// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/isofs/namei.c
 *
 *  (C) 1992  Eric Youngdale Modified for ISO 9660 filesystem.
 *
 *  (C) 1991  Linus Torvalds - minix filesystem
 */

#include <linux/gfp.h>
#include "isofs.h"

/*
 * ok, we cannot use strncmp, as the name is not in our data space.
 * Thus we'll have to use isofs_match. No big problem. Match also makes
 * some sanity tests.
 */
static int
isofs_cmp(struct dentry *dentry, const char *compare, int dlen)
{
        struct qstr qstr;
        qstr.name = compare;
        qstr.len = dlen;
        if (likely(!dentry->d_op))
                return dentry->d_name.len != dlen || memcmp(dentry->d_name.name, compare, dlen);
        return dentry->d_op->d_compare(NULL, dentry->d_name.len, dentry->d_name.name, &qstr);
}

/*
 *      isofs_find_entry()
 *
 * finds an entry in the specified directory with the wanted name. It
 * returns the inode number of the found entry, or 0 on error.
 */
static unsigned long
isofs_find_entry(struct inode *dir, struct dentry *dentry,
        unsigned long *block_rv, unsigned long *offset_rv,
        char *tmpname, struct iso_directory_record *tmpde)
{
        unsigned long bufsize = ISOFS_BUFFER_SIZE(dir);
        unsigned char bufbits = ISOFS_BUFFER_BITS(dir);
        unsigned long block, f_pos, offset, block_saved, offset_saved;
        struct buffer_head *bh = NULL;
        struct isofs_sb_info *sbi = ISOFS_SB(dir->i_sb);

        if (!ISOFS_I(dir)->i_first_extent)
                return 0;

        f_pos = 0;
        offset = 0;
        block = 0;

        while (f_pos < dir->i_size) {
                struct iso_directory_record *de;
                int de_len, match, i, dlen;
                char *dpnt;

                if (!bh) {
                        bh = isofs_bread(dir, block);
                        if (!bh)
                                return 0;
                }

                de = (struct iso_directory_record *) (bh->b_data + offset);

                de_len = *(unsigned char *) de;
                if (!de_len) {
                        brelse(bh);
                        bh = NULL;
                        f_pos = (f_pos + ISOFS_BLOCK_SIZE) & ~(ISOFS_BLOCK_SIZE - 1);
                        block = f_pos >> bufbits;
                        offset = 0;
                        continue;
                }

                block_saved = bh->b_blocknr;
                offset_saved = offset;
                offset += de_len;
                f_pos += de_len;

                /* Make sure we have a full directory entry */
                if (offset >= bufsize) {
                        int slop = bufsize - offset + de_len;
                        memcpy(tmpde, de, slop);
                        offset &= bufsize - 1;
                        block++;
                        brelse(bh);
                        bh = NULL;
                        if (offset) {
                                bh = isofs_bread(dir, block);
                                if (!bh)
                                        return 0;
                                memcpy((void *) tmpde + slop, bh->b_data, offset);
                        }
                        de = tmpde;
                }

                dlen = de->name_len[0];
                dpnt = de->name;
                /* Basic sanity check, whether name doesn't exceed dir entry */
                if (de_len < dlen + sizeof(struct iso_directory_record)) {
                        printk(KERN_NOTICE "iso9660: Corrupted directory entry"
                               " in block %lu of inode %lu\n", block,
                               dir->i_ino);
                        brelse(bh);
                        return 0;
                }

                if (sbi->s_rock &&
                    ((i = get_rock_ridge_filename(de, tmpname, dir)))) {
                        dlen = i;       /* possibly -1 */
                        dpnt = tmpname;
#ifdef CONFIG_JOLIET
                } else if (sbi->s_joliet_level) {
                        dlen = get_joliet_filename(de, tmpname, dir);
                        dpnt = tmpname;
#endif
                } else if (sbi->s_mapping == 'a') {
                        dlen = get_acorn_filename(de, tmpname, dir);
                        dpnt = tmpname;
                } else if (sbi->s_mapping == 'n') {
                        dlen = isofs_name_translate(de, tmpname, dir);
                        dpnt = tmpname;
                }

                /*
                 * Skip hidden or associated files unless hide or showassoc,
                 * respectively, is set
                 */
                match = 0;
                if (dlen > 0 &&
                        (!sbi->s_hide ||
                                (!(de->flags[-sbi->s_high_sierra] & 1))) &&
                        (sbi->s_showassoc ||
                                (!(de->flags[-sbi->s_high_sierra] & 4)))) {
                        if (dpnt && (dlen > 1 || dpnt[0] > 1))
                                match = (isofs_cmp(dentry, dpnt, dlen) == 0);
                }
                if (match) {
                        isofs_normalize_block_and_offset(de,
                                                         &block_saved,
                                                         &offset_saved);
                        *block_rv = block_saved;
                        *offset_rv = offset_saved;
                        brelse(bh);
                        return 1;
                }
        }
        brelse(bh);
        return 0;
}

struct dentry *isofs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
        int found;
        unsigned long block;
        unsigned long offset;
        struct inode *inode;
        struct page *page;

        page = alloc_page(GFP_USER);
        if (!page)
                return ERR_PTR(-ENOMEM);

        found = isofs_find_entry(dir, dentry,
                                &block, &offset,
                                page_address(page),
                                1024 + page_address(page));
        __free_page(page);

        inode = found ? isofs_iget(dir->i_sb, block, offset) : NULL;

        return d_splice_alias(inode, dentry);
}