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Catalin Marinas60ffc302012-03-05 11:49:27 +00001/*
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>
AKASHI Takahiro20380bb2015-12-15 17:33:41 +090020#include <linux/ftrace.h>
Catalin Marinas60ffc302012-03-05 11:49:27 +000021#include <linux/sched.h>
Ingo Molnarb17b0152017-02-08 18:51:35 +010022#include <linux/sched/debug.h>
Ingo Molnar68db0cf2017-02-08 18:51:37 +010023#include <linux/sched/task_stack.h>
Catalin Marinas60ffc302012-03-05 11:49:27 +000024#include <linux/stacktrace.h>
25
AKASHI Takahiro132cd882015-12-04 11:02:26 +000026#include <asm/irq.h>
Mark Rutlanda9ea0012016-11-03 20:23:05 +000027#include <asm/stack_pointer.h>
Catalin Marinas60ffc302012-03-05 11:49:27 +000028#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 */
AKASHI Takahirofe13f952015-12-15 17:33:40 +090043int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
Catalin Marinas60ffc302012-03-05 11:49:27 +000044{
Catalin Marinas60ffc302012-03-05 11:49:27 +000045 unsigned long fp = frame->fp;
Ard Biesheuvelc7365332017-07-22 12:48:34 +010046
47 if (fp & 0xf)
48 return -EINVAL;
AKASHI Takahiro132cd882015-12-04 11:02:26 +000049
Mark Rutlandb5e73072016-09-23 17:55:05 +010050 if (!tsk)
51 tsk = current;
52
Mark Rutland12964442017-08-01 18:51:15 +010053 if (!on_accessible_stack(tsk, fp))
Catalin Marinas60ffc302012-03-05 11:49:27 +000054 return -EINVAL;
55
Yang Shibcaf6692016-02-08 09:13:09 -080056 frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
57 frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
Catalin Marinas60ffc302012-03-05 11:49:27 +000058
AKASHI Takahiro20380bb2015-12-15 17:33:41 +090059#ifdef CONFIG_FUNCTION_GRAPH_TRACER
Mark Rutlandb5e73072016-09-23 17:55:05 +010060 if (tsk->ret_stack &&
AKASHI Takahiro20380bb2015-12-15 17:33:41 +090061 (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
AKASHI Takahiro132cd882015-12-04 11:02:26 +000072 /*
Ard Biesheuvel73267492017-07-22 18:45:33 +010073 * 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.
AKASHI Takahiro132cd882015-12-04 11:02:26 +000077 */
Ard Biesheuvel73267492017-07-22 18:45:33 +010078 if (!frame->fp && !frame->pc)
79 return -EINVAL;
AKASHI Takahiro132cd882015-12-04 11:02:26 +000080
Catalin Marinas60ffc302012-03-05 11:49:27 +000081 return 0;
82}
83
AKASHI Takahirofe13f952015-12-15 17:33:40 +090084void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
Catalin Marinas60ffc302012-03-05 11:49:27 +000085 int (*fn)(struct stackframe *, void *), void *data)
86{
87 while (1) {
88 int ret;
89
90 if (fn(frame, data))
91 break;
AKASHI Takahirofe13f952015-12-15 17:33:40 +090092 ret = unwind_frame(tsk, frame);
Catalin Marinas60ffc302012-03-05 11:49:27 +000093 if (ret < 0)
94 break;
95 }
96}
Catalin Marinas60ffc302012-03-05 11:49:27 +000097
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
Pratyush Anand98ab10e2016-09-05 08:03:16 +0530123void 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];
Pratyush Anand98ab10e2016-09-05 08:03:16 +0530133 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
Prakash Guptabb53c822017-09-13 16:28:32 -0700143static noinline void __save_stack_trace(struct task_struct *tsk,
144 struct stack_trace *trace, unsigned int nosched)
Catalin Marinas60ffc302012-03-05 11:49:27 +0000145{
146 struct stack_trace_data data;
147 struct stackframe frame;
148
Mark Rutland9bbd4c52016-11-03 20:23:08 +0000149 if (!try_get_task_stack(tsk))
150 return;
151
Catalin Marinas60ffc302012-03-05 11:49:27 +0000152 data.trace = trace;
153 data.skip = trace->skip;
Prakash Guptabb53c822017-09-13 16:28:32 -0700154 data.no_sched_functions = nosched;
Catalin Marinas60ffc302012-03-05 11:49:27 +0000155
156 if (tsk != current) {
Catalin Marinas60ffc302012-03-05 11:49:27 +0000157 frame.fp = thread_saved_fp(tsk);
Catalin Marinas60ffc302012-03-05 11:49:27 +0000158 frame.pc = thread_saved_pc(tsk);
159 } else {
Prakash Guptabb53c822017-09-13 16:28:32 -0700160 /* We don't want this function nor the caller */
161 data.skip += 2;
Catalin Marinas60ffc302012-03-05 11:49:27 +0000162 frame.fp = (unsigned long)__builtin_frame_address(0);
Prakash Guptabb53c822017-09-13 16:28:32 -0700163 frame.pc = (unsigned long)__save_stack_trace;
Catalin Marinas60ffc302012-03-05 11:49:27 +0000164 }
AKASHI Takahiro20380bb2015-12-15 17:33:41 +0900165#ifdef CONFIG_FUNCTION_GRAPH_TRACER
166 frame.graph = tsk->curr_ret_stack;
167#endif
Catalin Marinas60ffc302012-03-05 11:49:27 +0000168
AKASHI Takahirofe13f952015-12-15 17:33:40 +0900169 walk_stackframe(tsk, &frame, save_trace, &data);
Catalin Marinas60ffc302012-03-05 11:49:27 +0000170 if (trace->nr_entries < trace->max_entries)
171 trace->entries[trace->nr_entries++] = ULONG_MAX;
Mark Rutland9bbd4c52016-11-03 20:23:08 +0000172
173 put_task_stack(tsk);
Catalin Marinas60ffc302012-03-05 11:49:27 +0000174}
Dustin Browne27c7fa2017-06-13 11:40:56 -0700175EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
Catalin Marinas60ffc302012-03-05 11:49:27 +0000176
Prakash Guptabb53c822017-09-13 16:28:32 -0700177void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
178{
179 __save_stack_trace(tsk, trace, 1);
180}
181
Catalin Marinas60ffc302012-03-05 11:49:27 +0000182void save_stack_trace(struct stack_trace *trace)
183{
Prakash Guptabb53c822017-09-13 16:28:32 -0700184 __save_stack_trace(current, trace, 0);
Catalin Marinas60ffc302012-03-05 11:49:27 +0000185}
Prakash Guptabb53c822017-09-13 16:28:32 -0700186
Catalin Marinas60ffc302012-03-05 11:49:27 +0000187EXPORT_SYMBOL_GPL(save_stack_trace);
188#endif