arch/i386/kernel/stacktrace.c

   1 /*
   2  * arch/i386/kernel/stacktrace.c
   3  *
   4  * Stack trace management functions
   5  *
   6  *  Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
   7  */
   8 #include <linux/sched.h>
   9 #include <linux/stacktrace.h>
  10
  11 static inline int valid_stack_ptr(struct thread_info *tinfo, void *p)
  12 {
  13         return  p > (void *)tinfo &&
  14                 p < (void *)tinfo + THREAD_SIZE - 3;
  15 }
  16
  17 /*
  18  * Save stack-backtrace addresses into a stack_trace buffer:
  19  */
  20 static inline unsigned long
  21 save_context_stack(struct stack_trace *trace, unsigned int skip,
  22                    struct thread_info *tinfo, unsigned long *stack,
  23                    unsigned long ebp)
  24 {
  25         unsigned long addr;
  26
  27 #ifdef CONFIG_FRAME_POINTER
  28         while (valid_stack_ptr(tinfo, (void *)ebp)) {
  29                 addr = *(unsigned long *)(ebp + 4);
  30                 if (!skip)
  31                         trace->entries[trace->nr_entries++] = addr;
  32                 else
  33                         skip--;
  34                 if (trace->nr_entries >= trace->max_entries)
  35                         break;
  36                 /*
  37                  * break out of recursive entries (such as
  38                  * end_of_stack_stop_unwind_function):
  39                  */
  40                 if (ebp == *(unsigned long *)ebp)
  41                         break;
  42
  43                 ebp = *(unsigned long *)ebp;
  44         }
  45 #else
  46         while (valid_stack_ptr(tinfo, stack)) {
  47                 addr = *stack++;
  48                 if (__kernel_text_address(addr)) {
  49                         if (!skip)
  50                                 trace->entries[trace->nr_entries++] = addr;
  51                         else
  52                                 skip--;
  53                         if (trace->nr_entries >= trace->max_entries)
  54                                 break;
  55                 }
  56         }
  57 #endif
  58
  59         return ebp;
  60 }
  61
  62 /*
  63  * Save stack-backtrace addresses into a stack_trace buffer.
  64  */
  65 void save_stack_trace(struct stack_trace *trace, struct task_struct *task)
  66 {
  67         unsigned long ebp;
  68         unsigned long *stack = &ebp;
  69
  70         WARN_ON(trace->nr_entries || !trace->max_entries);
  71
  72         if (!task || task == current) {
  73                 /* Grab ebp right from our regs: */
  74                 asm ("movl %%ebp, %0" : "=r" (ebp));
  75         } else {
  76                 /* ebp is the last reg pushed by switch_to(): */
  77                 ebp = *(unsigned long *) task->thread.esp;
  78         }
  79
  80         while (1) {
  81                 struct thread_info *context = (struct thread_info *)
  82                                 ((unsigned long)stack & (~(THREAD_SIZE - 1)));
  83
  84                 ebp = save_context_stack(trace, trace->skip, context, stack, ebp);
  85                 stack = (unsigned long *)context->previous_esp;
  86                 if (!stack || trace->nr_entries >= trace->max_entries)
  87                         break;
  88                 trace->entries[trace->nr_entries++] = ULONG_MAX;
  89                 if (trace->nr_entries >= trace->max_entries)
  90                         break;
  91         }
  92 }
  93