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