[mirror_ubuntu-artful-kernel.git] / arch / mips / kernel / process.c

/*
 * 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) 1994 - 1999, 2000 by Ralf Baechle and others.
 * Copyright (C) 2005, 2006 by Ralf Baechle (ralf@linux-mips.org)
 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
 * Copyright (C) 2004 Thiemo Seufer
 */
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/tick.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/personality.h>
#include <linux/sys.h>
#include <linux/user.h>
#include <linux/init.h>
#include <linux/completion.h>
#include <linux/kallsyms.h>
#include <linux/random.h>

#include <asm/asm.h>
#include <asm/bootinfo.h>
#include <asm/cpu.h>
#include <asm/dsp.h>
#include <asm/fpu.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/mipsregs.h>
#include <asm/processor.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/elf.h>
#include <asm/isadep.h>
#include <asm/inst.h>
#include <asm/stacktrace.h>

/*
 * The idle thread. There's no useful work to be done, so just try to conserve
 * power and have a low exit latency (ie sit in a loop waiting for somebody to
 * say that they'd like to reschedule)
 */
void __noreturn cpu_idle(void)
{
	int cpu;

	/* CPU is going idle. */
	cpu = smp_processor_id();

	/* endless idle loop with no priority at all */
	while (1) {
		tick_nohz_stop_sched_tick(1);
		while (!need_resched() && cpu_online(cpu)) {
#ifdef CONFIG_MIPS_MT_SMTC
			extern void smtc_idle_loop_hook(void);

			smtc_idle_loop_hook();
#endif

			if (cpu_wait) {
				/* Don't trace irqs off for idle */
				stop_critical_timings();
				(*cpu_wait)();
				start_critical_timings();
			}
		}
#ifdef CONFIG_HOTPLUG_CPU
		if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map) &&
		    (system_state == SYSTEM_RUNNING ||
		     system_state == SYSTEM_BOOTING))
			play_dead();
#endif
		tick_nohz_restart_sched_tick();
		preempt_enable_no_resched();
		schedule();
		preempt_disable();
	}
}

asmlinkage void ret_from_fork(void);

void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
{
	unsigned long status;

	/* New thread loses kernel privileges. */
	status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
#ifdef CONFIG_64BIT
	status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
#endif
	status |= KU_USER;
	regs->cp0_status = status;
	clear_used_math();
	clear_fpu_owner();
	if (cpu_has_dsp)
		__init_dsp();
	regs->cp0_epc = pc;
	regs->regs[29] = sp;
	current_thread_info()->addr_limit = USER_DS;
}

void exit_thread(void)
{
}

void flush_thread(void)
{
}

int copy_thread(unsigned long clone_flags, unsigned long usp,
	unsigned long unused, struct task_struct *p, struct pt_regs *regs)
{
	struct thread_info *ti = task_thread_info(p);
	struct pt_regs *childregs;
	unsigned long childksp;
	p->set_child_tid = p->clear_child_tid = NULL;

	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;

	preempt_disable();

	if (is_fpu_owner())
		save_fp(p);

	if (cpu_has_dsp)
		save_dsp(p);

	preempt_enable();

	/* set up new TSS. */
	childregs = (struct pt_regs *) childksp - 1;
	/*  Put the stack after the struct pt_regs.  */
	childksp = (unsigned long) childregs;
	*childregs = *regs;
	childregs->regs[7] = 0;	/* Clear error flag */

	childregs->regs[2] = 0;	/* Child gets zero as return value */

	if (childregs->cp0_status & ST0_CU0) {
		childregs->regs[28] = (unsigned long) ti;
		childregs->regs[29] = childksp;
		ti->addr_limit = KERNEL_DS;
	} else {
		childregs->regs[29] = usp;
		ti->addr_limit = USER_DS;
	}
	p->thread.reg29 = (unsigned long) childregs;
	p->thread.reg31 = (unsigned long) ret_from_fork;

	/*
	 * New tasks lose permission to use the fpu. This accelerates context
	 * switching for most programs since they don't use the fpu.
	 */
	p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
	childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);

#ifdef CONFIG_MIPS_MT_SMTC
	/*
	 * SMTC restores TCStatus after Status, and the CU bits
	 * are aliased there.
	 */
	childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
#endif
	clear_tsk_thread_flag(p, TIF_USEDFPU);

#ifdef CONFIG_MIPS_MT_FPAFF
	clear_tsk_thread_flag(p, TIF_FPUBOUND);
#endif /* CONFIG_MIPS_MT_FPAFF */

	if (clone_flags & CLONE_SETTLS)
		ti->tp_value = regs->regs[7];

	return 0;
}

/* Fill in the fpu structure for a core dump.. */
int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
{
	memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));

	return 1;
}

void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
{
	int i;

	for (i = 0; i < EF_R0; i++)
		gp[i] = 0;
	gp[EF_R0] = 0;
	for (i = 1; i <= 31; i++)
		gp[EF_R0 + i] = regs->regs[i];
	gp[EF_R26] = 0;
	gp[EF_R27] = 0;
	gp[EF_LO] = regs->lo;
	gp[EF_HI] = regs->hi;
	gp[EF_CP0_EPC] = regs->cp0_epc;
	gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
	gp[EF_CP0_STATUS] = regs->cp0_status;
	gp[EF_CP0_CAUSE] = regs->cp0_cause;
#ifdef EF_UNUSED0
	gp[EF_UNUSED0] = 0;
#endif
}

int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
{
	elf_dump_regs(*regs, task_pt_regs(tsk));
	return 1;
}

int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
{
	memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));

	return 1;
}

/*
 * Create a kernel thread
 */
static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
{
	do_exit(fn(arg));
}

long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
{
	struct pt_regs regs;

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

	regs.regs[4] = (unsigned long) arg;
	regs.regs[5] = (unsigned long) fn;
	regs.cp0_epc = (unsigned long) kernel_thread_helper;
	regs.cp0_status = read_c0_status();
#if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
	regs.cp0_status = (regs.cp0_status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
			  ((regs.cp0_status & (ST0_KUC | ST0_IEC)) << 2);
#else
	regs.cp0_status |= ST0_EXL;
#endif

	/* Ok, create the new process.. */
	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
}

/*
 *
 */
struct mips_frame_info {
	void		*func;
	unsigned long	func_size;
	int		frame_size;
	int		pc_offset;
};

static inline int is_ra_save_ins(union mips_instruction *ip)
{
	/* sw / sd $ra, offset($sp) */
	return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
		ip->i_format.rs == 29 &&
		ip->i_format.rt == 31;
}

static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
{
	if (ip->j_format.opcode == jal_op)
		return 1;
	if (ip->r_format.opcode != spec_op)
		return 0;
	return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
}

static inline int is_sp_move_ins(union mips_instruction *ip)
{
	/* addiu/daddiu sp,sp,-imm */
	if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
		return 0;
	if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
		return 1;
	return 0;
}

static int get_frame_info(struct mips_frame_info *info)
{
	union mips_instruction *ip = info->func;
	unsigned max_insns = info->func_size / sizeof(union mips_instruction);
	unsigned i;

	info->pc_offset = -1;
	info->frame_size = 0;

	if (!ip)
		goto err;

	if (max_insns == 0)
		max_insns = 128U;	/* unknown function size */
	max_insns = min(128U, max_insns);

	for (i = 0; i < max_insns; i++, ip++) {

		if (is_jal_jalr_jr_ins(ip))
			break;
		if (!info->frame_size) {
			if (is_sp_move_ins(ip))
				info->frame_size = - ip->i_format.simmediate;
			continue;
		}
		if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
			info->pc_offset =
				ip->i_format.simmediate / sizeof(long);
			break;
		}
	}
	if (info->frame_size && info->pc_offset >= 0) /* nested */
		return 0;
	if (info->pc_offset < 0) /* leaf */
		return 1;
	/* prologue seems boggus... */
err:
	return -1;
}

static struct mips_frame_info schedule_mfi __read_mostly;

static int __init frame_info_init(void)
{
	unsigned long size = 0;
#ifdef CONFIG_KALLSYMS
	unsigned long ofs;

	kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
#endif
	schedule_mfi.func = schedule;
	schedule_mfi.func_size = size;

	get_frame_info(&schedule_mfi);

	/*
	 * Without schedule() frame info, result given by
	 * thread_saved_pc() and get_wchan() are not reliable.
	 */
	if (schedule_mfi.pc_offset < 0)
		printk("Can't analyze schedule() prologue at %p\n", schedule);

	return 0;
}

arch_initcall(frame_info_init);

/*
 * Return saved PC of a blocked thread.
 */
unsigned long thread_saved_pc(struct task_struct *tsk)
{
	struct thread_struct *t = &tsk->thread;

	/* New born processes are a special case */
	if (t->reg31 == (unsigned long) ret_from_fork)
		return t->reg31;
	if (schedule_mfi.pc_offset < 0)
		return 0;
	return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
}


#ifdef CONFIG_KALLSYMS
/* used by show_backtrace() */
unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
			   unsigned long pc, unsigned long *ra)
{
	unsigned long stack_page;
	struct mips_frame_info info;
	unsigned long size, ofs;
	int leaf;
	extern void ret_from_irq(void);
	extern void ret_from_exception(void);

	stack_page = (unsigned long)task_stack_page(task);
	if (!stack_page)
		return 0;

	/*
	 * If we reached the bottom of interrupt context,
	 * return saved pc in pt_regs.
	 */
	if (pc == (unsigned long)ret_from_irq ||
	    pc == (unsigned long)ret_from_exception) {
		struct pt_regs *regs;
		if (*sp >= stack_page &&
		    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
			regs = (struct pt_regs *)*sp;
			pc = regs->cp0_epc;
			if (__kernel_text_address(pc)) {
				*sp = regs->regs[29];
				*ra = regs->regs[31];
				return pc;
			}
		}
		return 0;
	}
	if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
		return 0;
	/*
	 * Return ra if an exception occured at the first instruction
	 */
	if (unlikely(ofs == 0)) {
		pc = *ra;
		*ra = 0;
		return pc;
	}

	info.func = (void *)(pc - ofs);
	info.func_size = ofs;	/* analyze from start to ofs */
	leaf = get_frame_info(&info);
	if (leaf < 0)
		return 0;

	if (*sp < stack_page ||
	    *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
		return 0;

	if (leaf)
		/*
		 * For some extreme cases, get_frame_info() can
		 * consider wrongly a nested function as a leaf
		 * one. In that cases avoid to return always the
		 * same value.
		 */
		pc = pc != *ra ? *ra : 0;
	else
		pc = ((unsigned long *)(*sp))[info.pc_offset];

	*sp += info.frame_size;
	*ra = 0;
	return __kernel_text_address(pc) ? pc : 0;
}
#endif

/*
 * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 */
unsigned long get_wchan(struct task_struct *task)
{
	unsigned long pc = 0;
#ifdef CONFIG_KALLSYMS
	unsigned long sp;
	unsigned long ra = 0;
#endif

	if (!task || task == current || task->state == TASK_RUNNING)
		goto out;
	if (!task_stack_page(task))
		goto out;

	pc = thread_saved_pc(task);

#ifdef CONFIG_KALLSYMS
	sp = task->thread.reg29 + schedule_mfi.frame_size;

	while (in_sched_functions(pc))
		pc = unwind_stack(task, &sp, pc, &ra);
#endif

out:
	return pc;
}

/*
 * Don't forget that the stack pointer must be aligned on a 8 bytes
 * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 */
unsigned long arch_align_stack(unsigned long sp)
{
	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
		sp -= get_random_int() & ~PAGE_MASK;

	return sp & ALMASK;
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* This file is subject to the terms and conditions of the GNU General Public
	3	* License. See the file "COPYING" in the main directory of this archive
	4	* for more details.
	5	*
	6	* Copyright (C) 1994 - 1999, 2000 by Ralf Baechle and others.
40ac5d47	7	* Copyright (C) 2005, 2006 by Ralf Baechle (ralf@linux-mips.org)
1da177e4 LT	8	* Copyright (C) 1999, 2000 Silicon Graphics, Inc.
	9	* Copyright (C) 2004 Thiemo Seufer
	10	*/
1da177e4 LT	11	#include <linux/errno.h>
	12	#include <linux/module.h>
	13	#include <linux/sched.h>
7bcf7717	14	#include <linux/tick.h>
1da177e4 LT	15	#include <linux/kernel.h>
	16	#include <linux/mm.h>
	17	#include <linux/stddef.h>
	18	#include <linux/unistd.h>
	19	#include <linux/ptrace.h>
1da177e4 LT	20	#include <linux/mman.h>
	21	#include <linux/personality.h>
	22	#include <linux/sys.h>
	23	#include <linux/user.h>
1da177e4 LT	24	#include <linux/init.h>
1da177e4 LT	25	#include <linux/completion.h>
63077519	26	#include <linux/kallsyms.h>
94109102	27	#include <linux/random.h>
1da177e4	28
94109102	29	#include <asm/asm.h>
1da177e4 LT	30	#include <asm/bootinfo.h>
1da177e4 LT	31	#include <asm/cpu.h>
e50c0a8f	32	#include <asm/dsp.h>
1da177e4 LT	33	#include <asm/fpu.h>
	34	#include <asm/pgtable.h>
	35	#include <asm/system.h>
	36	#include <asm/mipsregs.h>
	37	#include <asm/processor.h>
	38	#include <asm/uaccess.h>
	39	#include <asm/io.h>
	40	#include <asm/elf.h>
	41	#include <asm/isadep.h>
	42	#include <asm/inst.h>
1df0f0ff	43	#include <asm/stacktrace.h>
1da177e4	44
1da177e4 LT	45	/*
	46	* The idle thread. There's no useful work to be done, so just try to conserve
	47	* power and have a low exit latency (ie sit in a loop waiting for somebody to
	48	* say that they'd like to reschedule)
	49	*/
b3f6df9f	50	void __noreturn cpu_idle(void)
1da177e4	51	{
1b2bc75c RB	52	int cpu;
	53
	54	/* CPU is going idle. */
	55	cpu = smp_processor_id();
	56
1da177e4 LT	57	/* endless idle loop with no priority at all */
1da177e4 LT	58	while (1) {
b8f8c3cf	59	tick_nohz_stop_sched_tick(1);
1b2bc75c	60	while (!need_resched() && cpu_online(cpu)) {
9cc12363	61	#ifdef CONFIG_MIPS_MT_SMTC
447deafb RB	62	extern void smtc_idle_loop_hook(void);
447deafb RB	63
41c594ab	64	smtc_idle_loop_hook();
c68644d3	65	#endif
7a7ac952 WZ	66
	67	if (cpu_wait) {
	68	/* Don't trace irqs off for idle */
	69	stop_critical_timings();
1da177e4	70	(*cpu_wait)();
7a7ac952 WZ	71	start_critical_timings();
7a7ac952 WZ	72	}
41c594ab	73	}
1b2bc75c RB	74	#ifdef CONFIG_HOTPLUG_CPU
	75	if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map) &&
	76	(system_state == SYSTEM_RUNNING \|\|
	77	system_state == SYSTEM_BOOTING))
	78	play_dead();
	79	#endif
7bcf7717	80	tick_nohz_restart_sched_tick();
5bfb5d69	81	preempt_enable_no_resched();
1da177e4	82	schedule();
5bfb5d69	83	preempt_disable();
1da177e4 LT	84	}
	85	}
	86
	87	asmlinkage void ret_from_fork(void);
	88
	89	void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
	90	{
	91	unsigned long status;
	92
	93	/* New thread loses kernel privileges. */
bbaf238b	94	status = regs->cp0_status & ~(ST0_CU0\|ST0_CU1\|ST0_FR\|KU_MASK);
875d43e7	95	#ifdef CONFIG_64BIT
293c5bd1	96	status \|= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
1da177e4 LT	97	#endif
	98	status \|= KU_USER;
	99	regs->cp0_status = status;
	100	clear_used_math();
e04582b7	101	clear_fpu_owner();
e50c0a8f RB	102	if (cpu_has_dsp)
e50c0a8f RB	103	__init_dsp();
1da177e4 LT	104	regs->cp0_epc = pc;
	105	regs->regs[29] = sp;
	106	current_thread_info()->addr_limit = USER_DS;
	107	}
	108
	109	void exit_thread(void)
	110	{
	111	}
	112
	113	void flush_thread(void)
	114	{
	115	}
	116
6f2c55b8	117	int copy_thread(unsigned long clone_flags, unsigned long usp,
1da177e4 LT	118	unsigned long unused, struct task_struct p, struct pt_regs regs)
1da177e4 LT	119	{
75bb07e7	120	struct thread_info *ti = task_thread_info(p);
1da177e4	121	struct pt_regs *childregs;
484889fc	122	unsigned long childksp;
3c37026d	123	p->set_child_tid = p->clear_child_tid = NULL;
1da177e4	124
75bb07e7	125	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
1da177e4 LT	126
	127	preempt_disable();
	128
e50c0a8f	129	if (is_fpu_owner())
1da177e4	130	save_fp(p);
e50c0a8f RB	131
	132	if (cpu_has_dsp)
	133	save_dsp(p);
1da177e4 LT	134
	135	preempt_enable();
	136
	137	/* set up new TSS. */
	138	childregs = (struct pt_regs *) childksp - 1;
484889fc DD	139	/* Put the stack after the struct pt_regs. */
484889fc DD	140	childksp = (unsigned long) childregs;
1da177e4 LT	141	childregs = regs;
	142	childregs->regs[7] = 0; /* Clear error flag */
	143
1da177e4	144	childregs->regs[2] = 0; /* Child gets zero as return value */
1da177e4 LT	145
	146	if (childregs->cp0_status & ST0_CU0) {
	147	childregs->regs[28] = (unsigned long) ti;
	148	childregs->regs[29] = childksp;
	149	ti->addr_limit = KERNEL_DS;
	150	} else {
	151	childregs->regs[29] = usp;
	152	ti->addr_limit = USER_DS;
	153	}
	154	p->thread.reg29 = (unsigned long) childregs;
	155	p->thread.reg31 = (unsigned long) ret_from_fork;
	156
	157	/*
	158	* New tasks lose permission to use the fpu. This accelerates context
	159	* switching for most programs since they don't use the fpu.
	160	*/
	161	p->thread.cp0_status = read_c0_status() & ~(ST0_CU2\|ST0_CU1);
	162	childregs->cp0_status &= ~(ST0_CU2\|ST0_CU1);
1da177e4	163
9cc12363	164	#ifdef CONFIG_MIPS_MT_SMTC
f088fc84	165	/*
9cc12363 KK	166	* SMTC restores TCStatus after Status, and the CU bits
9cc12363 KK	167	* are aliased there.
f088fc84	168	*/
9cc12363 KK	169	childregs->cp0_tcstatus &= ~(ST0_CU2\|ST0_CU1);
9cc12363 KK	170	#endif
1da177e4 LT	171	clear_tsk_thread_flag(p, TIF_USEDFPU);
1da177e4 LT	172
f088fc84	173	#ifdef CONFIG_MIPS_MT_FPAFF
6657fe0a	174	clear_tsk_thread_flag(p, TIF_FPUBOUND);
f088fc84 RB	175	#endif /* CONFIG_MIPS_MT_FPAFF */
f088fc84 RB	176
3c37026d RB	177	if (clone_flags & CLONE_SETTLS)
	178	ti->tp_value = regs->regs[7];
	179
1da177e4 LT	180	return 0;
	181	}
	182
	183	/* Fill in the fpu structure for a core dump.. */
	184	int dump_fpu(struct pt_regs regs, elf_fpregset_t r)
	185	{
	186	memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
	187
	188	return 1;
	189	}
	190
d56efda4	191	void elf_dump_regs(elf_greg_t gp, struct pt_regs regs)
1da177e4 LT	192	{
	193	int i;
	194
	195	for (i = 0; i < EF_R0; i++)
	196	gp[i] = 0;
	197	gp[EF_R0] = 0;
	198	for (i = 1; i <= 31; i++)
	199	gp[EF_R0 + i] = regs->regs[i];
	200	gp[EF_R26] = 0;
	201	gp[EF_R27] = 0;
	202	gp[EF_LO] = regs->lo;
	203	gp[EF_HI] = regs->hi;
	204	gp[EF_CP0_EPC] = regs->cp0_epc;
	205	gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
	206	gp[EF_CP0_STATUS] = regs->cp0_status;
	207	gp[EF_CP0_CAUSE] = regs->cp0_cause;
	208	#ifdef EF_UNUSED0
	209	gp[EF_UNUSED0] = 0;
	210	#endif
	211	}
	212
49a89efb	213	int dump_task_regs(struct task_struct tsk, elf_gregset_t regs)
71e0e556	214	{
40bc9c67	215	elf_dump_regs(*regs, task_pt_regs(tsk));
71e0e556 RB	216	return 1;
	217	}
	218
49a89efb	219	int dump_task_fpu(struct task_struct t, elf_fpregset_t fpr)
1da177e4 LT	220	{
	221	memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
	222
	223	return 1;
	224	}
	225
	226	/*
	227	* Create a kernel thread
	228	*/
b3f6df9f	229	static void __noreturn kernel_thread_helper(void arg, int (fn)(void *))
1da177e4 LT	230	{
	231	do_exit(fn(arg));
	232	}
	233
	234	long kernel_thread(int (fn)(void ), void *arg, unsigned long flags)
	235	{
	236	struct pt_regs regs;
	237
	238	memset(&regs, 0, sizeof(regs));
	239
	240	regs.regs[4] = (unsigned long) arg;
	241	regs.regs[5] = (unsigned long) fn;
	242	regs.cp0_epc = (unsigned long) kernel_thread_helper;
	243	regs.cp0_status = read_c0_status();
	244	#if defined(CONFIG_CPU_R3000) \|\| defined(CONFIG_CPU_TX39XX)
e5d77754 MR	245	regs.cp0_status = (regs.cp0_status & ~(ST0_KUP \| ST0_IEP \| ST0_IEC)) \|
e5d77754 MR	246	((regs.cp0_status & (ST0_KUC \| ST0_IEC)) << 2);
1da177e4 LT	247	#else
	248	regs.cp0_status \|= ST0_EXL;
	249	#endif
	250
	251	/* Ok, create the new process.. */
	252	return do_fork(flags \| CLONE_VM \| CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
	253	}
	254
b5943182 FBH	255	/*
	256	*
	257	*/
	258	struct mips_frame_info {
	259	void *func;
	260	unsigned long func_size;
	261	int frame_size;
	262	int pc_offset;
	263	};
dc953df1	264
c0efbb6d FBH	265	static inline int is_ra_save_ins(union mips_instruction *ip)
	266	{
	267	/* sw / sd $ra, offset($sp) */
	268	return (ip->i_format.opcode == sw_op \|\| ip->i_format.opcode == sd_op) &&
	269	ip->i_format.rs == 29 &&
	270	ip->i_format.rt == 31;
	271	}
	272
	273	static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
	274	{
	275	if (ip->j_format.opcode == jal_op)
	276	return 1;
	277	if (ip->r_format.opcode != spec_op)
	278	return 0;
	279	return ip->r_format.func == jalr_op \|\| ip->r_format.func == jr_op;
	280	}
	281
	282	static inline int is_sp_move_ins(union mips_instruction *ip)
	283	{
	284	/* addiu/daddiu sp,sp,-imm */
	285	if (ip->i_format.rs != 29 \|\| ip->i_format.rt != 29)
	286	return 0;
	287	if (ip->i_format.opcode == addiu_op \|\| ip->i_format.opcode == daddiu_op)
	288	return 1;
	289	return 0;
	290	}
	291
f66686f7	292	static int get_frame_info(struct mips_frame_info *info)
1da177e4	293	{
c0efbb6d	294	union mips_instruction *ip = info->func;
29b376ff FBH	295	unsigned max_insns = info->func_size / sizeof(union mips_instruction);
29b376ff FBH	296	unsigned i;
c0efbb6d	297
1da177e4	298	info->pc_offset = -1;
63077519	299	info->frame_size = 0;
1da177e4	300
29b376ff FBH	301	if (!ip)
	302	goto err;
	303
	304	if (max_insns == 0)
	305	max_insns = 128U; /* unknown function size */
	306	max_insns = min(128U, max_insns);
	307
c0efbb6d FBH	308	for (i = 0; i < max_insns; i++, ip++) {
	309
	310	if (is_jal_jalr_jr_ins(ip))
63077519	311	break;
0cceb4aa FBH	312	if (!info->frame_size) {
	313	if (is_sp_move_ins(ip))
	314	info->frame_size = - ip->i_format.simmediate;
	315	continue;
63077519	316	}
0cceb4aa	317	if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
63077519 AN	318	info->pc_offset =
63077519 AN	319	ip->i_format.simmediate / sizeof(long);
0cceb4aa	320	break;
1da177e4 LT	321	}
1da177e4 LT	322	}
f66686f7 AN	323	if (info->frame_size && info->pc_offset >= 0) /* nested */
	324	return 0;
	325	if (info->pc_offset < 0) /* leaf */
	326	return 1;
	327	/* prologue seems boggus... */
29b376ff	328	err:
f66686f7	329	return -1;
1da177e4 LT	330	}
1da177e4 LT	331
b5943182 FBH	332	static struct mips_frame_info schedule_mfi __read_mostly;
b5943182 FBH	333
1da177e4 LT	334	static int __init frame_info_init(void)
1da177e4 LT	335	{
b5943182	336	unsigned long size = 0;
63077519	337	#ifdef CONFIG_KALLSYMS
b5943182	338	unsigned long ofs;
b5943182	339
55b74283	340	kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
63077519	341	#endif
b5943182 FBH	342	schedule_mfi.func = schedule;
	343	schedule_mfi.func_size = size;
	344
	345	get_frame_info(&schedule_mfi);
6057a798 FBH	346
	347	/*
	348	* Without schedule() frame info, result given by
	349	* thread_saved_pc() and get_wchan() are not reliable.
	350	*/
b5943182	351	if (schedule_mfi.pc_offset < 0)
6057a798	352	printk("Can't analyze schedule() prologue at %p\n", schedule);
63077519	353
1da177e4 LT	354	return 0;
	355	}
	356
	357	arch_initcall(frame_info_init);
	358
	359	/*
	360	* Return saved PC of a blocked thread.
	361	*/
	362	unsigned long thread_saved_pc(struct task_struct *tsk)
	363	{
	364	struct thread_struct *t = &tsk->thread;
	365
	366	/* New born processes are a special case */
	367	if (t->reg31 == (unsigned long) ret_from_fork)
	368	return t->reg31;
b5943182	369	if (schedule_mfi.pc_offset < 0)
1da177e4	370	return 0;
b5943182	371	return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
1da177e4 LT	372	}
1da177e4 LT	373
1da177e4	374
f66686f7	375	#ifdef CONFIG_KALLSYMS
4d157d5e FBH	376	/* used by show_backtrace() */
4d157d5e FBH	377	unsigned long unwind_stack(struct task_struct task, unsigned long sp,
1924600c	378	unsigned long pc, unsigned long *ra)
f66686f7 AN	379	{
	380	unsigned long stack_page;
	381	struct mips_frame_info info;
f66686f7	382	unsigned long size, ofs;
4d157d5e	383	int leaf;
1924600c AN	384	extern void ret_from_irq(void);
1924600c AN	385	extern void ret_from_exception(void);
f66686f7 AN	386
	387	stack_page = (unsigned long)task_stack_page(task);
	388	if (!stack_page)
	389	return 0;
	390
1924600c AN	391	/*
	392	* If we reached the bottom of interrupt context,
	393	* return saved pc in pt_regs.
	394	*/
	395	if (pc == (unsigned long)ret_from_irq \|\|
	396	pc == (unsigned long)ret_from_exception) {
	397	struct pt_regs *regs;
	398	if (*sp >= stack_page &&
	399	sp + sizeof(regs) <= stack_page + THREAD_SIZE - 32) {
	400	regs = (struct pt_regs )sp;
	401	pc = regs->cp0_epc;
	402	if (__kernel_text_address(pc)) {
	403	*sp = regs->regs[29];
	404	*ra = regs->regs[31];
	405	return pc;
	406	}
	407	}
	408	return 0;
	409	}
55b74283	410	if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
f66686f7	411	return 0;
1fd69098 FBH	412	/*
	413	* Return ra if an exception occured at the first instruction
	414	*/
1924600c AN	415	if (unlikely(ofs == 0)) {
	416	pc = *ra;
	417	*ra = 0;
	418	return pc;
	419	}
f66686f7 AN	420
	421	info.func = (void *)(pc - ofs);
	422	info.func_size = ofs; /* analyze from start to ofs */
4d157d5e FBH	423	leaf = get_frame_info(&info);
4d157d5e FBH	424	if (leaf < 0)
f66686f7	425	return 0;
4d157d5e FBH	426
	427	if (*sp < stack_page \|\|
	428	*sp + info.frame_size > stack_page + THREAD_SIZE - 32)
f66686f7 AN	429	return 0;
f66686f7 AN	430
4d157d5e FBH	431	if (leaf)
	432	/*
	433	* For some extreme cases, get_frame_info() can
	434	* consider wrongly a nested function as a leaf
	435	* one. In that cases avoid to return always the
	436	* same value.
	437	*/
1924600c	438	pc = pc != ra ? ra : 0;
4d157d5e FBH	439	else
	440	pc = ((unsigned long )(sp))[info.pc_offset];
	441
	442	*sp += info.frame_size;
1924600c	443	*ra = 0;
4d157d5e	444	return __kernel_text_address(pc) ? pc : 0;
f66686f7 AN	445	}
f66686f7 AN	446	#endif
b5943182 FBH	447
	448	/*
	449	* get_wchan - a maintenance nightmare^W^Wpain in the ass ...
	450	*/
	451	unsigned long get_wchan(struct task_struct *task)
	452	{
	453	unsigned long pc = 0;
	454	#ifdef CONFIG_KALLSYMS
	455	unsigned long sp;
1924600c	456	unsigned long ra = 0;
b5943182 FBH	457	#endif
	458
	459	if (!task \|\| task == current \|\| task->state == TASK_RUNNING)
	460	goto out;
	461	if (!task_stack_page(task))
	462	goto out;
	463
	464	pc = thread_saved_pc(task);
	465
	466	#ifdef CONFIG_KALLSYMS
	467	sp = task->thread.reg29 + schedule_mfi.frame_size;
	468
	469	while (in_sched_functions(pc))
1924600c	470	pc = unwind_stack(task, &sp, pc, &ra);
b5943182 FBH	471	#endif
	472
	473	out:
	474	return pc;
	475	}
94109102 FBH	476
	477	/*
	478	* Don't forget that the stack pointer must be aligned on a 8 bytes
	479	* boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
	480	*/
	481	unsigned long arch_align_stack(unsigned long sp)
	482	{
	483	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
	484	sp -= get_random_int() & ~PAGE_MASK;
	485
	486	return sp & ALMASK;
	487	}