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 notrace core_kernel_text(unsigned long addr) 66 { 67 if (is_kernel_text(addr)) 68 return 1; 69 70 if (system_state < SYSTEM_FREEING_INITMEM && 71 is_kernel_inittext(addr)) 72 return 1; 73 return 0; 74 } 75 76 int __kernel_text_address(unsigned long addr) 77 { 78 if (kernel_text_address(addr)) 79 return 1; 80 /* 81 * There might be init symbols in saved stacktraces. 82 * Give those symbols a chance to be printed in 83 * backtraces (such as lockdep traces). 84 * 85 * Since we are after the module-symbols check, there's 86 * no danger of address overlap: 87 */ 88 if (is_kernel_inittext(addr)) 89 return 1; 90 return 0; 91 } 92 93 int kernel_text_address(unsigned long addr) 94 { 95 bool no_rcu; 96 int ret = 1; 97 98 if (core_kernel_text(addr)) 99 return 1; 100 101 /* 102 * If a stack dump happens while RCU is not watching, then 103 * RCU needs to be notified that it requires to start 104 * watching again. This can happen either by tracing that 105 * triggers a stack trace, or a WARN() that happens during 106 * coming back from idle, or cpu on or offlining. 107 * 108 * is_module_text_address() as well as the kprobe slots, 109 * is_bpf_text_address() and is_bpf_image_address require 110 * RCU to be watching. 111 */ 112 no_rcu = !rcu_is_watching(); 113 114 /* Treat this like an NMI as it can happen anywhere */ 115 if (no_rcu) 116 rcu_nmi_enter(); 117 118 if (is_module_text_address(addr)) 119 goto out; 120 if (is_ftrace_trampoline(addr)) 121 goto out; 122 if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr)) 123 goto out; 124 if (is_bpf_text_address(addr)) 125 goto out; 126 ret = 0; 127 out: 128 if (no_rcu) 129 rcu_nmi_exit(); 130 131 return ret; 132 } 133 134 /* 135 * On some architectures (PPC64, IA64) function pointers 136 * are actually only tokens to some data that then holds the 137 * real function address. As a result, to find if a function 138 * pointer is part of the kernel text, we need to do some 139 * special dereferencing first. 140 */ 141 int func_ptr_is_kernel_text(void *ptr) 142 { 143 unsigned long addr; 144 addr = (unsigned long) dereference_function_descriptor(ptr); 145 if (core_kernel_text(addr)) 146 return 1; 147 return is_module_text_address(addr); 148 } 149