Root/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 */
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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