summaryrefslogtreecommitdiffstats
path: root/arch/xtensa/kernel/stacktrace.c
blob: ed324fdf2a2f9124527a5514ce14ac731996a2ad (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
/*
 * Kernel and userspace stack tracing.
 *
 * 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) 2001 - 2013 Tensilica Inc.
 * Copyright (C) 2015 Cadence Design Systems Inc.
 */
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/stacktrace.h>

#include <asm/ftrace.h>
#include <asm/sections.h>
#include <asm/stacktrace.h>
#include <asm/traps.h>
#include <linux/uaccess.h>

#if IS_ENABLED(CONFIG_PERF_EVENTS)

/* Address of common_exception_return, used to check the
 * transition from kernel to user space.
 */
extern int common_exception_return;

void xtensa_backtrace_user(struct pt_regs *regs, unsigned int depth,
			   int (*ufn)(struct stackframe *frame, void *data),
			   void *data)
{
	unsigned long windowstart = regs->windowstart;
	unsigned long windowbase = regs->windowbase;
	unsigned long a0 = regs->areg[0];
	unsigned long a1 = regs->areg[1];
	unsigned long pc = regs->pc;
	struct stackframe frame;
	int index;

	if (!depth--)
		return;

	frame.pc = pc;
	frame.sp = a1;

	if (pc == 0 || pc >= TASK_SIZE || ufn(&frame, data))
		return;

	if (IS_ENABLED(CONFIG_USER_ABI_CALL0_ONLY) ||
	    (IS_ENABLED(CONFIG_USER_ABI_CALL0_PROBE) &&
	     !(regs->ps & PS_WOE_MASK)))
		return;

	/* Two steps:
	 *
	 * 1. Look through the register window for the
	 * previous PCs in the call trace.
	 *
	 * 2. Look on the stack.
	 */

	/* Step 1.  */
	/* Rotate WINDOWSTART to move the bit corresponding to
	 * the current window to the bit #0.
	 */
	windowstart = (windowstart << WSBITS | windowstart) >> windowbase;

	/* Look for bits that are set, they correspond to
	 * valid windows.
	 */
	for (index = WSBITS - 1; (index > 0) && depth; depth--, index--)
		if (windowstart & (1 << index)) {
			/* Get the PC from a0 and a1. */
			pc = MAKE_PC_FROM_RA(a0, pc);
			/* Read a0 and a1 from the
			 * corresponding position in AREGs.
			 */
			a0 = regs->areg[index * 4];
			a1 = regs->areg[index * 4 + 1];

			frame.pc = pc;
			frame.sp = a1;

			if (pc == 0 || pc >= TASK_SIZE || ufn(&frame, data))
				return;
		}

	/* Step 2. */
	/* We are done with the register window, we need to
	 * look through the stack.
	 */
	if (!depth)
		return;

	/* Start from the a1 register. */
	/* a1 = regs->areg[1]; */
	while (a0 != 0 && depth--) {
		pc = MAKE_PC_FROM_RA(a0, pc);

		/* Check if the region is OK to access. */
		if (!access_ok(&SPILL_SLOT(a1, 0), 8))
			return;
		/* Copy a1, a0 from user space stack frame. */
		if (__get_user(a0, &SPILL_SLOT(a1, 0)) ||
		    __get_user(a1, &SPILL_SLOT(a1, 1)))
			return;

		frame.pc = pc;
		frame.sp = a1;

		if (pc == 0 || pc >= TASK_SIZE || ufn(&frame, data))
			return;
	}
}
EXPORT_SYMBOL(xtensa_backtrace_user);

void xtensa_backtrace_kernel(struct pt_regs *regs, unsigned int depth,
			     int (*kfn)(struct stackframe *frame, void *data),
			     int (*ufn)(struct stackframe *frame, void *data),
			     void *data)
{
	unsigned long pc = regs->depc > VALID_DOUBLE_EXCEPTION_ADDRESS ?
		regs->depc : regs->pc;
	unsigned long sp_start, sp_end;
	unsigned long a0 = regs->areg[0];
	unsigned long a1 = regs->areg[1];

	sp_start = a1 & ~(THREAD_SIZE - 1);
	sp_end = sp_start + THREAD_SIZE;

	/* Spill the register window to the stack first. */
	spill_registers();

	/* Read the stack frames one by one and create the PC
	 * from the a0 and a1 registers saved there.
	 */
	while (a1 > sp_start && a1 < sp_end && depth--) {
		struct stackframe frame;

		frame.pc = pc;
		frame.sp = a1;

		if (kernel_text_address(pc) && kfn(&frame, data))
			return;

		if (pc == (unsigned long)&common_exception_return) {
			regs = (struct pt_regs *)a1;
			if (user_mode(regs)) {
				if (ufn == NULL)
					return;
				xtensa_backtrace_user(regs, depth, ufn, data);
				return;
			}
			a0 = regs->areg[0];
			a1 = regs->areg[1];
			continue;
		}

		sp_start = a1;

		pc = MAKE_PC_FROM_RA(a0, pc);
		a0 = SPILL_SLOT(a1, 0);
		a1 = SPILL_SLOT(a1, 1);
	}
}
EXPORT_SYMBOL(xtensa_backtrace_kernel);

#endif

void walk_stackframe(unsigned long *sp,
		int (*fn)(struct stackframe *frame, void *data),
		void *data)
{
	unsigned long a0, a1;
	unsigned long sp_end;

	a1 = (unsigned long)sp;
	sp_end = ALIGN(a1, THREAD_SIZE);

	spill_registers();

	while (a1 < sp_end) {
		struct stackframe frame;

		sp = (unsigned long *)a1;

		a0 = SPILL_SLOT(a1, 0);
		a1 = SPILL_SLOT(a1, 1);

		if (a1 <= (unsigned long)sp)
			break;

		frame.pc = MAKE_PC_FROM_RA(a0, _text);
		frame.sp = a1;

		if (fn(&frame, data))
			return;
	}
}

#ifdef CONFIG_STACKTRACE

struct stack_trace_data {
	struct stack_trace *trace;
	unsigned skip;
};

static int stack_trace_cb(struct stackframe *frame, void *data)
{
	struct stack_trace_data *trace_data = data;
	struct stack_trace *trace = trace_data->trace;

	if (trace_data->skip) {
		--trace_data->skip;
		return 0;
	}
	if (!kernel_text_address(frame->pc))
		return 0;

	trace->entries[trace->nr_entries++] = frame->pc;
	return trace->nr_entries >= trace->max_entries;
}

void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
{
	struct stack_trace_data trace_data = {
		.trace = trace,
		.skip = trace->skip,
	};
	walk_stackframe(stack_pointer(task), stack_trace_cb, &trace_data);
}
EXPORT_SYMBOL_GPL(save_stack_trace_tsk);

void save_stack_trace(struct stack_trace *trace)
{
	save_stack_trace_tsk(current, trace);
}
EXPORT_SYMBOL_GPL(save_stack_trace);

#endif

struct return_addr_data {
	unsigned long addr;
	unsigned skip;
};

static int return_address_cb(struct stackframe *frame, void *data)
{
	struct return_addr_data *r = data;

	if (r->skip) {
		--r->skip;
		return 0;
	}
	if (!kernel_text_address(frame->pc))
		return 0;
	r->addr = frame->pc;
	return 1;
}

/*
 * level == 0 is for the return address from the caller of this function,
 * not from this function itself.
 */
unsigned long return_address(unsigned level)
{
	struct return_addr_data r = {
		.skip = level,
	};
	walk_stackframe(stack_pointer(NULL), return_address_cb, &r);
	return r.addr;
}
EXPORT_SYMBOL(return_address);