cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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extable.c (4354B)

      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 */
     27DEFINE_MUTEX(text_mutex);
     28
     29extern struct exception_table_entry __start___ex_table[];
     30extern struct exception_table_entry __stop___ex_table[];
     31
     32/* Cleared by build time tools if the table is already sorted. */
     33u32 __initdata __visible main_extable_sort_needed = 1;
     34
     35/* Sort the kernel's built-in exception table */
     36void __init sort_main_extable(void)
     37{
     38	if (main_extable_sort_needed &&
     39	    &__stop___ex_table > &__start___ex_table) {
     40		pr_notice("Sorting __ex_table...\n");
     41		sort_extable(__start___ex_table, __stop___ex_table);
     42	}
     43}
     44
     45/* Given an address, look for it in the kernel exception table */
     46const
     47struct exception_table_entry *search_kernel_exception_table(unsigned long addr)
     48{
     49	return search_extable(__start___ex_table,
     50			      __stop___ex_table - __start___ex_table, addr);
     51}
     52
     53/* Given an address, look for it in the exception tables. */
     54const struct exception_table_entry *search_exception_tables(unsigned long addr)
     55{
     56	const struct exception_table_entry *e;
     57
     58	e = search_kernel_exception_table(addr);
     59	if (!e)
     60		e = search_module_extables(addr);
     61	if (!e)
     62		e = search_bpf_extables(addr);
     63	return e;
     64}
     65
     66int notrace core_kernel_text(unsigned long addr)
     67{
     68	if (is_kernel_text(addr))
     69		return 1;
     70
     71	if (system_state < SYSTEM_FREEING_INITMEM &&
     72	    is_kernel_inittext(addr))
     73		return 1;
     74	return 0;
     75}
     76
     77int __kernel_text_address(unsigned long addr)
     78{
     79	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	if (is_kernel_inittext(addr))
     90		return 1;
     91	return 0;
     92}
     93
     94int kernel_text_address(unsigned long addr)
     95{
     96	bool no_rcu;
     97	int ret = 1;
     98
     99	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		rcu_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;
    128out:
    129	if (no_rcu)
    130		rcu_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
    143void *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}
    152EXPORT_SYMBOL_GPL(dereference_function_descriptor);
    153
    154void *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
    163int func_ptr_is_kernel_text(void *ptr)
    164{
    165	unsigned long addr;
    166	addr = (unsigned long) dereference_function_descriptor(ptr);
    167	if (core_kernel_text(addr))
    168		return 1;
    169	return is_module_text_address(addr);
    170}