projects/linux·blob v5.6-rc1 · refs

176 lines · 4.4 KiB

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 */
26DEFINE_MUTEX(text_mutex);
27
28extern struct exception_table_entry __start___ex_table[];
29extern struct exception_table_entry __stop___ex_table[];
30
31/* Cleared by build time tools if the table is already sorted. */
32u32 __initdata __visible main_extable_sort_needed = 1;
33
34/* Sort the kernel's built-in exception table */
35void __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 */
44const
45struct 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. */
52const 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 if (!e)
60 e = search_bpf_extables(addr);
61 return e;
62}
63
64int init_kernel_text(unsigned long addr)
65{
66 if (addr >= (unsigned long)_sinittext &&
67 addr < (unsigned long)_einittext)
68 return 1;
69 return 0;
70}
71
72int notrace core_kernel_text(unsigned long addr)
73{
74 if (addr >= (unsigned long)_stext &&
75 addr < (unsigned long)_etext)
76 return 1;
77
78 if (system_state < SYSTEM_RUNNING &&
79 init_kernel_text(addr))
80 return 1;
81 return 0;
82}
83
84/**
85 * core_kernel_data - tell if addr points to kernel data
86 * @addr: address to test
87 *
88 * Returns true if @addr passed in is from the core kernel data
89 * section.
90 *
91 * Note: On some archs it may return true for core RODATA, and false
92 * for others. But will always be true for core RW data.
93 */
94int core_kernel_data(unsigned long addr)
95{
96 if (addr >= (unsigned long)_sdata &&
97 addr < (unsigned long)_edata)
98 return 1;
99 return 0;
100}
101
102int __kernel_text_address(unsigned long addr)
103{
104 if (kernel_text_address(addr))
105 return 1;
106 /*
107 * There might be init symbols in saved stacktraces.
108 * Give those symbols a chance to be printed in
109 * backtraces (such as lockdep traces).
110 *
111 * Since we are after the module-symbols check, there's
112 * no danger of address overlap:
113 */
114 if (init_kernel_text(addr))
115 return 1;
116 return 0;
117}
118
119int kernel_text_address(unsigned long addr)
120{
121 bool no_rcu;
122 int ret = 1;
123
124 if (core_kernel_text(addr))
125 return 1;
126
127 /*
128 * If a stack dump happens while RCU is not watching, then
129 * RCU needs to be notified that it requires to start
130 * watching again. This can happen either by tracing that
131 * triggers a stack trace, or a WARN() that happens during
132 * coming back from idle, or cpu on or offlining.
133 *
134 * is_module_text_address() as well as the kprobe slots,
135 * is_bpf_text_address() and is_bpf_image_address require
136 * RCU to be watching.
137 */
138 no_rcu = !rcu_is_watching();
139
140 /* Treat this like an NMI as it can happen anywhere */
141 if (no_rcu)
142 rcu_nmi_enter();
143
144 if (is_module_text_address(addr))
145 goto out;
146 if (is_ftrace_trampoline(addr))
147 goto out;
148 if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
149 goto out;
150 if (is_bpf_text_address(addr))
151 goto out;
152 if (is_bpf_image_address(addr))
153 goto out;
154 ret = 0;
155out:
156 if (no_rcu)
157 rcu_nmi_exit();
158
159 return ret;
160}
161
162/*
163 * On some architectures (PPC64, IA64) function pointers
164 * are actually only tokens to some data that then holds the
165 * real function address. As a result, to find if a function
166 * pointer is part of the kernel text, we need to do some
167 * special dereferencing first.
168 */
169int func_ptr_is_kernel_text(void *ptr)
170{
171 unsigned long addr;
172 addr = (unsigned long) dereference_function_descriptor(ptr);
173 if (core_kernel_text(addr))
174 return 1;
175 return is_module_text_address(addr);
176}