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