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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(task, &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++);
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}