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/unwinder.h>
  21 #include <asm/ptrace.h>
  22 #include <asm/uaccess.h>
  23 #include <asm/sections.h>
  24 #include <asm/stacktrace.h>
  25
  26 static int backtrace_stack(void *data, char *name)
  27 {
  28         /* Yes, we want all stacks */
  29         return 0;
  30 }
  31
  32 static void backtrace_address(void *data, unsigned long addr, int reliable)
  33 {
  34         unsigned int *depth = data;
  35
  36         if ((*depth)--)
  37                 oprofile_add_trace(addr);
  38 }
  39
  40 static struct stacktrace_ops backtrace_ops = {
  41         .stack = backtrace_stack,
  42         .address = backtrace_address,
  43 };
  44
  45 /* Limit to stop backtracing too far. */
  46 static int backtrace_limit = 20;
  47
  48 static unsigned long *
  49 user_backtrace(unsigned long *stackaddr, struct pt_regs *regs)
  50 {
  51         unsigned long buf_stack;
  52
  53         /* Also check accessibility of address */
  54         if (!access_ok(VERIFY_READ, stackaddr, sizeof(unsigned long)))
  55                 return NULL;
  56
  57         if (__copy_from_user_inatomic(&buf_stack, stackaddr, sizeof(unsigned long)))
  58                 return NULL;
  59
  60         /* Quick paranoia check */
  61         if (buf_stack & 3)
  62                 return NULL;
  63
  64         oprofile_add_trace(buf_stack);
  65
  66         stackaddr++;
  67
  68         return stackaddr;
  69 }
  70
  71 void sh_backtrace(struct pt_regs * const regs, unsigned int depth)
  72 {
  73         unsigned long *stackaddr;
  74
  75         /*
  76          * Paranoia - clip max depth as we could get lost in the weeds.
  77          */
  78         if (depth > backtrace_limit)
  79                 depth = backtrace_limit;
  80
  81         stackaddr = (unsigned long *)kernel_stack_pointer(regs);
  82         if (!user_mode(regs)) {
  83                 if (depth)
  84                         unwind_stack(NULL, regs, stackaddr,
  85                                      &backtrace_ops, &depth);
  86                 return;
  87         }
  88
  89         while (depth-- && (stackaddr != NULL))
  90                 stackaddr = user_backtrace(stackaddr, regs);
  91 }