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/elf.h>
7#include <linux/ftrace.h>
8#include <linux/memory.h>
9#include <linux/extable.h>
10#include <linux/module.h>
11#include <linux/mutex.h>
12#include <linux/init.h>
13#include <linux/kprobes.h>
14#include <linux/filter.h>
15
16#include <asm/sections.h>
17#include <linux/uaccess.h>
18
19/*
20 * mutex protecting text section modification (dynamic code patching).
21 * some users need to sleep (allocating memory...) while they hold this lock.
22 *
23 * Note: Also protects SMP-alternatives modification on x86.
24 *
25 * NOT exported to modules - patching kernel text is a really delicate matter.
26 */
27DEFINE_MUTEX(text_mutex);
28
29extern struct exception_table_entry __start___ex_table[];
30extern struct exception_table_entry __stop___ex_table[];
31
32/* Cleared by build time tools if the table is already sorted. */
33u32 __initdata __visible main_extable_sort_needed = 1;
34
35/* Sort the kernel's built-in exception table */
36void __init sort_main_extable(void)
37{
38	if (main_extable_sort_needed &&
39	    &__stop___ex_table > &__start___ex_table) {
40		pr_notice("Sorting __ex_table...\n");
41		sort_extable(__start___ex_table, __stop___ex_table);
42	}
43}
44
45/* Given an address, look for it in the kernel exception table */
46const
47struct exception_table_entry *search_kernel_exception_table(unsigned long addr)
48{
49	return search_extable(__start___ex_table,
50			      __stop___ex_table - __start___ex_table, addr);
51}
52
53/* Given an address, look for it in the exception tables. */
54const struct exception_table_entry *search_exception_tables(unsigned long addr)
55{
56	const struct exception_table_entry *e;
57
58	e = search_kernel_exception_table(addr);
59	if (!e)
60		e = search_module_extables(addr);
61	if (!e)
62		e = search_bpf_extables(addr);
63	return e;
64}
65
66int notrace core_kernel_text(unsigned long addr)
67{
68	if (is_kernel_text(addr))
69		return 1;
70
71	if (system_state < SYSTEM_FREEING_INITMEM &&
72	    is_kernel_inittext(addr))
73		return 1;
74	return 0;
75}
76
77int __kernel_text_address(unsigned long addr)
78{
79	if (kernel_text_address(addr))
80		return 1;
81	/*
82	 * There might be init symbols in saved stacktraces.
83	 * Give those symbols a chance to be printed in
84	 * backtraces (such as lockdep traces).
85	 *
86	 * Since we are after the module-symbols check, there's
87	 * no danger of address overlap:
88	 */
89	if (is_kernel_inittext(addr))
90		return 1;
91	return 0;
92}
93
94int kernel_text_address(unsigned long addr)
95{
96	bool no_rcu;
97	int ret = 1;
98
99	if (core_kernel_text(addr))
100		return 1;
101
102	/*
103	 * If a stack dump happens while RCU is not watching, then
104	 * RCU needs to be notified that it requires to start
105	 * watching again. This can happen either by tracing that
106	 * triggers a stack trace, or a WARN() that happens during
107	 * coming back from idle, or cpu on or offlining.
108	 *
109	 * is_module_text_address() as well as the kprobe slots,
110	 * is_bpf_text_address() and is_bpf_image_address require
111	 * RCU to be watching.
112	 */
113	no_rcu = !rcu_is_watching();
114
115	/* Treat this like an NMI as it can happen anywhere */
116	if (no_rcu)
117		ct_nmi_enter();
118
119	if (is_module_text_address(addr))
120		goto out;
121	if (is_ftrace_trampoline(addr))
122		goto out;
123	if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
124		goto out;
125	if (is_bpf_text_address(addr))
126		goto out;
127	ret = 0;
128out:
129	if (no_rcu)
130		ct_nmi_exit();
131
132	return ret;
133}
134
135/*
136 * On some architectures (PPC64, IA64, PARISC) function pointers
137 * are actually only tokens to some data that then holds the
138 * real function address. As a result, to find if a function
139 * pointer is part of the kernel text, we need to do some
140 * special dereferencing first.
141 */
142#ifdef CONFIG_HAVE_FUNCTION_DESCRIPTORS
143void *dereference_function_descriptor(void *ptr)
144{
145	func_desc_t *desc = ptr;
146	void *p;
147
148	if (!get_kernel_nofault(p, (void *)&desc->addr))
149		ptr = p;
150	return ptr;
151}
152EXPORT_SYMBOL_GPL(dereference_function_descriptor);
153
154void *dereference_kernel_function_descriptor(void *ptr)
155{
156	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
157		return ptr;
158
159	return dereference_function_descriptor(ptr);
160}
161#endif
162
163int func_ptr_is_kernel_text(void *ptr)
164{
165	unsigned long addr;
166	addr = (unsigned long) dereference_function_descriptor(ptr);
167	if (core_kernel_text(addr))
168		return 1;
169	return is_module_text_address(addr);
170}
171