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 */ 26 DEFINE_MUTEX(text_mutex); 27 28 extern struct exception_table_entry __start___ex_table[]; 29 extern struct exception_table_entry __stop___ex_table[]; 30 31 /* Cleared by build time tools if the table is already sorted. */ 32 u32 __initdata __visible main_extable_sort_needed = 1; 33 34 /* Sort the kernel's built-in exception table */ 35 void __init sort_main_extable(void) 36 { 37 if (main_extable_sort_needed && 38 &__stop___ex_table > &__start___ex_table) { 39 pr_notice("Sorting __ex_table...\n"); 40 sort_extable(__start___ex_table, __stop___ex_table); 41 } 42 } 43 44 /* Given an address, look for it in the kernel exception table */ 45 const 46 struct exception_table_entry *search_kernel_exception_table(unsigned long addr) 47 { 48 return search_extable(__start___ex_table, 49 __stop___ex_table - __start___ex_table, addr); 50 } 51 52 /* Given an address, look for it in the exception tables. */ 53 const struct exception_table_entry *search_exception_tables(unsigned long addr) 54 { 55 const struct exception_table_entry *e; 56 57 e = search_kernel_exception_table(addr); 58 if (!e) 59 e = search_module_extables(addr); 60 if (!e) 61 e = search_bpf_extables(addr); 62 return e; 63 } 64 65 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_FREEING_INITMEM && 80 init_kernel_text(addr)) 81 return 1; 82 return 0; 83 } 84 85 int __kernel_text_address(unsigned long addr) 86 { 87 if (kernel_text_address(addr)) 88 return 1; 89 /* 90 * There might be init symbols in saved stacktraces. 91 * Give those symbols a chance to be printed in 92 * backtraces (such as lockdep traces). 93 * 94 * Since we are after the module-symbols check, there's 95 * no danger of address overlap: 96 */ 97 if (init_kernel_text(addr)) 98 return 1; 99 return 0; 100 } 101 102 int kernel_text_address(unsigned long addr) 103 { 104 bool no_rcu; 105 int ret = 1; 106 107 if (core_kernel_text(addr)) 108 return 1; 109 110 /* 111 * If a stack dump happens while RCU is not watching, then 112 * RCU needs to be notified that it requires to start 113 * watching again. This can happen either by tracing that 114 * triggers a stack trace, or a WARN() that happens during 115 * coming back from idle, or cpu on or offlining. 116 * 117 * is_module_text_address() as well as the kprobe slots, 118 * is_bpf_text_address() and is_bpf_image_address require 119 * RCU to be watching. 120 */ 121 no_rcu = !rcu_is_watching(); 122 123 /* Treat this like an NMI as it can happen anywhere */ 124 if (no_rcu) 125 rcu_nmi_enter(); 126 127 if (is_module_text_address(addr)) 128 goto out; 129 if (is_ftrace_trampoline(addr)) 130 goto out; 131 if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr)) 132 goto out; 133 if (is_bpf_text_address(addr)) 134 goto out; 135 ret = 0; 136 out: 137 if (no_rcu) 138 rcu_nmi_exit(); 139 140 return ret; 141 } 142 143 /* 144 * On some architectures (PPC64, IA64) function pointers 145 * are actually only tokens to some data that then holds the 146 * real function address. As a result, to find if a function 147 * pointer is part of the kernel text, we need to do some 148 * special dereferencing first. 149 */ 150 int func_ptr_is_kernel_text(void *ptr) 151 { 152 unsigned long addr; 153 addr = (unsigned long) dereference_function_descriptor(ptr); 154 if (core_kernel_text(addr)) 155 return 1; 156 return is_module_text_address(addr); 157 } 158