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_sp __asm__ ("sp");
 27		const register unsigned long current_fp __asm__ ("r8");
 28		fp = current_fp;
 29		sp = current_sp;
 30		pc = (unsigned long)walk_stackframe;
 31	} else {
 32		/* task blocked in __switch_to */
 33		fp = thread_saved_fp(task);
 34		sp = thread_saved_sp(task);
 35		pc = thread_saved_lr(task);
 36	}
 37
 38	for (;;) {
 39		unsigned long low, high;
 40		struct stackframe *frame;
 41
 42		if (unlikely(!__kernel_text_address(pc) || fn(pc, arg)))
 43			break;
 44
 45		/* Validate frame pointer */
 46		low = sp;
 47		high = ALIGN(sp, THREAD_SIZE);
 48		if (unlikely(fp < low || fp > high || fp & 0x3))
 49			break;
 50		/* Unwind stack frame */
 51		frame = (struct stackframe *)fp;
 52		sp = fp;
 53		fp = frame->fp;
 54		pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
 55					   (unsigned long *)(fp - 8));
 56	}
 57}
 58
 59#else /* !CONFIG_FRAME_POINTER */
 60
 61static void notrace walk_stackframe(struct task_struct *task,
 62	struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg)
 63{
 64	unsigned long sp, pc;
 65	unsigned long *ksp;
 66
 67	if (regs) {
 68		sp = user_stack_pointer(regs);
 69		pc = instruction_pointer(regs);
 70	} else if (task == NULL || task == current) {
 71		const register unsigned long current_sp __asm__ ("sp");
 72		sp = current_sp;
 73		pc = (unsigned long)walk_stackframe;
 74	} else {
 75		/* task blocked in __switch_to */
 76		sp = thread_saved_sp(task);
 77		pc = thread_saved_lr(task);
 78	}
 79
 80	if (unlikely(sp & 0x3))
 81		return;
 82
 83	ksp = (unsigned long *)sp;
 84	while (!kstack_end(ksp)) {
 85		if (__kernel_text_address(pc) && unlikely(fn(pc, arg)))
 86			break;
 87		pc = (*ksp++) - 0x4;
 88	}
 89}
 90#endif /* CONFIG_FRAME_POINTER */
 91
 92static bool print_trace_address(unsigned long pc, void *arg)
 93{
 94	print_ip_sym((const char *)arg, pc);
 95	return false;
 96}
 97
 98void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl)
 99{
100	pr_cont("Call Trace:\n");
101	walk_stackframe(task, NULL, print_trace_address, (void *)loglvl);
102}
103
104static bool save_wchan(unsigned long pc, void *arg)
105{
106	if (!in_sched_functions(pc)) {
107		unsigned long *p = arg;
108		*p = pc;
109		return true;
110	}
111	return false;
112}
113
114unsigned long get_wchan(struct task_struct *task)
115{
116	unsigned long pc = 0;
117
118	if (likely(task && task != current && task->state != TASK_RUNNING))
119		walk_stackframe(task, NULL, save_wchan, &pc);
120	return pc;
121}
122
123#ifdef CONFIG_STACKTRACE
124static bool __save_trace(unsigned long pc, void *arg, bool nosched)
125{
126	struct stack_trace *trace = arg;
127
128	if (unlikely(nosched && in_sched_functions(pc)))
129		return false;
130	if (unlikely(trace->skip > 0)) {
131		trace->skip--;
132		return false;
133	}
134
135	trace->entries[trace->nr_entries++] = pc;
136	return (trace->nr_entries >= trace->max_entries);
137}
138
139static bool save_trace(unsigned long pc, void *arg)
140{
141	return __save_trace(pc, arg, false);
142}
143
144/*
145 * Save stack-backtrace addresses into a stack_trace buffer.
146 */
147void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
148{
149	walk_stackframe(tsk, NULL, save_trace, trace);
150}
151EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
152
153void save_stack_trace(struct stack_trace *trace)
154{
155	save_stack_trace_tsk(NULL, trace);
156}
157EXPORT_SYMBOL_GPL(save_stack_trace);
158
159#endif /* CONFIG_STACKTRACE */