1/*
  2 * Copyright (C) 2008 ARM Limited
  3 * Copyright (C) 2014 Regents of the University of California
  4 *
  5 * This program is free software; you can redistribute it and/or modify
  6 * it under the terms of the GNU General Public License version 2 as
  7 * published by the Free Software Foundation.
  8 *
  9 * This program is distributed in the hope that it will be useful,
 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12 * GNU General Public License for more details.
 13 */
 14
 15#include <linux/export.h>
 16#include <linux/kallsyms.h>
 17#include <linux/sched.h>
 18#include <linux/sched/debug.h>
 19#include <linux/sched/task_stack.h>
 20#include <linux/stacktrace.h>
 21#include <linux/ftrace.h>
 22
 23#ifdef CONFIG_FRAME_POINTER
 24
 25struct stackframe {
 26	unsigned long fp;
 27	unsigned long ra;
 28};
 29
 30static void notrace walk_stackframe(struct task_struct *task,
 31	struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg)
 32{
 33	unsigned long fp, sp, pc;
 34
 35	if (regs) {
 36		fp = GET_FP(regs);
 37		sp = GET_USP(regs);
 38		pc = GET_IP(regs);
 39	} else if (task == NULL || task == current) {
 40		const register unsigned long current_sp __asm__ ("sp");
 41		fp = (unsigned long)__builtin_frame_address(0);
 42		sp = current_sp;
 43		pc = (unsigned long)walk_stackframe;
 44	} else {
 45		/* task blocked in __switch_to */
 46		fp = task->thread.s[0];
 47		sp = task->thread.sp;
 48		pc = task->thread.ra;
 49	}
 50
 51	for (;;) {
 52		unsigned long low, high;
 53		struct stackframe *frame;
 54
 55		if (unlikely(!__kernel_text_address(pc) || fn(pc, arg)))
 56			break;
 57
 58		/* Validate frame pointer */
 59		low = sp + sizeof(struct stackframe);
 60		high = ALIGN(sp, THREAD_SIZE);
 61		if (unlikely(fp < low || fp > high || fp & 0x7))
 62			break;
 63		/* Unwind stack frame */
 64		frame = (struct stackframe *)fp - 1;
 65		sp = fp;
 66		fp = frame->fp;
 67#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
 68		pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
 69					   (unsigned long *)(fp - 8));
 70#else
 71		pc = frame->ra - 0x4;
 72#endif
 73	}
 74}
 75
 76#else /* !CONFIG_FRAME_POINTER */
 77
 78static void notrace walk_stackframe(struct task_struct *task,
 79	struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg)
 80{
 81	unsigned long sp, pc;
 82	unsigned long *ksp;
 83
 84	if (regs) {
 85		sp = GET_USP(regs);
 86		pc = GET_IP(regs);
 87	} else if (task == NULL || task == current) {
 88		const register unsigned long current_sp __asm__ ("sp");
 89		sp = current_sp;
 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(pc, arg)))
103			break;
104		pc = (*ksp++) - 0x4;
105	}
106}
107
108#endif /* CONFIG_FRAME_POINTER */
109
110
111static bool print_trace_address(unsigned long pc, void *arg)
112{
113	print_ip_sym(pc);
114	return false;
115}
116
117void show_stack(struct task_struct *task, unsigned long *sp)
118{
119	pr_cont("Call Trace:\n");
120	walk_stackframe(task, NULL, print_trace_address, NULL);
121}
122
123
124static bool save_wchan(unsigned long pc, void *arg)
125{
126	if (!in_sched_functions(pc)) {
127		unsigned long *p = arg;
128		*p = pc;
129		return true;
130	}
131	return false;
132}
133
134unsigned long get_wchan(struct task_struct *task)
135{
136	unsigned long pc = 0;
137
138	if (likely(task && task != current && task->state != TASK_RUNNING))
139		walk_stackframe(task, NULL, save_wchan, &pc);
140	return pc;
141}
142
143
144#ifdef CONFIG_STACKTRACE
145
146static bool __save_trace(unsigned long pc, void *arg, bool nosched)
147{
148	struct stack_trace *trace = arg;
149
150	if (unlikely(nosched && in_sched_functions(pc)))
151		return false;
152	if (unlikely(trace->skip > 0)) {
153		trace->skip--;
154		return false;
155	}
156
157	trace->entries[trace->nr_entries++] = pc;
158	return (trace->nr_entries >= trace->max_entries);
159}
160
161static bool save_trace(unsigned long pc, void *arg)
162{
163	return __save_trace(pc, arg, false);
164}
165
166/*
167 * Save stack-backtrace addresses into a stack_trace buffer.
168 */
169void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
170{
171	walk_stackframe(tsk, NULL, save_trace, trace);
172	if (trace->nr_entries < trace->max_entries)
173		trace->entries[trace->nr_entries++] = ULONG_MAX;
174}
175EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
176
177void save_stack_trace(struct stack_trace *trace)
178{
179	save_stack_trace_tsk(NULL, trace);
180}
181EXPORT_SYMBOL_GPL(save_stack_trace);
182
183#endif /* CONFIG_STACKTRACE */