1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Rewritten by Rusty Russell, on the backs of many others...
3 Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
4
5 */
6 #include <linux/ftrace.h>
7 #include <linux/memory.h>
8 #include <linux/extable.h>
9 #include <linux/module.h>
10 #include <linux/mutex.h>
11 #include <linux/init.h>
12 #include <linux/kprobes.h>
13 #include <linux/filter.h>
14
15 #include <asm/sections.h>
16 #include <linux/uaccess.h>
17
18 /*
19 * mutex protecting text section modification (dynamic code patching).
20 * some users need to sleep (allocating memory...) while they hold this lock.
21 *
22 * Note: Also protects SMP-alternatives modification on x86.
23 *
24 * NOT exported to modules - patching kernel text is a really delicate matter.
25 */
26 DEFINE_MUTEX(text_mutex);
27
28 extern struct exception_table_entry __start___ex_table[];
29 extern struct exception_table_entry __stop___ex_table[];
30
31 /* Cleared by build time tools if the table is already sorted. */
32 u32 __initdata __visible main_extable_sort_needed = 1;
33
34 /* Sort the kernel's built-in exception table */
sort_main_extable(void)35 void __init sort_main_extable(void)
36 {
37 if (main_extable_sort_needed &&
38 &__stop___ex_table > &__start___ex_table) {
39 pr_notice("Sorting __ex_table...\n");
40 sort_extable(__start___ex_table, __stop___ex_table);
41 }
42 }
43
44 /* Given an address, look for it in the kernel exception table */
45 const
search_kernel_exception_table(unsigned long addr)46 struct exception_table_entry *search_kernel_exception_table(unsigned long addr)
47 {
48 return search_extable(__start___ex_table,
49 __stop___ex_table - __start___ex_table, addr);
50 }
51
52 /* Given an address, look for it in the exception tables. */
search_exception_tables(unsigned long addr)53 const struct exception_table_entry *search_exception_tables(unsigned long addr)
54 {
55 const struct exception_table_entry *e;
56
57 e = search_kernel_exception_table(addr);
58 if (!e)
59 e = search_module_extables(addr);
60 return e;
61 }
62
init_kernel_text(unsigned long addr)63 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
core_kernel_text(unsigned long addr)71 int notrace 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_RUNNING &&
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 */
core_kernel_data(unsigned long addr)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
__kernel_text_address(unsigned long addr)101 int __kernel_text_address(unsigned long addr)
102 {
103 if (kernel_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
kernel_text_address(unsigned long addr)118 int kernel_text_address(unsigned long addr)
119 {
120 bool no_rcu;
121 int ret = 1;
122
123 if (core_kernel_text(addr))
124 return 1;
125
126 /*
127 * If a stack dump happens while RCU is not watching, then
128 * RCU needs to be notified that it requires to start
129 * watching again. This can happen either by tracing that
130 * triggers a stack trace, or a WARN() that happens during
131 * coming back from idle, or cpu on or offlining.
132 *
133 * is_module_text_address() as well as the kprobe slots
134 * and is_bpf_text_address() require RCU to be watching.
135 */
136 no_rcu = !rcu_is_watching();
137
138 /* Treat this like an NMI as it can happen anywhere */
139 if (no_rcu)
140 rcu_nmi_enter();
141
142 if (is_module_text_address(addr))
143 goto out;
144 if (is_ftrace_trampoline(addr))
145 goto out;
146 if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
147 goto out;
148 if (is_bpf_text_address(addr))
149 goto out;
150 ret = 0;
151 out:
152 if (no_rcu)
153 rcu_nmi_exit();
154
155 return ret;
156 }
157
158 /*
159 * On some architectures (PPC64, IA64) function pointers
160 * are actually only tokens to some data that then holds the
161 * real function address. As a result, to find if a function
162 * pointer is part of the kernel text, we need to do some
163 * special dereferencing first.
164 */
func_ptr_is_kernel_text(void * ptr)165 int func_ptr_is_kernel_text(void *ptr)
166 {
167 unsigned long addr;
168 addr = (unsigned long) dereference_function_descriptor(ptr);
169 if (core_kernel_text(addr))
170 return 1;
171 return is_module_text_address(addr);
172 }
173