1 // SPDX-License-Identifier: GPL-2.0
2
3 #include <linux/sched/debug.h>
4 #include <linux/sched/task_stack.h>
5 #include <linux/stacktrace.h>
6 #include <linux/ftrace.h>
7 #include <linux/ptrace.h>
8
9 #ifdef CONFIG_FRAME_POINTER
10
11 struct stackframe {
12 unsigned long fp;
13 unsigned long ra;
14 };
15
16 void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
17 bool (*fn)(unsigned long, void *), void *arg)
18 {
19 unsigned long fp, sp, pc;
20
21 if (regs) {
22 fp = frame_pointer(regs);
23 sp = user_stack_pointer(regs);
24 pc = instruction_pointer(regs);
25 } else if (task == NULL || task == current) {
26 const register unsigned long current_fp __asm__ ("r8");
27 fp = current_fp;
28 sp = current_stack_pointer;
29 pc = (unsigned long)walk_stackframe;
30 } else {
31 /* task blocked in __switch_to */
32 fp = thread_saved_fp(task);
33 sp = thread_saved_sp(task);
34 pc = thread_saved_lr(task);
35 }
36
37 for (;;) {
38 unsigned long low, high;
39 struct stackframe *frame;
40
41 if (unlikely(!__kernel_text_address(pc) || fn(pc, arg)))
42 break;
43
44 /* Validate frame pointer */
45 low = sp;
46 high = ALIGN(sp, THREAD_SIZE);
47 if (unlikely(fp < low || fp > high || fp & 0x3))
48 break;
49 /* Unwind stack frame */
50 frame = (struct stackframe *)fp;
51 sp = fp;
52 fp = frame->fp;
53 pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
54 (unsigned long *)(fp - 8));
55 }
56 }
57
58 #else /* !CONFIG_FRAME_POINTER */
59
60 static void notrace walk_stackframe(struct task_struct *task,
61 struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg)
62 {
63 unsigned long sp, pc;
64 unsigned long *ksp;
65
66 if (regs) {
67 sp = user_stack_pointer(regs);
68 pc = instruction_pointer(regs);
69 } else if (task == NULL || task == current) {
70 sp = current_stack_pointer;
71 pc = (unsigned long)walk_stackframe;
72 } else {
73 /* task blocked in __switch_to */
74 sp = thread_saved_sp(task);
75 pc = thread_saved_lr(task);
76 }
77
78 if (unlikely(sp & 0x3))
79 return;
80
81 ksp = (unsigned long *)sp;
82 while (!kstack_end(ksp)) {
83 if (__kernel_text_address(pc) && unlikely(fn(pc, arg)))
84 break;
85 pc = (*ksp++) - 0x4;
86 }
87 }
88 #endif /* CONFIG_FRAME_POINTER */
89
90 static bool print_trace_address(unsigned long pc, void *arg)
91 {
92 print_ip_sym((const char *)arg, pc);
93 return false;
94 }
95
96 void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl)
97 {
98 pr_cont("Call Trace:\n");
99 walk_stackframe(task, NULL, print_trace_address, (void *)loglvl);
100 }
101
102 static bool save_wchan(unsigned long pc, void *arg)
103 {
104 if (!in_sched_functions(pc)) {
105 unsigned long *p = arg;
106 *p = pc;
107 return true;
108 }
109 return false;
110 }
111
112 unsigned long __get_wchan(struct task_struct *task)
113 {
114 unsigned long pc = 0;
115
116 walk_stackframe(task, NULL, save_wchan, &pc);
117 return pc;
118 }
119
120 #ifdef CONFIG_STACKTRACE
121 static bool __save_trace(unsigned long pc, void *arg, bool nosched)
122 {
123 struct stack_trace *trace = arg;
124
125 if (unlikely(nosched && in_sched_functions(pc)))
126 return false;
127 if (unlikely(trace->skip > 0)) {
128 trace->skip--;
129 return false;
130 }
131
132 trace->entries[trace->nr_entries++] = pc;
133 return (trace->nr_entries >= trace->max_entries);
134 }
135
136 static bool save_trace(unsigned long pc, void *arg)
137 {
138 return __save_trace(pc, arg, false);
139 }
140
141 /*
142 * Save stack-backtrace addresses into a stack_trace buffer.
143 */
144 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
145 {
146 walk_stackframe(tsk, NULL, save_trace, trace);
147 }
148 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
149
150 void save_stack_trace(struct stack_trace *trace)
151 {
152 save_stack_trace_tsk(NULL, trace);
153 }
154 EXPORT_SYMBOL_GPL(save_stack_trace);
155
156 #endif /* CONFIG_STACKTRACE */
157
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