[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 <linux/sched/debug.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>
44c8bb91 VG	30	#include <linux/kallsyms.h>
b17b0153 IM	31	#include <linux/sched/debug.h>
b17b0153 IM	32
44c8bb91 VG	33	#include <asm/arcregs.h>
	34	#include <asm/unwind.h>
	35	#include <asm/switch_to.h>
	36
	37	/*-------------------------------------------------------------------------
	38	* Unwinder Iterator
	39	*-------------------------------------------------------------------------
	40	*/
	41
	42	#ifdef CONFIG_ARC_DW2_UNWIND
	43
	44	static void seed_unwind_frame_info(struct task_struct *tsk,
	45	struct pt_regs *regs,
	46	struct unwind_frame_info *frame_info)
	47	{
3a51d50f VG	48	/*
	49	* synchronous unwinding (e.g. dump_stack)
	50	* - uses current values of SP and friends
	51	*/
44c8bb91 VG	52	if (tsk == NULL && regs == NULL) {
	53	unsigned long fp, sp, blink, ret;
	54	frame_info->task = current;
	55
	56	__asm__ __volatile__(
	57	"mov %0,r27\n\t"
	58	"mov %1,r28\n\t"
	59	"mov %2,r31\n\t"
	60	"mov %3,r63\n\t"
	61	: "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
	62	);
	63
	64	frame_info->regs.r27 = fp;
	65	frame_info->regs.r28 = sp;
	66	frame_info->regs.r31 = blink;
	67	frame_info->regs.r63 = ret;
	68	frame_info->call_frame = 0;
	69	} else if (regs == NULL) {
3a51d50f VG	70	/*
	71	* Asynchronous unwinding of sleeping task
	72	* - Gets SP etc from task's pt_regs (saved bottom of kernel
	73	* mode stack of task)
	74	*/
44c8bb91 VG	75
	76	frame_info->task = tsk;
	77
13648b01 VG	78	frame_info->regs.r27 = TSK_K_FP(tsk);
	79	frame_info->regs.r28 = TSK_K_ESP(tsk);
	80	frame_info->regs.r31 = TSK_K_BLINK(tsk);
44c8bb91 VG	81	frame_info->regs.r63 = (unsigned int)__switch_to;
	82
	83	/* In the prologue of __switch_to, first FP is saved on stack
	84	* and then SP is copied to FP. Dwarf assumes cfa as FP based
	85	* but we didn't save FP. The value retrieved above is FP's
	86	* state in previous frame.
	87	* As a work around for this, we unwind from __switch_to start
	88	* and adjust SP accordingly. The other limitation is that
	89	* __switch_to macro is dwarf rules are not generated for inline
	90	* assembly code
	91	*/
	92	frame_info->regs.r27 = 0;
16f9afe6	93	frame_info->regs.r28 += 60;
44c8bb91 VG	94	frame_info->call_frame = 0;
	95
	96	} else {
3a51d50f VG	97	/*
	98	* Asynchronous unwinding of intr/exception
	99	* - Just uses the pt_regs passed
	100	*/
44c8bb91 VG	101	frame_info->task = tsk;
	102
	103	frame_info->regs.r27 = regs->fp;
	104	frame_info->regs.r28 = regs->sp;
	105	frame_info->regs.r31 = regs->blink;
	106	frame_info->regs.r63 = regs->ret;
	107	frame_info->call_frame = 0;
	108	}
	109	}
	110
	111	#endif
	112
3a51d50f	113	notrace noinline unsigned int
44c8bb91 VG	114	arc_unwind_core(struct task_struct tsk, struct pt_regs regs,
	115	int (consumer_fn) (unsigned int, void ), void *arg)
	116	{
	117	#ifdef CONFIG_ARC_DW2_UNWIND
	118	int ret = 0;
	119	unsigned int address;
	120	struct unwind_frame_info frame_info;
	121
	122	seed_unwind_frame_info(tsk, regs, &frame_info);
	123
	124	while (1) {
	125	address = UNW_PC(&frame_info);
	126
def32fad VG	127	if (!address \|\| !__kernel_text_address(address))
def32fad VG	128	break;
44c8bb91	129
def32fad VG	130	if (consumer_fn(address, arg) == -1)
def32fad VG	131	break;
44c8bb91	132
def32fad VG	133	ret = arc_unwind(&frame_info);
def32fad VG	134	if (ret)
44c8bb91	135	break;
def32fad VG	136
def32fad VG	137	frame_info.regs.r63 = frame_info.regs.r31;
44c8bb91 VG	138	}
	139
	140	return address; /* return the last address it saw */
	141	#else
	142	/* On ARC, only Dward based unwinder works. fp based backtracing is
	143	* not possible (-fno-omit-frame-pointer) because of the way function
	144	* prelogue is setup (callee regs saved and then fp set and not other
	145	* way around
	146	*/
9bd54517	147	pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
44c8bb91 VG	148	return 0;
	149
	150	#endif
	151	}
	152
	153	/*-------------------------------------------------------------------------
	154	* callbacks called by unwinder iterator to implement kernel APIs
	155	*
	156	* The callback can return -1 to force the iterator to stop, which by default
	157	* keeps going till the bottom-most frame.
	158	*-------------------------------------------------------------------------
	159	*/
	160
	161	/* Call-back which plugs into unwinding core to dump the stack in
	162	* case of panic/OOPs/BUG etc
	163	*/
	164	static int __print_sym(unsigned int address, void *unused)
	165	{
	166	__print_symbol(" %s\n", address);
	167	return 0;
	168	}
	169
	170	#ifdef CONFIG_STACKTRACE
	171
	172	/* Call-back which plugs into unwinding core to capture the
	173	* traces needed by kernel on /proc/<pid>/stack
	174	*/
	175	static int __collect_all(unsigned int address, void *arg)
	176	{
	177	struct stack_trace *trace = arg;
	178
	179	if (trace->skip > 0)
	180	trace->skip--;
	181	else
	182	trace->entries[trace->nr_entries++] = address;
	183
	184	if (trace->nr_entries >= trace->max_entries)
	185	return -1;
	186
	187	return 0;
	188	}
	189
	190	static int __collect_all_but_sched(unsigned int address, void *arg)
	191	{
	192	struct stack_trace *trace = arg;
	193
	194	if (in_sched_functions(address))
	195	return 0;
	196
	197	if (trace->skip > 0)
	198	trace->skip--;
	199	else
	200	trace->entries[trace->nr_entries++] = address;
	201
	202	if (trace->nr_entries >= trace->max_entries)
	203	return -1;
	204
	205	return 0;
	206	}
	207
	208	#endif
	209
	210	static int __get_first_nonsched(unsigned int address, void *unused)
	211	{
212	if (in_sched_functions(address))
213	return 0;
214
215	return -1;
216	}
c08098f2 VG	217
	218	/*-------------------------------------------------------------------------
	219	* APIs expected by various kernel sub-systems
	220	*-------------------------------------------------------------------------
	221	*/
	222
	223	noinline void show_stacktrace(struct task_struct tsk, struct pt_regs regs)
	224	{
44c8bb91 VG	225	pr_info("\nStack Trace:\n");
44c8bb91 VG	226	arc_unwind_core(tsk, regs, __print_sym, NULL);
c08098f2 VG	227	}
	228	EXPORT_SYMBOL(show_stacktrace);
	229
	230	/* Expected by sched Code */
	231	void show_stack(struct task_struct tsk, unsigned long sp)
	232	{
	233	show_stacktrace(tsk, NULL);
	234	}
	235
c08098f2	236	/* Another API expected by schedular, shows up in "ps" as Wait Channel
7423cc0c	237	* Of course just returning schedule( ) would be pointless so unwind until
c08098f2 VG	238	* the function is not in schedular code
	239	*/
	240	unsigned int get_wchan(struct task_struct *tsk)
	241	{
44c8bb91 VG	242	return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
	243	}
	244
	245	#ifdef CONFIG_STACKTRACE
	246
	247	/*
	248	* API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
	249	* A typical use is when /proc/<pid>/stack is queried by userland
	250	*/
	251	void save_stack_trace_tsk(struct task_struct tsk, struct stack_trace trace)
	252	{
0dafafc3	253	/* Assumes @tsk is sleeping so unwinds from __switch_to */
44c8bb91 VG	254	arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
	255	}
	256
	257	void save_stack_trace(struct stack_trace *trace)
	258	{
0dafafc3 VG	259	/* Pass NULL for task so it unwinds the current call frame */
0dafafc3 VG	260	arc_unwind_core(NULL, NULL, __collect_all, trace);
c08098f2	261	}
8f146d02	262	EXPORT_SYMBOL_GPL(save_stack_trace);
44c8bb91	263	#endif