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 #include <asm/stacktrace.h>
  22
  23 static int report_trace(struct stackframe *frame, void *d)
  24 {
  25         unsigned int *depth = d;
  26
  27         if (*depth) {
  28                 oprofile_add_trace(frame->pc);
  29                 (*depth)--;
  30         }
  31
  32         return *depth == 0;
  33 }
  34
  35 /*
  36  * The registers we're interested in are at the end of the variable
  37  * length saved register structure. The fp points at the end of this
  38  * structure so the address of this struct is:
  39  * (struct frame_tail *)(xxx->fp)-1
  40  */
  41 struct frame_tail {
  42         struct frame_tail *fp;
  43         unsigned long sp;
  44         unsigned long lr;
  45 } __attribute__((packed));
  46
  47 static struct frame_tail* user_backtrace(struct frame_tail *tail)
  48 {
  49         struct frame_tail buftail[2];
  50
  51         /* Also check accessibility of one struct frame_tail beyond */
  52         if (!access_ok(VERIFY_READ, tail, sizeof(buftail)))
  53                 return NULL;
  54         if (__copy_from_user_inatomic(buftail, tail, sizeof(buftail)))
  55                 return NULL;
  56
  57         oprofile_add_trace(buftail[0].lr);
  58
  59         /* frame pointers should strictly progress back up the stack
  60          * (towards higher addresses) */
  61         if (tail >= buftail[0].fp)
  62                 return NULL;
  63
  64         return buftail[0].fp-1;
  65 }
  66
  67 void arm_backtrace(struct pt_regs * const regs, unsigned int depth)
  68 {
  69         struct frame_tail *tail = ((struct frame_tail *) regs->ARM_fp) - 1;
  70
  71         if (!user_mode(regs)) {
  72                 struct stackframe frame;
  73                 frame.fp = regs->ARM_fp;
  74                 frame.sp = regs->ARM_sp;
  75                 frame.lr = regs->ARM_lr;
  76                 frame.pc = regs->ARM_pc;
  77                 walk_stackframe(&frame, report_trace, &depth);
  78                 return;
  79         }
  80
  81         while (depth-- && tail && !((unsigned long) tail & 3))
  82                 tail = user_backtrace(tail);
  83 }