Linux Kernel  3.7.1
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stacktrace.c
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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  */
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 
46 void 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 }
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' 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 
126 void save_stack_trace(struct stack_trace *trace)
127 {
129 }
131 #endif