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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/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 if (WARN_ON_ONCE(frame->graph == -1))
63 return -EINVAL;
64 if (frame->graph < -1)
65 frame->graph += FTRACE_NOTRACE_DEPTH;
66
67 /*
68 * This is a case where function graph tracer has
69 * modified a return address (LR) in a stack frame
70 * to hook a function return.
71 * So replace it to an original value.
72 */
73 frame->pc = tsk->ret_stack[frame->graph--].ret;
74 }
75#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
76
77 /*
78 * Frames created upon entry from EL0 have NULL FP and PC values, so
79 * don't bother reporting these. Frames created by __noreturn functions
80 * might have a valid FP even if PC is bogus, so only terminate where
81 * both are NULL.
82 */
83 if (!frame->fp && !frame->pc)
84 return -EINVAL;
85
86 return 0;
87}
88
89void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
90 int (*fn)(struct stackframe *, void *), void *data)
91{
92 while (1) {
93 int ret;
94
95 if (fn(frame, data))
96 break;
97 ret = unwind_frame(tsk, frame);
98 if (ret < 0)
99 break;
100 }
101}
102
103#ifdef CONFIG_STACKTRACE
104struct stack_trace_data {
105 struct stack_trace *trace;
106 unsigned int no_sched_functions;
107 unsigned int skip;
108};
109
110static int save_trace(struct stackframe *frame, void *d)
111{
112 struct stack_trace_data *data = d;
113 struct stack_trace *trace = data->trace;
114 unsigned long addr = frame->pc;
115
116 if (data->no_sched_functions && in_sched_functions(addr))
117 return 0;
118 if (data->skip) {
119 data->skip--;
120 return 0;
121 }
122
123 trace->entries[trace->nr_entries++] = addr;
124
125 return trace->nr_entries >= trace->max_entries;
126}
127
128void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
129{
130 struct stack_trace_data data;
131 struct stackframe frame;
132
133 data.trace = trace;
134 data.skip = trace->skip;
135 data.no_sched_functions = 0;
136
137 frame.fp = regs->regs[29];
138 frame.pc = regs->pc;
139#ifdef CONFIG_FUNCTION_GRAPH_TRACER
140 frame.graph = current->curr_ret_stack;
141#endif
142
143 walk_stackframe(current, &frame, save_trace, &data);
144 if (trace->nr_entries < trace->max_entries)
145 trace->entries[trace->nr_entries++] = ULONG_MAX;
146}
147
148static noinline void __save_stack_trace(struct task_struct *tsk,
149 struct stack_trace *trace, unsigned int nosched)
150{
151 struct stack_trace_data data;
152 struct stackframe frame;
153
154 if (!try_get_task_stack(tsk))
155 return;
156
157 data.trace = trace;
158 data.skip = trace->skip;
159 data.no_sched_functions = nosched;
160
161 if (tsk != current) {
162 frame.fp = thread_saved_fp(tsk);
163 frame.pc = thread_saved_pc(tsk);
164 } else {
165 /* We don't want this function nor the caller */
166 data.skip += 2;
167 frame.fp = (unsigned long)__builtin_frame_address(0);
168 frame.pc = (unsigned long)__save_stack_trace;
169 }
170#ifdef CONFIG_FUNCTION_GRAPH_TRACER
171 frame.graph = tsk->curr_ret_stack;
172#endif
173
174 walk_stackframe(tsk, &frame, save_trace, &data);
175 if (trace->nr_entries < trace->max_entries)
176 trace->entries[trace->nr_entries++] = ULONG_MAX;
177
178 put_task_stack(tsk);
179}
180EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
181
182void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
183{
184 __save_stack_trace(tsk, trace, 1);
185}
186
187void save_stack_trace(struct stack_trace *trace)
188{
189 __save_stack_trace(current, trace, 0);
190}
191
192EXPORT_SYMBOL_GPL(save_stack_trace);
193#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/ftrace.h>
21#include <linux/sched.h>
22#include <linux/stacktrace.h>
23
24#include <asm/irq.h>
25#include <asm/stack_pointer.h>
26#include <asm/stacktrace.h>
27
28/*
29 * AArch64 PCS assigns the frame pointer to x29.
30 *
31 * A simple function prologue looks like this:
32 * sub sp, sp, #0x10
33 * stp x29, x30, [sp]
34 * mov x29, sp
35 *
36 * A simple function epilogue looks like this:
37 * mov sp, x29
38 * ldp x29, x30, [sp]
39 * add sp, sp, #0x10
40 */
41int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
42{
43 unsigned long high, low;
44 unsigned long fp = frame->fp;
45 unsigned long irq_stack_ptr;
46
47 if (!tsk)
48 tsk = current;
49
50 /*
51 * Switching between stacks is valid when tracing current and in
52 * non-preemptible context.
53 */
54 if (tsk == current && !preemptible())
55 irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
56 else
57 irq_stack_ptr = 0;
58
59 low = frame->sp;
60 /* irq stacks are not THREAD_SIZE aligned */
61 if (on_irq_stack(frame->sp, raw_smp_processor_id()))
62 high = irq_stack_ptr;
63 else
64 high = ALIGN(low, THREAD_SIZE) - 0x20;
65
66 if (fp < low || fp > high || fp & 0xf)
67 return -EINVAL;
68
69 frame->sp = fp + 0x10;
70 frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
71 frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
72
73#ifdef CONFIG_FUNCTION_GRAPH_TRACER
74 if (tsk->ret_stack &&
75 (frame->pc == (unsigned long)return_to_handler)) {
76 /*
77 * This is a case where function graph tracer has
78 * modified a return address (LR) in a stack frame
79 * to hook a function return.
80 * So replace it to an original value.
81 */
82 frame->pc = tsk->ret_stack[frame->graph--].ret;
83 }
84#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
85
86 /*
87 * Check whether we are going to walk through from interrupt stack
88 * to task stack.
89 * If we reach the end of the stack - and its an interrupt stack,
90 * unpack the dummy frame to find the original elr.
91 *
92 * Check the frame->fp we read from the bottom of the irq_stack,
93 * and the original task stack pointer are both in current->stack.
94 */
95 if (frame->sp == irq_stack_ptr) {
96 struct pt_regs *irq_args;
97 unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
98
99 if (object_is_on_stack((void *)orig_sp) &&
100 object_is_on_stack((void *)frame->fp)) {
101 frame->sp = orig_sp;
102
103 /* orig_sp is the saved pt_regs, find the elr */
104 irq_args = (struct pt_regs *)orig_sp;
105 frame->pc = irq_args->pc;
106 } else {
107 /*
108 * This frame has a non-standard format, and we
109 * didn't fix it, because the data looked wrong.
110 * Refuse to output this frame.
111 */
112 return -EINVAL;
113 }
114 }
115
116 return 0;
117}
118
119void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
120 int (*fn)(struct stackframe *, void *), void *data)
121{
122 while (1) {
123 int ret;
124
125 if (fn(frame, data))
126 break;
127 ret = unwind_frame(tsk, frame);
128 if (ret < 0)
129 break;
130 }
131}
132
133#ifdef CONFIG_STACKTRACE
134struct stack_trace_data {
135 struct stack_trace *trace;
136 unsigned int no_sched_functions;
137 unsigned int skip;
138};
139
140static int save_trace(struct stackframe *frame, void *d)
141{
142 struct stack_trace_data *data = d;
143 struct stack_trace *trace = data->trace;
144 unsigned long addr = frame->pc;
145
146 if (data->no_sched_functions && in_sched_functions(addr))
147 return 0;
148 if (data->skip) {
149 data->skip--;
150 return 0;
151 }
152
153 trace->entries[trace->nr_entries++] = addr;
154
155 return trace->nr_entries >= trace->max_entries;
156}
157
158void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
159{
160 struct stack_trace_data data;
161 struct stackframe frame;
162
163 data.trace = trace;
164 data.skip = trace->skip;
165 data.no_sched_functions = 0;
166
167 frame.fp = regs->regs[29];
168 frame.sp = regs->sp;
169 frame.pc = regs->pc;
170#ifdef CONFIG_FUNCTION_GRAPH_TRACER
171 frame.graph = current->curr_ret_stack;
172#endif
173
174 walk_stackframe(current, &frame, save_trace, &data);
175 if (trace->nr_entries < trace->max_entries)
176 trace->entries[trace->nr_entries++] = ULONG_MAX;
177}
178
179void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
180{
181 struct stack_trace_data data;
182 struct stackframe frame;
183
184 if (!try_get_task_stack(tsk))
185 return;
186
187 data.trace = trace;
188 data.skip = trace->skip;
189
190 if (tsk != current) {
191 data.no_sched_functions = 1;
192 frame.fp = thread_saved_fp(tsk);
193 frame.sp = thread_saved_sp(tsk);
194 frame.pc = thread_saved_pc(tsk);
195 } else {
196 data.no_sched_functions = 0;
197 frame.fp = (unsigned long)__builtin_frame_address(0);
198 frame.sp = current_stack_pointer;
199 frame.pc = (unsigned long)save_stack_trace_tsk;
200 }
201#ifdef CONFIG_FUNCTION_GRAPH_TRACER
202 frame.graph = tsk->curr_ret_stack;
203#endif
204
205 walk_stackframe(tsk, &frame, save_trace, &data);
206 if (trace->nr_entries < trace->max_entries)
207 trace->entries[trace->nr_entries++] = ULONG_MAX;
208
209 put_task_stack(tsk);
210}
211
212void save_stack_trace(struct stack_trace *trace)
213{
214 save_stack_trace_tsk(current, trace);
215}
216EXPORT_SYMBOL_GPL(save_stack_trace);
217#endif