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 #include <linux/filter.h>
  26
  27 #include <asm/sections.h>
  28 #include <linux/uaccess.h>
  29
  30 /*
  31  * mutex protecting text section modification (dynamic code patching).
  32  * some users need to sleep (allocating memory...) while they hold this lock.
  33  *
  34  * NOT exported to modules - patching kernel text is a really delicate matter.
  35  */
  36 DEFINE_MUTEX(text_mutex);
  37
  38 extern struct exception_table_entry __start___ex_table[];
  39 extern struct exception_table_entry __stop___ex_table[];
  40
  41 /* Cleared by build time tools if the table is already sorted. */
  42 u32 __initdata __visible main_extable_sort_needed = 1;
  43
  44 /* Sort the kernel's built-in exception table */
  45 void __init sort_main_extable(void)
  46 {
  47         if (main_extable_sort_needed && __stop___ex_table > __start___ex_table) {
  48                 pr_notice("Sorting __ex_table...\n");
  49                 sort_extable(__start___ex_table, __stop___ex_table);
  50         }
  51 }
  52
  53 /* Given an address, look for it in the exception tables. */
  54 const struct exception_table_entry *search_exception_tables(unsigned long addr)
  55 {
  56         const struct exception_table_entry *e;
  57
  58         e = search_extable(__start___ex_table, __stop___ex_table-1, addr);
  59         if (!e)
  60                 e = search_module_extables(addr);
  61         return e;
  62 }
  63
  64 static inline int init_kernel_text(unsigned long addr)
  65 {
  66         if (addr >= (unsigned long)_sinittext &&
  67             addr < (unsigned long)_einittext)
  68                 return 1;
  69         return 0;
  70 }
  71
  72 int core_kernel_text(unsigned long addr)
  73 {
  74         if (addr >= (unsigned long)_stext &&
  75             addr < (unsigned long)_etext)
  76                 return 1;
  77
  78         if (system_state == SYSTEM_BOOTING &&
  79             init_kernel_text(addr))
  80                 return 1;
  81         return 0;
  82 }
  83
  84 /**
  85  * core_kernel_data - tell if addr points to kernel data
  86  * @addr: address to test
  87  *
  88  * Returns true if @addr passed in is from the core kernel data
  89  * section.
  90  *
  91  * Note: On some archs it may return true for core RODATA, and false
  92  *  for others. But will always be true for core RW data.
  93  */
  94 int core_kernel_data(unsigned long addr)
  95 {
  96         if (addr >= (unsigned long)_sdata &&
  97             addr < (unsigned long)_edata)
  98                 return 1;
  99         return 0;
 100 }
 101
 102 int __kernel_text_address(unsigned long addr)
 103 {
 104         if (core_kernel_text(addr))
 105                 return 1;
 106         if (is_module_text_address(addr))
 107                 return 1;
 108         if (is_ftrace_trampoline(addr))
 109                 return 1;
 110         if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
 111                 return 1;
 112         if (is_bpf_text_address(addr))
 113                 return 1;
 114         /*
 115          * There might be init symbols in saved stacktraces.
 116          * Give those symbols a chance to be printed in
 117          * backtraces (such as lockdep traces).
 118          *
 119          * Since we are after the module-symbols check, there's
 120          * no danger of address overlap:
 121          */
 122         if (init_kernel_text(addr))
 123                 return 1;
 124         return 0;
 125 }
 126
 127 int kernel_text_address(unsigned long addr)
 128 {
 129         if (core_kernel_text(addr))
 130                 return 1;
 131         if (is_module_text_address(addr))
 132                 return 1;
 133         if (is_ftrace_trampoline(addr))
 134                 return 1;
 135         if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
 136                 return 1;
 137         if (is_bpf_text_address(addr))
 138                 return 1;
 139         return 0;
 140 }
 141
 142 /*
 143  * On some architectures (PPC64, IA64) function pointers
 144  * are actually only tokens to some data that then holds the
 145  * real function address. As a result, to find if a function
 146  * pointer is part of the kernel text, we need to do some
 147  * special dereferencing first.
 148  */
 149 int func_ptr_is_kernel_text(void *ptr)
 150 {
 151         unsigned long addr;
 152         addr = (unsigned long) dereference_function_descriptor(ptr);
 153         if (core_kernel_text(addr))
 154                 return 1;
 155         return is_module_text_address(addr);
 156 }