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backtrace.c

/**
 * @file backtrace.c
 *
 * @remark Copyright 2002 OProfile authors
 * @remark Read the file COPYING
 *
 * @author John Levon
 * @author David Smith
 */

#include <linux/oprofile.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <asm/ptrace.h>
#include <asm/uaccess.h>
#include <asm/stacktrace.h>

static void backtrace_warning_symbol(void *data, char *msg,
                             unsigned long symbol)
{
      /* Ignore warnings */
}

static void backtrace_warning(void *data, char *msg)
{
      /* Ignore warnings */
}

static int backtrace_stack(void *data, char *name)
{
      /* Yes, we want all stacks */
      return 0;
}

static void backtrace_address(void *data, unsigned long addr)
{
      unsigned int *depth = data;

      if ((*depth)--)
            oprofile_add_trace(addr);
}

static struct stacktrace_ops backtrace_ops = {
      .warning = backtrace_warning,
      .warning_symbol = backtrace_warning_symbol,
      .stack = backtrace_stack,
      .address = backtrace_address,
};

struct frame_head {
      struct frame_head *ebp;
      unsigned long ret;
} __attribute__((packed));

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].ret);

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

      return bufhead[0].ebp;
}

void
x86_backtrace(struct pt_regs * const regs, unsigned int depth)
{
      struct frame_head *head = (struct frame_head *)frame_pointer(regs);
      unsigned long stack = stack_pointer(regs);

      if (!user_mode_vm(regs)) {
            if (depth)
                  dump_trace(NULL, regs, (unsigned long *)stack,
                           &backtrace_ops, &depth);
            return;
      }

      while (depth-- && head)
            head = dump_user_backtrace(head);
}

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