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 void backtrace_warning_symbol(void *data, char *msg,
  27                                      unsigned long symbol)
  28 {
  29         /* Ignore warnings */
  30 }
  31
  32 static void backtrace_warning(void *data, char *msg)
  33 {
  34         /* Ignore warnings */
  35 }
  36
  37 static int backtrace_stack(void *data, char *name)
  38 {
  39         /* Yes, we want all stacks */
  40         return 0;
  41 }
  42
  43 static void backtrace_address(void *data, unsigned long addr, int reliable)
  44 {
  45         unsigned int *depth = data;
  46
  47         if ((*depth)--)
  48                 oprofile_add_trace(addr);
  49 }
  50
  51 static struct stacktrace_ops backtrace_ops = {
  52         .warning = backtrace_warning,
  53         .warning_symbol = backtrace_warning_symbol,
  54         .stack = backtrace_stack,
  55         .address = backtrace_address,
  56 };
  57
  58 /* Limit to stop backtracing too far. */
  59 static int backtrace_limit = 20;
  60
  61 static unsigned long *
  62 user_backtrace(unsigned long *stackaddr, struct pt_regs *regs)
  63 {
  64         unsigned long buf_stack;
  65
  66         /* Also check accessibility of address */
  67         if (!access_ok(VERIFY_READ, stackaddr, sizeof(unsigned long)))
  68                 return NULL;
  69
  70         if (__copy_from_user_inatomic(&buf_stack, stackaddr, sizeof(unsigned long)))
  71                 return NULL;
  72
  73         /* Quick paranoia check */
  74         if (buf_stack & 3)
  75                 return NULL;
  76
  77         oprofile_add_trace(buf_stack);
  78
  79         stackaddr++;
  80
  81         return stackaddr;
  82 }
  83
  84 void sh_backtrace(struct pt_regs * const regs, unsigned int depth)
  85 {
  86         unsigned long *stackaddr;
  87
  88         /*
  89          * Paranoia - clip max depth as we could get lost in the weeds.
  90          */
  91         if (depth > backtrace_limit)
  92                 depth = backtrace_limit;
  93
  94         stackaddr = (unsigned long *)regs->regs[15];
  95         if (!user_mode(regs)) {
  96                 if (depth)
  97                         unwind_stack(NULL, regs, stackaddr,
  98                                      &backtrace_ops, &depth);
  99                 return;
 100         }
 101
 102         while (depth-- && (stackaddr != NULL))
 103                 stackaddr = user_backtrace(stackaddr, regs);
 104 }