summaryrefslogtreecommitdiff
path: root/arch/arm64/kernel/stacktrace.c
blob: 62d395151abe650db40e14df52c9061c531a2bfa (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
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Stack tracing support
 *
 * Copyright (C) 2012 ARM Ltd.
 */
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/ftrace.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/stacktrace.h>

#include <asm/irq.h>
#include <asm/stack_pointer.h>
#include <asm/stacktrace.h>

/*
 * AArch64 PCS assigns the frame pointer to x29.
 *
 * A simple function prologue looks like this:
 * 	sub	sp, sp, #0x10
 *   	stp	x29, x30, [sp]
 *	mov	x29, sp
 *
 * A simple function epilogue looks like this:
 *	mov	sp, x29
 *	ldp	x29, x30, [sp]
 *	add	sp, sp, #0x10
 */
int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
{
	unsigned long fp = frame->fp;

	if (fp & 0xf)
		return -EINVAL;

	if (!tsk)
		tsk = current;

	if (!on_accessible_stack(tsk, fp, NULL))
		return -EINVAL;

	frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
	frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	if (tsk->ret_stack &&
			(frame->pc == (unsigned long)return_to_handler)) {
		struct ftrace_ret_stack *ret_stack;
		/*
		 * This is a case where function graph tracer has
		 * modified a return address (LR) in a stack frame
		 * to hook a function return.
		 * So replace it to an original value.
		 */
		ret_stack = ftrace_graph_get_ret_stack(tsk, frame->graph++);
		if (WARN_ON_ONCE(!ret_stack))
			return -EINVAL;
		frame->pc = ret_stack->ret;
	}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

	/*
	 * Frames created upon entry from EL0 have NULL FP and PC values, so
	 * don't bother reporting these. Frames created by __noreturn functions
	 * might have a valid FP even if PC is bogus, so only terminate where
	 * both are NULL.
	 */
	if (!frame->fp && !frame->pc)
		return -EINVAL;

	return 0;
}

void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
		     int (*fn)(struct stackframe *, void *), void *data)
{
	while (1) {
		int ret;

		if (fn(frame, data))
			break;
		ret = unwind_frame(tsk, frame);
		if (ret < 0)
			break;
	}
}

#ifdef CONFIG_STACKTRACE
struct stack_trace_data {
	struct stack_trace *trace;
	unsigned int no_sched_functions;
	unsigned int skip;
};

static int save_trace(struct stackframe *frame, void *d)
{
	struct stack_trace_data *data = d;
	struct stack_trace *trace = data->trace;
	unsigned long addr = frame->pc;

	if (data->no_sched_functions && in_sched_functions(addr))
		return 0;
	if (data->skip) {
		data->skip--;
		return 0;
	}

	trace->entries[trace->nr_entries++] = addr;

	return trace->nr_entries >= trace->max_entries;
}

void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
{
	struct stack_trace_data data;
	struct stackframe frame;

	data.trace = trace;
	data.skip = trace->skip;
	data.no_sched_functions = 0;

	frame.fp = regs->regs[29];
	frame.pc = regs->pc;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	frame.graph = 0;
#endif

	walk_stackframe(current, &frame, save_trace, &data);
}
EXPORT_SYMBOL_GPL(save_stack_trace_regs);

static noinline void __save_stack_trace(struct task_struct *tsk,
	struct stack_trace *trace, unsigned int nosched)
{
	struct stack_trace_data data;
	struct stackframe frame;

	if (!try_get_task_stack(tsk))
		return;

	data.trace = trace;
	data.skip = trace->skip;
	data.no_sched_functions = nosched;

	if (tsk != current) {
		frame.fp = thread_saved_fp(tsk);
		frame.pc = thread_saved_pc(tsk);
	} else {
		/* We don't want this function nor the caller */
		data.skip += 2;
		frame.fp = (unsigned long)__builtin_frame_address(0);
		frame.pc = (unsigned long)__save_stack_trace;
	}
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	frame.graph = 0;
#endif

	walk_stackframe(tsk, &frame, save_trace, &data);

	put_task_stack(tsk);
}
EXPORT_SYMBOL_GPL(save_stack_trace_tsk);

void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
	__save_stack_trace(tsk, trace, 1);
}

void save_stack_trace(struct stack_trace *trace)
{
	__save_stack_trace(current, trace, 0);
}

EXPORT_SYMBOL_GPL(save_stack_trace);
#endif