%1, 3(%2)\n\t"
 #endif
 #ifdef __LITTLE_ENDIAN
 			"1:\tswl\t%1, 3(%2)\n"
 			"2:\tswr\t%1, (%2)\n\t"
 #endif
 			"li\t%0, 0\n"
 			"3:\n\t"
 			".section\t.fixup,\"ax\"\n\t"
 			"4:\tli\t%0, %3\n\t"
 			"j\t3b\n\t"
 			".previous\n\t"
 			".section\t__ex_table,\"a\"\n\t"
 			STR(PTR)"\t1b, 4b\n\t"
 			STR(PTR)"\t2b, 4b\n\t"
 			".previous"
 		: "=r" (res)
 		: "r" (value), "r" (addr), "i" (-EFAULT));
 		if (res)
 			goto fault;
 		compute_return_epc(regs);
 		break;

 	case sd_op:
 #ifdef CONFIG_64BIT
 		/*
 		 * A 32-bit kernel might be running on a 64-bit processor.  But
 		 * if we're on a 32-bit processor and an i-cache incoherency
 		 * or race makes us see a 64-bit instruction here the sdl/sdr
 		 * would blow up, so for now we don't handle unaligned 64-bit
 		 * instructions on 32-bit kernels.
 		 */
 		if (!access_ok(VERIFY_WRITE, addr, 8))
 			goto sigbus;

 		value = regs->regs[insn.i_format.rt];
 		__asm__ __volatile__ (
 #ifdef __BIG_ENDIAN
 			"1:\tsdl\t%1,(%2)\n"
 			"2:\tsdr\t%1, 7(%2)\n\t"
 #endif
 #ifdef __LITTLE_ENDIAN
 			"1:\tsdl\t%1, 7(%2)\n"
 			"2:\tsdr\t%1, (%2)\n\t"
 #endif
 			"li\t%0, 0\n"
 			"3:\n\t"
 			".section\t.fixup,\"ax\"\n\t"
 			"4:\tli\t%0, %3\n\t"
 			"j\t3b\n\t"
 			".previous\n\t"
 			".section\t__ex_table,\"a\"\n\t"
 			STR(PTR)"\t1b, 4b\n\t"
 			STR(PTR)"\t2b, 4b\n\t"
 			".previous"
 		: "=r" (res)
 		: "r" (value), "r" (addr), "i" (-EFAULT));
 		if (res)
 			goto fault;
 		compute_return_epc(regs);
 		break;
 #endif /* CONFIG_64BIT */

 		/* Cannot handle 64-bit instructions in 32-bit kernel */
 		goto sigill;

 	case lwc1_op:
 	case ldc1_op:
 	case swc1_op:
 	case sdc1_op:
 		/*
 		 * I herewith declare: this does not happen.  So send SIGBUS.
 		 */
 		goto sigbus;

 	case lwc2_op:
 	case ldc2_op:
 	case swc2_op:
 	case sdc2_op:
 		/*
 		 * These are the coprocessor 2 load/stores.  The current
 		 * implementations don't use cp2 and cp2 should always be
 		 * disabled in c0_status.  So send SIGILL.
                  * (No longer true: The Sony Praystation uses cp2 for
                  * 3D matrix operations.  Dunno if that thingy has a MMU ...)
 		 */
 	default:
 		/*
 		 * Pheeee...  We encountered an yet unknown instruction or
 		 * cache coherence problem.  Die sucker, die ...
 		 */
 		goto sigill;
 	}

 #ifdef CONFIG_DEBUG_FS
 	unaligned_instructions++;
 #endif

 	return;

 fault:
 	/* Did we have an exception handler installed? */
 	if (fixup_exception(regs))
 		return;

 	die_if_kernel("Unhandled kernel unaligned access", regs);
 	send_sig(SIGSEGV, current, 1);

 	return;

 sigbus:
 	die_if_kernel("Unhandled kernel unaligned access", regs);
 	send_sig(SIGBUS, current, 1);

 	return;

 sigill:
 	die_if_kernel("Unhandled kernel unaligned access or invalid instruction", regs);
 	send_sig(SIGILL, current, 1);
 }

 asmlinkage void do_ade(struct pt_regs *regs)
 {
 	extern int do_dsemulret(struct pt_regs *);
 	unsigned int __user *pc;
 	mm_segment_t seg;

 	/*
 	 * Address errors may be deliberately induced by the FPU emulator to
 	 * retake control of the CPU after executing the instruction in the
 	 * delay slot of an emulated branch.
 	 */
 	/* Terminate if exception was recognized as a delay slot return */
 	if (do_dsemulret(regs))
 		return;

 	/* Otherwise handle as normal */

 	/*
 	 * Did we catch a fault trying to load an instruction?
 	 * Or are we running in MIPS16 mode?
 	 */
 	if ((regs->cp0_badvaddr == regs->cp0_epc) || (regs->cp0_epc & 0x1))
 		goto sigbus;

 	pc = (unsigned int __user *) exception_epc(regs);
 	if (user_mode(regs) && !test_thread_flag(TIF_FIXADE))
 		goto sigbus;
 	if (unaligned_action == UNALIGNED_ACTION_SIGNAL)
 		goto sigbus;
 	else if (unaligned_action == UNALIGNED_ACTION_SHOW)
 		show_registers(regs);

 	/*
 	 * Do branch emulation only if we didn't forward the exception.
 	 * This is all so but ugly ...
 	 */
 	seg = get_fs();
 	if (!user_mode(regs))
 		set_fs(KERNEL_DS);
 	emulate_load_store_insn(regs, (void __user *)regs->cp0_badvaddr, pc);
 	set_fs(seg);

 	return;

 sigbus:
 	die_if_kernel("Kernel unaligned instruction access", regs);
 	force_sig(SIGBUS, current);

 	/*
 	 * XXX On return from the signal handler we should advance the epc
 	 */
 }

 #ifdef CONFIG_DEBUG_FS
 extern struct dentry *mips_debugfs_dir;
 static int __init debugfs_unaligned(void)
 {
 	struct dentry *d;

 	if (!mips_debugfs_dir)
 		return -ENODEV;
 	d = debugfs_create_u32("unaligned_instructions", S_IRUGO,
 			       mips_debugfs_dir, &unaligned_instructions);
 	if (IS_ERR(d))
 		return PTR_ERR(d);
 	d = debugfs_create_u32("unaligned_action", S_IRUGO | S_IWUSR,
 			       mips_debugfs_dir, &unaligned_action);
 	if (IS_ERR(d))
 		return PTR_ERR(d);
 	return 0;
 }
 __initcall(debugfs_unaligned);
 #endif
	/*
	* Handle unaligned accesses by emulation.
	*
	* 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, 1998, 1999, 2002 by Ralf Baechle
	* Copyright (C) 1999 Silicon Graphics, Inc.
	*
	* This file contains exception handler for address error exception with the
	* special capability to execute faulting instructions in software. The
	* handler does not try to handle the case when the program counter points
	* to an address not aligned to a word boundary.
	*
	* Putting data to unaligned addresses is a bad practice even on Intel where
	* only the performance is affected. Much worse is that such code is non-
	* portable. Due to several programs that die on MIPS due to alignment
	* problems I decided to implement this handler anyway though I originally
	* didn't intend to do this at all for user code.
	*
	* For now I enable fixing of address errors by default to make life easier.
	* I however intend to disable this somewhen in the future when the alignment
	* problems with user programs have been fixed. For programmers this is the
	* right way to go.
	*
	* Fixing address errors is a per process option. The option is inherited
	* across fork(2) and execve(2) calls. If you really want to use the
	* option in your user programs - I discourage the use of the software
	* emulation strongly - use the following code in your userland stuff:
	*
	* #include <sys/sysmips.h>
	*
	* ...
	* sysmips(MIPS_FIXADE, x);
	* ...
	*
	* The argument x is 0 for disabling software emulation, enabled otherwise.
	*
	* Below a little program to play around with this feature.
	*
	* #include <stdio.h>
	* #include <sys/sysmips.h>
	*
	* struct foo {
	* unsigned char bar[8];
	* };
	*
	* main(int argc, char *argv[])
	* {
	* struct foo x = {0, 1, 2, 3, 4, 5, 6, 7};
	* unsigned int p = (unsigned int ) (x.bar + 3);
	* int i;
	*
	* if (argc > 1)
	* sysmips(MIPS_FIXADE, atoi(argv[1]));
	*
	* printf("p = %08lx\n", p);
	*
	* *p = 0xdeadface;
	*
	* for(i = 0; i <= 7; i++)
	* printf("%02x ", x.bar[i]);
	* printf("\n");
	* }
	*
	* Coprocessor loads are not supported; I think this case is unimportant
	* in the practice.
	*
	* TODO: Handle ndc (attempted store to doubleword in uncached memory)
	* exception for the R6000.
	* A store crossing a page boundary might be executed only partially.
	* Undo the partial store in this case.
	*/
	#include <linux/mm.h>
	#include <linux/module.h>
	#include <linux/signal.h>
	#include <linux/smp.h>
	#include <linux/sched.h>
	#include <linux/debugfs.h>
	#include <asm/asm.h>
	#include <asm/branch.h>
	#include <asm/byteorder.h>
	#include <asm/inst.h>
	#include <asm/uaccess.h>
	#include <asm/system.h>

	#define STR(x) __STR(x)
	#define __STR(x) #x

	enum {
	UNALIGNED_ACTION_QUIET,
	UNALIGNED_ACTION_SIGNAL,
	UNALIGNED_ACTION_SHOW,
	};
	#ifdef CONFIG_DEBUG_FS
	static u32 unaligned_instructions;
	static u32 unaligned_action;
	#else
	#define unaligned_action UNALIGNED_ACTION_QUIET
	#endif
	extern void show_registers(struct pt_regs *regs);

	static void emulate_load_store_insn(struct pt_regs *regs,
	void __user addr, unsigned int __user pc)
	{
	union mips_instruction insn;
	unsigned long value;
	unsigned int res;

	regs->regs[0] = 0;

	/*
	* This load never faults.
	*/
	__get_user(insn.word, pc);

	switch (insn.i_format.opcode) {
	/*
	* These are instructions that a compiler doesn't generate. We
	* can assume therefore that the code is MIPS-aware and
	* really buggy. Emulating these instructions would break the
	* semantics anyway.
	*/
	case ll_op:
	case lld_op:
	case sc_op:
	case scd_op:

	/*
	* For these instructions the only way to create an address
	* error is an attempted access to kernel/supervisor address
	* space.
	*/
	case ldl_op:
	case ldr_op:
	case lwl_op:
	case lwr_op:
	case sdl_op:
	case sdr_op:
	case swl_op:
	case swr_op:
	case lb_op:
	case lbu_op:
	case sb_op:
	goto sigbus;

	/*
	* The remaining opcodes are the ones that are really of interest.
	*/
	case lh_op:
	if (!access_ok(VERIFY_READ, addr, 2))
	goto sigbus;

	__asm__ __volatile__ (".set\tnoat\n"
	#ifdef __BIG_ENDIAN
	"1:\tlb\t%0, 0(%2)\n"
	"2:\tlbu\t$1, 1(%2)\n\t"
	#endif
	#ifdef __LITTLE_ENDIAN
	"1:\tlb\t%0, 1(%2)\n"
	"2:\tlbu\t$1, 0(%2)\n\t"
	#endif
	"sll\t%0, 0x8\n\t"
	"or\t%0, $1\n\t"
	"li\t%1, 0\n"
	"3:\t.set\tat\n\t"
	".section\t.fixup,\"ax\"\n\t"
	"4:\tli\t%1, %3\n\t"
	"j\t3b\n\t"
	".previous\n\t"
	".section\t__ex_table,\"a\"\n\t"
	STR(PTR)"\t1b, 4b\n\t"
	STR(PTR)"\t2b, 4b\n\t"
	".previous"
	: "=&r" (value), "=r" (res)
	: "r" (addr), "i" (-EFAULT));
	if (res)
	goto fault;
	compute_return_epc(regs);
	regs->regs[insn.i_format.rt] = value;
	break;

	case lw_op:
	if (!access_ok(VERIFY_READ, addr, 4))
	goto sigbus;

	__asm__ __volatile__ (
	#ifdef __BIG_ENDIAN
	"1:\tlwl\t%0, (%2)\n"
	"2:\tlwr\t%0, 3(%2)\n\t"
	#endif
	#ifdef __LITTLE_ENDIAN
	"1:\tlwl\t%0, 3(%2)\n"
	"2:\tlwr\t%0, (%2)\n\t"
	#endif
	"li\t%1, 0\n"
	"3:\t.section\t.fixup,\"ax\"\n\t"
	"4:\tli\t%1, %3\n\t"
	"j\t3b\n\t"
	".previous\n\t"
	".section\t__ex_table,\"a\"\n\t"
	STR(PTR)"\t1b, 4b\n\t"
	STR(PTR)"\t2b, 4b\n\t"
	".previous"
	: "=&r" (value), "=r" (res)
	: "r" (addr), "i" (-EFAULT));
	if (res)
	goto fault;
	compute_return_epc(regs);
	regs->regs[insn.i_format.rt] = value;
	break;

	case lhu_op:
	if (!access_ok(VERIFY_READ, addr, 2))
	goto sigbus;

	__asm__ __volatile__ (
	".set\tnoat\n"
	#ifdef __BIG_ENDIAN
	"1:\tlbu\t%0, 0(%2)\n"
	"2:\tlbu\t$1, 1(%2)\n\t"
	#endif
	#ifdef __LITTLE_ENDIAN
	"1:\tlbu\t%0, 1(%2)\n"
	"2:\tlbu\t$1, 0(%2)\n\t"
	#endif
	"sll\t%0, 0x8\n\t"
	"or\t%0, $1\n\t"
	"li\t%1, 0\n"
	"3:\t.set\tat\n\t"
	".section\t.fixup,\"ax\"\n\t"
	"4:\tli\t%1, %3\n\t"
	"j\t3b\n\t"
	".previous\n\t"
	".section\t__ex_table,\"a\"\n\t"
	STR(PTR)"\t1b, 4b\n\t"
	STR(PTR)"\t2b, 4b\n\t"
	".previous"
	: "=&r" (value), "=r" (res)
	: "r" (addr), "i" (-EFAULT));
	if (res)
	goto fault;
	compute_return_epc(regs);
	regs->regs[insn.i_format.rt] = value;
	break;

	case lwu_op:
	#ifdef CONFIG_64BIT
	/*
	* A 32-bit kernel might be running on a 64-bit processor. But
	* if we're on a 32-bit processor and an i-cache incoherency
	* or race makes us see a 64-bit instruction here the sdl/sdr
	* would blow up, so for now we don't handle unaligned 64-bit
	* instructions on 32-bit kernels.
	*/
	if (!access_ok(VERIFY_READ, addr, 4))
	goto sigbus;

	__asm__ __volatile__ (
	#ifdef __BIG_ENDIAN
	"1:\tlwl\t%0, (%2)\n"
	"2:\tlwr\t%0, 3(%2)\n\t"
	#endif
	#ifdef __LITTLE_ENDIAN
	"1:\tlwl\t%0, 3(%2)\n"
	"2:\tlwr\t%0, (%2)\n\t"
	#endif
	"dsll\t%0, %0, 32\n\t"
	"dsrl\t%0, %0, 32\n\t"
	"li\t%1, 0\n"
	"3:\t.section\t.fixup,\"ax\"\n\t"
	"4:\tli\t%1, %3\n\t"
	"j\t3b\n\t"
	".previous\n\t"
	".section\t__ex_table,\"a\"\n\t"
	STR(PTR)"\t1b, 4b\n\t"
	STR(PTR)"\t2b, 4b\n\t"
	".previous"
	: "=&r" (value), "=r" (res)
	: "r" (addr), "i" (-EFAULT));
	if (res)
	goto fault;
	compute_return_epc(regs);
	regs->regs[insn.i_format.rt] = value;
	break;
	#endif /* CONFIG_64BIT */

	/* Cannot handle 64-bit instructions in 32-bit kernel */
	goto sigill;

	case ld_op:
	#ifdef CONFIG_64BIT
	/*
	* A 32-bit kernel might be running on a 64-bit processor. But
	* if we're on a 32-bit processor and an i-cache incoherency
	* or race makes us see a 64-bit instruction here the sdl/sdr
	* would blow up, so for now we don't handle unaligned 64-bit
	* instructions on 32-bit kernels.
	*/
	if (!access_ok(VERIFY_READ, addr, 8))
	goto sigbus;

	__asm__ __volatile__ (
	#ifdef __BIG_ENDIAN
	"1:\tldl\t%0, (%2)\n"
	"2:\tldr\t%0, 7(%2)\n\t"
	#endif
	#ifdef __LITTLE_ENDIAN
	"1:\tldl\t%0, 7(%2)\n"
	"2:\tldr\t%0, (%2)\n\t"
	#endif
	"li\t%1, 0\n"
	"3:\t.section\t.fixup,\"ax\"\n\t"
	"4:\tli\t%1, %3\n\t"
	"j\t3b\n\t"
	".previous\n\t"
	".section\t__ex_table,\"a\"\n\t"
	STR(PTR)"\t1b, 4b\n\t"
	STR(PTR)"\t2b, 4b\n\t"
	".previous"
	: "=&r" (value), "=r" (res)
	: "r" (addr), "i" (-EFAULT));
	if (res)
	goto fault;
	compute_return_epc(regs);
	regs->regs[insn.i_format.rt] = value;
	break;
	#endif /* CONFIG_64BIT */

	/* Cannot handle 64-bit instructions in 32-bit kernel */
	goto sigill;

	case sh_op:
	if (!access_ok(VERIFY_WRITE, addr, 2))
	goto sigbus;

	value = regs->regs[insn.i_format.rt];
	__asm__ __volatile__ (
	#ifdef __BIG_ENDIAN
	".set\tnoat\n"
	"1:\tsb\t%1, 1(%2)\n\t"
	"srl\t$1, %1, 0x8\n"
	"2:\tsb\t$1, 0(%2)\n\t"
	".set\tat\n\t"
	#endif
	#ifdef __LITTLE_ENDIAN
	".set\tnoat\n"
	"1:\tsb\t%1, 0(%2)\n\t"
	"srl\t$1,%1, 0x8\n"
	"2:\tsb\t$1, 1(%2)\n\t"
	".set\tat\n\t"
	#endif
	"li\t%0, 0\n"
	"3:\n\t"
	".section\t.fixup,\"ax\"\n\t"
	"4:\tli\t%0, %3\n\t"
	"j\t3b\n\t"
	".previous\n\t"
	".section\t__ex_table,\"a\"\n\t"
	STR(PTR)"\t1b, 4b\n\t"
	STR(PTR)"\t2b, 4b\n\t"
	".previous"
	: "=r" (res)
	: "r" (value), "r" (addr), "i" (-EFAULT));
	if (res)
	goto fault;
	compute_return_epc(regs);
	break;

	case sw_op:
	if (!access_ok(VERIFY_WRITE, addr, 4))
	goto sigbus;

	value = regs->regs[insn.i_format.rt];
	__asm__ __volatile__ (
	#ifdef __BIG_ENDIAN
	"1:\tswl\t%1,(%2)\n"
	"2:\tswr\t%1, 3(%2)\n\t"
	#endif
	#ifdef __LITTLE_ENDIAN
	"1:\tswl\t%1, 3(%2)\n"
	"2:\tswr\t%1, (%2)\n\t"
	#endif
	"li\t%0, 0\n"
	"3:\n\t"
	".section\t.fixup,\"ax\"\n\t"
	"4:\tli\t%0, %3\n\t"
	"j\t3b\n\t"
	".previous\n\t"
	".section\t__ex_table,\"a\"\n\t"
	STR(PTR)"\t1b, 4b\n\t"
	STR(PTR)"\t2b, 4b\n\t"
	".previous"
	: "=r" (res)
	: "r" (value), "r" (addr), "i" (-EFAULT));
	if (res)
	goto fault;
	compute_return_epc(regs);
	break;

	case sd_op:
	#ifdef CONFIG_64BIT
	/*
	* A 32-bit kernel might be running on a 64-bit processor. But
	* if we're on a 32-bit processor and an i-cache incoherency
	* or race makes us see a 64-bit instruction here the sdl/sdr
	* would blow up, so for now we don't handle unaligned 64-bit
	* instructions on 32-bit kernels.
	*/
	if (!access_ok(VERIFY_WRITE, addr, 8))
	goto sigbus;

	value = regs->regs[insn.i_format.rt];
	__asm__ __volatile__ (
	#ifdef __BIG_ENDIAN
	"1:\tsdl\t%1,(%2)\n"
	"2:\tsdr\t%1, 7(%2)\n\t"
	#endif
	#ifdef __LITTLE_ENDIAN
	"1:\tsdl\t%1, 7(%2)\n"
	"2:\tsdr\t%1, (%2)\n\t"
	#endif
	"li\t%0, 0\n"
	"3:\n\t"
	".section\t.fixup,\"ax\"\n\t"
	"4:\tli\t%0, %3\n\t"
	"j\t3b\n\t"
	".previous\n\t"
	".section\t__ex_table,\"a\"\n\t"
	STR(PTR)"\t1b, 4b\n\t"
	STR(PTR)"\t2b, 4b\n\t"
	".previous"
	: "=r" (res)
	: "r" (value), "r" (addr), "i" (-EFAULT));
	if (res)
	goto fault;
	compute_return_epc(regs);
	break;
	#endif /* CONFIG_64BIT */

	/* Cannot handle 64-bit instructions in 32-bit kernel */
	goto sigill;

	case lwc1_op:
	case ldc1_op:
	case swc1_op:
	case sdc1_op:
	/*
	* I herewith declare: this does not happen. So send SIGBUS.
	*/
	goto sigbus;

	case lwc2_op:
	case ldc2_op:
	case swc2_op:
	case sdc2_op:
	/*
	* These are the coprocessor 2 load/stores. The current
	* implementations don't use cp2 and cp2 should always be
	* disabled in c0_status. So send SIGILL.
	* (No longer true: The Sony Praystation uses cp2 for
	* 3D matrix operations. Dunno if that thingy has a MMU ...)
	*/
	default:
	/*
	* Pheeee... We encountered an yet unknown instruction or
	* cache coherence problem. Die sucker, die ...
	*/
	goto sigill;
	}

	#ifdef CONFIG_DEBUG_FS
	unaligned_instructions++;
	#endif

	return;

	fault:
	/* Did we have an exception handler installed? */
	if (fixup_exception(regs))
	return;

	die_if_kernel("Unhandled kernel unaligned access", regs);
	send_sig(SIGSEGV, current, 1);

	return;

	sigbus:
	die_if_kernel("Unhandled kernel unaligned access", regs);
	send_sig(SIGBUS, current, 1);

	return;

	sigill:
	die_if_kernel("Unhandled kernel unaligned access or invalid instruction", regs);
	send_sig(SIGILL, current, 1);
	}

	asmlinkage void do_ade(struct pt_regs *regs)
	{
	extern int do_dsemulret(struct pt_regs *);
	unsigned int __user *pc;
	mm_segment_t seg;

	/*
	* Address errors may be deliberately induced by the FPU emulator to
	* retake control of the CPU after executing the instruction in the
	* delay slot of an emulated branch.
	*/
	/* Terminate if exception was recognized as a delay slot return */
	if (do_dsemulret(regs))
	return;

	/* Otherwise handle as normal */

	/*
	* Did we catch a fault trying to load an instruction?
	* Or are we running in MIPS16 mode?
	*/
	if ((regs->cp0_badvaddr == regs->cp0_epc) \|\| (regs->cp0_epc & 0x1))
	goto sigbus;

	pc = (unsigned int __user *) exception_epc(regs);
	if (user_mode(regs) && !test_thread_flag(TIF_FIXADE))
	goto sigbus;
	if (unaligned_action == UNALIGNED_ACTION_SIGNAL)
	goto sigbus;
	else if (unaligned_action == UNALIGNED_ACTION_SHOW)
	show_registers(regs);

	/*
	* Do branch emulation only if we didn't forward the exception.
	* This is all so but ugly ...
	*/
	seg = get_fs();
	if (!user_mode(regs))
	set_fs(KERNEL_DS);
	emulate_load_store_insn(regs, (void __user *)regs->cp0_badvaddr, pc);
	set_fs(seg);

	return;

	sigbus:
	die_if_kernel("Kernel unaligned instruction access", regs);
	force_sig(SIGBUS, current);

	/*
	* XXX On return from the signal handler we should advance the epc
	*/
	}

	#ifdef CONFIG_DEBUG_FS
	extern struct dentry *mips_debugfs_dir;
	static int __init debugfs_unaligned(void)
	{
	struct dentry *d;

	if (!mips_debugfs_dir)
	return -ENODEV;
	d = debugfs_create_u32("unaligned_instructions", S_IRUGO,
	mips_debugfs_dir, &unaligned_instructions);
	if (IS_ERR(d))
	return PTR_ERR(d);
	d = debugfs_create_u32("unaligned_action", S_IRUGO \| S_IWUSR,
	mips_debugfs_dir, &unaligned_action);
	if (IS_ERR(d))
	return PTR_ERR(d);
	return 0;
	}
	__initcall(debugfs_unaligned);
	#endif