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 if (!e)
61 e = search_bpf_extables(addr);
62 return e;
63 }
64
init_kernel_text(unsigned long addr)65 int init_kernel_text(unsigned long addr)
66 {
67 if (addr >= (unsigned long)_sinittext &&
68 addr < (unsigned long)_einittext)
69 return 1;
70 return 0;
71 }
72
core_kernel_text(unsigned long addr)73 int notrace core_kernel_text(unsigned long addr)
74 {
75 if (addr >= (unsigned long)_stext &&
76 addr < (unsigned long)_etext)
77 return 1;
78
79 if (system_state < SYSTEM_RUNNING &&
80 init_kernel_text(addr))
81 return 1;
82 return 0;
83 }
84
85 /**
86 * core_kernel_data - tell if addr points to kernel data
87 * @addr: address to test
88 *
89 * Returns true if @addr passed in is from the core kernel data
90 * section.
91 *
92 * Note: On some archs it may return true for core RODATA, and false
93 * for others. But will always be true for core RW data.
94 */
core_kernel_data(unsigned long addr)95 int core_kernel_data(unsigned long addr)
96 {
97 if (addr >= (unsigned long)_sdata &&
98 addr < (unsigned long)_edata)
99 return 1;
100 return 0;
101 }
102
__kernel_text_address(unsigned long addr)103 int __kernel_text_address(unsigned long addr)
104 {
105 if (kernel_text_address(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
kernel_text_address(unsigned long addr)120 int kernel_text_address(unsigned long addr)
121 {
122 bool no_rcu;
123 int ret = 1;
124
125 if (core_kernel_text(addr))
126 return 1;
127
128 /*
129 * If a stack dump happens while RCU is not watching, then
130 * RCU needs to be notified that it requires to start
131 * watching again. This can happen either by tracing that
132 * triggers a stack trace, or a WARN() that happens during
133 * coming back from idle, or cpu on or offlining.
134 *
135 * is_module_text_address() as well as the kprobe slots,
136 * is_bpf_text_address() and is_bpf_image_address require
137 * RCU to be watching.
138 */
139 no_rcu = !rcu_is_watching();
140
141 /* Treat this like an NMI as it can happen anywhere */
142 if (no_rcu)
143 rcu_nmi_enter();
144
145 if (is_module_text_address(addr))
146 goto out;
147 if (is_ftrace_trampoline(addr))
148 goto out;
149 if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
150 goto out;
151 if (is_bpf_text_address(addr))
152 goto out;
153 ret = 0;
154 out:
155 if (no_rcu)
156 rcu_nmi_exit();
157
158 return ret;
159 }
160
161 /*
162 * On some architectures (PPC64, IA64) function pointers
163 * are actually only tokens to some data that then holds the
164 * real function address. As a result, to find if a function
165 * pointer is part of the kernel text, we need to do some
166 * special dereferencing first.
167 */
func_ptr_is_kernel_text(void * ptr)168 int func_ptr_is_kernel_text(void *ptr)
169 {
170 unsigned long addr;
171 addr = (unsigned long) dereference_function_descriptor(ptr);
172 if (core_kernel_text(addr))
173 return 1;
174 return is_module_text_address(addr);
175 }
176