arch/nds32/kernel/traps.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 // Copyright (C) 2005-2017 Andes Technology Corporation

 #include <linux/module.h>
 #include <linux/personality.h>
 #include <linux/kallsyms.h>
 #include <linux/hardirq.h>
 #include <linux/kdebug.h>
 #include <linux/sched/task_stack.h>
 #include <linux/uaccess.h>
 #include <linux/ftrace.h>

 #include <asm/proc-fns.h>
 #include <asm/unistd.h>

 #include <linux/ptrace.h>
 #include <nds32_intrinsic.h>

 extern void show_pte(struct mm_struct *mm, unsigned long addr);

 /*
  * Dump out the contents of some memory nicely...
  */
 void dump_mem(const char *lvl, unsigned long bottom, unsigned long top)
 {
 	unsigned long first;
 	mm_segment_t fs;
 	int i;

 	/*
 	 * We need to switch to kernel mode so that we can use __get_user
 	 * to safely read from kernel space.  Note that we now dump the
 	 * code first, just in case the backtrace kills us.
 	 */
 	fs = get_fs();
 	set_fs(KERNEL_DS);

 	pr_emerg("%s(0x%08lx to 0x%08lx)\n", lvl, bottom, top);

 	for (first = bottom & ~31; first < top; first += 32) {
 		unsigned long p;
 		char str[sizeof(" 12345678") * 8 + 1];

 		memset(str, ' ', sizeof(str));
 		str[sizeof(str) - 1] = '\0';

 		for (p = first, i = 0; i < 8 && p < top; i++, p += 4) {
 			if (p >= bottom && p < top) {
 				unsigned long val;
 				if (__get_user(val, (unsigned long *)p) == 0)
 					sprintf(str + i * 9, " %08lx", val);
 				else
 					sprintf(str + i * 9, " ????????");
 			}
 		}
 		pr_emerg("%s%04lx:%s\n", lvl, first & 0xffff, str);
 	}

 	set_fs(fs);
 }

 EXPORT_SYMBOL(dump_mem);

 static void dump_instr(struct pt_regs *regs)
 {
 	unsigned long addr = instruction_pointer(regs);
 	mm_segment_t fs;
 	char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
 	int i;

 	return;
 	/*
 	 * We need to switch to kernel mode so that we can use __get_user
 	 * to safely read from kernel space.  Note that we now dump the
 	 * code first, just in case the backtrace kills us.
 	 */
 	fs = get_fs();
 	set_fs(KERNEL_DS);

 	pr_emerg("Code: ");
 	for (i = -4; i < 1; i++) {
 		unsigned int val, bad;

 		bad = __get_user(val, &((u32 *) addr)[i]);

 		if (!bad) {
 			p += sprintf(p, i == 0 ? "(%08x) " : "%08x ", val);
 		} else {
 			p += sprintf(p, "bad PC value");
 			break;
 		}
 	}
 	pr_emerg("Code: %s\n", str);

 	set_fs(fs);
 }

 #define LOOP_TIMES (100)
 static void __dump(struct task_struct *tsk, unsigned long *base_reg)
 {
 	unsigned long ret_addr;
 	int cnt = LOOP_TIMES, graph = 0;
 	pr_emerg("Call Trace:\n");
 	if (!IS_ENABLED(CONFIG_FRAME_POINTER)) {
 		while (!kstack_end(base_reg)) {
 			ret_addr = *base_reg++;
 			if (__kernel_text_address(ret_addr)) {
 				ret_addr = ftrace_graph_ret_addr(
 						tsk, &graph, ret_addr, NULL);
 				print_ip_sym(ret_addr);
 			}
 			if (--cnt < 0)
 				break;
 		}
 	} else {
 		while (!kstack_end((void *)base_reg) &&
 		       !((unsigned long)base_reg & 0x3) &&
 		       ((unsigned long)base_reg >= TASK_SIZE)) {
 			unsigned long next_fp;
 			ret_addr = base_reg[LP_OFFSET];
 			next_fp = base_reg[FP_OFFSET];
 			if (__kernel_text_address(ret_addr)) {

 				ret_addr = ftrace_graph_ret_addr(
 						tsk, &graph, ret_addr, NULL);
 				print_ip_sym(ret_addr);
 			}
 			if (--cnt < 0)
 				break;
 			base_reg = (unsigned long *)next_fp;
 		}
 	}
 	pr_emerg("\n");
 }

 void show_stack(struct task_struct *tsk, unsigned long *sp)
 {
 	unsigned long *base_reg;

 	if (!tsk)
 		tsk = current;
 	if (!IS_ENABLED(CONFIG_FRAME_POINTER)) {
 		if (tsk != current)
 			base_reg = (unsigned long *)(tsk->thread.cpu_context.sp);
 		else
 			__asm__ __volatile__("\tori\t%0, $sp, #0\n":"=r"(base_reg));
 	} else {
 		if (tsk != current)
 			base_reg = (unsigned long *)(tsk->thread.cpu_context.fp);
 		else
 			__asm__ __volatile__("\tori\t%0, $fp, #0\n":"=r"(base_reg));
 	}
 	__dump(tsk, base_reg);
 	barrier();
 }

 DEFINE_SPINLOCK(die_lock);

 /*
  * This function is protected against re-entrancy.
  */
 void die(const char *str, struct pt_regs *regs, int err)
 {
 	struct task_struct *tsk = current;
 	static int die_counter;

 	console_verbose();
 	spin_lock_irq(&die_lock);
 	bust_spinlocks(1);

 	pr_emerg("Internal error: %s: %x [#%d]\n", str, err, ++die_counter);
 	print_modules();
 	pr_emerg("CPU: %i\n", smp_processor_id());
 	show_regs(regs);
 	pr_emerg("Process %s (pid: %d, stack limit = 0x%p)\n",
 		 tsk->comm, tsk->pid, end_of_stack(tsk));

 	if (!user_mode(regs) || in_interrupt()) {
 		dump_mem("Stack: ", regs->sp, (regs->sp + PAGE_SIZE) & PAGE_MASK);
 		dump_instr(regs);
 		dump_stack();
 	}

 	bust_spinlocks(0);
 	spin_unlock_irq(&die_lock);
 	do_exit(SIGSEGV);
 }

 EXPORT_SYMBOL(die);

 void die_if_kernel(const char *str, struct pt_regs *regs, int err)
 {
 	if (user_mode(regs))
 		return;

 	die(str, regs, err);
 }

 int bad_syscall(int n, struct pt_regs *regs)
 {
 	if (current->personality != PER_LINUX) {
 		send_sig(SIGSEGV, current, 1);
 		return regs->uregs[0];
 	}

 	force_sig_fault(SIGILL, ILL_ILLTRP,
 			(void __user *)instruction_pointer(regs) - 4, current);
 	die_if_kernel("Oops - bad syscall", regs, n);
 	return regs->uregs[0];
 }

 void __pte_error(const char *file, int line, unsigned long val)
 {
 	pr_emerg("%s:%d: bad pte %08lx.\n", file, line, val);
 }

 void __pmd_error(const char *file, int line, unsigned long val)
 {
 	pr_emerg("%s:%d: bad pmd %08lx.\n", file, line, val);
 }

 void __pgd_error(const char *file, int line, unsigned long val)
 {
 	pr_emerg("%s:%d: bad pgd %08lx.\n", file, line, val);
 }

 extern char *exception_vector, *exception_vector_end;
 void __init trap_init(void)
 {
 	return;
 }

 void __init early_trap_init(void)
 {
 	unsigned long ivb = 0;
 	unsigned long base = PAGE_OFFSET;

 	memcpy((unsigned long *)base, (unsigned long *)&exception_vector,
 	       ((unsigned long)&exception_vector_end -
 		(unsigned long)&exception_vector));
 	ivb = __nds32__mfsr(NDS32_SR_IVB);
 	/* Check platform support. */
 	if (((ivb & IVB_mskNIVIC) >> IVB_offNIVIC) < 2)
 		panic
 		    ("IVIC mode is not allowed on the platform with interrupt controller\n");
 	__nds32__mtsr((ivb & ~IVB_mskESZ) | (IVB_valESZ16 << IVB_offESZ) |
 		      IVB_BASE, NDS32_SR_IVB);
 	__nds32__mtsr(INT_MASK_INITAIAL_VAL, NDS32_SR_INT_MASK);

 	/*
 	 * 0x800 = 128 vectors * 16byte.
 	 * It should be enough to flush a page.
 	 */
 	cpu_cache_wbinval_page(base, true);
 }

 void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
 		  int error_code, int si_code)
 {
 	tsk->thread.trap_no = ENTRY_DEBUG_RELATED;
 	tsk->thread.error_code = error_code;

 	force_sig_fault(SIGTRAP, si_code,
 			(void __user *)instruction_pointer(regs), tsk);
 }

 void do_debug_trap(unsigned long entry, unsigned long addr,
 		   unsigned long type, struct pt_regs *regs)
 {
 	if (notify_die(DIE_OOPS, "Oops", regs, addr, type, SIGTRAP)
 	    == NOTIFY_STOP)
 		return;

 	if (user_mode(regs)) {
 		/* trap_signal */
 		send_sigtrap(current, regs, 0, TRAP_BRKPT);
 	} else {
 		/* kernel_trap */
 		if (!fixup_exception(regs))
 			die("unexpected kernel_trap", regs, 0);
 	}
 }

 void unhandled_interruption(struct pt_regs *regs)
 {
 	pr_emerg("unhandled_interruption\n");
 	show_regs(regs);
 	if (!user_mode(regs))
 		do_exit(SIGKILL);
 	force_sig(SIGKILL, current);
 }

 void unhandled_exceptions(unsigned long entry, unsigned long addr,
 			  unsigned long type, struct pt_regs *regs)
 {
 	pr_emerg("Unhandled Exception: entry: %lx addr:%lx itype:%lx\n", entry,
 		 addr, type);
 	show_regs(regs);
 	if (!user_mode(regs))
 		do_exit(SIGKILL);
 	force_sig(SIGKILL, current);
 }

 extern int do_page_fault(unsigned long entry, unsigned long addr,
 			 unsigned int error_code, struct pt_regs *regs);

 /*
  * 2:DEF dispatch for TLB MISC exception handler
 */

 void do_dispatch_tlb_misc(unsigned long entry, unsigned long addr,
 			  unsigned long type, struct pt_regs *regs)
 {
 	type = type & (ITYPE_mskINST | ITYPE_mskETYPE);
 	if ((type & ITYPE_mskETYPE) < 5) {
 		/* Permission exceptions */
 		do_page_fault(entry, addr, type, regs);
 	} else
 		unhandled_exceptions(entry, addr, type, regs);
 }

 void do_revinsn(struct pt_regs *regs)
 {
 	pr_emerg("Reserved Instruction\n");
 	show_regs(regs);
 	if (!user_mode(regs))
 		do_exit(SIGILL);
 	force_sig(SIGILL, current);
 }

 #ifdef CONFIG_ALIGNMENT_TRAP
 extern int unalign_access_mode;
 extern int do_unaligned_access(unsigned long addr, struct pt_regs *regs);
 #endif
 void do_dispatch_general(unsigned long entry, unsigned long addr,
 			 unsigned long itype, struct pt_regs *regs,
 			 unsigned long oipc)
 {
 	unsigned int swid = itype >> ITYPE_offSWID;
 	unsigned long type = itype & (ITYPE_mskINST | ITYPE_mskETYPE);
 	if (type == ETYPE_ALIGNMENT_CHECK) {
 #ifdef CONFIG_ALIGNMENT_TRAP
 		/* Alignment check */
 		if (user_mode(regs) && unalign_access_mode) {
 			int ret;
 			ret = do_unaligned_access(addr, regs);

 			if (ret == 0)
 				return;

 			if (ret == -EFAULT)
 				pr_emerg
 				    ("Unhandled unaligned access exception\n");
 		}
 #endif
 		do_page_fault(entry, addr, type, regs);
 	} else if (type == ETYPE_RESERVED_INSTRUCTION) {
 		/* Reserved instruction */
 		do_revinsn(regs);
 	} else if (type == ETYPE_TRAP && swid == SWID_RAISE_INTERRUPT_LEVEL) {
 		/* trap, used on v3 EDM target debugging workaround */
 		/*
 		 * DIPC(OIPC) is passed as parameter before
 		 * interrupt is enabled, so the DIPC will not be corrupted
 		 * even though interrupts are coming in
 		 */
 		/*
 		 * 1. update ipc
 		 * 2. update pt_regs ipc with oipc
 		 * 3. update pt_regs ipsw (clear DEX)
 		 */
 		__asm__ volatile ("mtsr %0, $IPC\n\t"::"r" (oipc));
 		regs->ipc = oipc;
 		if (regs->pipsw & PSW_mskDEX) {
 			pr_emerg
 			    ("Nested Debug exception is possibly happened\n");
 			pr_emerg("ipc:%08x pipc:%08x\n",
 				 (unsigned int)regs->ipc,
 				 (unsigned int)regs->pipc);
 		}
 		do_debug_trap(entry, addr, itype, regs);
 		regs->ipsw &= ~PSW_mskDEX;
 	} else
 		unhandled_exceptions(entry, addr, type, regs);
 }
	// SPDX-License-Identifier: GPL-2.0
	// Copyright (C) 2005-2017 Andes Technology Corporation

	#include <linux/module.h>
	#include <linux/personality.h>
	#include <linux/kallsyms.h>
	#include <linux/hardirq.h>
	#include <linux/kdebug.h>
	#include <linux/sched/task_stack.h>
	#include <linux/uaccess.h>
	#include <linux/ftrace.h>

	#include <asm/proc-fns.h>
	#include <asm/unistd.h>

	#include <linux/ptrace.h>
	#include <nds32_intrinsic.h>

	extern void show_pte(struct mm_struct *mm, unsigned long addr);

	/*
	* Dump out the contents of some memory nicely...
	*/
	void dump_mem(const char *lvl, unsigned long bottom, unsigned long top)
	{
	unsigned long first;
	mm_segment_t fs;
	int i;

	/*
	* We need to switch to kernel mode so that we can use __get_user
	* to safely read from kernel space. Note that we now dump the
	* code first, just in case the backtrace kills us.
	*/
	fs = get_fs();
	set_fs(KERNEL_DS);

	pr_emerg("%s(0x%08lx to 0x%08lx)\n", lvl, bottom, top);

	for (first = bottom & ~31; first < top; first += 32) {
	unsigned long p;
	char str[sizeof(" 12345678") * 8 + 1];

	memset(str, ' ', sizeof(str));
	str[sizeof(str) - 1] = '\0';

	for (p = first, i = 0; i < 8 && p < top; i++, p += 4) {
	if (p >= bottom && p < top) {
	unsigned long val;
	if (__get_user(val, (unsigned long *)p) == 0)
	sprintf(str + i * 9, " %08lx", val);
	else
	sprintf(str + i * 9, " ????????");
	}
	}
	pr_emerg("%s%04lx:%s\n", lvl, first & 0xffff, str);
	}

	set_fs(fs);
	}

	EXPORT_SYMBOL(dump_mem);

	static void dump_instr(struct pt_regs *regs)
	{
	unsigned long addr = instruction_pointer(regs);
	mm_segment_t fs;
	char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
	int i;

	return;
	/*
	* We need to switch to kernel mode so that we can use __get_user
	* to safely read from kernel space. Note that we now dump the
	* code first, just in case the backtrace kills us.
	*/
	fs = get_fs();
	set_fs(KERNEL_DS);

	pr_emerg("Code: ");
	for (i = -4; i < 1; i++) {
	unsigned int val, bad;

	bad = __get_user(val, &((u32 *) addr)[i]);

	if (!bad) {
	p += sprintf(p, i == 0 ? "(%08x) " : "%08x ", val);
	} else {
	p += sprintf(p, "bad PC value");
	break;
	}
	}
	pr_emerg("Code: %s\n", str);

	set_fs(fs);
	}

	#define LOOP_TIMES (100)
	static void __dump(struct task_struct tsk, unsigned long base_reg)
	{
	unsigned long ret_addr;
	int cnt = LOOP_TIMES, graph = 0;
	pr_emerg("Call Trace:\n");
	if (!IS_ENABLED(CONFIG_FRAME_POINTER)) {
	while (!kstack_end(base_reg)) {
	ret_addr = *base_reg++;
	if (__kernel_text_address(ret_addr)) {
	ret_addr = ftrace_graph_ret_addr(
	tsk, &graph, ret_addr, NULL);
	print_ip_sym(ret_addr);
	}
	if (--cnt < 0)
	break;
	}
	} else {
	while (!kstack_end((void *)base_reg) &&
	!((unsigned long)base_reg & 0x3) &&
	((unsigned long)base_reg >= TASK_SIZE)) {
	unsigned long next_fp;
	ret_addr = base_reg[LP_OFFSET];
	next_fp = base_reg[FP_OFFSET];
	if (__kernel_text_address(ret_addr)) {

	ret_addr = ftrace_graph_ret_addr(
	tsk, &graph, ret_addr, NULL);
	print_ip_sym(ret_addr);
	}
	if (--cnt < 0)
	break;
	base_reg = (unsigned long *)next_fp;
	}
	}
	pr_emerg("\n");
	}

	void show_stack(struct task_struct tsk, unsigned long sp)
	{
	unsigned long *base_reg;

	if (!tsk)
	tsk = current;
	if (!IS_ENABLED(CONFIG_FRAME_POINTER)) {
	if (tsk != current)
	base_reg = (unsigned long *)(tsk->thread.cpu_context.sp);
	else
	__asm__ __volatile__("\tori\t%0, $sp, #0\n":"=r"(base_reg));
	} else {
	if (tsk != current)
	base_reg = (unsigned long *)(tsk->thread.cpu_context.fp);
	else
	__asm__ __volatile__("\tori\t%0, $fp, #0\n":"=r"(base_reg));
	}
	__dump(tsk, base_reg);
	barrier();
	}

	DEFINE_SPINLOCK(die_lock);

	/*
	* This function is protected against re-entrancy.
	*/
	void die(const char str, struct pt_regs regs, int err)
	{
	struct task_struct *tsk = current;
	static int die_counter;

	console_verbose();
	spin_lock_irq(&die_lock);
	bust_spinlocks(1);

	pr_emerg("Internal error: %s: %x [#%d]\n", str, err, ++die_counter);
	print_modules();
	pr_emerg("CPU: %i\n", smp_processor_id());
	show_regs(regs);
	pr_emerg("Process %s (pid: %d, stack limit = 0x%p)\n",
	tsk->comm, tsk->pid, end_of_stack(tsk));

	if (!user_mode(regs) \|\| in_interrupt()) {
	dump_mem("Stack: ", regs->sp, (regs->sp + PAGE_SIZE) & PAGE_MASK);
	dump_instr(regs);
	dump_stack();
	}

	bust_spinlocks(0);
	spin_unlock_irq(&die_lock);
	do_exit(SIGSEGV);
	}

	EXPORT_SYMBOL(die);

	void die_if_kernel(const char str, struct pt_regs regs, int err)
	{
	if (user_mode(regs))
	return;

	die(str, regs, err);
	}

	int bad_syscall(int n, struct pt_regs *regs)
	{
	if (current->personality != PER_LINUX) {
	send_sig(SIGSEGV, current, 1);
	return regs->uregs[0];
	}

	force_sig_fault(SIGILL, ILL_ILLTRP,
	(void __user *)instruction_pointer(regs) - 4, current);
	die_if_kernel("Oops - bad syscall", regs, n);
	return regs->uregs[0];
	}

	void __pte_error(const char *file, int line, unsigned long val)
	{
	pr_emerg("%s:%d: bad pte %08lx.\n", file, line, val);
	}

	void __pmd_error(const char *file, int line, unsigned long val)
	{
	pr_emerg("%s:%d: bad pmd %08lx.\n", file, line, val);
	}

	void __pgd_error(const char *file, int line, unsigned long val)
	{
	pr_emerg("%s:%d: bad pgd %08lx.\n", file, line, val);
	}

	extern char exception_vector, exception_vector_end;
	void __init trap_init(void)
	{
	return;
	}

	void __init early_trap_init(void)
	{
	unsigned long ivb = 0;
	unsigned long base = PAGE_OFFSET;

	memcpy((unsigned long )base, (unsigned long )&exception_vector,
	((unsigned long)&exception_vector_end -
	(unsigned long)&exception_vector));
	ivb = __nds32__mfsr(NDS32_SR_IVB);
	/* Check platform support. */
	if (((ivb & IVB_mskNIVIC) >> IVB_offNIVIC) < 2)
	panic
	("IVIC mode is not allowed on the platform with interrupt controller\n");
	__nds32__mtsr((ivb & ~IVB_mskESZ) \| (IVB_valESZ16 << IVB_offESZ) \|
	IVB_BASE, NDS32_SR_IVB);
	__nds32__mtsr(INT_MASK_INITAIAL_VAL, NDS32_SR_INT_MASK);

	/*
	* 0x800 = 128 vectors * 16byte.
	* It should be enough to flush a page.
	*/
	cpu_cache_wbinval_page(base, true);
	}

	void send_sigtrap(struct task_struct tsk, struct pt_regs regs,
	int error_code, int si_code)
	{
	tsk->thread.trap_no = ENTRY_DEBUG_RELATED;
	tsk->thread.error_code = error_code;

	force_sig_fault(SIGTRAP, si_code,
	(void __user *)instruction_pointer(regs), tsk);
	}

	void do_debug_trap(unsigned long entry, unsigned long addr,
	unsigned long type, struct pt_regs *regs)
	{
	if (notify_die(DIE_OOPS, "Oops", regs, addr, type, SIGTRAP)
	== NOTIFY_STOP)
	return;

	if (user_mode(regs)) {
	/* trap_signal */
	send_sigtrap(current, regs, 0, TRAP_BRKPT);
	} else {
	/* kernel_trap */
	if (!fixup_exception(regs))
	die("unexpected kernel_trap", regs, 0);
	}
	}

	void unhandled_interruption(struct pt_regs *regs)
	{
	pr_emerg("unhandled_interruption\n");
	show_regs(regs);
	if (!user_mode(regs))
	do_exit(SIGKILL);
	force_sig(SIGKILL, current);
	}

	void unhandled_exceptions(unsigned long entry, unsigned long addr,
	unsigned long type, struct pt_regs *regs)
	{
	pr_emerg("Unhandled Exception: entry: %lx addr:%lx itype:%lx\n", entry,
	addr, type);
	show_regs(regs);
	if (!user_mode(regs))
	do_exit(SIGKILL);
	force_sig(SIGKILL, current);
	}

	extern int do_page_fault(unsigned long entry, unsigned long addr,
	unsigned int error_code, struct pt_regs *regs);

	/*
	* 2:DEF dispatch for TLB MISC exception handler
	*/

	void do_dispatch_tlb_misc(unsigned long entry, unsigned long addr,
	unsigned long type, struct pt_regs *regs)
	{
	type = type & (ITYPE_mskINST \| ITYPE_mskETYPE);
	if ((type & ITYPE_mskETYPE) < 5) {
	/* Permission exceptions */
	do_page_fault(entry, addr, type, regs);
	} else
	unhandled_exceptions(entry, addr, type, regs);
	}

	void do_revinsn(struct pt_regs *regs)
	{
	pr_emerg("Reserved Instruction\n");
	show_regs(regs);
	if (!user_mode(regs))
	do_exit(SIGILL);
	force_sig(SIGILL, current);
	}

	#ifdef CONFIG_ALIGNMENT_TRAP
	extern int unalign_access_mode;
	extern int do_unaligned_access(unsigned long addr, struct pt_regs *regs);
	#endif
	void do_dispatch_general(unsigned long entry, unsigned long addr,
	unsigned long itype, struct pt_regs *regs,
	unsigned long oipc)
	{
	unsigned int swid = itype >> ITYPE_offSWID;
	unsigned long type = itype & (ITYPE_mskINST \| ITYPE_mskETYPE);
	if (type == ETYPE_ALIGNMENT_CHECK) {
	#ifdef CONFIG_ALIGNMENT_TRAP
	/* Alignment check */
	if (user_mode(regs) && unalign_access_mode) {
	int ret;
	ret = do_unaligned_access(addr, regs);

	if (ret == 0)
	return;

	if (ret == -EFAULT)
	pr_emerg
	("Unhandled unaligned access exception\n");
	}
	#endif
	do_page_fault(entry, addr, type, regs);
	} else if (type == ETYPE_RESERVED_INSTRUCTION) {
	/* Reserved instruction */
	do_revinsn(regs);
	} else if (type == ETYPE_TRAP && swid == SWID_RAISE_INTERRUPT_LEVEL) {
	/* trap, used on v3 EDM target debugging workaround */
	/*
	* DIPC(OIPC) is passed as parameter before
	* interrupt is enabled, so the DIPC will not be corrupted
	* even though interrupts are coming in
	*/
	/*
	* 1. update ipc
	* 2. update pt_regs ipc with oipc
	* 3. update pt_regs ipsw (clear DEX)
	*/
	__asm__ volatile ("mtsr %0, $IPC\n\t"::"r" (oipc));
	regs->ipc = oipc;
	if (regs->pipsw & PSW_mskDEX) {
	pr_emerg
	("Nested Debug exception is possibly happened\n");
	pr_emerg("ipc:%08x pipc:%08x\n",
	(unsigned int)regs->ipc,
	(unsigned int)regs->pipc);
	}
	do_debug_trap(entry, addr, itype, regs);
	regs->ipsw &= ~PSW_mskDEX;
	} else
	unhandled_exceptions(entry, addr, type, regs);
	}