[deliverable/linux.git] / arch / microblaze / kernel / unwind.c

/*
 * Backtrace support for Microblaze
 *
 * Copyright (C) 2010  Digital Design Corporation
 *
 * Based on arch/sh/kernel/cpu/sh5/unwind.c code which is:
 * Copyright (C) 2004  Paul Mundt
 * Copyright (C) 2004  Richard Curnow
 *
 * 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.
 */

/* #define DEBUG 1 */
#include <linux/export.h>
#include <linux/kallsyms.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/stacktrace.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/io.h>
#include <asm/sections.h>
#include <asm/exceptions.h>
#include <asm/unwind.h>
#include <asm/switch_to.h>

struct stack_trace;

/*
 * On Microblaze, finding the previous stack frame is a little tricky.
 * At this writing (3/2010), Microblaze does not support CONFIG_FRAME_POINTERS,
 * and even if it did, gcc (4.1.2) does not store the frame pointer at
 * a consistent offset within each frame. To determine frame size, it is
 * necessary to search for the assembly instruction that creates or reclaims
 * the frame and extract the size from it.
 *
 * Microblaze stores the stack pointer in r1, and creates a frame via
 *
 *     addik r1, r1, -FRAME_SIZE
 *
 * The frame is reclaimed via
 *
 *     addik r1, r1, FRAME_SIZE
 *
 * Frame creation occurs at or near the top of a function.
 * Depending on the compiler, reclaim may occur at the end, or before
 * a mid-function return.
 *
 * A stack frame is usually not created in a leaf function.
 *
 */

/**
 * get_frame_size - Extract the stack adjustment from an
 *                  "addik r1, r1, adjust" instruction
 * @instr : Microblaze instruction
 *
 * Return - Number of stack bytes the instruction reserves or reclaims
 */
inline long get_frame_size(unsigned long instr)
{
	return abs((s16)(instr & 0xFFFF));
}

/**
 * find_frame_creation - Search backward to find the instruction that creates
 *                       the stack frame (hopefully, for the same function the
 *                       initial PC is in).
 * @pc : Program counter at which to begin the search
 *
 * Return - PC at which stack frame creation occurs
 *          NULL if this cannot be found, i.e. a leaf function
 */
static unsigned long *find_frame_creation(unsigned long *pc)
{
	int i;

	/* NOTE: Distance to search is arbitrary
	 *	 250 works well for most things,
	 *	 750 picks up things like tcp_recvmsg(),
	 *	1000 needed for fat_fill_super()
	 */
	for (i = 0; i < 1000; i++, pc--) {
		unsigned long instr;
		s16 frame_size;

		if (!kernel_text_address((unsigned long) pc))
			return NULL;

		instr = *pc;

		/* addik r1, r1, foo ? */
		if ((instr & 0xFFFF0000) != 0x30210000)
			continue;	/* No */

		frame_size = get_frame_size(instr);
		if ((frame_size < 8) || (frame_size & 3)) {
			pr_debug("    Invalid frame size %d at 0x%p\n",
				 frame_size, pc);
			return NULL;
		}

		pr_debug("    Found frame creation at 0x%p, size %d\n", pc,
			 frame_size);
		return pc;
	}

	return NULL;
}

/**
 * lookup_prev_stack_frame - Find the stack frame of the previous function.
 * @fp          : Frame (stack) pointer for current function
 * @pc          : Program counter within current function
 * @leaf_return : r15 value within current function. If the current function
 *		  is a leaf, this is the caller's return address.
 * @pprev_fp    : On exit, set to frame (stack) pointer for previous function
 * @pprev_pc    : On exit, set to current function caller's return address
 *
 * Return - 0 on success, -EINVAL if the previous frame cannot be found
 */
static int lookup_prev_stack_frame(unsigned long fp, unsigned long pc,
				   unsigned long leaf_return,
				   unsigned long *pprev_fp,
				   unsigned long *pprev_pc)
{
	unsigned long *prologue = NULL;

	/* _switch_to is a special leaf function */
	if (pc != (unsigned long) &_switch_to)
		prologue = find_frame_creation((unsigned long *)pc);

	if (prologue) {
		long frame_size = get_frame_size(*prologue);

		*pprev_fp = fp + frame_size;
		*pprev_pc = *(unsigned long *)fp;
	} else {
		if (!leaf_return)
			return -EINVAL;
		*pprev_pc = leaf_return;
		*pprev_fp = fp;
	}

	/* NOTE: don't check kernel_text_address here, to allow display
	 *	 of userland return address
	 */
	return (!*pprev_pc || (*pprev_pc & 3)) ? -EINVAL : 0;
}

static void microblaze_unwind_inner(struct task_struct *task,
				    unsigned long pc, unsigned long fp,
				    unsigned long leaf_return,
				    struct stack_trace *trace);

/**
 * unwind_trap - Unwind through a system trap, that stored previous state
 *		 on the stack.
 */
#ifdef CONFIG_MMU
static inline void unwind_trap(struct task_struct *task, unsigned long pc,
				unsigned long fp, struct stack_trace *trace)
{
	/* To be implemented */
}
#else
static inline void unwind_trap(struct task_struct *task, unsigned long pc,
				unsigned long fp, struct stack_trace *trace)
{
	const struct pt_regs *regs = (const struct pt_regs *) fp;
	microblaze_unwind_inner(task, regs->pc, regs->r1, regs->r15, trace);
}
#endif

/**
 * microblaze_unwind_inner - Unwind the stack from the specified point
 * @task  : Task whose stack we are to unwind (may be NULL)
 * @pc    : Program counter from which we start unwinding
 * @fp    : Frame (stack) pointer from which we start unwinding
 * @leaf_return : Value of r15 at pc. If the function is a leaf, this is
 *				  the caller's return address.
 * @trace : Where to store stack backtrace (PC values).
 *	    NULL == print backtrace to kernel log
 */
static void microblaze_unwind_inner(struct task_struct *task,
			     unsigned long pc, unsigned long fp,
			     unsigned long leaf_return,
			     struct stack_trace *trace)
{
	int ofs = 0;

	pr_debug("    Unwinding with PC=%p, FP=%p\n", (void *)pc, (void *)fp);
	if (!pc || !fp || (pc & 3) || (fp & 3)) {
		pr_debug("    Invalid state for unwind, aborting\n");
		return;
	}
	for (; pc != 0;) {
		unsigned long next_fp, next_pc = 0;
		unsigned long return_to = pc +  2 * sizeof(unsigned long);
		const struct trap_handler_info *handler =
			&microblaze_trap_handlers;

		/* Is previous function the HW exception handler? */
		if ((return_to >= (unsigned long)&_hw_exception_handler)
		    &&(return_to < (unsigned long)&ex_handler_unhandled)) {
			/*
			 * HW exception handler doesn't save all registers,
			 * so we open-code a special case of unwind_trap()
			 */
#ifndef CONFIG_MMU
			const struct pt_regs *regs =
				(const struct pt_regs *) fp;
#endif
			pr_info("HW EXCEPTION\n");
#ifndef CONFIG_MMU
			microblaze_unwind_inner(task, regs->r17 - 4,
						fp + EX_HANDLER_STACK_SIZ,
						regs->r15, trace);
#endif
			return;
		}

		/* Is previous function a trap handler? */
		for (; handler->start_addr; ++handler) {
			if ((return_to >= handler->start_addr)
			    && (return_to <= handler->end_addr)) {
				if (!trace)
					pr_info("%s\n", handler->trap_name);
				unwind_trap(task, pc, fp, trace);
				return;
			}
		}
		pc -= ofs;

		if (trace) {
#ifdef CONFIG_STACKTRACE
			if (trace->skip > 0)
				trace->skip--;
			else
				trace->entries[trace->nr_entries++] = pc;

			if (trace->nr_entries >= trace->max_entries)
				break;
#endif
		} else {
			/* Have we reached userland? */
			if (unlikely(pc == task_pt_regs(task)->pc)) {
				pr_info("[<%p>] PID %lu [%s]\n",
					(void *) pc,
					(unsigned long) task->pid,
					task->comm);
				break;
			} else
				print_ip_sym(pc);
		}

		/* Stop when we reach anything not part of the kernel */
		if (!kernel_text_address(pc))
			break;

		if (lookup_prev_stack_frame(fp, pc, leaf_return, &next_fp,
					    &next_pc) == 0) {
			ofs = sizeof(unsigned long);
			pc = next_pc & ~3;
			fp = next_fp;
			leaf_return = 0;
		} else {
			pr_debug("    Failed to find previous stack frame\n");
			break;
		}

		pr_debug("    Next PC=%p, next FP=%p\n",
			 (void *)next_pc, (void *)next_fp);
	}
}

/**
 * microblaze_unwind - Stack unwinder for Microblaze (external entry point)
 * @task  : Task whose stack we are to unwind (NULL == current)
 * @trace : Where to store stack backtrace (PC values).
 *	    NULL == print backtrace to kernel log
 */
void microblaze_unwind(struct task_struct *task, struct stack_trace *trace)
{
	if (task) {
		if (task == current) {
			const struct pt_regs *regs = task_pt_regs(task);
			microblaze_unwind_inner(task, regs->pc, regs->r1,
						regs->r15, trace);
		} else {
			struct thread_info *thread_info =
				(struct thread_info *)(task->stack);
			const struct cpu_context *cpu_context =
				&thread_info->cpu_context;

			microblaze_unwind_inner(task,
						(unsigned long) &_switch_to,
						cpu_context->r1,
						cpu_context->r15, trace);
		}
	} else {
		unsigned long pc, fp;

		__asm__ __volatile__ ("or %0, r1, r0" : "=r" (fp));

		__asm__ __volatile__ (
			"brlid %0, 0f;"
			"nop;"
			"0:"
			: "=r" (pc)
		);

		/* Since we are not a leaf function, use leaf_return = 0 */
		microblaze_unwind_inner(current, pc, fp, 0, trace);
	}
}
Commit	Line	Data
ce3266c0 SM	1	/*
	2	* Backtrace support for Microblaze
	3	*
	4	* Copyright (C) 2010 Digital Design Corporation
	5	*
	6	* Based on arch/sh/kernel/cpu/sh5/unwind.c code which is:
	7	* Copyright (C) 2004 Paul Mundt
	8	* Copyright (C) 2004 Richard Curnow
	9	*
	10	* This file is subject to the terms and conditions of the GNU General Public
	11	* License. See the file "COPYING" in the main directory of this archive
	12	* for more details.
	13	*/
	14
	15	/* #define DEBUG 1 */
d64af918	16	#include <linux/export.h>
ce3266c0 SM	17	#include <linux/kallsyms.h>
	18	#include <linux/kernel.h>
	19	#include <linux/sched.h>
	20	#include <linux/stacktrace.h>
	21	#include <linux/types.h>
	22	#include <linux/errno.h>
ce3266c0 SM	23	#include <linux/io.h>
	24	#include <asm/sections.h>
	25	#include <asm/exceptions.h>
	26	#include <asm/unwind.h>
90c0d80d	27	#include <asm/switch_to.h>
ce3266c0 SM	28
	29	struct stack_trace;
	30
	31	/*
	32	* On Microblaze, finding the previous stack frame is a little tricky.
	33	* At this writing (3/2010), Microblaze does not support CONFIG_FRAME_POINTERS,
	34	* and even if it did, gcc (4.1.2) does not store the frame pointer at
	35	* a consistent offset within each frame. To determine frame size, it is
	36	* necessary to search for the assembly instruction that creates or reclaims
	37	* the frame and extract the size from it.
	38	*
	39	* Microblaze stores the stack pointer in r1, and creates a frame via
	40	*
	41	* addik r1, r1, -FRAME_SIZE
	42	*
	43	* The frame is reclaimed via
	44	*
	45	* addik r1, r1, FRAME_SIZE
	46	*
	47	* Frame creation occurs at or near the top of a function.
	48	* Depending on the compiler, reclaim may occur at the end, or before
	49	* a mid-function return.
	50	*
	51	* A stack frame is usually not created in a leaf function.
	52	*
	53	*/
	54
	55	/**
	56	* get_frame_size - Extract the stack adjustment from an
	57	* "addik r1, r1, adjust" instruction
	58	* @instr : Microblaze instruction
	59	*
	60	* Return - Number of stack bytes the instruction reserves or reclaims
	61	*/
	62	inline long get_frame_size(unsigned long instr)
	63	{
	64	return abs((s16)(instr & 0xFFFF));
	65	}
	66
	67	/**
	68	* find_frame_creation - Search backward to find the instruction that creates
	69	* the stack frame (hopefully, for the same function the
	70	* initial PC is in).
	71	* @pc : Program counter at which to begin the search
	72	*
	73	* Return - PC at which stack frame creation occurs
	74	* NULL if this cannot be found, i.e. a leaf function
	75	*/
	76	static unsigned long find_frame_creation(unsigned long pc)
	77	{
	78	int i;
	79
	80	/* NOTE: Distance to search is arbitrary
	81	* 250 works well for most things,
	82	* 750 picks up things like tcp_recvmsg(),
	83	* 1000 needed for fat_fill_super()
	84	*/
	85	for (i = 0; i < 1000; i++, pc--) {
	86	unsigned long instr;
	87	s16 frame_size;
	88
	89	if (!kernel_text_address((unsigned long) pc))
	90	return NULL;
	91
92	instr = *pc;
93
94	/* addik r1, r1, foo ? */
95	if ((instr & 0xFFFF0000) != 0x30210000)
96	continue; /* No */
97
98	frame_size = get_frame_size(instr);
99	if ((frame_size < 8) \|\| (frame_size & 3)) {
100	pr_debug(" Invalid frame size %d at 0x%p\n",
101	frame_size, pc);
102	return NULL;
103	}
104
105	pr_debug(" Found frame creation at 0x%p, size %d\n", pc,
106	frame_size);
107	return pc;
108	}
109
110	return NULL;
111	}
112
113	/**
114	* lookup_prev_stack_frame - Find the stack frame of the previous function.
115	* @fp : Frame (stack) pointer for current function
116	* @pc : Program counter within current function
117	* @leaf_return : r15 value within current function. If the current function
118	* is a leaf, this is the caller's return address.
119	* @pprev_fp : On exit, set to frame (stack) pointer for previous function
120	* @pprev_pc : On exit, set to current function caller's return address
121	*
122	* Return - 0 on success, -EINVAL if the previous frame cannot be found
123	*/
124	static int lookup_prev_stack_frame(unsigned long fp, unsigned long pc,
125	unsigned long leaf_return,
126	unsigned long *pprev_fp,
127	unsigned long *pprev_pc)
128	{
129	unsigned long *prologue = NULL;
130
131	/* _switch_to is a special leaf function */
132	if (pc != (unsigned long) &_switch_to)
133	prologue = find_frame_creation((unsigned long *)pc);
134
135	if (prologue) {
136	long frame_size = get_frame_size(*prologue);
137
138	*pprev_fp = fp + frame_size;
139	pprev_pc = (unsigned long *)fp;
140	} else {
141	if (!leaf_return)
142	return -EINVAL;
143	*pprev_pc = leaf_return;
144	*pprev_fp = fp;
145	}
146
147	/* NOTE: don't check kernel_text_address here, to allow display
148	* of userland return address
149	*/
150	return (!pprev_pc \|\| (pprev_pc & 3)) ? -EINVAL : 0;
151	}
152
153	static void microblaze_unwind_inner(struct task_struct *task,
154	unsigned long pc, unsigned long fp,
155	unsigned long leaf_return,
156	struct stack_trace *trace);
157
158	/**
159	* unwind_trap - Unwind through a system trap, that stored previous state
160	* on the stack.
161	*/
162	#ifdef CONFIG_MMU
163	static inline void unwind_trap(struct task_struct *task, unsigned long pc,
164	unsigned long fp, struct stack_trace *trace)
165	{
166	/* To be implemented */
167	}
168	#else
169	static inline void unwind_trap(struct task_struct *task, unsigned long pc,
170	unsigned long fp, struct stack_trace *trace)
171	{
172	const struct pt_regs regs = (const struct pt_regs ) fp;
173	microblaze_unwind_inner(task, regs->pc, regs->r1, regs->r15, trace);
174	}
175	#endif
176
177	/**
178	* microblaze_unwind_inner - Unwind the stack from the specified point
179	* @task : Task whose stack we are to unwind (may be NULL)
180	* @pc : Program counter from which we start unwinding
181	* @fp : Frame (stack) pointer from which we start unwinding
182	* @leaf_return : Value of r15 at pc. If the function is a leaf, this is
183	* the caller's return address.
184	* @trace : Where to store stack backtrace (PC values).
185	* NULL == print backtrace to kernel log
186	*/
419ef340	187	static void microblaze_unwind_inner(struct task_struct *task,
ce3266c0 SM	188	unsigned long pc, unsigned long fp,
	189	unsigned long leaf_return,
	190	struct stack_trace *trace)
	191	{
	192	int ofs = 0;
	193
	194	pr_debug(" Unwinding with PC=%p, FP=%p\n", (void )pc, (void )fp);
	195	if (!pc \|\| !fp \|\| (pc & 3) \|\| (fp & 3)) {
	196	pr_debug(" Invalid state for unwind, aborting\n");
	197	return;
	198	}
	199	for (; pc != 0;) {
	200	unsigned long next_fp, next_pc = 0;
	201	unsigned long return_to = pc + 2 * sizeof(unsigned long);
	202	const struct trap_handler_info *handler =
	203	&microblaze_trap_handlers;
	204
	205	/* Is previous function the HW exception handler? */
	206	if ((return_to >= (unsigned long)&_hw_exception_handler)
	207	&&(return_to < (unsigned long)&ex_handler_unhandled)) {
	208	/*
	209	* HW exception handler doesn't save all registers,
	210	* so we open-code a special case of unwind_trap()
	211	*/
	212	#ifndef CONFIG_MMU
	213	const struct pt_regs *regs =
	214	(const struct pt_regs *) fp;
	215	#endif
	216	pr_info("HW EXCEPTION\n");
	217	#ifndef CONFIG_MMU
	218	microblaze_unwind_inner(task, regs->r17 - 4,
	219	fp + EX_HANDLER_STACK_SIZ,
	220	regs->r15, trace);
	221	#endif
	222	return;
	223	}
	224
	225	/* Is previous function a trap handler? */
	226	for (; handler->start_addr; ++handler) {
	227	if ((return_to >= handler->start_addr)
	228	&& (return_to <= handler->end_addr)) {
	229	if (!trace)
	230	pr_info("%s\n", handler->trap_name);
	231	unwind_trap(task, pc, fp, trace);
	232	return;
	233	}
	234	}
	235	pc -= ofs;
	236
	237	if (trace) {
	238	#ifdef CONFIG_STACKTRACE
	239	if (trace->skip > 0)
	240	trace->skip--;
	241	else
	242	trace->entries[trace->nr_entries++] = pc;
	243
	244	if (trace->nr_entries >= trace->max_entries)
	245	break;
	246	#endif
	247	} else {
	248	/* Have we reached userland? */
	249	if (unlikely(pc == task_pt_regs(task)->pc)) {
	250	pr_info("[<%p>] PID %lu [%s]\n",
	251	(void *) pc,
252	(unsigned long) task->pid,
253	task->comm);
254	break;
255	} else
256	print_ip_sym(pc);
257	}
258
259	/* Stop when we reach anything not part of the kernel */
260	if (!kernel_text_address(pc))
261	break;
262
263	if (lookup_prev_stack_frame(fp, pc, leaf_return, &next_fp,
264	&next_pc) == 0) {
265	ofs = sizeof(unsigned long);
266	pc = next_pc & ~3;
267	fp = next_fp;
268	leaf_return = 0;
269	} else {
270	pr_debug(" Failed to find previous stack frame\n");
271	break;
272	}
273
274	pr_debug(" Next PC=%p, next FP=%p\n",
275	(void )next_pc, (void )next_fp);
276	}
277	}
278
279	/**
280	* microblaze_unwind - Stack unwinder for Microblaze (external entry point)
281	* @task : Task whose stack we are to unwind (NULL == current)
282	* @trace : Where to store stack backtrace (PC values).
283	* NULL == print backtrace to kernel log
284	*/
285	void microblaze_unwind(struct task_struct task, struct stack_trace trace)
286	{
287	if (task) {
288	if (task == current) {
289	const struct pt_regs *regs = task_pt_regs(task);
290	microblaze_unwind_inner(task, regs->pc, regs->r1,
291	regs->r15, trace);
292	} else {
293	struct thread_info *thread_info =
294	(struct thread_info *)(task->stack);
295	const struct cpu_context *cpu_context =
296	&thread_info->cpu_context;
297
298	microblaze_unwind_inner(task,
299	(unsigned long) &_switch_to,
300	cpu_context->r1,
301	cpu_context->r15, trace);
302	}
303	} else {
304	unsigned long pc, fp;
305
306	__asm__ __volatile__ ("or %0, r1, r0" : "=r" (fp));
307
308	__asm__ __volatile__ (
309	"brlid %0, 0f;"
310	"nop;"
311	"0:"
312	: "=r" (pc)
313	);
314
315	/* Since we are not a leaf function, use leaf_return = 0 */
316	microblaze_unwind_inner(current, pc, fp, 0, trace);
317	}
318	}
319