summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/stacktrace.c
blob: 20161ef53537c760d858388295f57d21ae2f7346 (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
/*
 * Stack trace management functions
 *
 *  Copyright (C) 2006-2009 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 */
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/stacktrace.h>
#include <linux/export.h>
#include <linux/uaccess.h>
#include <asm/stacktrace.h>
#include <asm/unwind.h>

static int save_stack_address(struct stack_trace *trace, unsigned long addr,
			      bool nosched)
{
	if (nosched && in_sched_functions(addr))
		return 0;

	if (trace->skip > 0) {
		trace->skip--;
		return 0;
	}

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

	trace->entries[trace->nr_entries++] = addr;
	return 0;
}

static void noinline __save_stack_trace(struct stack_trace *trace,
			       struct task_struct *task, struct pt_regs *regs,
			       bool nosched)
{
	struct unwind_state state;
	unsigned long addr;

	if (regs)
		save_stack_address(trace, regs->ip, nosched);

	for (unwind_start(&state, task, regs, NULL); !unwind_done(&state);
	     unwind_next_frame(&state)) {
		addr = unwind_get_return_address(&state);
		if (!addr || save_stack_address(trace, addr, nosched))
			break;
	}

	if (trace->nr_entries < trace->max_entries)
		trace->entries[trace->nr_entries++] = ULONG_MAX;
}

/*
 * Save stack-backtrace addresses into a stack_trace buffer.
 */
void save_stack_trace(struct stack_trace *trace)
{
	trace->skip++;
	__save_stack_trace(trace, current, NULL, false);
}
EXPORT_SYMBOL_GPL(save_stack_trace);

void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
{
	__save_stack_trace(trace, current, regs, false);
}

void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
	if (!try_get_task_stack(tsk))
		return;

	if (tsk == current)
		trace->skip++;
	__save_stack_trace(trace, tsk, NULL, true);

	put_task_stack(tsk);
}
EXPORT_SYMBOL_GPL(save_stack_trace_tsk);

#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE

#define STACKTRACE_DUMP_ONCE(task) ({				\
	static bool __section(.data.unlikely) __dumped;		\
								\
	if (!__dumped) {					\
		__dumped = true;				\
		WARN_ON(1);					\
		show_stack(task, NULL);				\
	}							\
})

static int __always_inline
__save_stack_trace_reliable(struct stack_trace *trace,
			    struct task_struct *task)
{
	struct unwind_state state;
	struct pt_regs *regs;
	unsigned long addr;

	for (unwind_start(&state, task, NULL, NULL); !unwind_done(&state);
	     unwind_next_frame(&state)) {

		regs = unwind_get_entry_regs(&state);
		if (regs) {
			/*
			 * Kernel mode registers on the stack indicate an
			 * in-kernel interrupt or exception (e.g., preemption
			 * or a page fault), which can make frame pointers
			 * unreliable.
			 */
			if (!user_mode(regs))
				return -EINVAL;

			/*
			 * The last frame contains the user mode syscall
			 * pt_regs.  Skip it and finish the unwind.
			 */
			unwind_next_frame(&state);
			if (!unwind_done(&state)) {
				STACKTRACE_DUMP_ONCE(task);
				return -EINVAL;
			}
			break;
		}

		addr = unwind_get_return_address(&state);

		/*
		 * A NULL or invalid return address probably means there's some
		 * generated code which __kernel_text_address() doesn't know
		 * about.
		 */
		if (!addr) {
			STACKTRACE_DUMP_ONCE(task);
			return -EINVAL;
		}

		if (save_stack_address(trace, addr, false))
			return -EINVAL;
	}

	/* Check for stack corruption */
	if (unwind_error(&state)) {
		STACKTRACE_DUMP_ONCE(task);
		return -EINVAL;
	}

	if (trace->nr_entries < trace->max_entries)
		trace->entries[trace->nr_entries++] = ULONG_MAX;

	return 0;
}

/*
 * This function returns an error if it detects any unreliable features of the
 * stack.  Otherwise it guarantees that the stack trace is reliable.
 *
 * If the task is not 'current', the caller *must* ensure the task is inactive.
 */
int save_stack_trace_tsk_reliable(struct task_struct *tsk,
				  struct stack_trace *trace)
{
	int ret;

	/*
	 * If the task doesn't have a stack (e.g., a zombie), the stack is
	 * "reliably" empty.
	 */
	if (!try_get_task_stack(tsk))
		return 0;

	ret = __save_stack_trace_reliable(trace, tsk);

	put_task_stack(tsk);

	return ret;
}
#endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */

/* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */

struct stack_frame_user {
	const void __user	*next_fp;
	unsigned long		ret_addr;
};

static int
copy_stack_frame(const void __user *fp, struct stack_frame_user *frame)
{
	int ret;

	if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
		return 0;

	ret = 1;
	pagefault_disable();
	if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
		ret = 0;
	pagefault_enable();

	return ret;
}

static inline void __save_stack_trace_user(struct stack_trace *trace)
{
	const struct pt_regs *regs = task_pt_regs(current);
	const void __user *fp = (const void __user *)regs->bp;

	if (trace->nr_entries < trace->max_entries)
		trace->entries[trace->nr_entries++] = regs->ip;

	while (trace->nr_entries < trace->max_entries) {
		struct stack_frame_user frame;

		frame.next_fp = NULL;
		frame.ret_addr = 0;
		if (!copy_stack_frame(fp, &frame))
			break;
		if ((unsigned long)fp < regs->sp)
			break;
		if (frame.ret_addr) {
			trace->entries[trace->nr_entries++] =
				frame.ret_addr;
		}
		if (fp == frame.next_fp)
			break;
		fp = frame.next_fp;
	}
}

void save_stack_trace_user(struct stack_trace *trace)
{
	/*
	 * Trace user stack if we are not a kernel thread
	 */
	if (current->mm) {
		__save_stack_trace_user(trace);
	}
	if (trace->nr_entries < trace->max_entries)
		trace->entries[trace->nr_entries++] = ULONG_MAX;
}