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
11struct stackframe {
12	unsigned long fp;
13	unsigned long ra;
14};
15
16void 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
60static 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
90static bool print_trace_address(unsigned long pc, void *arg)
91{
92	print_ip_sym((const char *)arg, pc);
93	return false;
94}
95
96void 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
102static 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
112unsigned 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
121static 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
136static 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 */
144void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
145{
146	walk_stackframe(tsk, NULL, save_trace, trace);
147}
148EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
149
150void save_stack_trace(struct stack_trace *trace)
151{
152	save_stack_trace_tsk(NULL, trace);
153}
154EXPORT_SYMBOL_GPL(save_stack_trace);
155
156#endif /* CONFIG_STACKTRACE */
157