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