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| 2 | |
| 3 | Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
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| 4 |
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| 5 |
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| 6 | #include <linux/ftrace.h>
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| 7 | #include <linux/memory.h>
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| 8 | #include <linux/extable.h>
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| 9 | #include <linux/module.h>
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| 10 | #include <linux/mutex.h>
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| 11 | #include <linux/init.h>
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| 12 | #include <linux/kprobes.h>
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| 13 | #include <linux/filter.h>
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| 14 |
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| 15 | #include <asm/sections.h>
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| 16 | #include <linux/uaccess.h>
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| 17 |
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| 18 | |
| 19 | * mutex protecting text section modification (dynamic code patching).
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| 20 | * some users need to sleep (allocating memory...) while they hold this lock.
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| 21 | *
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| 22 | * Note: Also protects SMP-alternatives modification on x86.
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| 23 | *
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| 24 | * NOT exported to modules - patching kernel text is a really delicate matter.
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| 25 |
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| 26 | DEFINE_MUTEX(text_mutex);
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| 27 |
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| 28 | extern struct exception_table_entry __start___ex_table[];
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| 29 | extern struct exception_table_entry __stop___ex_table[];
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| 30 |
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| 31 |
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| 32 | u32 __initdata __visible main_extable_sort_needed = 1;
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| 33 |
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| 34 |
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| 35 | void __init sort_main_extable(void)
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| 36 | {
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| 37 | if (main_extable_sort_needed && __stop___ex_table > __start___ex_table) {
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| 38 | pr_notice("Sorting __ex_table...\n");
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| 39 | sort_extable(__start___ex_table, __stop___ex_table);
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| 40 | }
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| 41 | }
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| 42 |
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| 43 |
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| 44 | const
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| 45 | struct exception_table_entry *search_kernel_exception_table(unsigned long addr)
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| 46 | {
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| 47 | return search_extable(__start___ex_table,
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| 48 | __stop___ex_table - __start___ex_table, addr);
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| 49 | }
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| 50 |
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| 51 |
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| 52 | const struct exception_table_entry *search_exception_tables(unsigned long addr)
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| 53 | {
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| 54 | const struct exception_table_entry *e;
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| 55 |
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| 56 | e = search_kernel_exception_table(addr);
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| 57 | if (!e)
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| 58 | e = search_module_extables(addr);
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| 59 | return e;
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| 60 | }
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| 61 |
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| 62 | int init_kernel_text(unsigned long addr)
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| 63 | {
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| 64 | if (addr >= (unsigned long)_sinittext &&
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| 65 | addr < (unsigned long)_einittext)
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| 66 | return 1;
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| 67 | return 0;
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| 68 | }
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| 69 |
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| 70 | int notrace core_kernel_text(unsigned long addr)
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| 71 | {
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| 72 | if (addr >= (unsigned long)_stext &&
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| 73 | addr < (unsigned long)_etext)
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| 74 | return 1;
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| 75 |
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| 76 | if (system_state < SYSTEM_RUNNING &&
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| 77 | init_kernel_text(addr))
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| 78 | return 1;
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| 79 | return 0;
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| 80 | }
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| 81 |
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| 82 | |
| 83 | * core_kernel_data - tell if addr points to kernel data
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| 84 | * @addr: address to test
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| 85 | *
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| 86 | * Returns true if @addr passed in is from the core kernel data
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| 87 | * section.
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| 88 | *
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| 89 | * Note: On some archs it may return true for core RODATA, and false
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| 90 | * for others. But will always be true for core RW data.
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| 91 |
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| 92 | int core_kernel_data(unsigned long addr)
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| 93 | {
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| 94 | if (addr >= (unsigned long)_sdata &&
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| 95 | addr < (unsigned long)_edata)
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| 96 | return 1;
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| 97 | return 0;
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| 98 | }
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| 99 |
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| 100 | int __kernel_text_address(unsigned long addr)
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| 101 | {
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| 102 | if (kernel_text_address(addr))
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| 103 | return 1;
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| 104 | |
| 105 | * There might be init symbols in saved stacktraces.
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| 106 | * Give those symbols a chance to be printed in
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| 107 | * backtraces (such as lockdep traces).
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| 108 | *
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| 109 | * Since we are after the module-symbols check, there's
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| 110 | * no danger of address overlap:
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| 111 |
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| 112 | if (init_kernel_text(addr))
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| 113 | return 1;
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| 114 | return 0;
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| 115 | }
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| 116 |
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| 117 | int kernel_text_address(unsigned long addr)
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| 118 | {
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| 119 | bool no_rcu;
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| 120 | int ret = 1;
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| 121 |
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| 122 | if (core_kernel_text(addr))
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| 123 | return 1;
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| 124 |
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| 125 | |
| 126 | * If a stack dump happens while RCU is not watching, then
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| 127 | * RCU needs to be notified that it requires to start
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| 128 | * watching again. This can happen either by tracing that
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| 129 | * triggers a stack trace, or a WARN() that happens during
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| 130 | * coming back from idle, or cpu on or offlining.
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| 131 | *
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| 132 | * is_module_text_address() as well as the kprobe slots
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| 133 | * and is_bpf_text_address() require RCU to be watching.
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| 134 |
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| 135 | no_rcu = !rcu_is_watching();
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| 136 |
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| 137 |
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| 138 | if (no_rcu)
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| 139 | rcu_nmi_enter();
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| 140 |
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| 141 | if (is_module_text_address(addr))
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| 142 | goto out;
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| 143 | if (is_ftrace_trampoline(addr))
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| 144 | goto out;
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| 145 | if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
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| 146 | goto out;
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| 147 | if (is_bpf_text_address(addr))
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| 148 | goto out;
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| 149 | ret = 0;
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| 150 | out:
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| 151 | if (no_rcu)
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| 152 | rcu_nmi_exit();
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| 153 |
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| 154 | return ret;
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| 155 | }
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| 156 |
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| 157 | |
| 158 | * On some architectures (PPC64, IA64) function pointers
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| 159 | * are actually only tokens to some data that then holds the
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| 160 | * real function address. As a result, to find if a function
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| 161 | * pointer is part of the kernel text, we need to do some
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| 162 | * special dereferencing first.
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| 163 |
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| 164 | int func_ptr_is_kernel_text(void *ptr)
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| 165 | {
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| 166 | unsigned long addr;
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| 167 | addr = (unsigned long) dereference_function_descriptor(ptr);
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| 168 | if (core_kernel_text(addr))
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| 169 | return 1;
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| 170 | return is_module_text_address(addr);
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| 171 | }
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