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| 2 | Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
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| 3 |
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| 4 | This program is free software; you can redistribute it and/or modify
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| 5 | it under the terms of the GNU General Public License as published by
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| 6 | the Free Software Foundation; either version 2 of the License, or
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| 7 | (at your option) any later version.
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| 8 |
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| 9 | This program is distributed in the hope that it will be useful,
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| 10 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 12 | GNU General Public License for more details.
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| 13 |
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| 14 | You should have received a copy of the GNU General Public License
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| 15 | along with this program; if not, write to the Free Software
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| 16 | Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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| 17 |
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| 18 | #include <linux/ftrace.h>
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| 19 | #include <linux/memory.h>
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| 20 | #include <linux/extable.h>
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| 21 | #include <linux/module.h>
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| 22 | #include <linux/mutex.h>
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| 23 | #include <linux/init.h>
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| 24 | #include <linux/kprobes.h>
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| 25 | #include <linux/filter.h>
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| 26 |
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| 27 | #include <asm/sections.h>
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| 28 | #include <linux/uaccess.h>
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| 29 |
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| 30 | |
| 31 | * mutex protecting text section modification (dynamic code patching).
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| 32 | * some users need to sleep (allocating memory...) while they hold this lock.
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| 33 | *
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| 34 | * NOT exported to modules - patching kernel text is a really delicate matter.
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| 35 |
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| 36 | DEFINE_MUTEX(text_mutex);
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| 37 |
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| 38 | extern struct exception_table_entry __start___ex_table[];
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| 39 | extern struct exception_table_entry __stop___ex_table[];
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| 40 |
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| 41 |
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| 42 | u32 __initdata __visible main_extable_sort_needed = 1;
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| 43 |
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| 44 |
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| 45 | void __init sort_main_extable(void)
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| 46 | {
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| 47 | if (main_extable_sort_needed && __stop___ex_table > __start___ex_table) {
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| 48 | pr_notice("Sorting __ex_table...\n");
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| 49 | sort_extable(__start___ex_table, __stop___ex_table);
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| 50 | }
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| 51 | }
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| 52 |
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| 53 |
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| 54 | const struct exception_table_entry *search_exception_tables(unsigned long addr)
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| 55 | {
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| 56 | const struct exception_table_entry *e;
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| 57 |
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| 58 | e = search_extable(__start___ex_table,
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| 59 | __stop___ex_table - __start___ex_table, addr);
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| 60 | if (!e)
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| 61 | e = search_module_extables(addr);
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| 62 | return e;
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| 63 | }
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| 64 |
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| 65 | static inline int init_kernel_text(unsigned long addr)
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| 66 | {
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| 67 | if (addr >= (unsigned long)_sinittext &&
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| 68 | addr < (unsigned long)_einittext)
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| 69 | return 1;
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| 70 | return 0;
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| 71 | }
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| 72 |
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| 73 | int notrace core_kernel_text(unsigned long addr)
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| 74 | {
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| 75 | if (addr >= (unsigned long)_stext &&
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| 76 | addr < (unsigned long)_etext)
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| 77 | return 1;
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| 78 |
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| 79 | if (system_state < SYSTEM_RUNNING &&
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| 80 | init_kernel_text(addr))
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| 81 | return 1;
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| 82 | return 0;
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| 83 | }
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| 84 |
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| 85 | |
| 86 | * core_kernel_data - tell if addr points to kernel data
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| 87 | * @addr: address to test
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| 88 | *
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| 89 | * Returns true if @addr passed in is from the core kernel data
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| 90 | * section.
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| 91 | *
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| 92 | * Note: On some archs it may return true for core RODATA, and false
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| 93 | * for others. But will always be true for core RW data.
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| 94 |
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| 95 | int core_kernel_data(unsigned long addr)
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| 96 | {
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| 97 | if (addr >= (unsigned long)_sdata &&
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| 98 | addr < (unsigned long)_edata)
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| 99 | return 1;
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| 100 | return 0;
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| 101 | }
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| 102 |
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| 103 | int __kernel_text_address(unsigned long addr)
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| 104 | {
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| 105 | if (kernel_text_address(addr))
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| 106 | return 1;
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| 107 | |
| 108 | * There might be init symbols in saved stacktraces.
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| 109 | * Give those symbols a chance to be printed in
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| 110 | * backtraces (such as lockdep traces).
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| 111 | *
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| 112 | * Since we are after the module-symbols check, there's
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| 113 | * no danger of address overlap:
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| 114 |
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| 115 | if (init_kernel_text(addr))
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| 116 | return 1;
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| 117 | return 0;
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| 118 | }
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| 119 |
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| 120 | int kernel_text_address(unsigned long addr)
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| 121 | {
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| 122 | bool no_rcu;
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| 123 | int ret = 1;
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| 124 |
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| 125 | if (core_kernel_text(addr))
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| 126 | return 1;
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| 127 |
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| 128 | |
| 129 | * If a stack dump happens while RCU is not watching, then
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| 130 | * RCU needs to be notified that it requires to start
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| 131 | * watching again. This can happen either by tracing that
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| 132 | * triggers a stack trace, or a WARN() that happens during
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| 133 | * coming back from idle, or cpu on or offlining.
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| 134 | *
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| 135 | * is_module_text_address() as well as the kprobe slots
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| 136 | * and is_bpf_text_address() require RCU to be watching.
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| 137 |
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| 138 | no_rcu = !rcu_is_watching();
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| 139 |
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| 140 |
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| 141 | if (no_rcu)
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| 142 | rcu_nmi_enter();
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| 143 |
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| 144 | if (is_module_text_address(addr))
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| 145 | goto out;
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| 146 | if (is_ftrace_trampoline(addr))
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| 147 | goto out;
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| 148 | if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
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| 149 | goto out;
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| 150 | if (is_bpf_text_address(addr))
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| 151 | goto out;
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| 152 | ret = 0;
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| 153 | out:
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| 154 | if (no_rcu)
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| 155 | rcu_nmi_exit();
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| 156 |
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| 157 | return ret;
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| 158 | }
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| 159 |
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| 160 | |
| 161 | * On some architectures (PPC64, IA64) function pointers
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| 162 | * are actually only tokens to some data that then holds the
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| 163 | * real function address. As a result, to find if a function
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| 164 | * pointer is part of the kernel text, we need to do some
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| 165 | * special dereferencing first.
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| 166 |
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| 167 | int func_ptr_is_kernel_text(void *ptr)
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| 168 | {
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| 169 | unsigned long addr;
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| 170 | addr = (unsigned long) dereference_function_descriptor(ptr);
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| 171 | if (core_kernel_text(addr))
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| 172 | return 1;
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| 173 | return is_module_text_address(addr);
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| 174 | }
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