arch/avr32/oprofile/backtrace.c

   1 /*
   2  * AVR32 specific backtracing code for oprofile
   3  *
   4  * Copyright 2008 Weinmann GmbH
   5  *
   6  * Author: Nikolaus Voss <n.voss@weinmann.de>
   7  *
   8  * Based on i386 oprofile backtrace code by John Levon and David Smith
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License version 2 as
  12  * published by the Free Software Foundation.
  13  *
  14  */
  15
  16 #include <linux/oprofile.h>
  17 #include <linux/ptrace.h>
  18 #include <linux/uaccess.h>
  19
  20 /* The first two words of each frame on the stack look like this if we have
  21  * frame pointers */
  22 struct frame_head {
  23         unsigned long lr;
  24         struct frame_head *fp;
  25 };
  26
  27 /* copied from arch/avr32/kernel/process.c */
  28 static inline int valid_stack_ptr(struct thread_info *tinfo, unsigned long p)
  29 {
  30         return (p > (unsigned long)tinfo)
  31                 && (p < (unsigned long)tinfo + THREAD_SIZE - 3);
  32 }
  33
  34 /* copied from arch/x86/oprofile/backtrace.c */
  35 static struct frame_head *dump_user_backtrace(struct frame_head *head)
  36 {
  37         struct frame_head bufhead[2];
  38
  39         /* Also check accessibility of one struct frame_head beyond */
  40         if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
  41                 return NULL;
  42         if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
  43                 return NULL;
  44
  45         oprofile_add_trace(bufhead[0].lr);
  46
  47         /* frame pointers should strictly progress back up the stack
  48          * (towards higher addresses) */
  49         if (bufhead[0].fp <= head)
  50                 return NULL;
  51
  52         return bufhead[0].fp;
  53 }
  54
  55 void avr32_backtrace(struct pt_regs * const regs, unsigned int depth)
  56 {
  57         /* Get first frame pointer */
  58         struct frame_head *head = (struct frame_head *)(regs->r7);
  59
  60         if (!user_mode(regs)) {
  61 #ifdef CONFIG_FRAME_POINTER
  62                 /*
  63                  * Traverse the kernel stack from frame to frame up to
  64                  * "depth" steps.
  65                  */
  66                 while (depth-- && valid_stack_ptr(task_thread_info(current),
  67                                                   (unsigned long)head)) {
  68                         oprofile_add_trace(head->lr);
  69                         if (head->fp <= head)
  70                                 break;
  71                         head = head->fp;
  72                 }
  73 #endif
  74         } else {
  75                 /* Assume we have frame pointers in user mode process */
  76                 while (depth-- && head)
  77                         head = dump_user_backtrace(head);
  78         }
  79 }
  80
  81