LXR linux/arch/arm/oprofile/backtrace.c

   1/*
   2 * Arm specific backtracing code for oprofile
   3 *
   4 * Copyright 2005 Openedhand Ltd.
   5 *
   6 * Author: Richard Purdie <rpurdie@openedhand.com>
   7 *
   8 * Based on i386 oprofile backtrace code by John Levon, 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/sched.h>
  18#include <linux/mm.h>
  19#include <asm/ptrace.h>
  20#include <asm/uaccess.h>
  21
  22#include "../kernel/stacktrace.h"
  23
  24static int report_trace(struct stackframe *frame, void *d)
  25{
  26        unsigned int *depth = d;
  27
  28        if (*depth) {
  29                oprofile_add_trace(frame->lr);
  30                (*depth)--;
  31        }
  32
  33        return *depth == 0;
  34}
  35
  36/*
  37 * The registers we're interested in are at the end of the variable
  38 * length saved register structure. The fp points at the end of this
  39 * structure so the address of this struct is:
  40 * (struct frame_tail *)(xxx->fp)-1
  41 */
  42struct frame_tail {
  43        struct frame_tail *fp;
  44        unsigned long sp;
  45        unsigned long lr;
  46} __attribute__((packed));
  47
  48static struct frame_tail* user_backtrace(struct frame_tail *tail)
  49{
  50        struct frame_tail buftail[2];
  51
  52        /* Also check accessibility of one struct frame_tail beyond */
  53        if (!access_ok(VERIFY_READ, tail, sizeof(buftail)))
  54                return NULL;
  55        if (__copy_from_user_inatomic(buftail, tail, sizeof(buftail)))
  56                return NULL;
  57
  58        oprofile_add_trace(buftail[0].lr);
  59
  60        /* frame pointers should strictly progress back up the stack
  61         * (towards higher addresses) */
  62        if (tail >= buftail[0].fp)
  63                return NULL;
  64
  65        return buftail[0].fp-1;
  66}
  67
  68void arm_backtrace(struct pt_regs * const regs, unsigned int depth)
  69{
  70        struct frame_tail *tail = ((struct frame_tail *) regs->ARM_fp) - 1;
  71
  72        if (!user_mode(regs)) {
  73                unsigned long base = ((unsigned long)regs) & ~(THREAD_SIZE - 1);
  74                walk_stackframe(regs->ARM_fp, base, base + THREAD_SIZE,
  75                                report_trace, &depth);
  76                return;
  77        }
  78
  79        while (depth-- && tail && !((unsigned long) tail & 3))
  80                tail = user_backtrace(tail);
  81}
  82