Linux kernel mirror (for testing)
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linux
1/*
2 * Stack tracing support
3 *
4 * Copyright (C) 2012 ARM Ltd.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program. If not, see <http://www.gnu.org/licenses/>.
17 */
18#include <linux/kernel.h>
19#include <linux/export.h>
20#include <linux/ftrace.h>
21#include <linux/sched.h>
22#include <linux/sched/debug.h>
23#include <linux/sched/task_stack.h>
24#include <linux/stacktrace.h>
25
26#include <asm/irq.h>
27#include <asm/stack_pointer.h>
28#include <asm/stacktrace.h>
29
30/*
31 * AArch64 PCS assigns the frame pointer to x29.
32 *
33 * A simple function prologue looks like this:
34 * sub sp, sp, #0x10
35 * stp x29, x30, [sp]
36 * mov x29, sp
37 *
38 * A simple function epilogue looks like this:
39 * mov sp, x29
40 * ldp x29, x30, [sp]
41 * add sp, sp, #0x10
42 */
43int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
44{
45 unsigned long fp = frame->fp;
46
47 if (fp & 0xf)
48 return -EINVAL;
49
50 if (!tsk)
51 tsk = current;
52
53 if (!on_accessible_stack(tsk, fp))
54 return -EINVAL;
55
56 frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
57 frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
58
59#ifdef CONFIG_FUNCTION_GRAPH_TRACER
60 if (tsk->ret_stack &&
61 (frame->pc == (unsigned long)return_to_handler)) {
62 /*
63 * This is a case where function graph tracer has
64 * modified a return address (LR) in a stack frame
65 * to hook a function return.
66 * So replace it to an original value.
67 */
68 frame->pc = tsk->ret_stack[frame->graph--].ret;
69 }
70#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
71
72 /*
73 * Frames created upon entry from EL0 have NULL FP and PC values, so
74 * don't bother reporting these. Frames created by __noreturn functions
75 * might have a valid FP even if PC is bogus, so only terminate where
76 * both are NULL.
77 */
78 if (!frame->fp && !frame->pc)
79 return -EINVAL;
80
81 return 0;
82}
83
84void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
85 int (*fn)(struct stackframe *, void *), void *data)
86{
87 while (1) {
88 int ret;
89
90 if (fn(frame, data))
91 break;
92 ret = unwind_frame(tsk, frame);
93 if (ret < 0)
94 break;
95 }
96}
97
98#ifdef CONFIG_STACKTRACE
99struct stack_trace_data {
100 struct stack_trace *trace;
101 unsigned int no_sched_functions;
102 unsigned int skip;
103};
104
105static int save_trace(struct stackframe *frame, void *d)
106{
107 struct stack_trace_data *data = d;
108 struct stack_trace *trace = data->trace;
109 unsigned long addr = frame->pc;
110
111 if (data->no_sched_functions && in_sched_functions(addr))
112 return 0;
113 if (data->skip) {
114 data->skip--;
115 return 0;
116 }
117
118 trace->entries[trace->nr_entries++] = addr;
119
120 return trace->nr_entries >= trace->max_entries;
121}
122
123void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
124{
125 struct stack_trace_data data;
126 struct stackframe frame;
127
128 data.trace = trace;
129 data.skip = trace->skip;
130 data.no_sched_functions = 0;
131
132 frame.fp = regs->regs[29];
133 frame.pc = regs->pc;
134#ifdef CONFIG_FUNCTION_GRAPH_TRACER
135 frame.graph = current->curr_ret_stack;
136#endif
137
138 walk_stackframe(current, &frame, save_trace, &data);
139 if (trace->nr_entries < trace->max_entries)
140 trace->entries[trace->nr_entries++] = ULONG_MAX;
141}
142
143static noinline void __save_stack_trace(struct task_struct *tsk,
144 struct stack_trace *trace, unsigned int nosched)
145{
146 struct stack_trace_data data;
147 struct stackframe frame;
148
149 if (!try_get_task_stack(tsk))
150 return;
151
152 data.trace = trace;
153 data.skip = trace->skip;
154 data.no_sched_functions = nosched;
155
156 if (tsk != current) {
157 frame.fp = thread_saved_fp(tsk);
158 frame.pc = thread_saved_pc(tsk);
159 } else {
160 /* We don't want this function nor the caller */
161 data.skip += 2;
162 frame.fp = (unsigned long)__builtin_frame_address(0);
163 frame.pc = (unsigned long)__save_stack_trace;
164 }
165#ifdef CONFIG_FUNCTION_GRAPH_TRACER
166 frame.graph = tsk->curr_ret_stack;
167#endif
168
169 walk_stackframe(tsk, &frame, save_trace, &data);
170 if (trace->nr_entries < trace->max_entries)
171 trace->entries[trace->nr_entries++] = ULONG_MAX;
172
173 put_task_stack(tsk);
174}
175EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
176
177void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
178{
179 __save_stack_trace(tsk, trace, 1);
180}
181
182void save_stack_trace(struct stack_trace *trace)
183{
184 __save_stack_trace(current, trace, 0);
185}
186
187EXPORT_SYMBOL_GPL(save_stack_trace);
188#endif