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
 17struct stackframe {
 18	unsigned long fp;
 19	unsigned long ra;
 20};
 21
 22void 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
 66static 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 = (*ksp++) - 0x4;
 93	}
 94}
 95
 96#endif /* CONFIG_FRAME_POINTER */
 97
 98
 99static bool print_trace_address(unsigned long pc, void *arg)
100{
101	print_ip_sym(pc);
102	return false;
103}
104
105void 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
112static 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
122unsigned 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
134static 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
149static 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 */
157void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
158{
159	walk_stackframe(tsk, NULL, save_trace, trace);
160}
161EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
162
163void save_stack_trace(struct stack_trace *trace)
164{
165	save_stack_trace_tsk(NULL, trace);
166}
167EXPORT_SYMBOL_GPL(save_stack_trace);
168
169#endif /* CONFIG_STACKTRACE */