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