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
core_kernel_text(unsigned long addr)65 int notrace core_kernel_text(unsigned long addr)
66 {
67 if (is_kernel_text(addr))
68 return 1;
69
70 if (system_state < SYSTEM_FREEING_INITMEM &&
71 is_kernel_inittext(addr))
72 return 1;
73 return 0;
74 }
75
__kernel_text_address(unsigned long addr)76 int __kernel_text_address(unsigned long addr)
77 {
78 if (kernel_text_address(addr))
79 return 1;
80 /*
81 * There might be init symbols in saved stacktraces.
82 * Give those symbols a chance to be printed in
83 * backtraces (such as lockdep traces).
84 *
85 * Since we are after the module-symbols check, there's
86 * no danger of address overlap:
87 */
88 if (is_kernel_inittext(addr))
89 return 1;
90 return 0;
91 }
92
kernel_text_address(unsigned long addr)93 int kernel_text_address(unsigned long addr)
94 {
95 bool no_rcu;
96 int ret = 1;
97
98 if (core_kernel_text(addr))
99 return 1;
100
101 /*
102 * If a stack dump happens while RCU is not watching, then
103 * RCU needs to be notified that it requires to start
104 * watching again. This can happen either by tracing that
105 * triggers a stack trace, or a WARN() that happens during
106 * coming back from idle, or cpu on or offlining.
107 *
108 * is_module_text_address() as well as the kprobe slots,
109 * is_bpf_text_address() and is_bpf_image_address require
110 * RCU to be watching.
111 */
112 no_rcu = !rcu_is_watching();
113
114 /* Treat this like an NMI as it can happen anywhere */
115 if (no_rcu)
116 rcu_nmi_enter();
117
118 if (is_module_text_address(addr))
119 goto out;
120 if (is_ftrace_trampoline(addr))
121 goto out;
122 if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
123 goto out;
124 if (is_bpf_text_address(addr))
125 goto out;
126 ret = 0;
127 out:
128 if (no_rcu)
129 rcu_nmi_exit();
130
131 return ret;
132 }
133
134 /*
135 * On some architectures (PPC64, IA64) function pointers
136 * are actually only tokens to some data that then holds the
137 * real function address. As a result, to find if a function
138 * pointer is part of the kernel text, we need to do some
139 * special dereferencing first.
140 */
func_ptr_is_kernel_text(void * ptr)141 int func_ptr_is_kernel_text(void *ptr)
142 {
143 unsigned long addr;
144 addr = (unsigned long) dereference_function_descriptor(ptr);
145 if (core_kernel_text(addr))
146 return 1;
147 return is_module_text_address(addr);
148 }
149