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bpf: perf event change needed for subsequent bpf helpers
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1 /* Rewritten by Rusty Russell, on the backs of many others...
2 Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
3
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2 of the License, or
7 (at your option) any later version.
8
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
13
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
17 */
18 #include <linux/ftrace.h>
19 #include <linux/memory.h>
20 #include <linux/extable.h>
21 #include <linux/module.h>
22 #include <linux/mutex.h>
23 #include <linux/init.h>
24 #include <linux/kprobes.h>
25 #include <linux/filter.h>
26
27 #include <asm/sections.h>
28 #include <linux/uaccess.h>
29
30 /*
31 * mutex protecting text section modification (dynamic code patching).
32 * some users need to sleep (allocating memory...) while they hold this lock.
33 *
34 * NOT exported to modules - patching kernel text is a really delicate matter.
35 */
36 DEFINE_MUTEX(text_mutex);
37
38 extern struct exception_table_entry __start___ex_table[];
39 extern struct exception_table_entry __stop___ex_table[];
40
41 /* Cleared by build time tools if the table is already sorted. */
42 u32 __initdata __visible main_extable_sort_needed = 1;
43
44 /* Sort the kernel's built-in exception table */
45 void __init sort_main_extable(void)
46 {
47 if (main_extable_sort_needed && __stop___ex_table > __start___ex_table) {
48 pr_notice("Sorting __ex_table...\n");
49 sort_extable(__start___ex_table, __stop___ex_table);
50 }
51 }
52
53 /* Given an address, look for it in the exception tables. */
54 const struct exception_table_entry *search_exception_tables(unsigned long addr)
55 {
56 const struct exception_table_entry *e;
57
58 e = search_extable(__start___ex_table,
59 __stop___ex_table - __start___ex_table, addr);
60 if (!e)
61 e = search_module_extables(addr);
62 return e;
63 }
64
65 static inline 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
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 */
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
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
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 * and is_bpf_text_address() require 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 ret = 0;
153 out:
154 if (no_rcu)
155 rcu_nmi_exit();
156
157 return ret;
158 }
159
160 /*
161 * On some architectures (PPC64, IA64) function pointers
162 * are actually only tokens to some data that then holds the
163 * real function address. As a result, to find if a function
164 * pointer is part of the kernel text, we need to do some
165 * special dereferencing first.
166 */
167 int func_ptr_is_kernel_text(void *ptr)
168 {
169 unsigned long addr;
170 addr = (unsigned long) dereference_function_descriptor(ptr);
171 if (core_kernel_text(addr))
172 return 1;
173 return is_module_text_address(addr);
174 }