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