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 } 175