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 (2945B)

      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/*
      3 * Derived from arch/ppc/mm/extable.c and arch/i386/mm/extable.c.
      4 *
      5 * Copyright (C) 2004 Paul Mackerras, IBM Corp.
      6 */
      7
      8#include <linux/bsearch.h>
      9#include <linux/module.h>
     10#include <linux/init.h>
     11#include <linux/sort.h>
     12#include <linux/uaccess.h>
     13#include <linux/extable.h>
     14
     15#ifndef ARCH_HAS_RELATIVE_EXTABLE
     16#define ex_to_insn(x)	((x)->insn)
     17#else
     18static inline unsigned long ex_to_insn(const struct exception_table_entry *x)
     19{
     20	return (unsigned long)&x->insn + x->insn;
     21}
     22#endif
     23
     24#ifndef ARCH_HAS_RELATIVE_EXTABLE
     25#define swap_ex		NULL
     26#else
     27static void swap_ex(void *a, void *b, int size)
     28{
     29	struct exception_table_entry *x = a, *y = b, tmp;
     30	int delta = b - a;
     31
     32	tmp = *x;
     33	x->insn = y->insn + delta;
     34	y->insn = tmp.insn - delta;
     35
     36#ifdef swap_ex_entry_fixup
     37	swap_ex_entry_fixup(x, y, tmp, delta);
     38#else
     39	x->fixup = y->fixup + delta;
     40	y->fixup = tmp.fixup - delta;
     41#endif
     42}
     43#endif /* ARCH_HAS_RELATIVE_EXTABLE */
     44
     45/*
     46 * The exception table needs to be sorted so that the binary
     47 * search that we use to find entries in it works properly.
     48 * This is used both for the kernel exception table and for
     49 * the exception tables of modules that get loaded.
     50 */
     51static int cmp_ex_sort(const void *a, const void *b)
     52{
     53	const struct exception_table_entry *x = a, *y = b;
     54
     55	/* avoid overflow */
     56	if (ex_to_insn(x) > ex_to_insn(y))
     57		return 1;
     58	if (ex_to_insn(x) < ex_to_insn(y))
     59		return -1;
     60	return 0;
     61}
     62
     63void sort_extable(struct exception_table_entry *start,
     64		  struct exception_table_entry *finish)
     65{
     66	sort(start, finish - start, sizeof(struct exception_table_entry),
     67	     cmp_ex_sort, swap_ex);
     68}
     69
     70#ifdef CONFIG_MODULES
     71/*
     72 * If the exception table is sorted, any referring to the module init
     73 * will be at the beginning or the end.
     74 */
     75void trim_init_extable(struct module *m)
     76{
     77	/*trim the beginning*/
     78	while (m->num_exentries &&
     79	       within_module_init(ex_to_insn(&m->extable[0]), m)) {
     80		m->extable++;
     81		m->num_exentries--;
     82	}
     83	/*trim the end*/
     84	while (m->num_exentries &&
     85	       within_module_init(ex_to_insn(&m->extable[m->num_exentries - 1]),
     86				  m))
     87		m->num_exentries--;
     88}
     89#endif /* CONFIG_MODULES */
     90
     91static int cmp_ex_search(const void *key, const void *elt)
     92{
     93	const struct exception_table_entry *_elt = elt;
     94	unsigned long _key = *(unsigned long *)key;
     95
     96	/* avoid overflow */
     97	if (_key > ex_to_insn(_elt))
     98		return 1;
     99	if (_key < ex_to_insn(_elt))
    100		return -1;
    101	return 0;
    102}
    103
    104/*
    105 * Search one exception table for an entry corresponding to the
    106 * given instruction address, and return the address of the entry,
    107 * or NULL if none is found.
    108 * We use a binary search, and thus we assume that the table is
    109 * already sorted.
    110 */
    111const struct exception_table_entry *
    112search_extable(const struct exception_table_entry *base,
    113	       const size_t num,
    114	       unsigned long value)
    115{
    116	return bsearch(&value, base, num,
    117		       sizeof(struct exception_table_entry), cmp_ex_search);
    118}