arch/x86/oprofile/backtrace.c

   1 /**
   2  * @file backtrace.c
   3  *
   4  * @remark Copyright 2002 OProfile authors
   5  * @remark Read the file COPYING
   6  *
   7  * @author John Levon
   8  * @author David Smith
   9  */
  10
  11 #include <linux/oprofile.h>
  12 #include <linux/sched.h>
  13 #include <linux/mm.h>
  14 #include <asm/ptrace.h>
  15 #include <asm/uaccess.h>
  16 #include <asm/stacktrace.h>
  17
  18 static void backtrace_warning_symbol(void *data, char *msg,
  19                                      unsigned long symbol)
  20 {
  21         /* Ignore warnings */
  22 }
  23
  24 static void backtrace_warning(void *data, char *msg)
  25 {
  26         /* Ignore warnings */
  27 }
  28
  29 static int backtrace_stack(void *data, char *name)
  30 {
  31         /* Yes, we want all stacks */
  32         return 0;
  33 }
  34
  35 static void backtrace_address(void *data, unsigned long addr, int reliable)
  36 {
  37         unsigned int *depth = data;
  38
  39         if ((*depth)--)
  40                 oprofile_add_trace(addr);
  41 }
  42
  43 static struct stacktrace_ops backtrace_ops = {
  44         .warning        = backtrace_warning,
  45         .warning_symbol = backtrace_warning_symbol,
  46         .stack          = backtrace_stack,
  47         .address        = backtrace_address,
  48         .walk_stack     = print_context_stack,
  49 };
  50
  51 struct frame_head {
  52         struct frame_head *bp;
  53         unsigned long ret;
  54 } __attribute__((packed));
  55
  56 static struct frame_head *dump_user_backtrace(struct frame_head *head)
  57 {
  58         struct frame_head bufhead[2];
  59
  60         /* Also check accessibility of one struct frame_head beyond */
  61         if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
  62                 return NULL;
  63         if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
  64                 return NULL;
  65
  66         oprofile_add_trace(bufhead[0].ret);
  67
  68         /* frame pointers should strictly progress back up the stack
  69          * (towards higher addresses) */
  70         if (head >= bufhead[0].bp)
  71                 return NULL;
  72
  73         return bufhead[0].bp;
  74 }
  75
  76 void
  77 x86_backtrace(struct pt_regs * const regs, unsigned int depth)
  78 {
  79         struct frame_head *head = (struct frame_head *)frame_pointer(regs);
  80
  81         if (!user_mode_vm(regs)) {
  82                 unsigned long stack = kernel_stack_pointer(regs);
  83                 if (depth)
  84                         dump_trace(NULL, regs, (unsigned long *)stack, 0,
  85                                    &backtrace_ops, &depth);
  86                 return;
  87         }
  88
  89         while (depth-- && head)
  90                 head = dump_user_backtrace(head);
  91 }