arch/hexagon/kernel/traps.c - kernel/windcharger - Git at Google

 /*
  * Kernel traps/events for Hexagon processor
  *
  * Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
  * only version 2 as published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  * 02110-1301, USA.
  */

 #include <linux/init.h>
 #include <linux/sched.h>
 #include <linux/module.h>
 #include <linux/kallsyms.h>
 #include <linux/kdebug.h>
 #include <linux/syscalls.h>
 #include <linux/signal.h>
 #include <linux/tracehook.h>
 #include <asm/traps.h>
 #include <asm/vm_fault.h>
 #include <asm/syscall.h>
 #include <asm/registers.h>
 #include <asm/unistd.h>
 #include <asm/sections.h>
 #ifdef CONFIG_KGDB
 # include <linux/kgdb.h>
 #endif

 #define TRAP_SYSCALL	1
 #define TRAP_DEBUG	0xdb

 void __init trap_init(void)
 {
 }

 #ifdef CONFIG_GENERIC_BUG
 /* Maybe should resemble arch/sh/kernel/traps.c ?? */
 int is_valid_bugaddr(unsigned long addr)
 {
 	return 1;
 }
 #endif /* CONFIG_GENERIC_BUG */

 static const char *ex_name(int ex)
 {
 	switch (ex) {
 	case HVM_GE_C_XPROT:
 	case HVM_GE_C_XUSER:
 		return "Execute protection fault";
 	case HVM_GE_C_RPROT:
 	case HVM_GE_C_RUSER:
 		return "Read protection fault";
 	case HVM_GE_C_WPROT:
 	case HVM_GE_C_WUSER:
 		return "Write protection fault";
 	case HVM_GE_C_XMAL:
 		return "Misaligned instruction";
 	case HVM_GE_C_RMAL:
 		return "Misaligned data load";
 	case HVM_GE_C_WMAL:
 		return "Misaligned data store";
 	case HVM_GE_C_INVI:
 	case HVM_GE_C_PRIVI:
 		return "Illegal instruction";
 	case HVM_GE_C_BUS:
 		return "Precise bus error";
 	case HVM_GE_C_CACHE:
 		return "Cache error";

 	case 0xdb:
 		return "Debugger trap";

 	default:
 		return "Unrecognized exception";
 	}
 }

 static void do_show_stack(struct task_struct *task, unsigned long *fp,
 			  unsigned long ip)
 {
 	int kstack_depth_to_print = 24;
 	unsigned long offset, size;
 	const char *name = NULL;
 	unsigned long *newfp;
 	unsigned long low, high;
 	char tmpstr[128];
 	char *modname;
 	int i;

 	if (task == NULL)
 		task = current;

 	printk(KERN_INFO "CPU#%d, %s/%d, Call Trace:\n",
 	       raw_smp_processor_id(), task->comm,
 	       task_pid_nr(task));

 	if (fp == NULL) {
 		if (task == current) {
 			asm("%0 = r30" : "=r" (fp));
 		} else {
 			fp = (unsigned long *)
 			     ((struct hexagon_switch_stack *)
 			     task->thread.switch_sp)->fp;
 		}
 	}

 	if ((((unsigned long) fp) & 0x3) || ((unsigned long) fp < 0x1000)) {
 		printk(KERN_INFO "-- Corrupt frame pointer %p\n", fp);
 		return;
 	}

 	/* Saved link reg is one word above FP */
 	if (!ip)
 		ip = *(fp+1);

 	/* Expect kernel stack to be in-bounds */
 	low = (unsigned long)task_stack_page(task);
 	high = low + THREAD_SIZE - 8;
 	low += sizeof(struct thread_info);

 	for (i = 0; i < kstack_depth_to_print; i++) {

 		name = kallsyms_lookup(ip, &size, &offset, &modname, tmpstr);

 		printk(KERN_INFO "[%p] 0x%lx: %s + 0x%lx", fp, ip, name,
 			offset);
 		if (((unsigned long) fp < low) || (high < (unsigned long) fp))
 			printk(KERN_CONT " (FP out of bounds!)");
 		if (modname)
 			printk(KERN_CONT " [%s] ", modname);
 		printk(KERN_CONT "\n");

 		newfp = (unsigned long *) *fp;

 		if (((unsigned long) newfp) & 0x3) {
 			printk(KERN_INFO "-- Corrupt frame pointer %p\n",
 				newfp);
 			break;
 		}

 		/* Attempt to continue past exception. */
 		if (0 == newfp) {
 			struct pt_regs *regs = (struct pt_regs *) (((void *)fp)
 						+ 8);

 			if (regs->syscall_nr != -1) {
 				printk(KERN_INFO "-- trap0 -- syscall_nr: %ld",
 					regs->syscall_nr);
 				printk(KERN_CONT "  psp: %lx  elr: %lx\n",
 					 pt_psp(regs), pt_elr(regs));
 				break;
 			} else {
 				/* really want to see more ... */
 				kstack_depth_to_print += 6;
 				printk(KERN_INFO "-- %s (0x%lx)  badva: %lx\n",
 					ex_name(pt_cause(regs)), pt_cause(regs),
 					pt_badva(regs));
 			}

 			newfp = (unsigned long *) regs->r30;
 			ip = pt_elr(regs);
 		} else {
 			ip = *(newfp + 1);
 		}

 		/* If link reg is null, we are done. */
 		if (ip == 0x0)
 			break;

 		/* If newfp isn't larger, we're tracing garbage. */
 		if (newfp > fp)
 			fp = newfp;
 		else
 			break;
 	}
 }

 void show_stack(struct task_struct *task, unsigned long *fp)
 {
 	/* Saved link reg is one word above FP */
 	do_show_stack(task, fp, 0);
 }

 void dump_stack(void)
 {
 	unsigned long *fp;
 	asm("%0 = r30" : "=r" (fp));
 	show_stack(current, fp);
 }
 EXPORT_SYMBOL(dump_stack);

 int die(const char *str, struct pt_regs *regs, long err)
 {
 	static struct {
 		spinlock_t lock;
 		int counter;
 	} die = {
 		.lock = __SPIN_LOCK_UNLOCKED(die.lock),
 		.counter = 0
 	};

 	console_verbose();
 	oops_enter();

 	spin_lock_irq(&die.lock);
 	bust_spinlocks(1);
 	printk(KERN_EMERG "Oops: %s[#%d]:\n", str, ++die.counter);

 	if (notify_die(DIE_OOPS, str, regs, err, pt_cause(regs), SIGSEGV) ==
 	    NOTIFY_STOP)
 		return 1;

 	print_modules();
 	show_regs(regs);
 	do_show_stack(current, &regs->r30, pt_elr(regs));

 	bust_spinlocks(0);
 	add_taint(TAINT_DIE);

 	spin_unlock_irq(&die.lock);

 	if (in_interrupt())
 		panic("Fatal exception in interrupt");

 	if (panic_on_oops)
 		panic("Fatal exception");

 	oops_exit();
 	do_exit(err);
 	return 0;
 }

 int die_if_kernel(char *str, struct pt_regs *regs, long err)
 {
 	if (!user_mode(regs))
 		return die(str, regs, err);
 	else
 		return 0;
 }

 /*
  * It's not clear that misaligned fetches are ever recoverable.
  */
 static void misaligned_instruction(struct pt_regs *regs)
 {
 	die_if_kernel("Misaligned Instruction", regs, 0);
 	force_sig(SIGBUS, current);
 }

 /*
  * Misaligned loads and stores, on the other hand, can be
  * emulated, and probably should be, some day.  But for now
  * they will be considered fatal.
  */
 static void misaligned_data_load(struct pt_regs *regs)
 {
 	die_if_kernel("Misaligned Data Load", regs, 0);
 	force_sig(SIGBUS, current);
 }

 static void misaligned_data_store(struct pt_regs *regs)
 {
 	die_if_kernel("Misaligned Data Store", regs, 0);
 	force_sig(SIGBUS, current);
 }

 static void illegal_instruction(struct pt_regs *regs)
 {
 	die_if_kernel("Illegal Instruction", regs, 0);
 	force_sig(SIGILL, current);
 }

 /*
  * Precise bus errors may be recoverable with a a retry,
  * but for now, treat them as irrecoverable.
  */
 static void precise_bus_error(struct pt_regs *regs)
 {
 	die_if_kernel("Precise Bus Error", regs, 0);
 	force_sig(SIGBUS, current);
 }

 /*
  * If anything is to be done here other than panic,
  * it will probably be complex and migrate to another
  * source module.  For now, just die.
  */
 static void cache_error(struct pt_regs *regs)
 {
 	die("Cache Error", regs, 0);
 }

 /*
  * General exception handler
  */
 void do_genex(struct pt_regs *regs)
 {
 	/*
 	 * Decode Cause and Dispatch
 	 */
 	switch (pt_cause(regs)) {
 	case HVM_GE_C_XPROT:
 	case HVM_GE_C_XUSER:
 		execute_protection_fault(regs);
 		break;
 	case HVM_GE_C_RPROT:
 	case HVM_GE_C_RUSER:
 		read_protection_fault(regs);
 		break;
 	case HVM_GE_C_WPROT:
 	case HVM_GE_C_WUSER:
 		write_protection_fault(regs);
 		break;
 	case HVM_GE_C_XMAL:
 		misaligned_instruction(regs);
 		break;
 	case HVM_GE_C_RMAL:
 		misaligned_data_load(regs);
 		break;
 	case HVM_GE_C_WMAL:
 		misaligned_data_store(regs);
 		break;
 	case HVM_GE_C_INVI:
 	case HVM_GE_C_PRIVI:
 		illegal_instruction(regs);
 		break;
 	case HVM_GE_C_BUS:
 		precise_bus_error(regs);
 		break;
 	case HVM_GE_C_CACHE:
 		cache_error(regs);
 		break;
 	default:
 		/* Halt and catch fire */
 		panic("Unrecognized exception 0x%lx\n", pt_cause(regs));
 		break;
 	}
 }

 /* Indirect system call dispatch */
 long sys_syscall(void)
 {
 	printk(KERN_ERR "sys_syscall invoked!\n");
 	return -ENOSYS;
 }

 void do_trap0(struct pt_regs *regs)
 {
 	unsigned long syscallret = 0;
 	syscall_fn syscall;

 	switch (pt_cause(regs)) {
 	case TRAP_SYSCALL:
 		/* System call is trap0 #1 */

 		/* allow strace to catch syscall args  */
 		if (unlikely(test_thread_flag(TIF_SYSCALL_TRACE) &&
 			tracehook_report_syscall_entry(regs)))
 			return;  /*  return -ENOSYS somewhere?  */

 		/* Interrupts should be re-enabled for syscall processing */
 		__vmsetie(VM_INT_ENABLE);

 		/*
 		 * System call number is in r6, arguments in r0..r5.
 		 * Fortunately, no Linux syscall has more than 6 arguments,
 		 * and Hexagon ABI passes first 6 arguments in registers.
 		 * 64-bit arguments are passed in odd/even register pairs.
 		 * Fortunately, we have no system calls that take more
 		 * than three arguments with more than one 64-bit value.
 		 * Should that change, we'd need to redesign to copy
 		 * between user and kernel stacks.
 		 */
 		regs->syscall_nr = regs->r06;

 		/*
 		 * GPR R0 carries the first parameter, and is also used
 		 * to report the return value.  We need a backup of
 		 * the user's value in case we need to do a late restart
 		 * of the system call.
 		 */
 		regs->restart_r0 = regs->r00;

 		if ((unsigned long) regs->syscall_nr >= __NR_syscalls) {
 			regs->r00 = -1;
 		} else {
 			syscall = (syscall_fn)
 				  (sys_call_table[regs->syscall_nr]);
 			syscallret = syscall(regs->r00, regs->r01,
 				   regs->r02, regs->r03,
 				   regs->r04, regs->r05);
 		}

 		/*
 		 * If it was a sigreturn system call, don't overwrite
 		 * r0 value in stack frame with return value.
 		 *
 		 * __NR_sigreturn doesn't seem to exist in new unistd.h
 		 */

 		if (regs->syscall_nr != __NR_rt_sigreturn)
 			regs->r00 = syscallret;

 		/* allow strace to get the syscall return state  */
 		if (unlikely(test_thread_flag(TIF_SYSCALL_TRACE)))
 			tracehook_report_syscall_exit(regs, 0);

 		break;
 	case TRAP_DEBUG:
 		/* Trap0 0xdb is debug breakpoint */
 		if (user_mode(regs)) {
 			struct siginfo info;

 			info.si_signo = SIGTRAP;
 			info.si_errno = 0;
 			/*
 			 * Some architecures add some per-thread state
 			 * to distinguish between breakpoint traps and
 			 * trace traps.  We may want to do that, and
 			 * set the si_code value appropriately, or we
 			 * may want to use a different trap0 flavor.
 			 */
 			info.si_code = TRAP_BRKPT;
 			info.si_addr = (void __user *) pt_elr(regs);
 			send_sig_info(SIGTRAP, &info, current);
 		} else {
 #ifdef CONFIG_KGDB
 			kgdb_handle_exception(pt_cause(regs), SIGTRAP,
 					      TRAP_BRKPT, regs);
 #endif
 		}
 		break;
 	}
 	/* Ignore other trap0 codes for now, especially 0 (Angel calls) */
 }

 /*
  * Machine check exception handler
  */
 void do_machcheck(struct pt_regs *regs)
 {
 	/* Halt and catch fire */
 	__vmstop();
 }
	/*
	* Kernel traps/events for Hexagon processor
	*
	* Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 and
	* only version 2 as published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
	* 02110-1301, USA.
	*/

	#include <linux/init.h>
	#include <linux/sched.h>
	#include <linux/module.h>
	#include <linux/kallsyms.h>
	#include <linux/kdebug.h>
	#include <linux/syscalls.h>
	#include <linux/signal.h>
	#include <linux/tracehook.h>
	#include <asm/traps.h>
	#include <asm/vm_fault.h>
	#include <asm/syscall.h>
	#include <asm/registers.h>
	#include <asm/unistd.h>
	#include <asm/sections.h>
	#ifdef CONFIG_KGDB
	# include <linux/kgdb.h>
	#endif

	#define TRAP_SYSCALL 1
	#define TRAP_DEBUG 0xdb

	void __init trap_init(void)
	{
	}

	#ifdef CONFIG_GENERIC_BUG
	/* Maybe should resemble arch/sh/kernel/traps.c ?? */
	int is_valid_bugaddr(unsigned long addr)
	{
	return 1;
	}
	#endif /* CONFIG_GENERIC_BUG */

	static const char *ex_name(int ex)
	{
	switch (ex) {
	case HVM_GE_C_XPROT:
	case HVM_GE_C_XUSER:
	return "Execute protection fault";
	case HVM_GE_C_RPROT:
	case HVM_GE_C_RUSER:
	return "Read protection fault";
	case HVM_GE_C_WPROT:
	case HVM_GE_C_WUSER:
	return "Write protection fault";
	case HVM_GE_C_XMAL:
	return "Misaligned instruction";
	case HVM_GE_C_RMAL:
	return "Misaligned data load";
	case HVM_GE_C_WMAL:
	return "Misaligned data store";
	case HVM_GE_C_INVI:
	case HVM_GE_C_PRIVI:
	return "Illegal instruction";
	case HVM_GE_C_BUS:
	return "Precise bus error";
	case HVM_GE_C_CACHE:
	return "Cache error";

	case 0xdb:
	return "Debugger trap";

	default:
	return "Unrecognized exception";
	}
	}

	static void do_show_stack(struct task_struct task, unsigned long fp,
	unsigned long ip)
	{
	int kstack_depth_to_print = 24;
	unsigned long offset, size;
	const char *name = NULL;
	unsigned long *newfp;
	unsigned long low, high;
	char tmpstr[128];
	char *modname;
	int i;

	if (task == NULL)
	task = current;

	printk(KERN_INFO "CPU#%d, %s/%d, Call Trace:\n",
	raw_smp_processor_id(), task->comm,
	task_pid_nr(task));

	if (fp == NULL) {
	if (task == current) {
	asm("%0 = r30" : "=r" (fp));
	} else {
	fp = (unsigned long *)
	((struct hexagon_switch_stack *)
	task->thread.switch_sp)->fp;
	}
	}

	if ((((unsigned long) fp) & 0x3) \|\| ((unsigned long) fp < 0x1000)) {
	printk(KERN_INFO "-- Corrupt frame pointer %p\n", fp);
	return;
	}

	/* Saved link reg is one word above FP */
	if (!ip)
	ip = *(fp+1);

	/* Expect kernel stack to be in-bounds */
	low = (unsigned long)task_stack_page(task);
	high = low + THREAD_SIZE - 8;
	low += sizeof(struct thread_info);

	for (i = 0; i < kstack_depth_to_print; i++) {

	name = kallsyms_lookup(ip, &size, &offset, &modname, tmpstr);

	printk(KERN_INFO "[%p] 0x%lx: %s + 0x%lx", fp, ip, name,
	offset);
	if (((unsigned long) fp < low) \|\| (high < (unsigned long) fp))
	printk(KERN_CONT " (FP out of bounds!)");
	if (modname)
	printk(KERN_CONT " [%s] ", modname);
	printk(KERN_CONT "\n");

	newfp = (unsigned long ) fp;

	if (((unsigned long) newfp) & 0x3) {
	printk(KERN_INFO "-- Corrupt frame pointer %p\n",
	newfp);
	break;
	}

	/* Attempt to continue past exception. */
	if (0 == newfp) {
	struct pt_regs regs = (struct pt_regs ) (((void *)fp)
	+ 8);

	if (regs->syscall_nr != -1) {
	printk(KERN_INFO "-- trap0 -- syscall_nr: %ld",
	regs->syscall_nr);
	printk(KERN_CONT " psp: %lx elr: %lx\n",
	pt_psp(regs), pt_elr(regs));
	break;
	} else {
	/* really want to see more ... */
	kstack_depth_to_print += 6;
	printk(KERN_INFO "-- %s (0x%lx) badva: %lx\n",
	ex_name(pt_cause(regs)), pt_cause(regs),
	pt_badva(regs));
	}

	newfp = (unsigned long *) regs->r30;
	ip = pt_elr(regs);
	} else {
	ip = *(newfp + 1);
	}

	/* If link reg is null, we are done. */
	if (ip == 0x0)
	break;

	/* If newfp isn't larger, we're tracing garbage. */
	if (newfp > fp)
	fp = newfp;
	else
	break;
	}
	}

	void show_stack(struct task_struct task, unsigned long fp)
	{
	/* Saved link reg is one word above FP */
	do_show_stack(task, fp, 0);
	}

	void dump_stack(void)
	{
	unsigned long *fp;
	asm("%0 = r30" : "=r" (fp));
	show_stack(current, fp);
	}
	EXPORT_SYMBOL(dump_stack);

	int die(const char str, struct pt_regs regs, long err)
	{
	static struct {
	spinlock_t lock;
	int counter;
	} die = {
	.lock = __SPIN_LOCK_UNLOCKED(die.lock),
	.counter = 0
	};

	console_verbose();
	oops_enter();

	spin_lock_irq(&die.lock);
	bust_spinlocks(1);
	printk(KERN_EMERG "Oops: %s[#%d]:\n", str, ++die.counter);

	if (notify_die(DIE_OOPS, str, regs, err, pt_cause(regs), SIGSEGV) ==
	NOTIFY_STOP)
	return 1;

	print_modules();
	show_regs(regs);
	do_show_stack(current, &regs->r30, pt_elr(regs));

	bust_spinlocks(0);
	add_taint(TAINT_DIE);

	spin_unlock_irq(&die.lock);

	if (in_interrupt())
	panic("Fatal exception in interrupt");

	if (panic_on_oops)
	panic("Fatal exception");

	oops_exit();
	do_exit(err);
	return 0;
	}

	int die_if_kernel(char str, struct pt_regs regs, long err)
	{
	if (!user_mode(regs))
	return die(str, regs, err);
	else
	return 0;
	}

	/*
	* It's not clear that misaligned fetches are ever recoverable.
	*/
	static void misaligned_instruction(struct pt_regs *regs)
	{
	die_if_kernel("Misaligned Instruction", regs, 0);
	force_sig(SIGBUS, current);
	}

	/*
	* Misaligned loads and stores, on the other hand, can be
	* emulated, and probably should be, some day. But for now
	* they will be considered fatal.
	*/
	static void misaligned_data_load(struct pt_regs *regs)
	{
	die_if_kernel("Misaligned Data Load", regs, 0);
	force_sig(SIGBUS, current);
	}

	static void misaligned_data_store(struct pt_regs *regs)
	{
	die_if_kernel("Misaligned Data Store", regs, 0);
	force_sig(SIGBUS, current);
	}

	static void illegal_instruction(struct pt_regs *regs)
	{
	die_if_kernel("Illegal Instruction", regs, 0);
	force_sig(SIGILL, current);
	}

	/*
	* Precise bus errors may be recoverable with a a retry,
	* but for now, treat them as irrecoverable.
	*/
	static void precise_bus_error(struct pt_regs *regs)
	{
	die_if_kernel("Precise Bus Error", regs, 0);
	force_sig(SIGBUS, current);
	}

	/*
	* If anything is to be done here other than panic,
	* it will probably be complex and migrate to another
	* source module. For now, just die.
	*/
	static void cache_error(struct pt_regs *regs)
	{
	die("Cache Error", regs, 0);
	}

	/*
	* General exception handler
	*/
	void do_genex(struct pt_regs *regs)
	{
	/*
	* Decode Cause and Dispatch
	*/
	switch (pt_cause(regs)) {
	case HVM_GE_C_XPROT:
	case HVM_GE_C_XUSER:
	execute_protection_fault(regs);
	break;
	case HVM_GE_C_RPROT:
	case HVM_GE_C_RUSER:
	read_protection_fault(regs);
	break;
	case HVM_GE_C_WPROT:
	case HVM_GE_C_WUSER:
	write_protection_fault(regs);
	break;
	case HVM_GE_C_XMAL:
	misaligned_instruction(regs);
	break;
	case HVM_GE_C_RMAL:
	misaligned_data_load(regs);
	break;
	case HVM_GE_C_WMAL:
	misaligned_data_store(regs);
	break;
	case HVM_GE_C_INVI:
	case HVM_GE_C_PRIVI:
	illegal_instruction(regs);
	break;
	case HVM_GE_C_BUS:
	precise_bus_error(regs);
	break;
	case HVM_GE_C_CACHE:
	cache_error(regs);
	break;
	default:
	/* Halt and catch fire */
	panic("Unrecognized exception 0x%lx\n", pt_cause(regs));
	break;
	}
	}

	/* Indirect system call dispatch */
	long sys_syscall(void)
	{
	printk(KERN_ERR "sys_syscall invoked!\n");
	return -ENOSYS;
	}

	void do_trap0(struct pt_regs *regs)
	{
	unsigned long syscallret = 0;
	syscall_fn syscall;

	switch (pt_cause(regs)) {
	case TRAP_SYSCALL:
	/* System call is trap0 #1 */

	/* allow strace to catch syscall args */
	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACE) &&
	tracehook_report_syscall_entry(regs)))
	return; /* return -ENOSYS somewhere? */

	/* Interrupts should be re-enabled for syscall processing */
	__vmsetie(VM_INT_ENABLE);

	/*
	* System call number is in r6, arguments in r0..r5.
	* Fortunately, no Linux syscall has more than 6 arguments,
	* and Hexagon ABI passes first 6 arguments in registers.
	* 64-bit arguments are passed in odd/even register pairs.
	* Fortunately, we have no system calls that take more
	* than three arguments with more than one 64-bit value.
	* Should that change, we'd need to redesign to copy
	* between user and kernel stacks.
	*/
	regs->syscall_nr = regs->r06;

	/*
	* GPR R0 carries the first parameter, and is also used
	* to report the return value. We need a backup of
	* the user's value in case we need to do a late restart
	* of the system call.
	*/
	regs->restart_r0 = regs->r00;

	if ((unsigned long) regs->syscall_nr >= __NR_syscalls) {
	regs->r00 = -1;
	} else {
	syscall = (syscall_fn)
	(sys_call_table[regs->syscall_nr]);
	syscallret = syscall(regs->r00, regs->r01,
	regs->r02, regs->r03,
	regs->r04, regs->r05);
	}

	/*
	* If it was a sigreturn system call, don't overwrite
	* r0 value in stack frame with return value.
	*
	* __NR_sigreturn doesn't seem to exist in new unistd.h
	*/

	if (regs->syscall_nr != __NR_rt_sigreturn)
	regs->r00 = syscallret;

	/* allow strace to get the syscall return state */
	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACE)))
	tracehook_report_syscall_exit(regs, 0);

	break;
	case TRAP_DEBUG:
	/* Trap0 0xdb is debug breakpoint */
	if (user_mode(regs)) {
	struct siginfo info;

	info.si_signo = SIGTRAP;
	info.si_errno = 0;
	/*
	* Some architecures add some per-thread state
	* to distinguish between breakpoint traps and
	* trace traps. We may want to do that, and
	* set the si_code value appropriately, or we
	* may want to use a different trap0 flavor.
	*/
	info.si_code = TRAP_BRKPT;
	info.si_addr = (void __user *) pt_elr(regs);
	send_sig_info(SIGTRAP, &info, current);
	} else {
	#ifdef CONFIG_KGDB
	kgdb_handle_exception(pt_cause(regs), SIGTRAP,
	TRAP_BRKPT, regs);
	#endif
	}
	break;
	}
	/* Ignore other trap0 codes for now, especially 0 (Angel calls) */
	}

	/*
	* Machine check exception handler
	*/
	void do_machcheck(struct pt_regs *regs)
	{
	/* Halt and catch fire */
	__vmstop();
	}