arch/arm/kernel/stacktrace.c

   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  */
  24 int 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 > high - 4)
  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 }
  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 /* This must be noinline to so that our skip calculation works correctly */
  87 static noinline void __save_stack_trace(struct task_struct *tsk,
  88         struct stack_trace *trace, unsigned int nosched)
  89 {
  90         struct stack_trace_data data;
  91         struct stackframe frame;
  92
  93         data.trace = trace;
  94         data.skip = trace->skip;
  95         data.no_sched_functions = nosched;
  96
  97         if (tsk != current) {
  98 #ifdef CONFIG_SMP
  99                 /*
 100                  * What guarantees do we have here that 'tsk' is not
 101                  * running on another CPU?  For now, ignore it as we
 102                  * can't guarantee we won't explode.
 103                  */
 104                 if (trace->nr_entries < trace->max_entries)
 105                         trace->entries[trace->nr_entries++] = ULONG_MAX;
 106                 return;
 107 #else
 108                 frame.fp = thread_saved_fp(tsk);
 109                 frame.sp = thread_saved_sp(tsk);
 110                 frame.lr = 0;           /* recovered from the stack */
 111                 frame.pc = thread_saved_pc(tsk);
 112 #endif
 113         } else {
 114                 register unsigned long current_sp asm ("sp");
 115
 116                 /* We don't want this function nor the caller */
 117                 data.skip += 2;
 118                 frame.fp = (unsigned long)__builtin_frame_address(0);
 119                 frame.sp = current_sp;
 120                 frame.lr = (unsigned long)__builtin_return_address(0);
 121                 frame.pc = (unsigned long)__save_stack_trace;
 122         }
 123
 124         walk_stackframe(&frame, save_trace, &data);
 125         if (trace->nr_entries < trace->max_entries)
 126                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 127 }
 128
 129 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 130 {
 131         __save_stack_trace(tsk, trace, 1);
 132 }
 133
 134 void save_stack_trace(struct stack_trace *trace)
 135 {
 136         __save_stack_trace(current, trace, 0);
 137 }
 138 EXPORT_SYMBOL_GPL(save_stack_trace);
 139 #endif