arch/sh/oprofile/backtrace.c

   1 /*
   2  * SH specific backtracing code for oprofile
   3  *
   4  * Copyright 2007 STMicroelectronics Ltd.
   5  *
   6  * Author: Dave Peverley <dpeverley@mpc-data.co.uk>
   7  *
   8  * Based on ARM oprofile backtrace code by Richard Purdie and in turn, i386
   9  * oprofile backtrace code by John Levon, David Smith
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License version 2 as
  13  * published by the Free Software Foundation.
  14  *
  15  */
  16 #include <linux/oprofile.h>
  17 #include <linux/sched.h>
  18 #include <linux/kallsyms.h>
  19 #include <linux/mm.h>
  20 #include <asm/ptrace.h>
  21 #include <asm/uaccess.h>
  22 #include <asm/sections.h>
  23
  24 /* Limit to stop backtracing too far. */
  25 static int backtrace_limit = 20;
  26
  27 static unsigned long *
  28 user_backtrace(unsigned long *stackaddr, struct pt_regs *regs)
  29 {
  30         unsigned long buf_stack;
  31
  32         /* Also check accessibility of address */
  33         if (!access_ok(VERIFY_READ, stackaddr, sizeof(unsigned long)))
  34                 return NULL;
  35
  36         if (__copy_from_user_inatomic(&buf_stack, stackaddr, sizeof(unsigned long)))
  37                 return NULL;
  38
  39         /* Quick paranoia check */
  40         if (buf_stack & 3)
  41                 return NULL;
  42
  43         oprofile_add_trace(buf_stack);
  44
  45         stackaddr++;
  46
  47         return stackaddr;
  48 }
  49
  50 /*
  51  * |             | /\ Higher addresses
  52  * |             |
  53  * --------------- stack base (address of current_thread_info)
  54  * | thread info |
  55  * .             .
  56  * |    stack    |
  57  * --------------- saved regs->regs[15] value if valid
  58  * .             .
  59  * --------------- struct pt_regs stored on stack (struct pt_regs *)
  60  * |             |
  61  * .             .
  62  * |             |
  63  * --------------- ???
  64  * |             |
  65  * |             | \/ Lower addresses
  66  *
  67  * Thus, &pt_regs <-> stack base restricts the valid(ish) fp values
  68  */
  69 static int valid_kernel_stack(unsigned long *stackaddr, struct pt_regs *regs)
  70 {
  71         unsigned long stack = (unsigned long)regs;
  72         unsigned long stack_base = (stack & ~(THREAD_SIZE - 1)) + THREAD_SIZE;
  73
  74         return ((unsigned long)stackaddr > stack) && ((unsigned long)stackaddr < stack_base);
  75 }
  76
  77 static unsigned long *
  78 kernel_backtrace(unsigned long *stackaddr, struct pt_regs *regs)
  79 {
  80         unsigned long addr;
  81
  82         /*
  83          * If not a valid kernel address, keep going till we find one
  84          * or the SP stops being a valid address.
  85          */
  86         do {
  87                 addr = *stackaddr++;
  88                 oprofile_add_trace(addr);
  89         } while (valid_kernel_stack(stackaddr, regs));
  90
  91         return stackaddr;
  92 }
  93
  94 void sh_backtrace(struct pt_regs * const regs, unsigned int depth)
  95 {
  96         unsigned long *stackaddr;
  97
  98         /*
  99          * Paranoia - clip max depth as we could get lost in the weeds.
 100          */
 101         if (depth > backtrace_limit)
 102                 depth = backtrace_limit;
 103
 104         stackaddr = (unsigned long *)regs->regs[15];
 105         if (!user_mode(regs)) {
 106                 while (depth-- && valid_kernel_stack(stackaddr, regs))
 107                         stackaddr = kernel_backtrace(stackaddr, regs);
 108
 109                 return;
 110         }
 111
 112         while (depth-- && (stackaddr != NULL))
 113                 stackaddr = user_backtrace(stackaddr, regs);
 114 }