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1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2008 ARM Limited
4  * Copyright (C) 2014 Regents of the University of California
5  */
6 
7 #include <linux/export.h>
8 #include <linux/kallsyms.h>
9 #include <linux/sched.h>
10 #include <linux/sched/debug.h>
11 #include <linux/sched/task_stack.h>
12 #include <linux/stacktrace.h>
13 #include <linux/ftrace.h>
14 
15 #ifdef CONFIG_FRAME_POINTER
16 
17 struct stackframe {
18 	unsigned long fp;
19 	unsigned long ra;
20 };
21 
walk_stackframe(struct task_struct * task,struct pt_regs * regs,bool (* fn)(unsigned long,void *),void * arg)22 void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
23 			     bool (*fn)(unsigned long, void *), void *arg)
24 {
25 	unsigned long fp, sp, pc;
26 
27 	if (regs) {
28 		fp = frame_pointer(regs);
29 		sp = user_stack_pointer(regs);
30 		pc = instruction_pointer(regs);
31 	} else if (task == NULL || task == current) {
32 		const register unsigned long current_sp __asm__ ("sp");
33 		fp = (unsigned long)__builtin_frame_address(0);
34 		sp = current_sp;
35 		pc = (unsigned long)walk_stackframe;
36 	} else {
37 		/* task blocked in __switch_to */
38 		fp = task->thread.s[0];
39 		sp = task->thread.sp;
40 		pc = task->thread.ra;
41 	}
42 
43 	for (;;) {
44 		unsigned long low, high;
45 		struct stackframe *frame;
46 
47 		if (unlikely(!__kernel_text_address(pc) || fn(pc, arg)))
48 			break;
49 
50 		/* Validate frame pointer */
51 		low = sp + sizeof(struct stackframe);
52 		high = ALIGN(sp, THREAD_SIZE);
53 		if (unlikely(fp < low || fp > high || fp & 0x7))
54 			break;
55 		/* Unwind stack frame */
56 		frame = (struct stackframe *)fp - 1;
57 		sp = fp;
58 		fp = frame->fp;
59 		pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
60 					   (unsigned long *)(fp - 8));
61 	}
62 }
63 
64 #else /* !CONFIG_FRAME_POINTER */
65 
walk_stackframe(struct task_struct * task,struct pt_regs * regs,bool (* fn)(unsigned long,void *),void * arg)66 void notrace walk_stackframe(struct task_struct *task,
67 	struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg)
68 {
69 	unsigned long sp, pc;
70 	unsigned long *ksp;
71 
72 	if (regs) {
73 		sp = user_stack_pointer(regs);
74 		pc = instruction_pointer(regs);
75 	} else if (task == NULL || task == current) {
76 		const register unsigned long current_sp __asm__ ("sp");
77 		sp = current_sp;
78 		pc = (unsigned long)walk_stackframe;
79 	} else {
80 		/* task blocked in __switch_to */
81 		sp = task->thread.sp;
82 		pc = task->thread.ra;
83 	}
84 
85 	if (unlikely(sp & 0x7))
86 		return;
87 
88 	ksp = (unsigned long *)sp;
89 	while (!kstack_end(ksp)) {
90 		if (__kernel_text_address(pc) && unlikely(fn(pc, arg)))
91 			break;
92 		pc = READ_ONCE_NOCHECK(*ksp++) - 0x4;
93 	}
94 }
95 
96 #endif /* CONFIG_FRAME_POINTER */
97 
98 
print_trace_address(unsigned long pc,void * arg)99 static bool print_trace_address(unsigned long pc, void *arg)
100 {
101 	print_ip_sym(pc);
102 	return false;
103 }
104 
show_stack(struct task_struct * task,unsigned long * sp)105 void show_stack(struct task_struct *task, unsigned long *sp)
106 {
107 	pr_cont("Call Trace:\n");
108 	walk_stackframe(task, NULL, print_trace_address, NULL);
109 }
110 
111 
save_wchan(unsigned long pc,void * arg)112 static bool save_wchan(unsigned long pc, void *arg)
113 {
114 	if (!in_sched_functions(pc)) {
115 		unsigned long *p = arg;
116 		*p = pc;
117 		return true;
118 	}
119 	return false;
120 }
121 
get_wchan(struct task_struct * task)122 unsigned long get_wchan(struct task_struct *task)
123 {
124 	unsigned long pc = 0;
125 
126 	if (likely(task && task != current && task->state != TASK_RUNNING))
127 		walk_stackframe(task, NULL, save_wchan, &pc);
128 	return pc;
129 }
130 
131 
132 #ifdef CONFIG_STACKTRACE
133 
__save_trace(unsigned long pc,void * arg,bool nosched)134 static bool __save_trace(unsigned long pc, void *arg, bool nosched)
135 {
136 	struct stack_trace *trace = arg;
137 
138 	if (unlikely(nosched && in_sched_functions(pc)))
139 		return false;
140 	if (unlikely(trace->skip > 0)) {
141 		trace->skip--;
142 		return false;
143 	}
144 
145 	trace->entries[trace->nr_entries++] = pc;
146 	return (trace->nr_entries >= trace->max_entries);
147 }
148 
save_trace(unsigned long pc,void * arg)149 static bool save_trace(unsigned long pc, void *arg)
150 {
151 	return __save_trace(pc, arg, false);
152 }
153 
154 /*
155  * Save stack-backtrace addresses into a stack_trace buffer.
156  */
save_stack_trace_tsk(struct task_struct * tsk,struct stack_trace * trace)157 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
158 {
159 	walk_stackframe(tsk, NULL, save_trace, trace);
160 }
161 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
162 
save_stack_trace(struct stack_trace * trace)163 void save_stack_trace(struct stack_trace *trace)
164 {
165 	save_stack_trace_tsk(NULL, trace);
166 }
167 EXPORT_SYMBOL_GPL(save_stack_trace);
168 
169 #endif /* CONFIG_STACKTRACE */
170