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 && __stop___ex_table > __start___ex_table) {
38 pr_notice("Sorting __ex_table...\n");
39 sort_extable(__start___ex_table, __stop___ex_table);
40 }
41 }
42
43 /* Given an address, look for it in the kernel exception table */
44 const
search_kernel_exception_table(unsigned long addr)45 struct exception_table_entry *search_kernel_exception_table(unsigned long addr)
46 {
47 return search_extable(__start___ex_table,
48 __stop___ex_table - __start___ex_table, addr);
49 }
50
51 /* Given an address, look for it in the exception tables. */
search_exception_tables(unsigned long addr)52 const struct exception_table_entry *search_exception_tables(unsigned long addr)
53 {
54 const struct exception_table_entry *e;
55
56 e = search_kernel_exception_table(addr);
57 if (!e)
58 e = search_module_extables(addr);
59 return e;
60 }
61
init_kernel_text(unsigned long addr)62 int init_kernel_text(unsigned long addr)
63 {
64 if (addr >= (unsigned long)_sinittext &&
65 addr < (unsigned long)_einittext)
66 return 1;
67 return 0;
68 }
69
core_kernel_text(unsigned long addr)70 int notrace core_kernel_text(unsigned long addr)
71 {
72 if (addr >= (unsigned long)_stext &&
73 addr < (unsigned long)_etext)
74 return 1;
75
76 if (system_state < SYSTEM_RUNNING &&
77 init_kernel_text(addr))
78 return 1;
79 return 0;
80 }
81
82 /**
83 * core_kernel_data - tell if addr points to kernel data
84 * @addr: address to test
85 *
86 * Returns true if @addr passed in is from the core kernel data
87 * section.
88 *
89 * Note: On some archs it may return true for core RODATA, and false
90 * for others. But will always be true for core RW data.
91 */
core_kernel_data(unsigned long addr)92 int core_kernel_data(unsigned long addr)
93 {
94 if (addr >= (unsigned long)_sdata &&
95 addr < (unsigned long)_edata)
96 return 1;
97 return 0;
98 }
99
__kernel_text_address(unsigned long addr)100 int __kernel_text_address(unsigned long addr)
101 {
102 if (kernel_text_address(addr))
103 return 1;
104 /*
105 * There might be init symbols in saved stacktraces.
106 * Give those symbols a chance to be printed in
107 * backtraces (such as lockdep traces).
108 *
109 * Since we are after the module-symbols check, there's
110 * no danger of address overlap:
111 */
112 if (init_kernel_text(addr))
113 return 1;
114 return 0;
115 }
116
kernel_text_address(unsigned long addr)117 int kernel_text_address(unsigned long addr)
118 {
119 bool no_rcu;
120 int ret = 1;
121
122 if (core_kernel_text(addr))
123 return 1;
124
125 /*
126 * If a stack dump happens while RCU is not watching, then
127 * RCU needs to be notified that it requires to start
128 * watching again. This can happen either by tracing that
129 * triggers a stack trace, or a WARN() that happens during
130 * coming back from idle, or cpu on or offlining.
131 *
132 * is_module_text_address() as well as the kprobe slots
133 * and is_bpf_text_address() require RCU to be watching.
134 */
135 no_rcu = !rcu_is_watching();
136
137 /* Treat this like an NMI as it can happen anywhere */
138 if (no_rcu)
139 rcu_nmi_enter();
140
141 if (is_module_text_address(addr))
142 goto out;
143 if (is_ftrace_trampoline(addr))
144 goto out;
145 if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
146 goto out;
147 if (is_bpf_text_address(addr))
148 goto out;
149 ret = 0;
150 out:
151 if (no_rcu)
152 rcu_nmi_exit();
153
154 return ret;
155 }
156
157 /*
158 * On some architectures (PPC64, IA64) function pointers
159 * are actually only tokens to some data that then holds the
160 * real function address. As a result, to find if a function
161 * pointer is part of the kernel text, we need to do some
162 * special dereferencing first.
163 */
func_ptr_is_kernel_text(void * ptr)164 int func_ptr_is_kernel_text(void *ptr)
165 {
166 unsigned long addr;
167 addr = (unsigned long) dereference_function_descriptor(ptr);
168 if (core_kernel_text(addr))
169 return 1;
170 return is_module_text_address(addr);
171 }
172