summaryrefslogtreecommitdiffstats
path: root/arch/arm64/kernel/stacktrace.c
blob: 17f66a74c745c8570c3d4e534313e73cb990716a (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
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Stack tracing support
 *
 * Copyright (C) 2012 ARM Ltd.
 */
#include <linux/kernel.h>
#include <linux/efi.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/efi.h>
#include <asm/irq.h>
#include <asm/stack_pointer.h>
#include <asm/stacktrace.h>

/*
 * Start an unwind from a pt_regs.
 *
 * The unwind will begin at the PC within the regs.
 *
 * The regs must be on a stack currently owned by the calling task.
 */
static __always_inline void
unwind_init_from_regs(struct unwind_state *state,
		      struct pt_regs *regs)
{
	unwind_init_common(state, current);

	state->fp = regs->regs[29];
	state->pc = regs->pc;
}

/*
 * Start an unwind from a caller.
 *
 * The unwind will begin at the caller of whichever function this is inlined
 * into.
 *
 * The function which invokes this must be noinline.
 */
static __always_inline void
unwind_init_from_caller(struct unwind_state *state)
{
	unwind_init_common(state, current);

	state->fp = (unsigned long)__builtin_frame_address(1);
	state->pc = (unsigned long)__builtin_return_address(0);
}

/*
 * Start an unwind from a blocked task.
 *
 * The unwind will begin at the blocked tasks saved PC (i.e. the caller of
 * cpu_switch_to()).
 *
 * The caller should ensure the task is blocked in cpu_switch_to() for the
 * duration of the unwind, or the unwind will be bogus. It is never valid to
 * call this for the current task.
 */
static __always_inline void
unwind_init_from_task(struct unwind_state *state,
		      struct task_struct *task)
{
	unwind_init_common(state, task);

	state->fp = thread_saved_fp(task);
	state->pc = thread_saved_pc(task);
}

static __always_inline int
unwind_recover_return_address(struct unwind_state *state)
{
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	if (state->task->ret_stack &&
	    (state->pc == (unsigned long)return_to_handler)) {
		unsigned long orig_pc;
		orig_pc = ftrace_graph_ret_addr(state->task, NULL, state->pc,
						(void *)state->fp);
		if (WARN_ON_ONCE(state->pc == orig_pc))
			return -EINVAL;
		state->pc = orig_pc;
	}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

#ifdef CONFIG_KRETPROBES
	if (is_kretprobe_trampoline(state->pc)) {
		state->pc = kretprobe_find_ret_addr(state->task,
						    (void *)state->fp,
						    &state->kr_cur);
	}
#endif /* CONFIG_KRETPROBES */

	return 0;
}

/*
 * Unwind from one frame record (A) to the next frame record (B).
 *
 * We terminate early if the location of B indicates a malformed chain of frame
 * records (e.g. a cycle), determined based on the location and fp value of A
 * and the location (but not the fp value) of B.
 */
static __always_inline int
unwind_next(struct unwind_state *state)
{
	struct task_struct *tsk = state->task;
	unsigned long fp = state->fp;
	int err;

	/* Final frame; nothing to unwind */
	if (fp == (unsigned long)task_pt_regs(tsk)->stackframe)
		return -ENOENT;

	err = unwind_next_frame_record(state);
	if (err)
		return err;

	state->pc = ptrauth_strip_kernel_insn_pac(state->pc);

	return unwind_recover_return_address(state);
}

static __always_inline void
unwind(struct unwind_state *state, stack_trace_consume_fn consume_entry,
       void *cookie)
{
	if (unwind_recover_return_address(state))
		return;

	while (1) {
		int ret;

		if (!consume_entry(cookie, state->pc))
			break;
		ret = unwind_next(state);
		if (ret < 0)
			break;
	}
}

/*
 * Per-cpu stacks are only accessible when unwinding the current task in a
 * non-preemptible context.
 */
#define STACKINFO_CPU(name)					\
	({							\
		((task == current) && !preemptible())		\
			? stackinfo_get_##name()		\
			: stackinfo_get_unknown();		\
	})

/*
 * SDEI stacks are only accessible when unwinding the current task in an NMI
 * context.
 */
#define STACKINFO_SDEI(name)					\
	({							\
		((task == current) && in_nmi())			\
			? stackinfo_get_sdei_##name()		\
			: stackinfo_get_unknown();		\
	})

#define STACKINFO_EFI						\
	({							\
		((task == current) && current_in_efi())		\
			? stackinfo_get_efi()			\
			: stackinfo_get_unknown();		\
	})

noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry,
			      void *cookie, struct task_struct *task,
			      struct pt_regs *regs)
{
	struct stack_info stacks[] = {
		stackinfo_get_task(task),
		STACKINFO_CPU(irq),
#if defined(CONFIG_VMAP_STACK)
		STACKINFO_CPU(overflow),
#endif
#if defined(CONFIG_VMAP_STACK) && defined(CONFIG_ARM_SDE_INTERFACE)
		STACKINFO_SDEI(normal),
		STACKINFO_SDEI(critical),
#endif
#ifdef CONFIG_EFI
		STACKINFO_EFI,
#endif
	};
	struct unwind_state state = {
		.stacks = stacks,
		.nr_stacks = ARRAY_SIZE(stacks),
	};

	if (regs) {
		if (task != current)
			return;
		unwind_init_from_regs(&state, regs);
	} else if (task == current) {
		unwind_init_from_caller(&state);
	} else {
		unwind_init_from_task(&state, task);
	}

	unwind(&state, consume_entry, cookie);
}

static bool dump_backtrace_entry(void *arg, unsigned long where)
{
	char *loglvl = arg;
	printk("%s %pSb\n", loglvl, (void *)where);
	return true;
}

void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
		    const char *loglvl)
{
	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);

	if (regs && user_mode(regs))
		return;

	if (!tsk)
		tsk = current;

	if (!try_get_task_stack(tsk))
		return;

	printk("%sCall trace:\n", loglvl);
	arch_stack_walk(dump_backtrace_entry, (void *)loglvl, tsk, regs);

	put_task_stack(tsk);
}

void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
{
	dump_backtrace(NULL, tsk, loglvl);
	barrier();
}