Line data    Source code

       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/elf.h>
       7             : #include <linux/ftrace.h>
       8             : #include <linux/memory.h>
       9             : #include <linux/extable.h>
      10             : #include <linux/module.h>
      11             : #include <linux/mutex.h>
      12             : #include <linux/init.h>
      13             : #include <linux/kprobes.h>
      14             : #include <linux/filter.h>
      15             : 
      16             : #include <asm/sections.h>
      17             : #include <linux/uaccess.h>
      18             : 
      19             : /*
      20             :  * mutex protecting text section modification (dynamic code patching).
      21             :  * some users need to sleep (allocating memory...) while they hold this lock.
      22             :  *
      23             :  * Note: Also protects SMP-alternatives modification on x86.
      24             :  *
      25             :  * NOT exported to modules - patching kernel text is a really delicate matter.
      26             :  */
      27             : DEFINE_MUTEX(text_mutex);
      28             : 
      29             : extern struct exception_table_entry __start___ex_table[];
      30             : extern struct exception_table_entry __stop___ex_table[];
      31             : 
      32             : /* Cleared by build time tools if the table is already sorted. */
      33             : u32 __initdata __visible main_extable_sort_needed = 1;
      34             : 
      35             : /* Sort the kernel's built-in exception table */
      36           1 : void __init sort_main_extable(void)
      37             : {
      38           1 :         if (main_extable_sort_needed &&
      39             :             &__stop___ex_table > &__start___ex_table) {
      40           1 :                 pr_notice("Sorting __ex_table...\n");
      41           1 :                 sort_extable(__start___ex_table, __stop___ex_table);
      42             :         }
      43           1 : }
      44             : 
      45             : /* Given an address, look for it in the kernel exception table */
      46             : const
      47           0 : struct exception_table_entry *search_kernel_exception_table(unsigned long addr)
      48             : {
      49           0 :         return search_extable(__start___ex_table,
      50           0 :                               __stop___ex_table - __start___ex_table, addr);
      51             : }
      52             : 
      53             : /* Given an address, look for it in the exception tables. */
      54           0 : const struct exception_table_entry *search_exception_tables(unsigned long addr)
      55             : {
      56             :         const struct exception_table_entry *e;
      57             : 
      58           0 :         e = search_kernel_exception_table(addr);
      59           0 :         if (!e)
      60           0 :                 e = search_module_extables(addr);
      61           0 :         if (!e)
      62           0 :                 e = search_bpf_extables(addr);
      63           0 :         return e;
      64             : }
      65             : 
      66           0 : int notrace core_kernel_text(unsigned long addr)
      67             : {
      68         118 :         if (is_kernel_text(addr))
      69             :                 return 1;
      70             : 
      71         196 :         if (system_state < SYSTEM_FREEING_INITMEM &&
      72          98 :             is_kernel_inittext(addr))
      73             :                 return 1;
      74             :         return 0;
      75             : }
      76             : 
      77         118 : int __kernel_text_address(unsigned long addr)
      78             : {
      79         118 :         if (kernel_text_address(addr))
      80             :                 return 1;
      81             :         /*
      82             :          * There might be init symbols in saved stacktraces.
      83             :          * Give those symbols a chance to be printed in
      84             :          * backtraces (such as lockdep traces).
      85             :          *
      86             :          * Since we are after the module-symbols check, there's
      87             :          * no danger of address overlap:
      88             :          */
      89          91 :         if (is_kernel_inittext(addr))
      90             :                 return 1;
      91          91 :         return 0;
      92             : }
      93             : 
      94         118 : int kernel_text_address(unsigned long addr)
      95             : {
      96             :         bool no_rcu;
      97         118 :         int ret = 1;
      98             : 
      99         118 :         if (core_kernel_text(addr))
     100             :                 return 1;
     101             : 
     102             :         /*
     103             :          * If a stack dump happens while RCU is not watching, then
     104             :          * RCU needs to be notified that it requires to start
     105             :          * watching again. This can happen either by tracing that
     106             :          * triggers a stack trace, or a WARN() that happens during
     107             :          * coming back from idle, or cpu on or offlining.
     108             :          *
     109             :          * is_module_text_address() as well as the kprobe slots,
     110             :          * is_bpf_text_address() and is_bpf_image_address require
     111             :          * RCU to be watching.
     112             :          */
     113             :         no_rcu = !rcu_is_watching();
     114             : 
     115             :         /* Treat this like an NMI as it can happen anywhere */
     116             :         if (no_rcu)
     117             :                 ct_nmi_enter();
     118             : 
     119             :         if (is_module_text_address(addr))
     120             :                 goto out;
     121             :         if (is_ftrace_trampoline(addr))
     122             :                 goto out;
     123             :         if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
     124             :                 goto out;
     125             :         if (is_bpf_text_address(addr))
     126             :                 goto out;
     127             :         ret = 0;
     128             : out:
     129             :         if (no_rcu)
     130             :                 ct_nmi_exit();
     131             : 
     132             :         return ret;
     133             : }
     134             : 
     135             : /*
     136             :  * On some architectures (PPC64, IA64, PARISC) function pointers
     137             :  * are actually only tokens to some data that then holds the
     138             :  * real function address. As a result, to find if a function
     139             :  * pointer is part of the kernel text, we need to do some
     140             :  * special dereferencing first.
     141             :  */
     142             : #ifdef CONFIG_HAVE_FUNCTION_DESCRIPTORS
     143             : void *dereference_function_descriptor(void *ptr)
     144             : {
     145             :         func_desc_t *desc = ptr;
     146             :         void *p;
     147             : 
     148             :         if (!get_kernel_nofault(p, (void *)&desc->addr))
     149             :                 ptr = p;
     150             :         return ptr;
     151             : }
     152             : EXPORT_SYMBOL_GPL(dereference_function_descriptor);
     153             : 
     154             : void *dereference_kernel_function_descriptor(void *ptr)
     155             : {
     156             :         if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
     157             :                 return ptr;
     158             : 
     159             :         return dereference_function_descriptor(ptr);
     160             : }
     161             : #endif
     162             : 
     163           0 : int func_ptr_is_kernel_text(void *ptr)
     164             : {
     165             :         unsigned long addr;
     166           0 :         addr = (unsigned long) dereference_function_descriptor(ptr);
     167           0 :         if (core_kernel_text(addr))
     168             :                 return 1;
     169           0 :         return is_module_text_address(addr);
     170             : }