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#include <asm/stacktrace.h>
 16
 17#ifdef CONFIG_FRAME_POINTER
 18
 19extern asmlinkage void ret_from_exception(void);
 20
 21void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
 22			     bool (*fn)(void *, unsigned long), void *arg)
 23{
 24	unsigned long fp, sp, pc;
 25	int level = 0;
 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		fp = (unsigned long)__builtin_frame_address(0);
 33		sp = current_stack_pointer;
 34		pc = (unsigned long)walk_stackframe;
 35		level = -1;
 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) || (level++ >= 0 && !fn(arg, pc))))
 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		if (regs && (regs->epc == pc) && (frame->fp & 0x7)) {
 59			fp = frame->ra;
 60			pc = regs->ra;
 61		} else {
 62			fp = frame->fp;
 63			pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
 64						   &frame->ra);
 65			if (pc == (unsigned long)ret_from_exception) {
 66				if (unlikely(!__kernel_text_address(pc) || !fn(arg, pc)))
 67					break;
 68
 69				pc = ((struct pt_regs *)sp)->epc;
 70				fp = ((struct pt_regs *)sp)->s0;
 71			}
 72		}
 73
 74	}
 75}
 76
 77#else /* !CONFIG_FRAME_POINTER */
 78
 79void notrace walk_stackframe(struct task_struct *task,
 80	struct pt_regs *regs, bool (*fn)(void *, unsigned long), void *arg)
 81{
 82	unsigned long sp, pc;
 83	unsigned long *ksp;
 84
 85	if (regs) {
 86		sp = user_stack_pointer(regs);
 87		pc = instruction_pointer(regs);
 88	} else if (task == NULL || task == current) {
 89		sp = current_stack_pointer;
 90		pc = (unsigned long)walk_stackframe;
 91	} else {
 92		/* task blocked in __switch_to */
 93		sp = task->thread.sp;
 94		pc = task->thread.ra;
 95	}
 96
 97	if (unlikely(sp & 0x7))
 98		return;
 99
100	ksp = (unsigned long *)sp;
101	while (!kstack_end(ksp)) {
102		if (__kernel_text_address(pc) && unlikely(!fn(arg, pc)))
103			break;
104		pc = READ_ONCE_NOCHECK(*ksp++) - 0x4;
105	}
106}
107
108#endif /* CONFIG_FRAME_POINTER */
109
110static bool print_trace_address(void *arg, unsigned long pc)
111{
112	const char *loglvl = arg;
113
114	print_ip_sym(loglvl, pc);
115	return true;
116}
117
118noinline void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
119		    const char *loglvl)
120{
121	walk_stackframe(task, regs, print_trace_address, (void *)loglvl);
122}
123
124void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl)
125{
126	pr_cont("%sCall Trace:\n", loglvl);
127	dump_backtrace(NULL, task, loglvl);
128}
129
130static bool save_wchan(void *arg, unsigned long pc)
131{
132	if (!in_sched_functions(pc)) {
133		unsigned long *p = arg;
134		*p = pc;
135		return false;
136	}
137	return true;
138}
139
140unsigned long __get_wchan(struct task_struct *task)
141{
142	unsigned long pc = 0;
143
144	if (!try_get_task_stack(task))
145		return 0;
146	walk_stackframe(task, NULL, save_wchan, &pc);
147	put_task_stack(task);
148	return pc;
149}
150
151noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
152		     struct task_struct *task, struct pt_regs *regs)
153{
154	walk_stackframe(task, regs, consume_entry, cookie);
155}