kernel/extable.c

   1 /* Rewritten by Rusty Russell, on the backs of many others...
   2    Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
   3
   4     This program is free software; you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation; either version 2 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12     GNU General Public License for more details.
  13
  14     You should have received a copy of the GNU General Public License
  15     along with this program; if not, write to the Free Software
  16     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17 */
  18 #include <linux/ftrace.h>
  19 #include <linux/memory.h>
  20 #include <linux/module.h>
  21 #include <linux/ftrace.h>
  22 #include <linux/mutex.h>
  23 #include <linux/init.h>
  24
  25 #include <asm/sections.h>
  26 #include <asm/uaccess.h>
  27
  28 /*
  29  * mutex protecting text section modification (dynamic code patching).
  30  * some users need to sleep (allocating memory...) while they hold this lock.
  31  *
  32  * NOT exported to modules - patching kernel text is a really delicate matter.
  33  */
  34 DEFINE_MUTEX(text_mutex);
  35
  36 extern struct exception_table_entry __start___ex_table[];
  37 extern struct exception_table_entry __stop___ex_table[];
  38
  39 /* Cleared by build time tools if the table is already sorted. */
  40 u32 __initdata __visible main_extable_sort_needed = 1;
  41
  42 /* Sort the kernel's built-in exception table */
  43 void __init sort_main_extable(void)
  44 {
  45         if (main_extable_sort_needed && __stop___ex_table > __start___ex_table) {
  46                 pr_notice("Sorting __ex_table...\n");
  47                 sort_extable(__start___ex_table, __stop___ex_table);
  48         }
  49 }
  50
  51 /* Given an address, look for it in the exception tables. */
  52 const struct exception_table_entry *search_exception_tables(unsigned long addr)
  53 {
  54         const struct exception_table_entry *e;
  55
  56         e = search_extable(__start___ex_table, __stop___ex_table-1, addr);
  57         if (!e)
  58                 e = search_module_extables(addr);
  59         return e;
  60 }
  61
  62 static inline int init_kernel_text(unsigned long addr)
  63 {
  64         if (addr >= (unsigned long)_sinittext &&
  65             addr < (unsigned long)_einittext)
  66                 return 1;
  67         return 0;
  68 }
  69
  70 int core_kernel_text(unsigned long addr)
  71 {
  72         if (addr >= (unsigned long)_stext &&
  73             addr < (unsigned long)_etext)
  74                 return 1;
  75
  76         if (system_state == SYSTEM_BOOTING &&
  77             init_kernel_text(addr))
  78                 return 1;
  79         return 0;
  80 }
  81
  82 /**
  83  * core_kernel_data - tell if addr points to kernel data
  84  * @addr: address to test
  85  *
  86  * Returns true if @addr passed in is from the core kernel data
  87  * section.
  88  *
  89  * Note: On some archs it may return true for core RODATA, and false
  90  *  for others. But will always be true for core RW data.
  91  */
  92 int core_kernel_data(unsigned long addr)
  93 {
  94         if (addr >= (unsigned long)_sdata &&
  95             addr < (unsigned long)_edata)
  96                 return 1;
  97         return 0;
  98 }
  99
 100 int __kernel_text_address(unsigned long addr)
 101 {
 102         if (core_kernel_text(addr))
 103                 return 1;
 104         if (is_module_text_address(addr))
 105                 return 1;
 106         if (is_ftrace_trampoline(addr))
 107                 return 1;
 108         /*
 109          * There might be init symbols in saved stacktraces.
 110          * Give those symbols a chance to be printed in
 111          * backtraces (such as lockdep traces).
 112          *
 113          * Since we are after the module-symbols check, there's
 114          * no danger of address overlap:
 115          */
 116         if (init_kernel_text(addr))
 117                 return 1;
 118         return 0;
 119 }
 120
 121 int kernel_text_address(unsigned long addr)
 122 {
 123         if (core_kernel_text(addr))
 124                 return 1;
 125         if (is_module_text_address(addr))
 126                 return 1;
 127         return is_ftrace_trampoline(addr);
 128 }
 129
 130 /*
 131  * On some architectures (PPC64, IA64) function pointers
 132  * are actually only tokens to some data that then holds the
 133  * real function address. As a result, to find if a function
 134  * pointer is part of the kernel text, we need to do some
 135  * special dereferencing first.
 136  */
 137 int func_ptr_is_kernel_text(void *ptr)
 138 {
 139         unsigned long addr;
 140         addr = (unsigned long) dereference_function_descriptor(ptr);
 141         if (core_kernel_text(addr))
 142                 return 1;
 143         return is_module_text_address(addr);
 144 }