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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>
22#include <linux/stacktrace.h>
23
AKASHI Takahiro132cd882015-12-04 11:02:26 +000024#include <asm/irq.h>
Mark Rutlanda9ea0012016-11-03 20:23:05 +000025#include <asm/stack_pointer.h>
Catalin Marinas60ffc302012-03-05 11:49:27 +000026#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 */
AKASHI Takahirofe13f952015-12-15 17:33:40 +090041int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
Catalin Marinas60ffc302012-03-05 11:49:27 +000042{
43 unsigned long high, low;
44 unsigned long fp = frame->fp;
AKASHI Takahiro132cd882015-12-04 11:02:26 +000045 unsigned long irq_stack_ptr;
46
Mark Rutlandb5e73072016-09-23 17:55:05 +010047 if (!tsk)
48 tsk = current;
49
AKASHI Takahiro132cd882015-12-04 11:02:26 +000050 /*
Yang Shia80a0eb2016-02-11 13:53:10 -080051 * Switching between stacks is valid when tracing current and in
52 * non-preemptible context.
AKASHI Takahiro132cd882015-12-04 11:02:26 +000053 */
Yang Shia80a0eb2016-02-11 13:53:10 -080054 if (tsk == current && !preemptible())
55 irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
56 else
57 irq_stack_ptr = 0;
Catalin Marinas60ffc302012-03-05 11:49:27 +000058
59 low = frame->sp;
AKASHI Takahiro132cd882015-12-04 11:02:26 +000060 /* 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;
Catalin Marinas60ffc302012-03-05 11:49:27 +000065
AKASHI Takahiro132cd882015-12-04 11:02:26 +000066 if (fp < low || fp > high || fp & 0xf)
Catalin Marinas60ffc302012-03-05 11:49:27 +000067 return -EINVAL;
68
69 frame->sp = fp + 0x10;
Yang Shibcaf6692016-02-08 09:13:09 -080070 frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
71 frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
Catalin Marinas60ffc302012-03-05 11:49:27 +000072
AKASHI Takahiro20380bb2015-12-15 17:33:41 +090073#ifdef CONFIG_FUNCTION_GRAPH_TRACER
Mark Rutlandb5e73072016-09-23 17:55:05 +010074 if (tsk->ret_stack &&
AKASHI Takahiro20380bb2015-12-15 17:33:41 +090075 (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
AKASHI Takahiro132cd882015-12-04 11:02:26 +000086 /*
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,
James Morse971c67c2015-12-15 11:21:25 +000090 * unpack the dummy frame to find the original elr.
James Morse1ffe1992015-12-10 10:22:40 +000091 *
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.
AKASHI Takahiro132cd882015-12-04 11:02:26 +000094 */
James Morse1ffe1992015-12-10 10:22:40 +000095 if (frame->sp == irq_stack_ptr) {
James Morse971c67c2015-12-15 11:21:25 +000096 struct pt_regs *irq_args;
James Morse1ffe1992015-12-10 10:22:40 +000097 unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
98
James Morse971c67c2015-12-15 11:21:25 +000099 if (object_is_on_stack((void *)orig_sp) &&
100 object_is_on_stack((void *)frame->fp)) {
James Morse1ffe1992015-12-10 10:22:40 +0000101 frame->sp = orig_sp;
James Morse971c67c2015-12-15 11:21:25 +0000102
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 }
James Morse1ffe1992015-12-10 10:22:40 +0000114 }
AKASHI Takahiro132cd882015-12-04 11:02:26 +0000115
Catalin Marinas60ffc302012-03-05 11:49:27 +0000116 return 0;
117}
118
AKASHI Takahirofe13f952015-12-15 17:33:40 +0900119void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
Catalin Marinas60ffc302012-03-05 11:49:27 +0000120 int (*fn)(struct stackframe *, void *), void *data)
121{
122 while (1) {
123 int ret;
124
125 if (fn(frame, data))
126 break;
AKASHI Takahirofe13f952015-12-15 17:33:40 +0900127 ret = unwind_frame(tsk, frame);
Catalin Marinas60ffc302012-03-05 11:49:27 +0000128 if (ret < 0)
129 break;
130 }
131}
132EXPORT_SYMBOL(walk_stackframe);
133
134#ifdef CONFIG_STACKTRACE
135struct stack_trace_data {
136 struct stack_trace *trace;
137 unsigned int no_sched_functions;
138 unsigned int skip;
139};
140
141static int save_trace(struct stackframe *frame, void *d)
142{
143 struct stack_trace_data *data = d;
144 struct stack_trace *trace = data->trace;
145 unsigned long addr = frame->pc;
146
147 if (data->no_sched_functions && in_sched_functions(addr))
148 return 0;
149 if (data->skip) {
150 data->skip--;
151 return 0;
152 }
153
154 trace->entries[trace->nr_entries++] = addr;
155
156 return trace->nr_entries >= trace->max_entries;
157}
158
Pratyush Anand98ab10e2016-09-05 08:03:16 +0530159void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
160{
161 struct stack_trace_data data;
162 struct stackframe frame;
163
164 data.trace = trace;
165 data.skip = trace->skip;
166 data.no_sched_functions = 0;
167
168 frame.fp = regs->regs[29];
169 frame.sp = regs->sp;
170 frame.pc = regs->pc;
171#ifdef CONFIG_FUNCTION_GRAPH_TRACER
172 frame.graph = current->curr_ret_stack;
173#endif
174
175 walk_stackframe(current, &frame, save_trace, &data);
176 if (trace->nr_entries < trace->max_entries)
177 trace->entries[trace->nr_entries++] = ULONG_MAX;
178}
179
Catalin Marinas60ffc302012-03-05 11:49:27 +0000180void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
181{
182 struct stack_trace_data data;
183 struct stackframe frame;
184
185 data.trace = trace;
186 data.skip = trace->skip;
187
188 if (tsk != current) {
189 data.no_sched_functions = 1;
190 frame.fp = thread_saved_fp(tsk);
191 frame.sp = thread_saved_sp(tsk);
192 frame.pc = thread_saved_pc(tsk);
193 } else {
Catalin Marinas60ffc302012-03-05 11:49:27 +0000194 data.no_sched_functions = 0;
195 frame.fp = (unsigned long)__builtin_frame_address(0);
Behan Websterbb28cec2014-08-27 05:29:30 +0100196 frame.sp = current_stack_pointer;
Catalin Marinas60ffc302012-03-05 11:49:27 +0000197 frame.pc = (unsigned long)save_stack_trace_tsk;
198 }
AKASHI Takahiro20380bb2015-12-15 17:33:41 +0900199#ifdef CONFIG_FUNCTION_GRAPH_TRACER
200 frame.graph = tsk->curr_ret_stack;
201#endif
Catalin Marinas60ffc302012-03-05 11:49:27 +0000202
AKASHI Takahirofe13f952015-12-15 17:33:40 +0900203 walk_stackframe(tsk, &frame, save_trace, &data);
Catalin Marinas60ffc302012-03-05 11:49:27 +0000204 if (trace->nr_entries < trace->max_entries)
205 trace->entries[trace->nr_entries++] = ULONG_MAX;
206}
207
208void save_stack_trace(struct stack_trace *trace)
209{
210 save_stack_trace_tsk(current, trace);
211}
212EXPORT_SYMBOL_GPL(save_stack_trace);
213#endif