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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/stacktrace.h>
23
24#include <asm/irq.h>
25#include <asm/stacktrace.h>
26
27/*
28 * AArch64 PCS assigns the frame pointer to x29.
29 *
30 * A simple function prologue looks like this:
31 * sub sp, sp, #0x10
32 * stp x29, x30, [sp]
33 * mov x29, sp
34 *
35 * A simple function epilogue looks like this:
36 * mov sp, x29
37 * ldp x29, x30, [sp]
38 * add sp, sp, #0x10
39 */
40int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
41{
42 unsigned long high, low;
43 unsigned long fp = frame->fp;
44 unsigned long irq_stack_ptr;
45
46 /*
47 * Switching between stacks is valid when tracing current and in
48 * non-preemptible context.
49 */
50 if (tsk == current && !preemptible())
51 irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
52 else
53 irq_stack_ptr = 0;
54
55 low = frame->sp;
56 /* irq stacks are not THREAD_SIZE aligned */
57 if (on_irq_stack(frame->sp, raw_smp_processor_id()))
58 high = irq_stack_ptr;
59 else
60 high = ALIGN(low, THREAD_SIZE) - 0x20;
61
62 if (fp < low || fp > high || fp & 0xf)
63 return -EINVAL;
64
65 frame->sp = fp + 0x10;
66 frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
67 frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
68
69#ifdef CONFIG_FUNCTION_GRAPH_TRACER
70 if (tsk && tsk->ret_stack &&
71 (frame->pc == (unsigned long)return_to_handler)) {
72 /*
73 * This is a case where function graph tracer has
74 * modified a return address (LR) in a stack frame
75 * to hook a function return.
76 * So replace it to an original value.
77 */
78 frame->pc = tsk->ret_stack[frame->graph--].ret;
79 }
80#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
81
82 /*
83 * Check whether we are going to walk through from interrupt stack
84 * to task stack.
85 * If we reach the end of the stack - and its an interrupt stack,
86 * unpack the dummy frame to find the original elr.
87 *
88 * Check the frame->fp we read from the bottom of the irq_stack,
89 * and the original task stack pointer are both in current->stack.
90 */
91 if (frame->sp == irq_stack_ptr) {
92 struct pt_regs *irq_args;
93 unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
94
95 if (object_is_on_stack((void *)orig_sp) &&
96 object_is_on_stack((void *)frame->fp)) {
97 frame->sp = orig_sp;
98
99 /* orig_sp is the saved pt_regs, find the elr */
100 irq_args = (struct pt_regs *)orig_sp;
101 frame->pc = irq_args->pc;
102 } else {
103 /*
104 * This frame has a non-standard format, and we
105 * didn't fix it, because the data looked wrong.
106 * Refuse to output this frame.
107 */
108 return -EINVAL;
109 }
110 }
111
112 return 0;
113}
114
115void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
116 int (*fn)(struct stackframe *, void *), void *data)
117{
118 while (1) {
119 int ret;
120
121 if (fn(frame, data))
122 break;
123 ret = unwind_frame(tsk, frame);
124 if (ret < 0)
125 break;
126 }
127}
128EXPORT_SYMBOL(walk_stackframe);
129
130#ifdef CONFIG_STACKTRACE
131struct stack_trace_data {
132 struct stack_trace *trace;
133 unsigned int no_sched_functions;
134 unsigned int skip;
135};
136
137static int save_trace(struct stackframe *frame, void *d)
138{
139 struct stack_trace_data *data = d;
140 struct stack_trace *trace = data->trace;
141 unsigned long addr = frame->pc;
142
143 if (data->no_sched_functions && in_sched_functions(addr))
144 return 0;
145 if (data->skip) {
146 data->skip--;
147 return 0;
148 }
149
150 trace->entries[trace->nr_entries++] = addr;
151
152 return trace->nr_entries >= trace->max_entries;
153}
154
155void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
156{
157 struct stack_trace_data data;
158 struct stackframe frame;
159
160 data.trace = trace;
161 data.skip = trace->skip;
162
163 if (tsk != current) {
164 data.no_sched_functions = 1;
165 frame.fp = thread_saved_fp(tsk);
166 frame.sp = thread_saved_sp(tsk);
167 frame.pc = thread_saved_pc(tsk);
168 } else {
169 data.no_sched_functions = 0;
170 frame.fp = (unsigned long)__builtin_frame_address(0);
171 frame.sp = current_stack_pointer;
172 frame.pc = (unsigned long)save_stack_trace_tsk;
173 }
174#ifdef CONFIG_FUNCTION_GRAPH_TRACER
175 frame.graph = tsk->curr_ret_stack;
176#endif
177
178 walk_stackframe(tsk, &frame, save_trace, &data);
179 if (trace->nr_entries < trace->max_entries)
180 trace->entries[trace->nr_entries++] = ULONG_MAX;
181}
182
183void save_stack_trace(struct stack_trace *trace)
184{
185 save_stack_trace_tsk(current, trace);
186}
187EXPORT_SYMBOL_GPL(save_stack_trace);
188#endif
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/sched.h>
21#include <linux/stacktrace.h>
22
23#include <asm/stacktrace.h>
24
25/*
26 * AArch64 PCS assigns the frame pointer to x29.
27 *
28 * A simple function prologue looks like this:
29 * sub sp, sp, #0x10
30 * stp x29, x30, [sp]
31 * mov x29, sp
32 *
33 * A simple function epilogue looks like this:
34 * mov sp, x29
35 * ldp x29, x30, [sp]
36 * add sp, sp, #0x10
37 */
38int unwind_frame(struct stackframe *frame)
39{
40 unsigned long high, low;
41 unsigned long fp = frame->fp;
42
43 low = frame->sp;
44 high = ALIGN(low, THREAD_SIZE);
45
46 if (fp < low || fp > high - 0x18 || fp & 0xf)
47 return -EINVAL;
48
49 frame->sp = fp + 0x10;
50 frame->fp = *(unsigned long *)(fp);
51 /*
52 * -4 here because we care about the PC at time of bl,
53 * not where the return will go.
54 */
55 frame->pc = *(unsigned long *)(fp + 8) - 4;
56
57 return 0;
58}
59
60void notrace walk_stackframe(struct stackframe *frame,
61 int (*fn)(struct stackframe *, void *), void *data)
62{
63 while (1) {
64 int ret;
65
66 if (fn(frame, data))
67 break;
68 ret = unwind_frame(frame);
69 if (ret < 0)
70 break;
71 }
72}
73EXPORT_SYMBOL(walk_stackframe);
74
75#ifdef CONFIG_STACKTRACE
76struct stack_trace_data {
77 struct stack_trace *trace;
78 unsigned int no_sched_functions;
79 unsigned int skip;
80};
81
82static int save_trace(struct stackframe *frame, void *d)
83{
84 struct stack_trace_data *data = d;
85 struct stack_trace *trace = data->trace;
86 unsigned long addr = frame->pc;
87
88 if (data->no_sched_functions && in_sched_functions(addr))
89 return 0;
90 if (data->skip) {
91 data->skip--;
92 return 0;
93 }
94
95 trace->entries[trace->nr_entries++] = addr;
96
97 return trace->nr_entries >= trace->max_entries;
98}
99
100void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
101{
102 struct stack_trace_data data;
103 struct stackframe frame;
104
105 data.trace = trace;
106 data.skip = trace->skip;
107
108 if (tsk != current) {
109 data.no_sched_functions = 1;
110 frame.fp = thread_saved_fp(tsk);
111 frame.sp = thread_saved_sp(tsk);
112 frame.pc = thread_saved_pc(tsk);
113 } else {
114 register unsigned long current_sp asm("sp");
115 data.no_sched_functions = 0;
116 frame.fp = (unsigned long)__builtin_frame_address(0);
117 frame.sp = current_sp;
118 frame.pc = (unsigned long)save_stack_trace_tsk;
119 }
120
121 walk_stackframe(&frame, save_trace, &data);
122 if (trace->nr_entries < trace->max_entries)
123 trace->entries[trace->nr_entries++] = ULONG_MAX;
124}
125
126void save_stack_trace(struct stack_trace *trace)
127{
128 save_stack_trace_tsk(current, trace);
129}
130EXPORT_SYMBOL_GPL(save_stack_trace);
131#endif