// SPDX-License-Identifier: GPL-2.0
/*
 *  fs/partitions/amiga.c
 *
 *  Code extracted from drivers/block/genhd.c
 *
 *  Copyright (C) 1991-1998  Linus Torvalds
 *  Re-organised Feb 1998 Russell King
 */

#define pr_fmt(fmt) fmt

#include <linux/types.h>
#include <linux/mm_types.h>
#include <linux/overflow.h>
#include <linux/affs_hardblocks.h>

#include "check.h"

/* magic offsets in partition DosEnvVec */
#define NR_HD   3
#define NR_SECT 5
#define LO_CYL  9
#define HI_CYL  10

static __inline__ u32
checksum_block(__be32 *m, int size)
{
        u32 sum = 0;

        while (size--)
                sum += be32_to_cpu(*m++);
        return sum;
}

int amiga_partition(struct parsed_partitions *state)
{
        Sector sect;
        unsigned char *data;
        struct RigidDiskBlock *rdb;
        struct PartitionBlock *pb;
        u64 start_sect, nr_sects;
        sector_t blk, end_sect;
        u32 cylblk;             /* rdb_CylBlocks = nr_heads*sect_per_track */
        u32 nr_hd, nr_sect, lo_cyl, hi_cyl;
        int part, res = 0;
        unsigned int blksize = 1;       /* Multiplier for disk block size */
        int slot = 1;

        for (blk = 0; ; blk++, put_dev_sector(sect)) {
                if (blk == RDB_ALLOCATION_LIMIT)
                        goto rdb_done;
                data = read_part_sector(state, blk, &sect);
                if (!data) {
                        pr_err("Dev %s: unable to read RDB block %llu\n",
                               state->disk->disk_name, blk);
                        res = -1;
                        goto rdb_done;
                }
                if (*(__be32 *)data != cpu_to_be32(IDNAME_RIGIDDISK))
                        continue;

                rdb = (struct RigidDiskBlock *)data;
                if (checksum_block((__be32 *)data, be32_to_cpu(rdb->rdb_SummedLongs) & 0x7F) == 0)
                        break;
                /* Try again with 0xdc..0xdf zeroed, Windows might have
                 * trashed it.
                 */
                *(__be32 *)(data+0xdc) = 0;
                if (checksum_block((__be32 *)data,
                                be32_to_cpu(rdb->rdb_SummedLongs) & 0x7F)==0) {
                        pr_err("Trashed word at 0xd0 in block %llu ignored in checksum calculation\n",
                               blk);
                        break;
                }

                pr_err("Dev %s: RDB in block %llu has bad checksum\n",
                       state->disk->disk_name, blk);
        }

        /* blksize is blocks per 512 byte standard block */
        blksize = be32_to_cpu( rdb->rdb_BlockBytes ) / 512;

        {
                char tmp[7 + 10 + 1 + 1];

                /* Be more informative */
                snprintf(tmp, sizeof(tmp), " RDSK (%d)", blksize * 512);
                strlcat(state->pp_buf, tmp, PAGE_SIZE);
        }
        blk = be32_to_cpu(rdb->rdb_PartitionList);
        put_dev_sector(sect);
        for (part = 1; (s32) blk>0 && part<=16; part++, put_dev_sector(sect)) {
                /* Read in terms partition table understands */
                if (check_mul_overflow(blk, (sector_t) blksize, &blk)) {
                        pr_err("Dev %s: overflow calculating partition block %llu! Skipping partitions %u and beyond\n",
                                state->disk->disk_name, blk, part);
                        break;
                }
                data = read_part_sector(state, blk, &sect);
                if (!data) {
                        pr_err("Dev %s: unable to read partition block %llu\n",
                               state->disk->disk_name, blk);
                        res = -1;
                        goto rdb_done;
                }
                pb  = (struct PartitionBlock *)data;
                blk = be32_to_cpu(pb->pb_Next);
                if (pb->pb_ID != cpu_to_be32(IDNAME_PARTITION))
                        continue;
                if (checksum_block((__be32 *)pb, be32_to_cpu(pb->pb_SummedLongs) & 0x7F) != 0 )
                        continue;

                /* RDB gives us more than enough rope to hang ourselves with,
                 * many times over (2^128 bytes if all fields max out).
                 * Some careful checks are in order, so check for potential
                 * overflows.
                 * We are multiplying four 32 bit numbers to one sector_t!
                 */

                nr_hd   = be32_to_cpu(pb->pb_Environment[NR_HD]);
                nr_sect = be32_to_cpu(pb->pb_Environment[NR_SECT]);

                /* CylBlocks is total number of blocks per cylinder */
                if (check_mul_overflow(nr_hd, nr_sect, &cylblk)) {
                        pr_err("Dev %s: heads*sects %u overflows u32, skipping partition!\n",
                                state->disk->disk_name, cylblk);
                        continue;
                }

                /* check for consistency with RDB defined CylBlocks */
                if (cylblk > be32_to_cpu(rdb->rdb_CylBlocks)) {
                        pr_warn("Dev %s: cylblk %u > rdb_CylBlocks %u!\n",
                                state->disk->disk_name, cylblk,
                                be32_to_cpu(rdb->rdb_CylBlocks));
                }

                /* RDB allows for variable logical block size -
                 * normalize to 512 byte blocks and check result.
                 */

                if (check_mul_overflow(cylblk, blksize, &cylblk)) {
                        pr_err("Dev %s: partition %u bytes per cyl. overflows u32, skipping partition!\n",
                                state->disk->disk_name, part);
                        continue;
                }

                /* Calculate partition start and end. Limit of 32 bit on cylblk
                 * guarantees no overflow occurs if LBD support is enabled.
                 */

                lo_cyl = be32_to_cpu(pb->pb_Environment[LO_CYL]);
                start_sect = ((u64) lo_cyl * cylblk);

                hi_cyl = be32_to_cpu(pb->pb_Environment[HI_CYL]);
                nr_sects = (((u64) hi_cyl - lo_cyl + 1) * cylblk);

                if (!nr_sects)
                        continue;

                /* Warn user if partition end overflows u32 (AmigaDOS limit) */

                if ((start_sect + nr_sects) > UINT_MAX) {
                        pr_warn("Dev %s: partition %u (%llu-%llu) needs 64 bit device support!\n",
                                state->disk->disk_name, part,
                                start_sect, start_sect + nr_sects);
                }

                if (check_add_overflow(start_sect, nr_sects, &end_sect)) {
                        pr_err("Dev %s: partition %u (%llu-%llu) needs LBD device support, skipping partition!\n",
                                state->disk->disk_name, part,
                                start_sect, end_sect);
                        continue;
                }

                /* Tell Kernel about it */

                put_partition(state,slot++,start_sect,nr_sects);
                {
                        /* Be even more informative to aid mounting */
                        char dostype[4];
                        char tmp[42];

                        __be32 *dt = (__be32 *)dostype;
                        *dt = pb->pb_Environment[16];
                        if (dostype[3] < ' ')
                                snprintf(tmp, sizeof(tmp), " (%c%c%c^%c)",
                                        dostype[0], dostype[1],
                                        dostype[2], dostype[3] + '@' );
                        else
                                snprintf(tmp, sizeof(tmp), " (%c%c%c%c)",
                                        dostype[0], dostype[1],
                                        dostype[2], dostype[3]);
                        strlcat(state->pp_buf, tmp, PAGE_SIZE);
                        snprintf(tmp, sizeof(tmp), "(res %d spb %d)",
                                be32_to_cpu(pb->pb_Environment[6]),
                                be32_to_cpu(pb->pb_Environment[4]));
                        strlcat(state->pp_buf, tmp, PAGE_SIZE);
                }
                res = 1;
        }
        strlcat(state->pp_buf, "\n", PAGE_SIZE);

rdb_done:
        return res;
}