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/extable.h>
  21 #include <linux/module.h>
  22 #include <linux/mutex.h>
  23 #include <linux/init.h>
  24 #include <linux/kprobes.h>
  25
  26 #include <asm/sections.h>
  27 #include <linux/uaccess.h>
  28
  29 /*
  30  * mutex protecting text section modification (dynamic code patching).
  31  * some users need to sleep (allocating memory...) while they hold this lock.
  32  *
  33  * NOT exported to modules - patching kernel text is a really delicate matter.
  34  */
  35 DEFINE_MUTEX(text_mutex);
  36
  37 extern struct exception_table_entry __start___ex_table[];
  38 extern struct exception_table_entry __stop___ex_table[];
  39
  40 /* Cleared by build time tools if the table is already sorted. */
  41 u32 __initdata __visible main_extable_sort_needed = 1;
  42
  43 /* Sort the kernel's built-in exception table */
  44 void __init sort_main_extable(void)
  45 {
  46         if (main_extable_sort_needed && __stop___ex_table > __start___ex_table) {
  47                 pr_notice("Sorting __ex_table...\n");
  48                 sort_extable(__start___ex_table, __stop___ex_table);
  49         }
  50 }
  51
  52 /* Given an address, look for it in the exception tables. */
  53 const struct exception_table_entry *search_exception_tables(unsigned long addr)
  54 {
  55         const struct exception_table_entry *e;
  56
  57         e = search_extable(__start___ex_table, __stop___ex_table-1, addr);
  58         if (!e)
  59                 e = search_module_extables(addr);
  60         return e;
  61 }
  62
  63 static inline int init_kernel_text(unsigned long addr)
  64 {
  65         if (addr >= (unsigned long)_sinittext &&
  66             addr < (unsigned long)_einittext)
  67                 return 1;
  68         return 0;
  69 }
  70
  71 int core_kernel_text(unsigned long addr)
  72 {
  73         if (addr >= (unsigned long)_stext &&
  74             addr < (unsigned long)_etext)
  75                 return 1;
  76
  77         if (system_state == SYSTEM_BOOTING &&
  78             init_kernel_text(addr))
  79                 return 1;
  80         return 0;
  81 }
  82
  83 /**
  84  * core_kernel_data - tell if addr points to kernel data
  85  * @addr: address to test
  86  *
  87  * Returns true if @addr passed in is from the core kernel data
  88  * section.
  89  *
  90  * Note: On some archs it may return true for core RODATA, and false
  91  *  for others. But will always be true for core RW data.
  92  */
  93 int core_kernel_data(unsigned long addr)
  94 {
  95         if (addr >= (unsigned long)_sdata &&
  96             addr < (unsigned long)_edata)
  97                 return 1;
  98         return 0;
  99 }
 100
 101 int __kernel_text_address(unsigned long addr)
 102 {
 103         if (core_kernel_text(addr))
 104                 return 1;
 105         if (is_module_text_address(addr))
 106                 return 1;
 107         if (is_ftrace_trampoline(addr))
 108                 return 1;
 109         if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
 110                 return 1;
 111         /*
 112          * There might be init symbols in saved stacktraces.
 113          * Give those symbols a chance to be printed in
 114          * backtraces (such as lockdep traces).
 115          *
 116          * Since we are after the module-symbols check, there's
 117          * no danger of address overlap:
 118          */
 119         if (init_kernel_text(addr))
 120                 return 1;
 121         return 0;
 122 }
 123
 124 int kernel_text_address(unsigned long addr)
 125 {
 126         if (core_kernel_text(addr))
 127                 return 1;
 128         if (is_module_text_address(addr))
 129                 return 1;
 130         if (is_ftrace_trampoline(addr))
 131                 return 1;
 132         if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
 133                 return 1;
 134         return 0;
 135 }
 136
 137 /*
 138  * On some architectures (PPC64, IA64) function pointers
 139  * are actually only tokens to some data that then holds the
 140  * real function address. As a result, to find if a function
 141  * pointer is part of the kernel text, we need to do some
 142  * special dereferencing first.
 143  */
 144 int func_ptr_is_kernel_text(void *ptr)
 145 {
 146         unsigned long addr;
 147         addr = (unsigned long) dereference_function_descriptor(ptr);
 148         if (core_kernel_text(addr))
 149                 return 1;
 150         return is_module_text_address(addr);
 151 }