| 1 | |
| 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 | * Note: Also protects SMP-alternatives modification on x86.
|
| 35 | *
|
| 36 | * NOT exported to modules - patching kernel text is a really delicate matter.
|
| 37 |
|
| 38 | DEFINE_MUTEX(text_mutex);
|
| 39 |
|
| 40 | extern struct exception_table_entry __start___ex_table[];
|
| 41 | extern struct exception_table_entry __stop___ex_table[];
|
| 42 |
|
| 43 |
|
| 44 | u32 __initdata __visible main_extable_sort_needed = 1;
|
| 45 |
|
| 46 |
|
| 47 | void __init sort_main_extable(void)
|
| 48 | {
|
| 49 | if (main_extable_sort_needed && __stop___ex_table > __start___ex_table) {
|
| 50 | pr_notice("Sorting __ex_table...\n");
|
| 51 | sort_extable(__start___ex_table, __stop___ex_table);
|
| 52 | }
|
| 53 | }
|
| 54 |
|
| 55 |
|
| 56 | const struct exception_table_entry *search_exception_tables(unsigned long addr)
|
| 57 | {
|
| 58 | const struct exception_table_entry *e;
|
| 59 |
|
| 60 | e = search_extable(__start___ex_table,
|
| 61 | __stop___ex_table - __start___ex_table, addr);
|
| 62 | if (!e)
|
| 63 | e = search_module_extables(addr);
|
| 64 | return e;
|
| 65 | }
|
| 66 |
|
| 67 | int init_kernel_text(unsigned long addr)
|
| 68 | {
|
| 69 | if (addr >= (unsigned long)_sinittext &&
|
| 70 | addr < (unsigned long)_einittext)
|
| 71 | return 1;
|
| 72 | return 0;
|
| 73 | }
|
| 74 |
|
| 75 | int notrace core_kernel_text(unsigned long addr)
|
| 76 | {
|
| 77 | if (addr >= (unsigned long)_stext &&
|
| 78 | addr < (unsigned long)_etext)
|
| 79 | return 1;
|
| 80 |
|
| 81 | if (system_state < SYSTEM_RUNNING &&
|
| 82 | init_kernel_text(addr))
|
| 83 | return 1;
|
| 84 | return 0;
|
| 85 | }
|
| 86 |
|
| 87 | |
| 88 | * core_kernel_data - tell if addr points to kernel data
|
| 89 | * @addr: address to test
|
| 90 | *
|
| 91 | * Returns true if @addr passed in is from the core kernel data
|
| 92 | * section.
|
| 93 | *
|
| 94 | * Note: On some archs it may return true for core RODATA, and false
|
| 95 | * for others. But will always be true for core RW data.
|
| 96 |
|
| 97 | int core_kernel_data(unsigned long addr)
|
| 98 | {
|
| 99 | if (addr >= (unsigned long)_sdata &&
|
| 100 | addr < (unsigned long)_edata)
|
| 101 | return 1;
|
| 102 | return 0;
|
| 103 | }
|
| 104 |
|
| 105 | int __kernel_text_address(unsigned long addr)
|
| 106 | {
|
| 107 | if (kernel_text_address(addr))
|
| 108 | return 1;
|
| 109 | |
| 110 | * There might be init symbols in saved stacktraces.
|
| 111 | * Give those symbols a chance to be printed in
|
| 112 | * backtraces (such as lockdep traces).
|
| 113 | *
|
| 114 | * Since we are after the module-symbols check, there's
|
| 115 | * no danger of address overlap:
|
| 116 |
|
| 117 | if (init_kernel_text(addr))
|
| 118 | return 1;
|
| 119 | return 0;
|
| 120 | }
|
| 121 |
|
| 122 | int kernel_text_address(unsigned long addr)
|
| 123 | {
|
| 124 | bool no_rcu;
|
| 125 | int ret = 1;
|
| 126 |
|
| 127 | if (core_kernel_text(addr))
|
| 128 | return 1;
|
| 129 |
|
| 130 | |
| 131 | * If a stack dump happens while RCU is not watching, then
|
| 132 | * RCU needs to be notified that it requires to start
|
| 133 | * watching again. This can happen either by tracing that
|
| 134 | * triggers a stack trace, or a WARN() that happens during
|
| 135 | * coming back from idle, or cpu on or offlining.
|
| 136 | *
|
| 137 | * is_module_text_address() as well as the kprobe slots
|
| 138 | * and is_bpf_text_address() require RCU to be watching.
|
| 139 |
|
| 140 | no_rcu = !rcu_is_watching();
|
| 141 |
|
| 142 |
|
| 143 | if (no_rcu)
|
| 144 | rcu_nmi_enter();
|
| 145 |
|
| 146 | if (is_module_text_address(addr))
|
| 147 | goto out;
|
| 148 | if (is_ftrace_trampoline(addr))
|
| 149 | goto out;
|
| 150 | if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
|
| 151 | goto out;
|
| 152 | if (is_bpf_text_address(addr))
|
| 153 | goto out;
|
| 154 | ret = 0;
|
| 155 | out:
|
| 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 |
|
| 169 | int 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 | }
|