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