1 #include <linux/module.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 */
24 int 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) + 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
46 void 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 }
59 EXPORT_SYMBOL(walk_stackframe);
60
61 #ifdef CONFIG_STACKTRACE
62 struct stack_trace_data {
63 struct stack_trace *trace;
64 unsigned int no_sched_functions;
65 unsigned int skip;
66 };
67
68 static 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
86 void 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'
98 * is not running on another CPU?
99 */
100 BUG();
101 #else
102 data.no_sched_functions = 1;
103 frame.fp = thread_saved_fp(tsk);
104 frame.sp = thread_saved_sp(tsk);
105 frame.lr = 0; /* recovered from the stack */
106 frame.pc = thread_saved_pc(tsk);
107 #endif
108 } else {
109 register unsigned long current_sp asm ("sp");
110
111 data.no_sched_functions = 0;
112 frame.fp = (unsigned long)__builtin_frame_address(0);
113 frame.sp = current_sp;
114 frame.lr = (unsigned long)__builtin_return_address(0);
115 frame.pc = (unsigned long)save_stack_trace_tsk;
116 }
117
118 walk_stackframe(&frame, save_trace, &data);
119 if (trace->nr_entries < trace->max_entries)
120 trace->entries[trace->nr_entries++] = ULONG_MAX;
121 }
122
123 void save_stack_trace(struct stack_trace *trace)
124 {
125 save_stack_trace_tsk(current, trace);
126 }
127 EXPORT_SYMBOL_GPL(save_stack_trace);
128 #endif
129
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