[deliverable/linux.git] / arch / arc / kernel / stacktrace.c

/*
 *	stacktrace.c : stacktracing APIs needed by rest of kernel
 *			(wrappers over ARC dwarf based unwinder)
 *
 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 *
 * 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.
 *
 *  vineetg: aug 2009
 *  -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( )
 *   for displaying task's kernel mode call stack in /proc/<pid>/stack
 *  -Iterator based approach to have single copy of unwinding core and APIs
 *   needing unwinding, implement the logic in iterator regarding:
 *      = which frame onwards to start capture
 *      = which frame to stop capturing (wchan)
 *      = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc)
 *
 *  vineetg: March 2009
 *  -Implemented correct versions of thread_saved_pc() and get_wchan()
 *
 *  rajeshwarr: 2008
 *  -Initial implementation
 */

#include <linux/ptrace.h>
#include <linux/export.h>
#include <linux/stacktrace.h>
#include <linux/kallsyms.h>
#include <asm/arcregs.h>
#include <asm/unwind.h>
#include <asm/switch_to.h>

/*-------------------------------------------------------------------------
 *              Unwinder Iterator
 *-------------------------------------------------------------------------
 */

#ifdef CONFIG_ARC_DW2_UNWIND

static void seed_unwind_frame_info(struct task_struct *tsk,
				   struct pt_regs *regs,
				   struct unwind_frame_info *frame_info)
{
	/*
	 * synchronous unwinding (e.g. dump_stack)
	 *  - uses current values of SP and friends
	 */
	if (tsk == NULL && regs == NULL) {
		unsigned long fp, sp, blink, ret;
		frame_info->task = current;

		__asm__ __volatile__(
			"mov %0,r27\n\t"
			"mov %1,r28\n\t"
			"mov %2,r31\n\t"
			"mov %3,r63\n\t"
			: "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
		);

		frame_info->regs.r27 = fp;
		frame_info->regs.r28 = sp;
		frame_info->regs.r31 = blink;
		frame_info->regs.r63 = ret;
		frame_info->call_frame = 0;
	} else if (regs == NULL) {
		/*
		 * Asynchronous unwinding of sleeping task
		 *  - Gets SP etc from task's pt_regs (saved bottom of kernel
		 *    mode stack of task)
		 */

		frame_info->task = tsk;

		frame_info->regs.r27 = TSK_K_FP(tsk);
		frame_info->regs.r28 = TSK_K_ESP(tsk);
		frame_info->regs.r31 = TSK_K_BLINK(tsk);
		frame_info->regs.r63 = (unsigned int)__switch_to;

		/* In the prologue of __switch_to, first FP is saved on stack
		 * and then SP is copied to FP. Dwarf assumes cfa as FP based
		 * but we didn't save FP. The value retrieved above is FP's
		 * state in previous frame.
		 * As a work around for this, we unwind from __switch_to start
		 * and adjust SP accordingly. The other limitation is that
		 * __switch_to macro is dwarf rules are not generated for inline
		 * assembly code
		 */
		frame_info->regs.r27 = 0;
		frame_info->regs.r28 += 60;
		frame_info->call_frame = 0;

	} else {
		/*
		 * Asynchronous unwinding of intr/exception
		 *  - Just uses the pt_regs passed
		 */
		frame_info->task = tsk;

		frame_info->regs.r27 = regs->fp;
		frame_info->regs.r28 = regs->sp;
		frame_info->regs.r31 = regs->blink;
		frame_info->regs.r63 = regs->ret;
		frame_info->call_frame = 0;
	}
}

#endif

notrace noinline unsigned int
arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
		int (*consumer_fn) (unsigned int, void *), void *arg)
{
#ifdef CONFIG_ARC_DW2_UNWIND
	int ret = 0;
	unsigned int address;
	struct unwind_frame_info frame_info;

	seed_unwind_frame_info(tsk, regs, &frame_info);

	while (1) {
		address = UNW_PC(&frame_info);

		if (!address || !__kernel_text_address(address))
			break;

		if (consumer_fn(address, arg) == -1)
			break;

		ret = arc_unwind(&frame_info);
		if (ret)
			break;

		frame_info.regs.r63 = frame_info.regs.r31;
	}

	return address;		/* return the last address it saw */
#else
	/* On ARC, only Dward based unwinder works. fp based backtracing is
	 * not possible (-fno-omit-frame-pointer) because of the way function
	 * prelogue is setup (callee regs saved and then fp set and not other
	 * way around
	 */
	pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
	return 0;

#endif
}

/*-------------------------------------------------------------------------
 * callbacks called by unwinder iterator to implement kernel APIs
 *
 * The callback can return -1 to force the iterator to stop, which by default
 * keeps going till the bottom-most frame.
 *-------------------------------------------------------------------------
 */

/* Call-back which plugs into unwinding core to dump the stack in
 * case of panic/OOPs/BUG etc
 */
static int __print_sym(unsigned int address, void *unused)
{
	__print_symbol("  %s\n", address);
	return 0;
}

#ifdef CONFIG_STACKTRACE

/* Call-back which plugs into unwinding core to capture the
 * traces needed by kernel on /proc/<pid>/stack
 */
static int __collect_all(unsigned int address, void *arg)
{
	struct stack_trace *trace = arg;

	if (trace->skip > 0)
		trace->skip--;
	else
		trace->entries[trace->nr_entries++] = address;

	if (trace->nr_entries >= trace->max_entries)
		return -1;

	return 0;
}

static int __collect_all_but_sched(unsigned int address, void *arg)
{
	struct stack_trace *trace = arg;

	if (in_sched_functions(address))
		return 0;

	if (trace->skip > 0)
		trace->skip--;
	else
		trace->entries[trace->nr_entries++] = address;

	if (trace->nr_entries >= trace->max_entries)
		return -1;

	return 0;
}

#endif

static int __get_first_nonsched(unsigned int address, void *unused)
{
	if (in_sched_functions(address))
		return 0;

	return -1;
}

/*-------------------------------------------------------------------------
 *              APIs expected by various kernel sub-systems
 *-------------------------------------------------------------------------
 */

noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs)
{
	pr_info("\nStack Trace:\n");
	arc_unwind_core(tsk, regs, __print_sym, NULL);
}
EXPORT_SYMBOL(show_stacktrace);

/* Expected by sched Code */
void show_stack(struct task_struct *tsk, unsigned long *sp)
{
	show_stacktrace(tsk, NULL);
}

/* Another API expected by schedular, shows up in "ps" as Wait Channel
 * Of course just returning schedule( ) would be pointless so unwind until
 * the function is not in schedular code
 */
unsigned int get_wchan(struct task_struct *tsk)
{
	return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
}

#ifdef CONFIG_STACKTRACE

/*
 * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
 * A typical use is when /proc/<pid>/stack is queried by userland
 */
void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
	/* Assumes @tsk is sleeping so unwinds from __switch_to */
	arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
}

void save_stack_trace(struct stack_trace *trace)
{
	/* Pass NULL for task so it unwinds the current call frame */
	arc_unwind_core(NULL, NULL, __collect_all, trace);
}
EXPORT_SYMBOL_GPL(save_stack_trace);
#endif
Commit	Line	Data
c08098f2	1	/*
44c8bb91 VG	2	* stacktrace.c : stacktracing APIs needed by rest of kernel
	3	* (wrappers over ARC dwarf based unwinder)
	4	*
c08098f2 VG	5	* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
	6	*
	7	* This program is free software; you can redistribute it and/or modify
	8	* it under the terms of the GNU General Public License version 2 as
	9	* published by the Free Software Foundation.
44c8bb91 VG	10	*
	11	* vineetg: aug 2009
	12	* -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( )
	13	* for displaying task's kernel mode call stack in /proc/<pid>/stack
	14	* -Iterator based approach to have single copy of unwinding core and APIs
	15	* needing unwinding, implement the logic in iterator regarding:
	16	* = which frame onwards to start capture
	17	* = which frame to stop capturing (wchan)
	18	* = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc)
	19	*
	20	* vineetg: March 2009
	21	* -Implemented correct versions of thread_saved_pc() and get_wchan()
	22	*
	23	* rajeshwarr: 2008
	24	* -Initial implementation
c08098f2 VG	25	*/
	26
	27	#include <linux/ptrace.h>
	28	#include <linux/export.h>
44c8bb91 VG	29	#include <linux/stacktrace.h>
	30	#include <linux/kallsyms.h>
	31	#include <asm/arcregs.h>
	32	#include <asm/unwind.h>
	33	#include <asm/switch_to.h>
	34
	35	/*-------------------------------------------------------------------------
	36	* Unwinder Iterator
	37	*-------------------------------------------------------------------------
	38	*/
	39
	40	#ifdef CONFIG_ARC_DW2_UNWIND
	41
	42	static void seed_unwind_frame_info(struct task_struct *tsk,
	43	struct pt_regs *regs,
	44	struct unwind_frame_info *frame_info)
	45	{
3a51d50f VG	46	/*
	47	* synchronous unwinding (e.g. dump_stack)
	48	* - uses current values of SP and friends
	49	*/
44c8bb91 VG	50	if (tsk == NULL && regs == NULL) {
	51	unsigned long fp, sp, blink, ret;
	52	frame_info->task = current;
	53
	54	__asm__ __volatile__(
	55	"mov %0,r27\n\t"
	56	"mov %1,r28\n\t"
	57	"mov %2,r31\n\t"
	58	"mov %3,r63\n\t"
	59	: "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
	60	);
	61
	62	frame_info->regs.r27 = fp;
	63	frame_info->regs.r28 = sp;
	64	frame_info->regs.r31 = blink;
	65	frame_info->regs.r63 = ret;
	66	frame_info->call_frame = 0;
	67	} else if (regs == NULL) {
3a51d50f VG	68	/*
	69	* Asynchronous unwinding of sleeping task
	70	* - Gets SP etc from task's pt_regs (saved bottom of kernel
	71	* mode stack of task)
	72	*/
44c8bb91 VG	73
	74	frame_info->task = tsk;
	75
13648b01 VG	76	frame_info->regs.r27 = TSK_K_FP(tsk);
	77	frame_info->regs.r28 = TSK_K_ESP(tsk);
	78	frame_info->regs.r31 = TSK_K_BLINK(tsk);
44c8bb91 VG	79	frame_info->regs.r63 = (unsigned int)__switch_to;
	80
	81	/* In the prologue of __switch_to, first FP is saved on stack
	82	* and then SP is copied to FP. Dwarf assumes cfa as FP based
	83	* but we didn't save FP. The value retrieved above is FP's
	84	* state in previous frame.
	85	* As a work around for this, we unwind from __switch_to start
	86	* and adjust SP accordingly. The other limitation is that
	87	* __switch_to macro is dwarf rules are not generated for inline
	88	* assembly code
	89	*/
	90	frame_info->regs.r27 = 0;
16f9afe6	91	frame_info->regs.r28 += 60;
44c8bb91 VG	92	frame_info->call_frame = 0;
	93
	94	} else {
3a51d50f VG	95	/*
	96	* Asynchronous unwinding of intr/exception
	97	* - Just uses the pt_regs passed
	98	*/
44c8bb91 VG	99	frame_info->task = tsk;
	100
	101	frame_info->regs.r27 = regs->fp;
	102	frame_info->regs.r28 = regs->sp;
	103	frame_info->regs.r31 = regs->blink;
	104	frame_info->regs.r63 = regs->ret;
	105	frame_info->call_frame = 0;
	106	}
	107	}
	108
	109	#endif
	110
3a51d50f	111	notrace noinline unsigned int
44c8bb91 VG	112	arc_unwind_core(struct task_struct tsk, struct pt_regs regs,
	113	int (consumer_fn) (unsigned int, void ), void *arg)
	114	{
	115	#ifdef CONFIG_ARC_DW2_UNWIND
	116	int ret = 0;
	117	unsigned int address;
	118	struct unwind_frame_info frame_info;
	119
	120	seed_unwind_frame_info(tsk, regs, &frame_info);
	121
	122	while (1) {
	123	address = UNW_PC(&frame_info);
	124
def32fad VG	125	if (!address \|\| !__kernel_text_address(address))
def32fad VG	126	break;
44c8bb91	127
def32fad VG	128	if (consumer_fn(address, arg) == -1)
def32fad VG	129	break;
44c8bb91	130
def32fad VG	131	ret = arc_unwind(&frame_info);
def32fad VG	132	if (ret)
44c8bb91	133	break;
def32fad VG	134
def32fad VG	135	frame_info.regs.r63 = frame_info.regs.r31;
44c8bb91 VG	136	}
	137
	138	return address; /* return the last address it saw */
	139	#else
	140	/* On ARC, only Dward based unwinder works. fp based backtracing is
	141	* not possible (-fno-omit-frame-pointer) because of the way function
	142	* prelogue is setup (callee regs saved and then fp set and not other
	143	* way around
	144	*/
9bd54517	145	pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
44c8bb91 VG	146	return 0;
	147
	148	#endif
	149	}
	150
	151	/*-------------------------------------------------------------------------
	152	* callbacks called by unwinder iterator to implement kernel APIs
	153	*
	154	* The callback can return -1 to force the iterator to stop, which by default
	155	* keeps going till the bottom-most frame.
	156	*-------------------------------------------------------------------------
	157	*/
	158
	159	/* Call-back which plugs into unwinding core to dump the stack in
	160	* case of panic/OOPs/BUG etc
	161	*/
	162	static int __print_sym(unsigned int address, void *unused)
	163	{
	164	__print_symbol(" %s\n", address);
	165	return 0;
	166	}
	167
	168	#ifdef CONFIG_STACKTRACE
	169
	170	/* Call-back which plugs into unwinding core to capture the
	171	* traces needed by kernel on /proc/<pid>/stack
	172	*/
	173	static int __collect_all(unsigned int address, void *arg)
	174	{
	175	struct stack_trace *trace = arg;
	176
	177	if (trace->skip > 0)
	178	trace->skip--;
	179	else
	180	trace->entries[trace->nr_entries++] = address;
	181
	182	if (trace->nr_entries >= trace->max_entries)
	183	return -1;
	184
	185	return 0;
	186	}
	187
	188	static int __collect_all_but_sched(unsigned int address, void *arg)
	189	{
	190	struct stack_trace *trace = arg;
	191
	192	if (in_sched_functions(address))
	193	return 0;
	194
	195	if (trace->skip > 0)
	196	trace->skip--;
	197	else
	198	trace->entries[trace->nr_entries++] = address;
	199
	200	if (trace->nr_entries >= trace->max_entries)
	201	return -1;
	202
	203	return 0;
	204	}
	205
	206	#endif
	207
	208	static int __get_first_nonsched(unsigned int address, void *unused)
	209	{
210	if (in_sched_functions(address))
211	return 0;
212
213	return -1;
214	}
c08098f2 VG	215
	216	/*-------------------------------------------------------------------------
	217	* APIs expected by various kernel sub-systems
	218	*-------------------------------------------------------------------------
	219	*/
	220
	221	noinline void show_stacktrace(struct task_struct tsk, struct pt_regs regs)
	222	{
44c8bb91 VG	223	pr_info("\nStack Trace:\n");
44c8bb91 VG	224	arc_unwind_core(tsk, regs, __print_sym, NULL);
c08098f2 VG	225	}
	226	EXPORT_SYMBOL(show_stacktrace);
	227
	228	/* Expected by sched Code */
	229	void show_stack(struct task_struct tsk, unsigned long sp)
	230	{
	231	show_stacktrace(tsk, NULL);
	232	}
	233
c08098f2	234	/* Another API expected by schedular, shows up in "ps" as Wait Channel
7423cc0c	235	* Of course just returning schedule( ) would be pointless so unwind until
c08098f2 VG	236	* the function is not in schedular code
	237	*/
	238	unsigned int get_wchan(struct task_struct *tsk)
	239	{
44c8bb91 VG	240	return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
	241	}
	242
	243	#ifdef CONFIG_STACKTRACE
	244
	245	/*
	246	* API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
	247	* A typical use is when /proc/<pid>/stack is queried by userland
	248	*/
	249	void save_stack_trace_tsk(struct task_struct tsk, struct stack_trace trace)
	250	{
0dafafc3	251	/* Assumes @tsk is sleeping so unwinds from __switch_to */
44c8bb91 VG	252	arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
	253	}
	254
	255	void save_stack_trace(struct stack_trace *trace)
	256	{
0dafafc3 VG	257	/* Pass NULL for task so it unwinds the current call frame */
0dafafc3 VG	258	arc_unwind_core(NULL, NULL, __collect_all, trace);
c08098f2	259	}
8f146d02	260	EXPORT_SYMBOL_GPL(save_stack_trace);
44c8bb91	261	#endif