arch/unicore32/kernel/process.c - maze/linux - Git at Google

 /*
  * linux/arch/unicore32/kernel/process.c
  *
  * Code specific to PKUnity SoC and UniCore ISA
  *
  * Copyright (C) 2001-2010 GUAN Xue-tao
  *
  * 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/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 <linux/random.h>
 #include <linux/gpio.h>
 #include <linux/stacktrace.h>

 #include <asm/cacheflush.h>
 #include <asm/processor.h>
 #include <asm/stacktrace.h>

 #include "setup.h"

 static const char * const processor_modes[] = {
 	"UK00", "UK01", "UK02", "UK03", "UK04", "UK05", "UK06", "UK07",
 	"UK08", "UK09", "UK0A", "UK0B", "UK0C", "UK0D", "UK0E", "UK0F",
 	"USER", "REAL", "INTR", "PRIV", "UK14", "UK15", "UK16", "ABRT",
 	"UK18", "UK19", "UK1A", "EXTN", "UK1C", "UK1D", "UK1E", "SUSR"
 };

 /*
  * 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.
  */
 void cpu_idle(void)
 {
 	/* endless idle loop with no priority at all */
 	while (1) {
 		tick_nohz_idle_enter();
 		rcu_idle_enter();
 		while (!need_resched()) {
 			local_irq_disable();
 			stop_critical_timings();
 			cpu_do_idle();
 			local_irq_enable();
 			start_critical_timings();
 		}
 		rcu_idle_exit();
 		tick_nohz_idle_exit();
 		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)
 {
 	gpio_set_value(GPO_SOFT_OFF, 0);
 }

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

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

 void machine_restart(char *cmd)
 {
 	/* Disable interrupts first */
 	local_irq_disable();

 	/*
 	 * 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(reboot_mode);

 	/* Clean and invalidate caches */
 	flush_cache_all();

 	/* Turn off caching */
 	cpu_proc_fin();

 	/* Push out any further dirty data, and ensure cache is empty */
 	flush_cache_all();

 	/*
 	 * Now handle reboot code.
 	 */
 	if (reboot_mode == 's') {
 		/* Jump into ROM at address 0xffff0000 */
 		cpu_reset(VECTORS_BASE);
 	} else {
 		writel(0x00002001, PM_PLLSYSCFG); /* cpu clk = 250M */
 		writel(0x00100800, PM_PLLDDRCFG); /* ddr clk =  44M */
 		writel(0x00002001, PM_PLLVGACFG); /* vga clk = 250M */

 		/* Use on-chip reset capability */
 		/* following instructions must be in one icache line */
 		__asm__ __volatile__(
 			"	.align 5\n\t"
 			"	stw	%1, [%0]\n\t"
 			"201:	ldw	r0, [%0]\n\t"
 			"	cmpsub.a	r0, #0\n\t"
 			"	bne	201b\n\t"
 			"	stw	%3, [%2]\n\t"
 			"	nop; nop; nop\n\t"
 			/* prefetch 3 instructions at most */
 			:
 			: "r" (PM_PMCR),
 			  "r" (PM_PMCR_CFBSYS | PM_PMCR_CFBDDR
 				| PM_PMCR_CFBVGA),
 			  "r" (RESETC_SWRR),
 			  "r" (RESETC_SWRR_SRB)
 			: "r0", "memory");
 	}

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

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

 	printk(KERN_DEFAULT "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->UCreg_lr);
 	printk(KERN_DEFAULT "pc : [<%08lx>]    lr : [<%08lx>]    psr: %08lx\n"
 	       "sp : %08lx  ip : %08lx  fp : %08lx\n",
 		regs->UCreg_pc, regs->UCreg_lr, regs->UCreg_asr,
 		regs->UCreg_sp, regs->UCreg_ip, regs->UCreg_fp);
 	printk(KERN_DEFAULT "r26: %08lx  r25: %08lx  r24: %08lx\n",
 		regs->UCreg_26, regs->UCreg_25,
 		regs->UCreg_24);
 	printk(KERN_DEFAULT "r23: %08lx  r22: %08lx  r21: %08lx  r20: %08lx\n",
 		regs->UCreg_23, regs->UCreg_22,
 		regs->UCreg_21, regs->UCreg_20);
 	printk(KERN_DEFAULT "r19: %08lx  r18: %08lx  r17: %08lx  r16: %08lx\n",
 		regs->UCreg_19, regs->UCreg_18,
 		regs->UCreg_17, regs->UCreg_16);
 	printk(KERN_DEFAULT "r15: %08lx  r14: %08lx  r13: %08lx  r12: %08lx\n",
 		regs->UCreg_15, regs->UCreg_14,
 		regs->UCreg_13, regs->UCreg_12);
 	printk(KERN_DEFAULT "r11: %08lx  r10: %08lx  r9 : %08lx  r8 : %08lx\n",
 		regs->UCreg_11, regs->UCreg_10,
 		regs->UCreg_09, regs->UCreg_08);
 	printk(KERN_DEFAULT "r7 : %08lx  r6 : %08lx  r5 : %08lx  r4 : %08lx\n",
 		regs->UCreg_07, regs->UCreg_06,
 		regs->UCreg_05, regs->UCreg_04);
 	printk(KERN_DEFAULT "r3 : %08lx  r2 : %08lx  r1 : %08lx  r0 : %08lx\n",
 		regs->UCreg_03, regs->UCreg_02,
 		regs->UCreg_01, regs->UCreg_00);

 	flags = regs->UCreg_asr;
 	buf[0] = flags & PSR_S_BIT ? 'S' : 's';
 	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(KERN_DEFAULT "Flags: %s  INTR o%s  REAL o%s  Mode %s  Segment %s\n",
 		buf, interrupts_enabled(regs) ? "n" : "ff",
 		fast_interrupts_enabled(regs) ? "n" : "ff",
 		processor_modes[processor_mode(regs)],
 		segment_eq(get_fs(), get_ds()) ? "kernel" : "user");
 	{
 		unsigned int ctrl;

 		buf[0] = '\0';
 		{
 			unsigned int transbase;
 			asm("movc %0, p0.c2, #0\n"
 			    : "=r" (transbase));
 			snprintf(buf, sizeof(buf), "  Table: %08x", transbase);
 		}
 		asm("movc %0, p0.c1, #0\n" : "=r" (ctrl));

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

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

 /*
  * Free current thread data structures etc..
  */
 void exit_thread(void)
 {
 }

 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));
 #ifdef CONFIG_UNICORE_FPU_F64
 	memset(&thread->fpstate, 0, sizeof(struct fp_state));
 #endif
 }

 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->UCreg_00 = 0;
 	childregs->UCreg_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)
 		childregs->UCreg_16 = regs->UCreg_03;

 	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, elf_fpregset_t *fp)
 {
 	struct thread_info *thread = current_thread_info();
 	int used_math = thread->used_cp[1] | thread->used_cp[2];

 #ifdef CONFIG_UNICORE_FPU_F64
 	if (used_math)
 		memcpy(fp, &thread->fpstate, sizeof(*fp));
 #endif
 	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.
  */
 asm(".pushsection .text\n"
 "	.align\n"
 "	.type	kernel_thread_helper, #function\n"
 "kernel_thread_helper:\n"
 "	mov.a	asr, r7\n"
 "	mov	r0, r4\n"
 "	mov	lr, r6\n"
 "	mov	pc, r5\n"
 "	.size	kernel_thread_helper, . - kernel_thread_helper\n"
 "	.popsection");

 /*
  * 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.UCreg_04 = (unsigned long)arg;
 	regs.UCreg_05 = (unsigned long)fn;
 	regs.UCreg_06 = (unsigned long)do_exit;
 	regs.UCreg_07 = PRIV_MODE;
 	regs.UCreg_pc = (unsigned long)kernel_thread_helper;
 	regs.UCreg_asr = regs.UCreg_07 | PSR_I_BIT;

 	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;
 }

 unsigned long arch_randomize_brk(struct mm_struct *mm)
 {
 	unsigned long range_end = mm->brk + 0x02000000;
 	return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
 }

 /*
  * The vectors page is always readable from user space for the
  * atomic helpers and the signal restart code.  Let's declare a mapping
  * for it so it is visible through ptrace and /proc/<pid>/mem.
  */

 int vectors_user_mapping(void)
 {
 	struct mm_struct *mm = current->mm;
 	return install_special_mapping(mm, 0xffff0000, PAGE_SIZE,
 				       VM_READ | VM_EXEC |
 				       VM_MAYREAD | VM_MAYEXEC |
 				       VM_DONTEXPAND | VM_DONTDUMP,
 				       NULL);
 }

 const char *arch_vma_name(struct vm_area_struct *vma)
 {
 	return (vma->vm_start == 0xffff0000) ? "[vectors]" : NULL;
 }
	/*
	* linux/arch/unicore32/kernel/process.c
	*
	* Code specific to PKUnity SoC and UniCore ISA
	*
	* Copyright (C) 2001-2010 GUAN Xue-tao
	*
	* 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/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 <linux/random.h>
	#include <linux/gpio.h>
	#include <linux/stacktrace.h>

	#include <asm/cacheflush.h>
	#include <asm/processor.h>
	#include <asm/stacktrace.h>

	#include "setup.h"

	static const char * const processor_modes[] = {
	"UK00", "UK01", "UK02", "UK03", "UK04", "UK05", "UK06", "UK07",
	"UK08", "UK09", "UK0A", "UK0B", "UK0C", "UK0D", "UK0E", "UK0F",
	"USER", "REAL", "INTR", "PRIV", "UK14", "UK15", "UK16", "ABRT",
	"UK18", "UK19", "UK1A", "EXTN", "UK1C", "UK1D", "UK1E", "SUSR"
	};

	/*
	* 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.
	*/
	void cpu_idle(void)
	{
	/* endless idle loop with no priority at all */
	while (1) {
	tick_nohz_idle_enter();
	rcu_idle_enter();
	while (!need_resched()) {
	local_irq_disable();
	stop_critical_timings();
	cpu_do_idle();
	local_irq_enable();
	start_critical_timings();
	}
	rcu_idle_exit();
	tick_nohz_idle_exit();
	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)
	{
	gpio_set_value(GPO_SOFT_OFF, 0);
	}

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

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

	void machine_restart(char *cmd)
	{
	/* Disable interrupts first */
	local_irq_disable();

	/*
	* 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(reboot_mode);

	/* Clean and invalidate caches */
	flush_cache_all();

	/* Turn off caching */
	cpu_proc_fin();

	/* Push out any further dirty data, and ensure cache is empty */
	flush_cache_all();

	/*
	* Now handle reboot code.
	*/
	if (reboot_mode == 's') {
	/* Jump into ROM at address 0xffff0000 */
	cpu_reset(VECTORS_BASE);
	} else {
	writel(0x00002001, PM_PLLSYSCFG); /* cpu clk = 250M */
	writel(0x00100800, PM_PLLDDRCFG); /* ddr clk = 44M */
	writel(0x00002001, PM_PLLVGACFG); /* vga clk = 250M */

	/* Use on-chip reset capability */
	/* following instructions must be in one icache line */
	__asm__ __volatile__(
	" .align 5\n\t"
	" stw %1, [%0]\n\t"
	"201: ldw r0, [%0]\n\t"
	" cmpsub.a r0, #0\n\t"
	" bne 201b\n\t"
	" stw %3, [%2]\n\t"
	" nop; nop; nop\n\t"
	/* prefetch 3 instructions at most */
	:
	: "r" (PM_PMCR),
	"r" (PM_PMCR_CFBSYS \| PM_PMCR_CFBDDR
	\| PM_PMCR_CFBVGA),
	"r" (RESETC_SWRR),
	"r" (RESETC_SWRR_SRB)
	: "r0", "memory");
	}

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

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

	printk(KERN_DEFAULT "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->UCreg_lr);
	printk(KERN_DEFAULT "pc : [<%08lx>] lr : [<%08lx>] psr: %08lx\n"
	"sp : %08lx ip : %08lx fp : %08lx\n",
	regs->UCreg_pc, regs->UCreg_lr, regs->UCreg_asr,
	regs->UCreg_sp, regs->UCreg_ip, regs->UCreg_fp);
	printk(KERN_DEFAULT "r26: %08lx r25: %08lx r24: %08lx\n",
	regs->UCreg_26, regs->UCreg_25,
	regs->UCreg_24);
	printk(KERN_DEFAULT "r23: %08lx r22: %08lx r21: %08lx r20: %08lx\n",
	regs->UCreg_23, regs->UCreg_22,
	regs->UCreg_21, regs->UCreg_20);
	printk(KERN_DEFAULT "r19: %08lx r18: %08lx r17: %08lx r16: %08lx\n",
	regs->UCreg_19, regs->UCreg_18,
	regs->UCreg_17, regs->UCreg_16);
	printk(KERN_DEFAULT "r15: %08lx r14: %08lx r13: %08lx r12: %08lx\n",
	regs->UCreg_15, regs->UCreg_14,
	regs->UCreg_13, regs->UCreg_12);
	printk(KERN_DEFAULT "r11: %08lx r10: %08lx r9 : %08lx r8 : %08lx\n",
	regs->UCreg_11, regs->UCreg_10,
	regs->UCreg_09, regs->UCreg_08);
	printk(KERN_DEFAULT "r7 : %08lx r6 : %08lx r5 : %08lx r4 : %08lx\n",
	regs->UCreg_07, regs->UCreg_06,
	regs->UCreg_05, regs->UCreg_04);
	printk(KERN_DEFAULT "r3 : %08lx r2 : %08lx r1 : %08lx r0 : %08lx\n",
	regs->UCreg_03, regs->UCreg_02,
	regs->UCreg_01, regs->UCreg_00);

	flags = regs->UCreg_asr;
	buf[0] = flags & PSR_S_BIT ? 'S' : 's';
	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(KERN_DEFAULT "Flags: %s INTR o%s REAL o%s Mode %s Segment %s\n",
	buf, interrupts_enabled(regs) ? "n" : "ff",
	fast_interrupts_enabled(regs) ? "n" : "ff",
	processor_modes[processor_mode(regs)],
	segment_eq(get_fs(), get_ds()) ? "kernel" : "user");
	{
	unsigned int ctrl;

	buf[0] = '\0';
	{
	unsigned int transbase;
	asm("movc %0, p0.c2, #0\n"
	: "=r" (transbase));
	snprintf(buf, sizeof(buf), " Table: %08x", transbase);
	}
	asm("movc %0, p0.c1, #0\n" : "=r" (ctrl));

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

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

	/*
	* Free current thread data structures etc..
	*/
	void exit_thread(void)
	{
	}

	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));
	#ifdef CONFIG_UNICORE_FPU_F64
	memset(&thread->fpstate, 0, sizeof(struct fp_state));
	#endif
	}

	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->UCreg_00 = 0;
	childregs->UCreg_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)
	childregs->UCreg_16 = regs->UCreg_03;

	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, elf_fpregset_t fp)
	{
	struct thread_info *thread = current_thread_info();
	int used_math = thread->used_cp[1] \| thread->used_cp[2];

	#ifdef CONFIG_UNICORE_FPU_F64
	if (used_math)
	memcpy(fp, &thread->fpstate, sizeof(*fp));
	#endif
	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.
	*/
	asm(".pushsection .text\n"
	" .align\n"
	" .type kernel_thread_helper, #function\n"
	"kernel_thread_helper:\n"
	" mov.a asr, r7\n"
	" mov r0, r4\n"
	" mov lr, r6\n"
	" mov pc, r5\n"
	" .size kernel_thread_helper, . - kernel_thread_helper\n"
	" .popsection");

	/*
	* 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.UCreg_04 = (unsigned long)arg;
	regs.UCreg_05 = (unsigned long)fn;
	regs.UCreg_06 = (unsigned long)do_exit;
	regs.UCreg_07 = PRIV_MODE;
	regs.UCreg_pc = (unsigned long)kernel_thread_helper;
	regs.UCreg_asr = regs.UCreg_07 \| PSR_I_BIT;

	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;
	}

	unsigned long arch_randomize_brk(struct mm_struct *mm)
	{
	unsigned long range_end = mm->brk + 0x02000000;
	return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
	}

	/*
	* The vectors page is always readable from user space for the
	* atomic helpers and the signal restart code. Let's declare a mapping
	* for it so it is visible through ptrace and /proc/<pid>/mem.
	*/

	int vectors_user_mapping(void)
	{
	struct mm_struct *mm = current->mm;
	return install_special_mapping(mm, 0xffff0000, PAGE_SIZE,
	VM_READ \| VM_EXEC \|
	VM_MAYREAD \| VM_MAYEXEC \|
	VM_DONTEXPAND \| VM_DONTDUMP,
	NULL);
	}

	const char arch_vma_name(struct vm_area_struct vma)
	{
	return (vma->vm_start == 0xffff0000) ? "[vectors]" : NULL;
	}