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backtrace.c

/*
 * AVR32 specific backtracing code for oprofile
 *
 * Copyright 2008 Weinmann GmbH
 *
 * Author: Nikolaus Voss <n.voss@weinmann.de>
 *
 * Based on i386 oprofile backtrace code by John Levon and David Smith
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#include <linux/oprofile.h>
#include <linux/sched.h>
#include <linux/uaccess.h>

/* The first two words of each frame on the stack look like this if we have
 * frame pointers */
00022 struct frame_head {
      unsigned long lr;
      struct frame_head *fp;
};

/* copied from arch/avr32/kernel/process.c */
static inline int valid_stack_ptr(struct thread_info *tinfo, unsigned long p)
{
      return (p > (unsigned long)tinfo)
            && (p < (unsigned long)tinfo + THREAD_SIZE - 3);
}

/* copied from arch/x86/oprofile/backtrace.c */
static struct frame_head *dump_user_backtrace(struct frame_head *head)
{
      struct frame_head bufhead[2];

      /* Also check accessibility of one struct frame_head beyond */
      if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
            return NULL;
      if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
            return NULL;

      oprofile_add_trace(bufhead[0].lr);

      /* frame pointers should strictly progress back up the stack
       * (towards higher addresses) */
      if (bufhead[0].fp <= head)
            return NULL;

      return bufhead[0].fp;
}

void avr32_backtrace(struct pt_regs * const regs, unsigned int depth)
{
      /* Get first frame pointer */
      struct frame_head *head = (struct frame_head *)(regs->r7);

      if (!user_mode(regs)) {
#ifdef CONFIG_FRAME_POINTER
            /*
             * Traverse the kernel stack from frame to frame up to
             * "depth" steps.
             */
            while (depth-- && valid_stack_ptr(task_thread_info(current),
                                      (unsigned long)head)) {
                  oprofile_add_trace(head->lr);
                  if (head->fp <= head)
                        break;
                  head = head->fp;
            }
#endif
      } else {
            /* Assume we have frame pointers in user mode process */
            while (depth-- && head)
                  head = dump_user_backtrace(head);
      }
}



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