stacktrace.c

  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
 19/*
 20 * This disables KASAN checking when reading a value from another task's stack,
 21 * since the other task could be running on another CPU and could have poisoned
 22 * the stack in the meantime.
 23 */
 24#define READ_ONCE_TASK_STACK(task, x)			\
 25({							\
 26	unsigned long val;				\
 27	unsigned long addr = x;				\
 28	if ((task) == current)				\
 29		val = READ_ONCE(addr);			\
 30	else						\
 31		val = READ_ONCE_NOCHECK(addr);		\
 32	val;						\
 33})
 34
 35extern asmlinkage void handle_exception(void);
 36extern unsigned long ret_from_exception_end;
 37
 38static inline int fp_is_valid(unsigned long fp, unsigned long sp)
 39{
 40	unsigned long low, high;
 41
 42	low = sp + sizeof(struct stackframe);
 43	high = ALIGN(sp, THREAD_SIZE);
 44
 45	return !(fp < low || fp > high || fp & 0x07);
 46}
 47
 48void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
 49			     bool (*fn)(void *, unsigned long), void *arg)
 50{
 51	unsigned long fp, sp, pc;
 52	int graph_idx = 0;
 53	int level = 0;
 54
 55	if (regs) {
 56		fp = frame_pointer(regs);
 57		sp = user_stack_pointer(regs);
 58		pc = instruction_pointer(regs);
 59	} else if (task == NULL || task == current) {
 60		fp = (unsigned long)__builtin_frame_address(0);
 61		sp = current_stack_pointer;
 62		pc = (unsigned long)walk_stackframe;
 63		level = -1;
 64	} else {
 65		/* task blocked in __switch_to */
 66		fp = task->thread.s[0];
 67		sp = task->thread.sp;
 68		pc = task->thread.ra;
 69	}
 70
 71	for (;;) {
 72		struct stackframe *frame;
 73
 74		if (unlikely(!__kernel_text_address(pc) || (level++ >= 0 && !fn(arg, pc))))
 75			break;
 76
 77		if (unlikely(!fp_is_valid(fp, sp)))
 78			break;
 79
 80		/* Unwind stack frame */
 81		frame = (struct stackframe *)fp - 1;
 82		sp = fp;
 83		if (regs && (regs->epc == pc) && fp_is_valid(frame->ra, sp)) {
 84			/* We hit function where ra is not saved on the stack */
 85			fp = frame->ra;
 86			pc = regs->ra;
 87		} else {
 88			fp = READ_ONCE_TASK_STACK(task, frame->fp);
 89			pc = READ_ONCE_TASK_STACK(task, frame->ra);
 90			pc = ftrace_graph_ret_addr(current, &graph_idx, pc,
 91						   &frame->ra);
 92			if (pc >= (unsigned long)handle_exception &&
 93			    pc < (unsigned long)&ret_from_exception_end) {
 94				if (unlikely(!fn(arg, pc)))
 95					break;
 96
 97				pc = ((struct pt_regs *)sp)->epc;
 98				fp = ((struct pt_regs *)sp)->s0;
 99			}
100		}
101
102	}
103}
104
105#else /* !CONFIG_FRAME_POINTER */
106
107void notrace walk_stackframe(struct task_struct *task,
108	struct pt_regs *regs, bool (*fn)(void *, unsigned long), void *arg)
109{
110	unsigned long sp, pc;
111	unsigned long *ksp;
112
113	if (regs) {
114		sp = user_stack_pointer(regs);
115		pc = instruction_pointer(regs);
116	} else if (task == NULL || task == current) {
117		sp = current_stack_pointer;
118		pc = (unsigned long)walk_stackframe;
119	} else {
120		/* task blocked in __switch_to */
121		sp = task->thread.sp;
122		pc = task->thread.ra;
123	}
124
125	if (unlikely(sp & 0x7))
126		return;
127
128	ksp = (unsigned long *)sp;
129	while (!kstack_end(ksp)) {
130		if (__kernel_text_address(pc) && unlikely(!fn(arg, pc)))
131			break;
132		pc = READ_ONCE_NOCHECK(*ksp++) - 0x4;
133	}
134}
135
136#endif /* CONFIG_FRAME_POINTER */
137
138static bool print_trace_address(void *arg, unsigned long pc)
139{
140	const char *loglvl = arg;
141
142	print_ip_sym(loglvl, pc);
143	return true;
144}
145
146noinline void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
147		    const char *loglvl)
148{
149	walk_stackframe(task, regs, print_trace_address, (void *)loglvl);
150}
151
152void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl)
153{
154	pr_cont("%sCall Trace:\n", loglvl);
155	dump_backtrace(NULL, task, loglvl);
156}
157
158static bool save_wchan(void *arg, unsigned long pc)
159{
160	if (!in_sched_functions(pc)) {
161		unsigned long *p = arg;
162		*p = pc;
163		return false;
164	}
165	return true;
166}
167
168unsigned long __get_wchan(struct task_struct *task)
169{
170	unsigned long pc = 0;
171
172	if (!try_get_task_stack(task))
173		return 0;
174	walk_stackframe(task, NULL, save_wchan, &pc);
175	put_task_stack(task);
176	return pc;
177}
178
179noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
180		     struct task_struct *task, struct pt_regs *regs)
181{
182	walk_stackframe(task, regs, consume_entry, cookie);
183}
184
185/*
186 * Get the return address for a single stackframe and return a pointer to the
187 * next frame tail.
188 */
189static unsigned long unwind_user_frame(stack_trace_consume_fn consume_entry,
190				       void *cookie, unsigned long fp,
191				       unsigned long reg_ra)
192{
193	struct stackframe buftail;
194	unsigned long ra = 0;
195	unsigned long __user *user_frame_tail =
196		(unsigned long __user *)(fp - sizeof(struct stackframe));
197
198	/* Check accessibility of one struct frame_tail beyond */
199	if (!access_ok(user_frame_tail, sizeof(buftail)))
200		return 0;
201	if (__copy_from_user_inatomic(&buftail, user_frame_tail,
202				      sizeof(buftail)))
203		return 0;
204
205	ra = reg_ra ? : buftail.ra;
206
207	fp = buftail.fp;
208	if (!ra || !consume_entry(cookie, ra))
209		return 0;
210
211	return fp;
212}
213
214void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
215			  const struct pt_regs *regs)
216{
217	unsigned long fp = 0;
218
219	fp = regs->s0;
220	if (!consume_entry(cookie, regs->epc))
221		return;
222
223	fp = unwind_user_frame(consume_entry, cookie, fp, regs->ra);
224	while (fp && !(fp & 0x7))
225		fp = unwind_user_frame(consume_entry, cookie, fp, 0);
226}