// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Derived from arch/ppc/mm/extable.c and arch/i386/mm/extable.c.
 *
 * Copyright (C) 2004 Paul Mackerras, IBM Corp.
 */

#include <linux/bsearch.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sort.h>
#include <linux/uaccess.h>
#include <linux/extable.h>

#ifndef ARCH_HAS_RELATIVE_EXTABLE
#define ex_to_insn(x)   ((x)->insn)
#else
static inline unsigned long ex_to_insn(const struct exception_table_entry *x)
{
        return (unsigned long)&x->insn + x->insn;
}
#endif

#ifndef ARCH_HAS_RELATIVE_EXTABLE
#define swap_ex         NULL
#else
static void swap_ex(void *a, void *b, int size)
{
        struct exception_table_entry *x = a, *y = b, tmp;
        int delta = b - a;

        tmp = *x;
        x->insn = y->insn + delta;
        y->insn = tmp.insn - delta;

#ifdef swap_ex_entry_fixup
        swap_ex_entry_fixup(x, y, tmp, delta);
#else
        x->fixup = y->fixup + delta;
        y->fixup = tmp.fixup - delta;
#endif
}
#endif /* ARCH_HAS_RELATIVE_EXTABLE */

/*
 * The exception table needs to be sorted so that the binary
 * search that we use to find entries in it works properly.
 * This is used both for the kernel exception table and for
 * the exception tables of modules that get loaded.
 */
static int cmp_ex_sort(const void *a, const void *b)
{
        const struct exception_table_entry *x = a, *y = b;

        /* avoid overflow */
        if (ex_to_insn(x) > ex_to_insn(y))
                return 1;
        if (ex_to_insn(x) < ex_to_insn(y))
                return -1;
        return 0;
}

void sort_extable(struct exception_table_entry *start,
                  struct exception_table_entry *finish)
{
        sort(start, finish - start, sizeof(struct exception_table_entry),
             cmp_ex_sort, swap_ex);
}

#ifdef CONFIG_MODULES
/*
 * If the exception table is sorted, any referring to the module init
 * will be at the beginning or the end.
 */
void trim_init_extable(struct module *m)
{
        /*trim the beginning*/
        while (m->num_exentries &&
               within_module_init(ex_to_insn(&m->extable[0]), m)) {
                m->extable++;
                m->num_exentries--;
        }
        /*trim the end*/
        while (m->num_exentries &&
               within_module_init(ex_to_insn(&m->extable[m->num_exentries - 1]),
                                  m))
                m->num_exentries--;
}
#endif /* CONFIG_MODULES */

static int cmp_ex_search(const void *key, const void *elt)
{
        const struct exception_table_entry *_elt = elt;
        unsigned long _key = *(unsigned long *)key;

        /* avoid overflow */
        if (_key > ex_to_insn(_elt))
                return 1;
        if (_key < ex_to_insn(_elt))
                return -1;
        return 0;
}

/*
 * Search one exception table for an entry corresponding to the
 * given instruction address, and return the address of the entry,
 * or NULL if none is found.
 * We use a binary search, and thus we assume that the table is
 * already sorted.
 */
const struct exception_table_entry *
search_extable(const struct exception_table_entry *base,
               const size_t num,
               unsigned long value)
{
        return bsearch(&value, base, num,
                       sizeof(struct exception_table_entry), cmp_ex_search);
}