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 <linux/uaccess.h>
  20 #include <asm/ptrace.h>
  21
  22 #include "../kernel/stacktrace.h"
  23
  24 static 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  */
  42 struct frame_tail {
  43         struct frame_tail *fp;
  44         unsigned long sp;
  45         unsigned long lr;
  46 } __attribute__((packed));
  47
  48 static 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
  68 void 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 }