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 && __stop___ex_table > __start___ex_table) { 38 pr_notice("Sorting __ex_table...\n"); 39 sort_extable(__start___ex_table, __stop___ex_table); 40 } 41 } 42 43 /* Given an address, look for it in the kernel exception table */ 44 const 45 struct exception_table_entry *search_kernel_exception_table(unsigned long addr) 46 { 47 return search_extable(__start___ex_table, 48 __stop___ex_table - __start___ex_table, addr); 49 } 50 51 /* Given an address, look for it in the exception tables. */ 52 const struct exception_table_entry *search_exception_tables(unsigned long addr) 53 { 54 const struct exception_table_entry *e; 55 56 e = search_kernel_exception_table(addr); 57 if (!e) 58 e = search_module_extables(addr); 59 if (!e) 60 e = search_bpf_extables(addr); 61 return e; 62 } 63 64 int init_kernel_text(unsigned long addr) 65 { 66 if (addr >= (unsigned long)_sinittext && 67 addr < (unsigned long)_einittext) 68 return 1; 69 return 0; 70 } 71 72 int notrace core_kernel_text(unsigned long addr) 73 { 74 if (addr >= (unsigned long)_stext && 75 addr < (unsigned long)_etext) 76 return 1; 77 78 if (system_state < SYSTEM_RUNNING && 79 init_kernel_text(addr)) 80 return 1; 81 return 0; 82 } 83 84 /** 85 * core_kernel_data - tell if addr points to kernel data 86 * @addr: address to test 87 * 88 * Returns true if @addr passed in is from the core kernel data 89 * section. 90 * 91 * Note: On some archs it may return true for core RODATA, and false 92 * for others. But will always be true for core RW data. 93 */ 94 int core_kernel_data(unsigned long addr) 95 { 96 if (addr >= (unsigned long)_sdata && 97 addr < (unsigned long)_edata) 98 return 1; 99 return 0; 100 } 101 102 int __kernel_text_address(unsigned long addr) 103 { 104 if (kernel_text_address(addr)) 105 return 1; 106 /* 107 * There might be init symbols in saved stacktraces. 108 * Give those symbols a chance to be printed in 109 * backtraces (such as lockdep traces). 110 * 111 * Since we are after the module-symbols check, there's 112 * no danger of address overlap: 113 */ 114 if (init_kernel_text(addr)) 115 return 1; 116 return 0; 117 } 118 119 int kernel_text_address(unsigned long addr) 120 { 121 bool no_rcu; 122 int ret = 1; 123 124 if (core_kernel_text(addr)) 125 return 1; 126 127 /* 128 * If a stack dump happens while RCU is not watching, then 129 * RCU needs to be notified that it requires to start 130 * watching again. This can happen either by tracing that 131 * triggers a stack trace, or a WARN() that happens during 132 * coming back from idle, or cpu on or offlining. 133 * 134 * is_module_text_address() as well as the kprobe slots 135 * and is_bpf_text_address() require RCU to be watching. 136 */ 137 no_rcu = !rcu_is_watching(); 138 139 /* Treat this like an NMI as it can happen anywhere */ 140 if (no_rcu) 141 rcu_nmi_enter(); 142 143 if (is_module_text_address(addr)) 144 goto out; 145 if (is_ftrace_trampoline(addr)) 146 goto out; 147 if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr)) 148 goto out; 149 if (is_bpf_text_address(addr)) 150 goto out; 151 ret = 0; 152 out: 153 if (no_rcu) 154 rcu_nmi_exit(); 155 156 return ret; 157 } 158 159 /* 160 * On some architectures (PPC64, IA64) function pointers 161 * are actually only tokens to some data that then holds the 162 * real function address. As a result, to find if a function 163 * pointer is part of the kernel text, we need to do some 164 * special dereferencing first. 165 */ 166 int func_ptr_is_kernel_text(void *ptr) 167 { 168 unsigned long addr; 169 addr = (unsigned long) dereference_function_descriptor(ptr); 170 if (core_kernel_text(addr)) 171 return 1; 172 return is_module_text_address(addr); 173 } 174