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_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 * is_bpf_text_address() and is_bpf_image_address require 137 * RCU to be watching. 138 */ 139 no_rcu = !rcu_is_watching(); 140 141 /* Treat this like an NMI as it can happen anywhere */ 142 if (no_rcu) 143 rcu_nmi_enter(); 144 145 if (is_module_text_address(addr)) 146 goto out; 147 if (is_ftrace_trampoline(addr)) 148 goto out; 149 if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr)) 150 goto out; 151 if (is_bpf_text_address(addr)) 152 goto out; 153 ret = 0; 154 out: 155 if (no_rcu) 156 rcu_nmi_exit(); 157 158 return ret; 159 } 160 161 /* 162 * On some architectures (PPC64, IA64) function pointers 163 * are actually only tokens to some data that then holds the 164 * real function address. As a result, to find if a function 165 * pointer is part of the kernel text, we need to do some 166 * special dereferencing first. 167 */ 168 int func_ptr_is_kernel_text(void *ptr) 169 { 170 unsigned long addr; 171 addr = (unsigned long) dereference_function_descriptor(ptr); 172 if (core_kernel_text(addr)) 173 return 1; 174 return is_module_text_address(addr); 175 } 176