arch/arm/kernel/process.c - maze/linux - Git at Google

 /*
  *  linux/arch/arm/kernel/process.c
  *
  *  Copyright (C) 1996-2000 Russell King - Converted to ARM.
  *  Original Copyright (C) 1995  Linus Torvalds
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
 #include <stdarg.h>

 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/stddef.h>
 #include <linux/unistd.h>
 #include <linux/user.h>
 #include <linux/delay.h>
 #include <linux/reboot.h>
 #include <linux/interrupt.h>
 #include <linux/kallsyms.h>
 #include <linux/init.h>
 #include <linux/cpu.h>
 #include <linux/elfcore.h>
 #include <linux/pm.h>
 #include <linux/tick.h>
 #include <linux/utsname.h>
 #include <linux/uaccess.h>

 #include <asm/leds.h>
 #include <asm/processor.h>
 #include <asm/system.h>
 #include <asm/thread_notify.h>
 #include <asm/stacktrace.h>
 #include <asm/mach/time.h>

 static const char *processor_modes[] = {
   "USER_26", "FIQ_26" , "IRQ_26" , "SVC_26" , "UK4_26" , "UK5_26" , "UK6_26" , "UK7_26" ,
   "UK8_26" , "UK9_26" , "UK10_26", "UK11_26", "UK12_26", "UK13_26", "UK14_26", "UK15_26",
   "USER_32", "FIQ_32" , "IRQ_32" , "SVC_32" , "UK4_32" , "UK5_32" , "UK6_32" , "ABT_32" ,
   "UK8_32" , "UK9_32" , "UK10_32", "UND_32" , "UK12_32", "UK13_32", "UK14_32", "SYS_32"
 };

 static const char *isa_modes[] = {
   "ARM" , "Thumb" , "Jazelle", "ThumbEE"
 };

 extern void setup_mm_for_reboot(char mode);

 static volatile int hlt_counter;

 #include <mach/system.h>

 void disable_hlt(void)
 {
 	hlt_counter++;
 }

 EXPORT_SYMBOL(disable_hlt);

 void enable_hlt(void)
 {
 	hlt_counter--;
 }

 EXPORT_SYMBOL(enable_hlt);

 static int __init nohlt_setup(char *__unused)
 {
 	hlt_counter = 1;
 	return 1;
 }

 static int __init hlt_setup(char *__unused)
 {
 	hlt_counter = 0;
 	return 1;
 }

 __setup("nohlt", nohlt_setup);
 __setup("hlt", hlt_setup);

 void arm_machine_restart(char mode, const char *cmd)
 {
 	/*
 	 * Clean and disable cache, and turn off interrupts
 	 */
 	cpu_proc_fin();

 	/*
 	 * Tell the mm system that we are going to reboot -
 	 * we may need it to insert some 1:1 mappings so that
 	 * soft boot works.
 	 */
 	setup_mm_for_reboot(mode);

 	/*
 	 * Now call the architecture specific reboot code.
 	 */
 	arch_reset(mode, cmd);

 	/*
 	 * Whoops - the architecture was unable to reboot.
 	 * Tell the user!
 	 */
 	mdelay(1000);
 	printk("Reboot failed -- System halted\n");
 	while (1);
 }

 /*
  * Function pointers to optional machine specific functions
  */
 void (*pm_power_off)(void);
 EXPORT_SYMBOL(pm_power_off);

 void (*arm_pm_restart)(char str, const char *cmd) = arm_machine_restart;
 EXPORT_SYMBOL_GPL(arm_pm_restart);


 /*
  * This is our default idle handler.  We need to disable
  * interrupts here to ensure we don't miss a wakeup call.
  */
 static void default_idle(void)
 {
 	if (!need_resched())
 		arch_idle();
 	local_irq_enable();
 }

 void (*pm_idle)(void) = default_idle;
 EXPORT_SYMBOL(pm_idle);

 /*
  * The idle thread, has rather strange semantics for calling pm_idle,
  * but this is what x86 does and we need to do the same, so that
  * things like cpuidle get called in the same way.  The only difference
  * is that we always respect 'hlt_counter' to prevent low power idle.
  */
 void cpu_idle(void)
 {
 	local_fiq_enable();

 	/* endless idle loop with no priority at all */
 	while (1) {
 		tick_nohz_stop_sched_tick(1);
 		leds_event(led_idle_start);
 		while (!need_resched()) {
 #ifdef CONFIG_HOTPLUG_CPU
 			if (cpu_is_offline(smp_processor_id()))
 				cpu_die();
 #endif

 			local_irq_disable();
 			if (hlt_counter) {
 				local_irq_enable();
 				cpu_relax();
 			} else {
 				stop_critical_timings();
 				pm_idle();
 				start_critical_timings();
 				/*
 				 * This will eventually be removed - pm_idle
 				 * functions should always return with IRQs
 				 * enabled.
 				 */
 				WARN_ON(irqs_disabled());
 				local_irq_enable();
 			}
 		}
 		leds_event(led_idle_end);
 		tick_nohz_restart_sched_tick();
 		preempt_enable_no_resched();
 		schedule();
 		preempt_disable();
 	}
 }

 static char reboot_mode = 'h';

 int __init reboot_setup(char *str)
 {
 	reboot_mode = str[0];
 	return 1;
 }

 __setup("reboot=", reboot_setup);

 void machine_halt(void)
 {
 }


 void machine_power_off(void)
 {
 	if (pm_power_off)
 		pm_power_off();
 }

 void machine_restart(char *cmd)
 {
 	arm_pm_restart(reboot_mode, cmd);
 }

 void __show_regs(struct pt_regs *regs)
 {
 	unsigned long flags;
 	char buf[64];

 	printk("CPU: %d    %s  (%s %.*s)\n",
 		raw_smp_processor_id(), print_tainted(),
 		init_utsname()->release,
 		(int)strcspn(init_utsname()->version, " "),
 		init_utsname()->version);
 	print_symbol("PC is at %s\n", instruction_pointer(regs));
 	print_symbol("LR is at %s\n", regs->ARM_lr);
 	printk("pc : [<%08lx>]    lr : [<%08lx>]    psr: %08lx\n"
 	       "sp : %08lx  ip : %08lx  fp : %08lx\n",
 		regs->ARM_pc, regs->ARM_lr, regs->ARM_cpsr,
 		regs->ARM_sp, regs->ARM_ip, regs->ARM_fp);
 	printk("r10: %08lx  r9 : %08lx  r8 : %08lx\n",
 		regs->ARM_r10, regs->ARM_r9,
 		regs->ARM_r8);
 	printk("r7 : %08lx  r6 : %08lx  r5 : %08lx  r4 : %08lx\n",
 		regs->ARM_r7, regs->ARM_r6,
 		regs->ARM_r5, regs->ARM_r4);
 	printk("r3 : %08lx  r2 : %08lx  r1 : %08lx  r0 : %08lx\n",
 		regs->ARM_r3, regs->ARM_r2,
 		regs->ARM_r1, regs->ARM_r0);

 	flags = regs->ARM_cpsr;
 	buf[0] = flags & PSR_N_BIT ? 'N' : 'n';
 	buf[1] = flags & PSR_Z_BIT ? 'Z' : 'z';
 	buf[2] = flags & PSR_C_BIT ? 'C' : 'c';
 	buf[3] = flags & PSR_V_BIT ? 'V' : 'v';
 	buf[4] = '\0';

 	printk("Flags: %s  IRQs o%s  FIQs o%s  Mode %s  ISA %s  Segment %s\n",
 		buf, interrupts_enabled(regs) ? "n" : "ff",
 		fast_interrupts_enabled(regs) ? "n" : "ff",
 		processor_modes[processor_mode(regs)],
 		isa_modes[isa_mode(regs)],
 		get_fs() == get_ds() ? "kernel" : "user");
 #ifdef CONFIG_CPU_CP15
 	{
 		unsigned int ctrl;

 		buf[0] = '\0';
 #ifdef CONFIG_CPU_CP15_MMU
 		{
 			unsigned int transbase, dac;
 			asm("mrc p15, 0, %0, c2, c0\n\t"
 			    "mrc p15, 0, %1, c3, c0\n"
 			    : "=r" (transbase), "=r" (dac));
 			snprintf(buf, sizeof(buf), "  Table: %08x  DAC: %08x",
 			  	transbase, dac);
 		}
 #endif
 		asm("mrc p15, 0, %0, c1, c0\n" : "=r" (ctrl));

 		printk("Control: %08x%s\n", ctrl, buf);
 	}
 #endif
 }

 void show_regs(struct pt_regs * regs)
 {
 	printk("\n");
 	printk("Pid: %d, comm: %20s\n", task_pid_nr(current), current->comm);
 	__show_regs(regs);
 	__backtrace();
 }

 ATOMIC_NOTIFIER_HEAD(thread_notify_head);

 EXPORT_SYMBOL_GPL(thread_notify_head);

 /*
  * Free current thread data structures etc..
  */
 void exit_thread(void)
 {
 	thread_notify(THREAD_NOTIFY_EXIT, current_thread_info());
 }

 void flush_thread(void)
 {
 	struct thread_info *thread = current_thread_info();
 	struct task_struct *tsk = current;

 	memset(thread->used_cp, 0, sizeof(thread->used_cp));
 	memset(&tsk->thread.debug, 0, sizeof(struct debug_info));
 	memset(&thread->fpstate, 0, sizeof(union fp_state));

 	thread_notify(THREAD_NOTIFY_FLUSH, thread);
 }

 void release_thread(struct task_struct *dead_task)
 {
 }

 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");

 int
 copy_thread(unsigned long clone_flags, unsigned long stack_start,
 	    unsigned long stk_sz, struct task_struct *p, struct pt_regs *regs)
 {
 	struct thread_info *thread = task_thread_info(p);
 	struct pt_regs *childregs = task_pt_regs(p);

 	*childregs = *regs;
 	childregs->ARM_r0 = 0;
 	childregs->ARM_sp = stack_start;

 	memset(&thread->cpu_context, 0, sizeof(struct cpu_context_save));
 	thread->cpu_context.sp = (unsigned long)childregs;
 	thread->cpu_context.pc = (unsigned long)ret_from_fork;

 	if (clone_flags & CLONE_SETTLS)
 		thread->tp_value = regs->ARM_r3;

 	return 0;
 }

 /*
  * Fill in the task's elfregs structure for a core dump.
  */
 int dump_task_regs(struct task_struct *t, elf_gregset_t *elfregs)
 {
 	elf_core_copy_regs(elfregs, task_pt_regs(t));
 	return 1;
 }

 /*
  * fill in the fpe structure for a core dump...
  */
 int dump_fpu (struct pt_regs *regs, struct user_fp *fp)
 {
 	struct thread_info *thread = current_thread_info();
 	int used_math = thread->used_cp[1] | thread->used_cp[2];

 	if (used_math)
 		memcpy(fp, &thread->fpstate.soft, sizeof (*fp));

 	return used_math != 0;
 }
 EXPORT_SYMBOL(dump_fpu);

 /*
  * Shuffle the argument into the correct register before calling the
  * thread function.  r1 is the thread argument, r2 is the pointer to
  * the thread function, and r3 points to the exit function.
  */
 extern void kernel_thread_helper(void);
 asm(	".pushsection .text\n"
 "	.align\n"
 "	.type	kernel_thread_helper, #function\n"
 "kernel_thread_helper:\n"
 "	mov	r0, r1\n"
 "	mov	lr, r3\n"
 "	mov	pc, r2\n"
 "	.size	kernel_thread_helper, . - kernel_thread_helper\n"
 "	.popsection");

 #ifdef CONFIG_ARM_UNWIND
 extern void kernel_thread_exit(long code);
 asm(	".pushsection .text\n"
 "	.align\n"
 "	.type	kernel_thread_exit, #function\n"
 "kernel_thread_exit:\n"
 "	.fnstart\n"
 "	.cantunwind\n"
 "	bl	do_exit\n"
 "	nop\n"
 "	.fnend\n"
 "	.size	kernel_thread_exit, . - kernel_thread_exit\n"
 "	.popsection");
 #else
 #define kernel_thread_exit	do_exit
 #endif

 /*
  * Create a kernel thread.
  */
 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 {
 	struct pt_regs regs;

 	memset(&regs, 0, sizeof(regs));

 	regs.ARM_r1 = (unsigned long)arg;
 	regs.ARM_r2 = (unsigned long)fn;
 	regs.ARM_r3 = (unsigned long)kernel_thread_exit;
 	regs.ARM_pc = (unsigned long)kernel_thread_helper;
 	regs.ARM_cpsr = SVC_MODE | PSR_ENDSTATE | PSR_ISETSTATE;

 	return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 }
 EXPORT_SYMBOL(kernel_thread);

 unsigned long get_wchan(struct task_struct *p)
 {
 	struct stackframe frame;
 	int count = 0;
 	if (!p || p == current || p->state == TASK_RUNNING)
 		return 0;

 	frame.fp = thread_saved_fp(p);
 	frame.sp = thread_saved_sp(p);
 	frame.lr = 0;			/* recovered from the stack */
 	frame.pc = thread_saved_pc(p);
 	do {
 		int ret = unwind_frame(&frame);
 		if (ret < 0)
 			return 0;
 		if (!in_sched_functions(frame.pc))
 			return frame.pc;
 	} while (count ++ < 16);
 	return 0;
 }
	/*
	* linux/arch/arm/kernel/process.c
	*
	* Copyright (C) 1996-2000 Russell King - Converted to ARM.
	* Original Copyright (C) 1995 Linus Torvalds
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/
	#include <stdarg.h>

	#include <linux/module.h>
	#include <linux/sched.h>
	#include <linux/kernel.h>
	#include <linux/mm.h>
	#include <linux/stddef.h>
	#include <linux/unistd.h>
	#include <linux/user.h>
	#include <linux/delay.h>
	#include <linux/reboot.h>
	#include <linux/interrupt.h>
	#include <linux/kallsyms.h>
	#include <linux/init.h>
	#include <linux/cpu.h>
	#include <linux/elfcore.h>
	#include <linux/pm.h>
	#include <linux/tick.h>
	#include <linux/utsname.h>
	#include <linux/uaccess.h>

	#include <asm/leds.h>
	#include <asm/processor.h>
	#include <asm/system.h>
	#include <asm/thread_notify.h>
	#include <asm/stacktrace.h>
	#include <asm/mach/time.h>

	static const char *processor_modes[] = {
	"USER_26", "FIQ_26" , "IRQ_26" , "SVC_26" , "UK4_26" , "UK5_26" , "UK6_26" , "UK7_26" ,
	"UK8_26" , "UK9_26" , "UK10_26", "UK11_26", "UK12_26", "UK13_26", "UK14_26", "UK15_26",
	"USER_32", "FIQ_32" , "IRQ_32" , "SVC_32" , "UK4_32" , "UK5_32" , "UK6_32" , "ABT_32" ,
	"UK8_32" , "UK9_32" , "UK10_32", "UND_32" , "UK12_32", "UK13_32", "UK14_32", "SYS_32"
	};

	static const char *isa_modes[] = {
	"ARM" , "Thumb" , "Jazelle", "ThumbEE"
	};

	extern void setup_mm_for_reboot(char mode);

	static volatile int hlt_counter;

	#include <mach/system.h>

	void disable_hlt(void)
	{
	hlt_counter++;
	}

	EXPORT_SYMBOL(disable_hlt);

	void enable_hlt(void)
	{
	hlt_counter--;
	}

	EXPORT_SYMBOL(enable_hlt);

	static int __init nohlt_setup(char *__unused)
	{
	hlt_counter = 1;
	return 1;
	}

	static int __init hlt_setup(char *__unused)
	{
	hlt_counter = 0;
	return 1;
	}

	__setup("nohlt", nohlt_setup);
	__setup("hlt", hlt_setup);

	void arm_machine_restart(char mode, const char *cmd)
	{
	/*
	* Clean and disable cache, and turn off interrupts
	*/
	cpu_proc_fin();

	/*
	* Tell the mm system that we are going to reboot -
	* we may need it to insert some 1:1 mappings so that
	* soft boot works.
	*/
	setup_mm_for_reboot(mode);

	/*
	* Now call the architecture specific reboot code.
	*/
	arch_reset(mode, cmd);

	/*
	* Whoops - the architecture was unable to reboot.
	* Tell the user!
	*/
	mdelay(1000);
	printk("Reboot failed -- System halted\n");
	while (1);
	}

	/*
	* Function pointers to optional machine specific functions
	*/
	void (*pm_power_off)(void);
	EXPORT_SYMBOL(pm_power_off);

	void (arm_pm_restart)(char str, const char cmd) = arm_machine_restart;
	EXPORT_SYMBOL_GPL(arm_pm_restart);


	/*
	* This is our default idle handler. We need to disable
	* interrupts here to ensure we don't miss a wakeup call.
	*/
	static void default_idle(void)
	{
	if (!need_resched())
	arch_idle();
	local_irq_enable();
	}

	void (*pm_idle)(void) = default_idle;
	EXPORT_SYMBOL(pm_idle);

	/*
	* The idle thread, has rather strange semantics for calling pm_idle,
	* but this is what x86 does and we need to do the same, so that
	* things like cpuidle get called in the same way. The only difference
	* is that we always respect 'hlt_counter' to prevent low power idle.
	*/
	void cpu_idle(void)
	{
	local_fiq_enable();

	/* endless idle loop with no priority at all */
	while (1) {
	tick_nohz_stop_sched_tick(1);
	leds_event(led_idle_start);
	while (!need_resched()) {
	#ifdef CONFIG_HOTPLUG_CPU
	if (cpu_is_offline(smp_processor_id()))
	cpu_die();
	#endif

	local_irq_disable();
	if (hlt_counter) {
	local_irq_enable();
	cpu_relax();
	} else {
	stop_critical_timings();
	pm_idle();
	start_critical_timings();
	/*
	* This will eventually be removed - pm_idle
	* functions should always return with IRQs
	* enabled.
	*/
	WARN_ON(irqs_disabled());
	local_irq_enable();
	}
	}
	leds_event(led_idle_end);
	tick_nohz_restart_sched_tick();
	preempt_enable_no_resched();
	schedule();
	preempt_disable();
	}
	}

	static char reboot_mode = 'h';

	int __init reboot_setup(char *str)
	{
	reboot_mode = str[0];
	return 1;
	}

	__setup("reboot=", reboot_setup);

	void machine_halt(void)
	{
	}


	void machine_power_off(void)
	{
	if (pm_power_off)
	pm_power_off();
	}

	void machine_restart(char *cmd)
	{
	arm_pm_restart(reboot_mode, cmd);
	}

	void __show_regs(struct pt_regs *regs)
	{
	unsigned long flags;
	char buf[64];

	printk("CPU: %d %s (%s %.*s)\n",
	raw_smp_processor_id(), print_tainted(),
	init_utsname()->release,
	(int)strcspn(init_utsname()->version, " "),
	init_utsname()->version);
	print_symbol("PC is at %s\n", instruction_pointer(regs));
	print_symbol("LR is at %s\n", regs->ARM_lr);
	printk("pc : [<%08lx>] lr : [<%08lx>] psr: %08lx\n"
	"sp : %08lx ip : %08lx fp : %08lx\n",
	regs->ARM_pc, regs->ARM_lr, regs->ARM_cpsr,
	regs->ARM_sp, regs->ARM_ip, regs->ARM_fp);
	printk("r10: %08lx r9 : %08lx r8 : %08lx\n",
	regs->ARM_r10, regs->ARM_r9,
	regs->ARM_r8);
	printk("r7 : %08lx r6 : %08lx r5 : %08lx r4 : %08lx\n",
	regs->ARM_r7, regs->ARM_r6,
	regs->ARM_r5, regs->ARM_r4);
	printk("r3 : %08lx r2 : %08lx r1 : %08lx r0 : %08lx\n",
	regs->ARM_r3, regs->ARM_r2,
	regs->ARM_r1, regs->ARM_r0);

	flags = regs->ARM_cpsr;
	buf[0] = flags & PSR_N_BIT ? 'N' : 'n';
	buf[1] = flags & PSR_Z_BIT ? 'Z' : 'z';
	buf[2] = flags & PSR_C_BIT ? 'C' : 'c';
	buf[3] = flags & PSR_V_BIT ? 'V' : 'v';
	buf[4] = '\0';

	printk("Flags: %s IRQs o%s FIQs o%s Mode %s ISA %s Segment %s\n",
	buf, interrupts_enabled(regs) ? "n" : "ff",
	fast_interrupts_enabled(regs) ? "n" : "ff",
	processor_modes[processor_mode(regs)],
	isa_modes[isa_mode(regs)],
	get_fs() == get_ds() ? "kernel" : "user");
	#ifdef CONFIG_CPU_CP15
	{
	unsigned int ctrl;

	buf[0] = '\0';
	#ifdef CONFIG_CPU_CP15_MMU
	{
	unsigned int transbase, dac;
	asm("mrc p15, 0, %0, c2, c0\n\t"
	"mrc p15, 0, %1, c3, c0\n"
	: "=r" (transbase), "=r" (dac));
	snprintf(buf, sizeof(buf), " Table: %08x DAC: %08x",
	transbase, dac);
	}
	#endif
	asm("mrc p15, 0, %0, c1, c0\n" : "=r" (ctrl));

	printk("Control: %08x%s\n", ctrl, buf);
	}
	#endif
	}

	void show_regs(struct pt_regs * regs)
	{
	printk("\n");
	printk("Pid: %d, comm: %20s\n", task_pid_nr(current), current->comm);
	__show_regs(regs);
	__backtrace();
	}

	ATOMIC_NOTIFIER_HEAD(thread_notify_head);

	EXPORT_SYMBOL_GPL(thread_notify_head);

	/*
	* Free current thread data structures etc..
	*/
	void exit_thread(void)
	{
	thread_notify(THREAD_NOTIFY_EXIT, current_thread_info());
	}

	void flush_thread(void)
	{
	struct thread_info *thread = current_thread_info();
	struct task_struct *tsk = current;

	memset(thread->used_cp, 0, sizeof(thread->used_cp));
	memset(&tsk->thread.debug, 0, sizeof(struct debug_info));
	memset(&thread->fpstate, 0, sizeof(union fp_state));

	thread_notify(THREAD_NOTIFY_FLUSH, thread);
	}

	void release_thread(struct task_struct *dead_task)
	{
	}

	asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");

	int
	copy_thread(unsigned long clone_flags, unsigned long stack_start,
	unsigned long stk_sz, struct task_struct p, struct pt_regs regs)
	{
	struct thread_info *thread = task_thread_info(p);
	struct pt_regs *childregs = task_pt_regs(p);

	childregs = regs;
	childregs->ARM_r0 = 0;
	childregs->ARM_sp = stack_start;

	memset(&thread->cpu_context, 0, sizeof(struct cpu_context_save));
	thread->cpu_context.sp = (unsigned long)childregs;
	thread->cpu_context.pc = (unsigned long)ret_from_fork;

	if (clone_flags & CLONE_SETTLS)
	thread->tp_value = regs->ARM_r3;

	return 0;
	}

	/*
	* Fill in the task's elfregs structure for a core dump.
	*/
	int dump_task_regs(struct task_struct t, elf_gregset_t elfregs)
	{
	elf_core_copy_regs(elfregs, task_pt_regs(t));
	return 1;
	}

	/*
	* fill in the fpe structure for a core dump...
	*/
	int dump_fpu (struct pt_regs regs, struct user_fp fp)
	{
	struct thread_info *thread = current_thread_info();
	int used_math = thread->used_cp[1] \| thread->used_cp[2];

	if (used_math)
	memcpy(fp, &thread->fpstate.soft, sizeof (*fp));

	return used_math != 0;
	}
	EXPORT_SYMBOL(dump_fpu);

	/*
	* Shuffle the argument into the correct register before calling the
	* thread function. r1 is the thread argument, r2 is the pointer to
	* the thread function, and r3 points to the exit function.
	*/
	extern void kernel_thread_helper(void);
	asm( ".pushsection .text\n"
	" .align\n"
	" .type kernel_thread_helper, #function\n"
	"kernel_thread_helper:\n"
	" mov r0, r1\n"
	" mov lr, r3\n"
	" mov pc, r2\n"
	" .size kernel_thread_helper, . - kernel_thread_helper\n"
	" .popsection");

	#ifdef CONFIG_ARM_UNWIND
	extern void kernel_thread_exit(long code);
	asm( ".pushsection .text\n"
	" .align\n"
	" .type kernel_thread_exit, #function\n"
	"kernel_thread_exit:\n"
	" .fnstart\n"
	" .cantunwind\n"
	" bl do_exit\n"
	" nop\n"
	" .fnend\n"
	" .size kernel_thread_exit, . - kernel_thread_exit\n"
	" .popsection");
	#else
	#define kernel_thread_exit do_exit
	#endif

	/*
	* Create a kernel thread.
	*/
	pid_t kernel_thread(int (fn)(void ), void *arg, unsigned long flags)
	{
	struct pt_regs regs;

	memset(&regs, 0, sizeof(regs));

	regs.ARM_r1 = (unsigned long)arg;
	regs.ARM_r2 = (unsigned long)fn;
	regs.ARM_r3 = (unsigned long)kernel_thread_exit;
	regs.ARM_pc = (unsigned long)kernel_thread_helper;
	regs.ARM_cpsr = SVC_MODE \| PSR_ENDSTATE \| PSR_ISETSTATE;

	return do_fork(flags\|CLONE_VM\|CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
	}
	EXPORT_SYMBOL(kernel_thread);

	unsigned long get_wchan(struct task_struct *p)
	{
	struct stackframe frame;
	int count = 0;
	if (!p \|\| p == current \|\| p->state == TASK_RUNNING)
	return 0;

	frame.fp = thread_saved_fp(p);
	frame.sp = thread_saved_sp(p);
	frame.lr = 0; /* recovered from the stack */
	frame.pc = thread_saved_pc(p);
	do {
	int ret = unwind_frame(&frame);
	if (ret < 0)
	return 0;
	if (!in_sched_functions(frame.pc))
	return frame.pc;
	} while (count ++ < 16);
	return 0;
	}