/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T
 *        All Rights Reserved
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 * Copyright 2024 MNX Cloud, Inc.
 */

/*
 * Portions of this source code were derived from Berkeley 4.3 BSD
 * under license from the Regents of the University of California.
 */

/*
 * libfstyp module for pcfs
 */
#include <sys/param.h>
#include <sys/types.h>
#include <sys/mntent.h>
#include <errno.h>
#include <sys/fs/pc_fs.h>
#include <sys/fs/pc_label.h>
#include <sys/fs/pc_dir.h>
#include <sys/stat.h>
#include <sys/vfs.h>
#include <sys/dkio.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <strings.h>
#include <sys/mnttab.h>
#include <locale.h>
#include <libfstyp_module.h>

#define PC_LABEL_SIZE 11

/* for the <sys/fs/pc_dir.h> PCDL_IS_LFN macro */
int     enable_long_filenames = 1;

struct fstyp_fat16_bs {
        uint8_t         f_drvnum;
        uint8_t         f_reserved1;
        uint8_t         f_bootsig;
        uint8_t         f_volid[4];
        uint8_t         f_label[11];
        uint8_t         f_typestring[8];
};

struct fstyp_fat32_bs {
        uint32_t        f_fatlength;
        uint16_t        f_flags;
        uint8_t         f_major;
        uint8_t         f_minor;
        uint32_t        f_rootcluster;
        uint16_t        f_infosector;
        uint16_t        f_backupboot;
        uint8_t         f_reserved2[12];
        uint8_t         f_drvnum;
        uint8_t         f_reserved1;
        uint8_t         f_bootsig;
        uint8_t         f_volid[4];
        uint8_t         f_label[11];
        uint8_t         f_typestring[8];
};

typedef struct fstyp_pcfs {
        int             fd;
        off_t           offset;
        nvlist_t        *attr;
        struct bootsec  bs;
        struct fstyp_fat16_bs bs16;
        struct fstyp_fat32_bs bs32;
        ushort_t        bps;
        int             fattype;
        char            volume_label[PC_LABEL_SIZE + 1];

        /* parameters derived or calculated per FAT spec */
        ulong_t         FATSz;
        ulong_t         TotSec;
        ulong_t         RootDirSectors;
        ulong_t         FirstDataSector;
        ulong_t         DataSec;
        ulong_t         CountOfClusters;
} fstyp_pcfs_t;


/* We should eventually make the structs "packed" so these won't be needed */
#define PC_BPSEC(h)     ltohs((h)->bs.bps[0])
#define PC_RESSEC(h)    ltohs((h)->bs.res_sec[0])
#define PC_NROOTENT(h)  ltohs((h)->bs.rdirents[0])
#define PC_NSEC(h)      ltohs((h)->bs.numsect[0])
#define PC_DRVNUM(h)    (FSTYP_IS_32(h) ? (h)->bs32.f_drvnum : \
                            (h)->bs16.f_drvnum)
#define PC_VOLID(a)     (FSTYP_IS_32(h) ? ltohi((h)->bs32.f_volid[0]) : \
                            ltohi((h)->bs16.f_volid[0]))
#define PC_LABEL_ADDR(a) (FSTYP_IS_32(h) ? \
                            &((h)->bs32.f_label[0]) : &((h)->bs16.f_label[0]))

#define FSTYP_IS_32(h)  ((h)->fattype == 32)

#define FSTYP_MAX_CLUSTER_SIZE  (64 * 1024)     /* though officially 32K */
#define FSTYP_MAX_DIR_SIZE      (65536 * 32)

static int      read_bootsec(fstyp_pcfs_t *h);
static int      valid_media(fstyp_pcfs_t *h);
static int      well_formed(fstyp_pcfs_t *h);
static void     calculate_parameters(fstyp_pcfs_t *h);
static void     determine_fattype(fstyp_pcfs_t *h);
static void     get_label(fstyp_pcfs_t *h);
static void     get_label_16(fstyp_pcfs_t *h);
static void     get_label_32(fstyp_pcfs_t *h);
static int      next_cluster_32(fstyp_pcfs_t *h, int n);
static boolean_t dir_find_label(fstyp_pcfs_t *h, struct pcdir *d, int nent);
static int      is_pcfs(fstyp_pcfs_t *h);
static int      dumpfs(fstyp_pcfs_t *h, FILE *fout, FILE *ferr);
static int      get_attr(fstyp_pcfs_t *h);

int     fstyp_mod_init(int fd, off_t offset, fstyp_mod_handle_t *handle);
void    fstyp_mod_fini(fstyp_mod_handle_t handle);
int     fstyp_mod_ident(fstyp_mod_handle_t handle);
int     fstyp_mod_get_attr(fstyp_mod_handle_t handle, nvlist_t **attrp);
int     fstyp_mod_dump(fstyp_mod_handle_t handle, FILE *fout, FILE *ferr);

int
fstyp_mod_init(int fd, off_t offset, fstyp_mod_handle_t *handle)
{
        struct fstyp_pcfs *h;

        if ((h = calloc(1, sizeof (struct fstyp_pcfs))) == NULL) {
                return (FSTYP_ERR_NOMEM);
        }
        h->fd = fd;
        h->offset = offset;

        *handle = (fstyp_mod_handle_t)h;
        return (0);
}

void
fstyp_mod_fini(fstyp_mod_handle_t handle)
{
        struct fstyp_pcfs *h = (struct fstyp_pcfs *)handle;

        if (h->attr == NULL) {
                nvlist_free(h->attr);
                h->attr = NULL;
        }
        free(h);
}

int
fstyp_mod_ident(fstyp_mod_handle_t handle)
{
        struct fstyp_pcfs *h = (struct fstyp_pcfs *)handle;

        return (is_pcfs(h));
}

int
fstyp_mod_get_attr(fstyp_mod_handle_t handle, nvlist_t **attrp)
{
        struct fstyp_pcfs *h = (struct fstyp_pcfs *)handle;
        int error;

        if (h->attr == NULL) {
                if (nvlist_alloc(&h->attr, NV_UNIQUE_NAME_TYPE, 0)) {
                        return (FSTYP_ERR_NOMEM);
                }
                if ((error = get_attr(h)) != 0) {
                        nvlist_free(h->attr);
                        h->attr = NULL;
                        return (error);
                }
        }

        *attrp = h->attr;
        return (0);
}

int
fstyp_mod_dump(fstyp_mod_handle_t handle, FILE *fout, FILE *ferr)
{
        struct fstyp_pcfs *h = (struct fstyp_pcfs *)handle;

        return (dumpfs(h, fout, ferr));
}


/*
 * Read in boot sector. Convert into host endianness where possible.
 */
static int
read_bootsec(fstyp_pcfs_t *h)
{
        struct dk_minfo dkminfo;
        char  *buf;
        size_t size = PC_SECSIZE;

        if (ioctl(h->fd, DKIOCGMEDIAINFO, &dkminfo) != -1) {
                if (dkminfo.dki_lbsize != 0)
                        size = dkminfo.dki_lbsize;
        }

        buf = malloc(size);
        if (buf == NULL)
                return (FSTYP_ERR_NOMEM);

        (void) lseek(h->fd, h->offset, SEEK_SET);
        if (read(h->fd, buf, size) != (ssize_t)size) {
                free(buf);
                return (FSTYP_ERR_IO);
        }

        bcopy(buf, &h->bs, sizeof (h->bs));
        bcopy(buf + sizeof (struct bootsec), &h->bs16, sizeof (h->bs16));
        bcopy(buf + sizeof (struct bootsec), &h->bs32, sizeof (h->bs32));
        free(buf);

        h->bs.fatsec = ltohs(h->bs.fatsec);
        h->bs.spt = ltohs(h->bs.spt);
        h->bs.nhead = ltohs(h->bs.nhead);
        h->bs.hiddensec = ltohi(h->bs.hiddensec);
        h->bs.totalsec = ltohi(h->bs.totalsec);

        h->bs32.f_fatlength = ltohi(h->bs32.f_fatlength);
        h->bs32.f_flags = ltohs(h->bs32.f_flags);
        h->bs32.f_rootcluster = ltohi(h->bs32.f_rootcluster);
        h->bs32.f_infosector = ltohs(h->bs32.f_infosector);
        h->bs32.f_backupboot = ltohs(h->bs32.f_backupboot);

        h->bps = PC_BPSEC(h);

        return (0);
}

static int
valid_media(fstyp_pcfs_t *h)
{
        switch (h->bs.mediadesriptor) {
        case MD_FIXED:
        case SS8SPT:
        case DS8SPT:
        case SS9SPT:
        case DS9SPT:
        case DS18SPT:
        case DS9_15SPT:
                return (1);
        default:
                return (0);
        }
}

static int
well_formed(fstyp_pcfs_t *h)
{
        int fatmatch;

        if (h->bs16.f_bootsig == 0x29) {
                fatmatch = ((h->bs16.f_typestring[0] == 'F' &&
                    h->bs16.f_typestring[1] == 'A' &&
                    h->bs16.f_typestring[2] == 'T') &&
                    (h->bs.fatsec > 0) &&
                    ((PC_NSEC(h) == 0 && h->bs.totalsec > 0) ||
                    PC_NSEC(h) > 0));
        } else if (h->bs32.f_bootsig == 0x29) {
                fatmatch = ((h->bs32.f_typestring[0] == 'F' &&
                    h->bs32.f_typestring[1] == 'A' &&
                    h->bs32.f_typestring[2] == 'T') &&
                    (h->bs.fatsec == 0 && h->bs32.f_fatlength > 0) &&
                    ((PC_NSEC(h) == 0 && h->bs.totalsec > 0) ||
                    PC_NSEC(h) > 0));
        } else {
                fatmatch = (PC_NSEC(h) > 0 && h->bs.fatsec > 0);
        }

        return (fatmatch && h->bps > 0 && h->bps % 512 == 0 &&
            h->bs.spcl > 0 && PC_RESSEC(h) >= 1 && h->bs.nfat > 0);
}

static void
calculate_parameters(fstyp_pcfs_t *h)
{
        if (PC_NSEC(h) != 0) {
                h->TotSec = PC_NSEC(h);
        } else {
                h->TotSec = h->bs.totalsec;
        }
        if (h->bs.fatsec != 0) {
                h->FATSz = h->bs.fatsec;
        } else {
                h->FATSz = h->bs32.f_fatlength;
        }
        if ((h->bps == 0) || (h->bs.spcl == 0)) {
                return;
        }
        h->RootDirSectors =
            ((PC_NROOTENT(h) * 32) + (h->bps - 1)) / h->bps;
        h->FirstDataSector =
            PC_RESSEC(h) + h->bs.nfat * h->FATSz + h->RootDirSectors;
        h->DataSec = h->TotSec - h->FirstDataSector;
        h->CountOfClusters = h->DataSec / h->bs.spcl;
}

static void
determine_fattype(fstyp_pcfs_t *h)
{
        if (h->CountOfClusters == 0) {
                h->fattype = 0;
                return;
        }

        if (h->CountOfClusters < 4085) {
                h->fattype = 12;
        } else if (h->CountOfClusters < 65525) {
                h->fattype = 16;
        } else {
                h->fattype = 32;
        }
}

static void
get_label(fstyp_pcfs_t *h)
{
        /*
         * Use label from the boot sector by default.
         * Can overwrite later with the one from root directory.
         */
        (void) memcpy(h->volume_label, PC_LABEL_ADDR(h), PC_LABEL_SIZE);
        h->volume_label[PC_LABEL_SIZE] = '\0';

        if (h->fattype == 0) {
                return;
        } else if (FSTYP_IS_32(h)) {
                get_label_32(h);
        } else {
                get_label_16(h);
        }
}

/*
 * Get volume label from the root directory entry.
 * In FAT12/16 the root directory is of fixed size.
 * It immediately follows the FATs
 */
static void
get_label_16(fstyp_pcfs_t *h)
{
        ulong_t FirstRootDirSecNum;
        int     secsize;
        off_t   offset;
        uint8_t buf[PC_SECSIZE * 4];
        int     i;
        int     nent, resid;

        if ((secsize = h->bps) > sizeof (buf)) {
                return;
        }

        FirstRootDirSecNum = PC_RESSEC(h) + h->bs.nfat * h->bs.fatsec;
        offset = h->offset + FirstRootDirSecNum * secsize;
        resid = PC_NROOTENT(h);

        for (i = 0; i < h->RootDirSectors; i++) {
                (void) lseek(h->fd, offset, SEEK_SET);
                if (read(h->fd, buf, secsize) != secsize) {
                        return;
                }

                nent = secsize / sizeof (struct pcdir);
                if (nent > resid) {
                        nent = resid;
                }
                if (dir_find_label(h, (struct pcdir *)buf, nent)) {
                        return;
                }

                resid -= nent;
                offset += PC_SECSIZE;
        }
}

/*
 * Get volume label from the root directory entry.
 * In FAT32 root is a usual directory, a cluster chain.
 * It starts at BPB_RootClus.
 */
static void
get_label_32(fstyp_pcfs_t *h)
{
        off_t   offset;
        int     clustersize;
        int     n;
        ulong_t FirstSectorofCluster;
        uint8_t *buf;
        int     nent;
        int     cnt = 0;

        clustersize = h->bs.spcl * h->bps;
        if ((clustersize == 0) || (clustersize > FSTYP_MAX_CLUSTER_SIZE) ||
            ((buf = calloc(1, clustersize)) == NULL)) {
                return;
        }

        for (n = h->bs32.f_rootcluster; n != 0; n = next_cluster_32(h, n)) {
                FirstSectorofCluster =
                    (n - 2) * h->bs.spcl + h->FirstDataSector;
                offset = h->offset + FirstSectorofCluster * h->bps;
                (void) lseek(h->fd, offset, SEEK_SET);
                if (read(h->fd, buf, clustersize) != clustersize) {
                        break;
                }

                nent = clustersize / sizeof (struct pcdir);
                if (dir_find_label(h, (struct pcdir *)buf, nent)) {
                        break;
                }

                if (++cnt > FSTYP_MAX_DIR_SIZE / clustersize) {
                        break;
                }
        }

        free(buf);
}

/*
 * Get a FAT entry pointing to the next file cluster
 */
int
next_cluster_32(fstyp_pcfs_t *h, int n)
{
        uint8_t buf[PC_SECSIZE];
        ulong_t ThisFATSecNum;
        ulong_t ThisFATEntOffset;
        off_t   offset;
        uint32_t val;
        int     next = 0;

        ThisFATSecNum = PC_RESSEC(h) + (n * 4) / h->bps;
        ThisFATEntOffset = (n * 4) % h->bps;
        offset = h->offset + ThisFATSecNum * h->bps;

        (void) lseek(h->fd, offset, SEEK_SET);
        if (read(h->fd, buf, sizeof (buf)) == sizeof (buf)) {
                val = buf[ThisFATEntOffset] & 0x0fffffff;
                next = ltohi(val);
        }

        return (next);
}

/*
 * Given an array of pcdir structs, find one containing volume label.
 */
static boolean_t
dir_find_label(fstyp_pcfs_t *h, struct pcdir *d, int nent)
{
        int     i;

        for (i = 0; i < nent; i++, d++) {
                if (PCDL_IS_LFN(d))
                        continue;
                if ((d->pcd_filename[0] != PCD_UNUSED) &&
                    (d->pcd_filename[0] != PCD_ERASED) &&
                    ((d->pcd_attr & (PCA_LABEL | PCA_DIR)) == PCA_LABEL) &&
                    (d->un.pcd_scluster_hi == 0) &&
                    (d->pcd_scluster_lo == 0)) {
                        (void) memcpy(h->volume_label, d->pcd_filename,
                            PC_LABEL_SIZE);
                        h->volume_label[PC_LABEL_SIZE] = '\0';
                        return (B_TRUE);
                }
        }
        return (B_FALSE);
}

static int
is_pcfs(fstyp_pcfs_t *h)
{
        int     error;

        if ((error = read_bootsec(h)) != 0) {
                return (error);
        }
        if (!valid_media(h)) {
                return (FSTYP_ERR_NO_MATCH);
        }
        if (!well_formed(h)) {
                return (FSTYP_ERR_NO_MATCH);
        }

        calculate_parameters(h);
        determine_fattype(h);
        get_label(h);

        return (0);
}

static int
dumpfs(fstyp_pcfs_t *h, FILE *fout, FILE *ferr __unused)
{
        /*
         * If fat type was not detected, then the other data is
         * likely bogus.
         */
        if (h->fattype == 0)
                return (FSTYP_ERR_NO_MATCH);

        (void) fprintf(fout, "Filesystem type: FAT%d\n", h->fattype);
        (void) fprintf(fout,
            "Bytes Per Sector  %d\t\tSectors Per Cluster    %d\n",
            h->bps, h->bs.spcl);
        (void) fprintf(fout,
            "Reserved Sectors  %d\t\tNumber of FATs         %d\n",
            (unsigned short)PC_RESSEC(h), h->bs.nfat);
        (void) fprintf(fout,
            "Root Dir Entries  %d\t\tNumber of Sectors      %d\n",
            (unsigned short)PC_NROOTENT(h), h->TotSec);
        (void) fprintf(fout,
            "Sectors Per FAT   %d\t\tSectors Per Track      %d\n",
            h->FATSz, h->bs.spt);
        (void) fprintf(fout,
            "Number of Heads   %d\t\tNumber Hidden Sectors  %d\n",
            h->bs.nhead, h->bs.hiddensec);
        (void) fprintf(fout, "Volume ID: 0x%x\n", PC_VOLID(h));
        (void) fprintf(fout, "Volume Label: %s\n", h->volume_label);
        (void) fprintf(fout, "Drive Number: 0x%x\n", PC_DRVNUM(h));
        (void) fprintf(fout, "Media Type: 0x%x   ", h->bs.mediadesriptor);

        switch (h->bs.mediadesriptor) {
        case MD_FIXED:
                (void) fprintf(fout, "\"Fixed\" Disk\n");
                break;
        case SS8SPT:
                (void) fprintf(fout, "Single Sided, 8 Sectors Per Track\n");
                break;
        case DS8SPT:
                (void) fprintf(fout, "Double Sided, 8 Sectors Per Track\n");
                break;
        case SS9SPT:
                (void) fprintf(fout, "Single Sided, 9 Sectors Per Track\n");
                break;
        case DS9SPT:
                (void) fprintf(fout, "Double Sided, 9 Sectors Per Track\n");
                break;
        case DS18SPT:
                (void) fprintf(fout, "Double Sided, 18 Sectors Per Track\n");
                break;
        case DS9_15SPT:
                (void) fprintf(fout, "Double Sided, 9-15 Sectors Per Track\n");
                break;
        default:
                (void) fprintf(fout, "Unknown Media Type\n");
        }

        return (0);
}

#define ADD_STRING(h, name, value) \
        if (nvlist_add_string(h->attr, name, value) != 0) { \
                return (FSTYP_ERR_NOMEM); \
        }

#define ADD_UINT32(h, name, value) \
        if (nvlist_add_uint32(h->attr, name, value) != 0) { \
                return (FSTYP_ERR_NOMEM); \
        }

#define ADD_UINT64(h, name, value) \
        if (nvlist_add_uint64(h->attr, name, value) != 0) { \
                return (FSTYP_ERR_NOMEM); \
        }

#define ADD_BOOL(h, name, value) \
        if (nvlist_add_boolean_value(h->attr, name, value) != 0) { \
                return (FSTYP_ERR_NOMEM); \
        }

static int
get_attr(fstyp_pcfs_t *h)
{
        char    s[64];

        ADD_UINT32(h, "bytes_per_sector", h->bps);
        ADD_UINT32(h, "sectors_per_cluster", h->bs.spcl);
        ADD_UINT32(h, "reserved_sectors", PC_RESSEC(h));
        ADD_UINT32(h, "fats", h->bs.nfat);
        ADD_UINT32(h, "root_entry_count", PC_NROOTENT(h));
        ADD_UINT32(h, "total_sectors_16", PC_NSEC(h));
        ADD_UINT32(h, "media", h->bs.mediadesriptor);
        ADD_UINT32(h, "fat_size_16", h->bs.fatsec);
        ADD_UINT32(h, "sectors_per_track", h->bs.spt);
        ADD_UINT32(h, "heads", h->bs.nhead);
        ADD_UINT32(h, "hidden_sectors", h->bs.hiddensec);
        ADD_UINT32(h, "total_sectors_32", h->bs.totalsec);
        ADD_UINT32(h, "drive_number", PC_DRVNUM(h));
        ADD_UINT32(h, "volume_id", PC_VOLID(h));
        ADD_STRING(h, "volume_label", h->volume_label);
        if (FSTYP_IS_32(h)) {
                ADD_UINT32(h, "fat_size_32", h->bs32.f_fatlength);
        }
        ADD_UINT32(h, "total_sectors", h->TotSec);
        ADD_UINT32(h, "fat_size", h->FATSz);
        ADD_UINT32(h, "count_of_clusters", h->CountOfClusters);
        ADD_UINT32(h, "fat_entry_size", h->fattype);

        ADD_BOOL(h, "gen_clean", B_TRUE);
        if (PC_VOLID(a) != 0) {
                (void) snprintf(s, sizeof (s), "%08x", PC_VOLID(a));
                ADD_STRING(h, "gen_guid", s);
        }
        (void) snprintf(s, sizeof (s), "%d", h->fattype);
        ADD_STRING(h, "gen_version", s);
        ADD_STRING(h, "gen_volume_label", h->volume_label);

        return (0);
}