linux/kernel/extable.c
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   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 */
  33DEFINE_MUTEX(text_mutex);
  34
  35extern struct exception_table_entry __start___ex_table[];
  36extern struct exception_table_entry __stop___ex_table[];
  37
  38/* Cleared by build time tools if the table is already sorted. */
  39u32 __initdata main_extable_sort_needed = 1;
  40
  41/* Sort the kernel's built-in exception table */
  42void __init sort_main_extable(void)
  43{
  44        if (main_extable_sort_needed)
  45                sort_extable(__start___ex_table, __stop___ex_table);
  46        else
  47                pr_notice("__ex_table already sorted, skipping sort\n");
  48}
  49
  50/* Given an address, look for it in the exception tables. */
  51const 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
  61static 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
  69int 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 */
  91int 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
  99int __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        /*
 106         * There might be init symbols in saved stacktraces.
 107         * Give those symbols a chance to be printed in
 108         * backtraces (such as lockdep traces).
 109         *
 110         * Since we are after the module-symbols check, there's
 111         * no danger of address overlap:
 112         */
 113        if (init_kernel_text(addr))
 114                return 1;
 115        return 0;
 116}
 117
 118int kernel_text_address(unsigned long addr)
 119{
 120        if (core_kernel_text(addr))
 121                return 1;
 122        return is_module_text_address(addr);
 123}
 124
 125/*
 126 * On some architectures (PPC64, IA64) function pointers
 127 * are actually only tokens to some data that then holds the
 128 * real function address. As a result, to find if a function
 129 * pointer is part of the kernel text, we need to do some
 130 * special dereferencing first.
 131 */
 132int func_ptr_is_kernel_text(void *ptr)
 133{
 134        unsigned long addr;
 135        addr = (unsigned long) dereference_function_descriptor(ptr);
 136        if (core_kernel_text(addr))
 137                return 1;
 138        return is_module_text_address(addr);
 139}
 140
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