Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0-only
2#include <linux/export.h>
3#include <linux/kprobes.h>
4#include <linux/sched.h>
5#include <linux/sched/debug.h>
6#include <linux/stacktrace.h>
7
8#include <asm/sections.h>
9#include <asm/stacktrace.h>
10#include <asm/traps.h>
11
12#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
13/*
14 * Unwind the current stack frame and store the new register values in the
15 * structure passed as argument. Unwinding is equivalent to a function return,
16 * hence the new PC value rather than LR should be used for backtrace.
17 *
18 * With framepointer enabled, a simple function prologue looks like this:
19 * mov ip, sp
20 * stmdb sp!, {fp, ip, lr, pc}
21 * sub fp, ip, #4
22 *
23 * A simple function epilogue looks like this:
24 * ldm sp, {fp, sp, pc}
25 *
26 * When compiled with clang, pc and sp are not pushed. A simple function
27 * prologue looks like this when built with clang:
28 *
29 * stmdb {..., fp, lr}
30 * add fp, sp, #x
31 * sub sp, sp, #y
32 *
33 * A simple function epilogue looks like this when built with clang:
34 *
35 * sub sp, fp, #x
36 * ldm {..., fp, pc}
37 *
38 *
39 * Note that with framepointer enabled, even the leaf functions have the same
40 * prologue and epilogue, therefore we can ignore the LR value in this case.
41 */
42int notrace unwind_frame(struct stackframe *frame)
43{
44 unsigned long high, low;
45 unsigned long fp = frame->fp;
46
47 /* only go to a higher address on the stack */
48 low = frame->sp;
49 high = ALIGN(low, THREAD_SIZE);
50
51#ifdef CONFIG_CC_IS_CLANG
52 /* check current frame pointer is within bounds */
53 if (fp < low + 4 || fp > high - 4)
54 return -EINVAL;
55
56 frame->sp = frame->fp;
57 frame->fp = *(unsigned long *)(fp);
58 frame->pc = *(unsigned long *)(fp + 4);
59#else
60 /* check current frame pointer is within bounds */
61 if (fp < low + 12 || fp > high - 4)
62 return -EINVAL;
63
64 /* restore the registers from the stack frame */
65 frame->fp = *(unsigned long *)(fp - 12);
66 frame->sp = *(unsigned long *)(fp - 8);
67 frame->pc = *(unsigned long *)(fp - 4);
68#endif
69#ifdef CONFIG_KRETPROBES
70 if (is_kretprobe_trampoline(frame->pc))
71 frame->pc = kretprobe_find_ret_addr(frame->tsk,
72 (void *)frame->fp, &frame->kr_cur);
73#endif
74
75 return 0;
76}
77#endif
78
79void notrace walk_stackframe(struct stackframe *frame,
80 int (*fn)(struct stackframe *, void *), void *data)
81{
82 while (1) {
83 int ret;
84
85 if (fn(frame, data))
86 break;
87 ret = unwind_frame(frame);
88 if (ret < 0)
89 break;
90 }
91}
92EXPORT_SYMBOL(walk_stackframe);
93
94#ifdef CONFIG_STACKTRACE
95struct stack_trace_data {
96 struct stack_trace *trace;
97 unsigned int no_sched_functions;
98 unsigned int skip;
99};
100
101static int save_trace(struct stackframe *frame, void *d)
102{
103 struct stack_trace_data *data = d;
104 struct stack_trace *trace = data->trace;
105 struct pt_regs *regs;
106 unsigned long addr = frame->pc;
107
108 if (data->no_sched_functions && in_sched_functions(addr))
109 return 0;
110 if (data->skip) {
111 data->skip--;
112 return 0;
113 }
114
115 trace->entries[trace->nr_entries++] = addr;
116
117 if (trace->nr_entries >= trace->max_entries)
118 return 1;
119
120 if (!in_entry_text(frame->pc))
121 return 0;
122
123 regs = (struct pt_regs *)frame->sp;
124 if ((unsigned long)®s[1] > ALIGN(frame->sp, THREAD_SIZE))
125 return 0;
126
127 trace->entries[trace->nr_entries++] = regs->ARM_pc;
128
129 return trace->nr_entries >= trace->max_entries;
130}
131
132/* This must be noinline to so that our skip calculation works correctly */
133static noinline void __save_stack_trace(struct task_struct *tsk,
134 struct stack_trace *trace, unsigned int nosched)
135{
136 struct stack_trace_data data;
137 struct stackframe frame;
138
139 data.trace = trace;
140 data.skip = trace->skip;
141 data.no_sched_functions = nosched;
142
143 if (tsk != current) {
144#ifdef CONFIG_SMP
145 /*
146 * What guarantees do we have here that 'tsk' is not
147 * running on another CPU? For now, ignore it as we
148 * can't guarantee we won't explode.
149 */
150 return;
151#else
152 frame.fp = thread_saved_fp(tsk);
153 frame.sp = thread_saved_sp(tsk);
154 frame.lr = 0; /* recovered from the stack */
155 frame.pc = thread_saved_pc(tsk);
156#endif
157 } else {
158 /* We don't want this function nor the caller */
159 data.skip += 2;
160 frame.fp = (unsigned long)__builtin_frame_address(0);
161 frame.sp = current_stack_pointer;
162 frame.lr = (unsigned long)__builtin_return_address(0);
163 frame.pc = (unsigned long)__save_stack_trace;
164 }
165#ifdef CONFIG_KRETPROBES
166 frame.kr_cur = NULL;
167 frame.tsk = tsk;
168#endif
169
170 walk_stackframe(&frame, save_trace, &data);
171}
172
173void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
174{
175 struct stack_trace_data data;
176 struct stackframe frame;
177
178 data.trace = trace;
179 data.skip = trace->skip;
180 data.no_sched_functions = 0;
181
182 frame.fp = regs->ARM_fp;
183 frame.sp = regs->ARM_sp;
184 frame.lr = regs->ARM_lr;
185 frame.pc = regs->ARM_pc;
186#ifdef CONFIG_KRETPROBES
187 frame.kr_cur = NULL;
188 frame.tsk = current;
189#endif
190
191 walk_stackframe(&frame, save_trace, &data);
192}
193
194void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
195{
196 __save_stack_trace(tsk, trace, 1);
197}
198EXPORT_SYMBOL(save_stack_trace_tsk);
199
200void save_stack_trace(struct stack_trace *trace)
201{
202 __save_stack_trace(current, trace, 0);
203}
204EXPORT_SYMBOL_GPL(save_stack_trace);
205#endif