/*
 * QEMU S390 bootmap interpreter
 *
 * Copyright (c) 2009 Alexander Graf <agraf@suse.de>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or (at
 * your option) any later version. See the COPYING file in the top-level
 * directory.
 */

#include "s390-ccw.h"

// #define DEBUG_FALLBACK

#ifdef DEBUG_FALLBACK
#define dputs(txt) \
    do { sclp_print("zipl: " txt); } while (0)
#else
#define dputs(fmt, ...) \
    do { } while (0)
#endif

struct scsi_blockptr {
    uint64_t blockno;
    uint16_t size;
    uint16_t blockct;
    uint8_t reserved[4];
} __attribute__ ((packed));

struct component_entry {
    struct scsi_blockptr data;
    uint8_t pad[7];
    uint8_t component_type;
    uint64_t load_address;
} __attribute((packed));

struct component_header {
    uint8_t magic[4];
    uint8_t type;
    uint8_t reserved[27];
} __attribute((packed));

struct mbr {
    uint8_t magic[4];
    uint32_t version_id;
    uint8_t reserved[8];
    struct scsi_blockptr blockptr;
} __attribute__ ((packed));

#define ZIPL_MAGIC			"zIPL"

#define ZIPL_COMP_HEADER_IPL		0x00
#define ZIPL_COMP_HEADER_DUMP		0x01

#define ZIPL_COMP_ENTRY_LOAD		0x02
#define ZIPL_COMP_ENTRY_EXEC		0x01

/* Scratch space */
static uint8_t sec[SECTOR_SIZE] __attribute__((__aligned__(SECTOR_SIZE)));

typedef struct ResetInfo {
    uint32_t ipl_mask;
    uint32_t ipl_addr;
    uint32_t ipl_continue;
} ResetInfo;

ResetInfo save;

static void jump_to_IPL_2(void)
{
    ResetInfo *current = 0;

    void (*ipl)(void) = (void *) (uint64_t) current->ipl_continue;
    debug_print_addr("set IPL addr to", ipl);

    /* Ensure the guest output starts fresh */
    sclp_print("\n");

    *current = save;
    ipl(); /* should not return */
}

static void jump_to_IPL_code(uint64_t address)
{
    /*
     * The IPL PSW is at address 0. We also must not overwrite the
     * content of non-BIOS memory after we loaded the guest, so we
     * save the original content and restore it in jump_to_IPL_2.
     */
    ResetInfo *current = 0;

    save = *current;
    current->ipl_addr = (uint32_t) (uint64_t) &jump_to_IPL_2;
    current->ipl_continue = address & 0x7fffffff;

    /*
     * HACK ALERT.
     * We use the load normal reset to keep r15 unchanged. jump_to_IPL_2
     * can then use r15 as its stack pointer.
     */
    asm volatile("lghi 1,1\n\t"
                 "diag 1,1,0x308\n\t"
                 : : : "1", "memory");
    virtio_panic("\n! IPL returns !\n");
}

/* Check for ZIPL magic. Returns 0 if not matched. */
static int zipl_magic(uint8_t *ptr)
{
    uint32_t *p = (void*)ptr;
    uint32_t *z = (void*)ZIPL_MAGIC;

    if (*p != *z) {
        debug_print_int("invalid magic", *p);
        virtio_panic("invalid magic");
    }

    return 1;
}

#define FREE_SPACE_FILLER '\xAA'

static inline bool unused_space(const void *p, unsigned int size)
{
    int i;
    const unsigned char *m = p;

    for (i = 0; i < size; i++) {
        if (m[i] != FREE_SPACE_FILLER) {
            return false;
        }
    }
    return true;
}

static int zipl_load_segment(struct component_entry *entry)
{
    const int max_entries = (SECTOR_SIZE / sizeof(struct scsi_blockptr));
    struct scsi_blockptr *bprs = (void*)sec;
    const int bprs_size = sizeof(sec);
    uint64_t blockno;
    long address;
    int i;

    blockno = entry->data.blockno;
    address = entry->load_address;

    debug_print_int("loading segment at block", blockno);
    debug_print_int("addr", address);

    do {
        memset(bprs, FREE_SPACE_FILLER, bprs_size);
        if (virtio_read(blockno, (uint8_t *)bprs)) {
            debug_print_int("failed reading bprs at", blockno);
            goto fail;
        }

        for (i = 0;; i++) {
            u64 *cur_desc = (void*)&bprs[i];

            blockno = bprs[i].blockno;
            if (!blockno)
                break;

            /* we need the updated blockno for the next indirect entry in the
               chain, but don't want to advance address */
            if (i == (max_entries - 1))
                break;

            if (bprs[i].blockct == 0 && unused_space(&bprs[i + 1],
                sizeof(struct scsi_blockptr))) {
                /* This is a "continue" pointer.
                 * This ptr is the last one in the current script section.
                 * I.e. the next ptr must point to the unused memory area.
                 * The blockno is not zero, so the upper loop must continue
                 * reading next section of BPRS.
                 */
                break;
            }
            address = virtio_load_direct(cur_desc[0], cur_desc[1], 0,
                                         (void*)address);
            if (address == -1)
                goto fail;
        }
    } while (blockno);

    return 0;

fail:
    sclp_print("failed loading segment\n");
    return -1;
}

/* Run a zipl program */
static int zipl_run(struct scsi_blockptr *pte)
{
    struct component_header *header;
    struct component_entry *entry;
    uint8_t tmp_sec[SECTOR_SIZE];

    virtio_read(pte->blockno, tmp_sec);
    header = (struct component_header *)tmp_sec;

    if (!zipl_magic(tmp_sec)) {
        goto fail;
    }

    if (header->type != ZIPL_COMP_HEADER_IPL) {
        goto fail;
    }

    dputs("start loading images\n");

    /* Load image(s) into RAM */
    entry = (struct component_entry *)(&header[1]);
    while (entry->component_type == ZIPL_COMP_ENTRY_LOAD) {
        if (zipl_load_segment(entry) < 0) {
            goto fail;
        }

        entry++;

        if ((uint8_t*)(&entry[1]) > (tmp_sec + SECTOR_SIZE)) {
            goto fail;
        }
    }

    if (entry->component_type != ZIPL_COMP_ENTRY_EXEC) {
        goto fail;
    }

    /* should not return */
    jump_to_IPL_code(entry->load_address);

    return 0;

fail:
    sclp_print("failed running zipl\n");
    return -1;
}

int zipl_load(void)
{
    struct mbr *mbr = (void*)sec;
    uint8_t *ns, *ns_end;
    int program_table_entries = 0;
    int pte_len = sizeof(struct scsi_blockptr);
    struct scsi_blockptr *prog_table_entry;
    const char *error = "";

    /* Grab the MBR */
    virtio_read(0, (void*)mbr);

    dputs("checking magic\n");

    if (!zipl_magic(mbr->magic)) {
        error = "zipl_magic 1";
        goto fail;
    }

    debug_print_int("program table", mbr->blockptr.blockno);

    /* Parse the program table */
    if (virtio_read(mbr->blockptr.blockno, sec)) {
        error = "virtio_read";
        goto fail;
    }

    if (!zipl_magic(sec)) {
        error = "zipl_magic 2";
        goto fail;
    }

    ns_end = sec + SECTOR_SIZE;
    for (ns = (sec + pte_len); (ns + pte_len) < ns_end; ns++) {
        prog_table_entry = (struct scsi_blockptr *)ns;
        if (!prog_table_entry->blockno) {
            break;
        }

        program_table_entries++;
    }

    debug_print_int("program table entries", program_table_entries);

    if (!program_table_entries) {
        goto fail;
    }

    /* Run the default entry */

    prog_table_entry = (struct scsi_blockptr *)(sec + pte_len);

    return zipl_run(prog_table_entry);

fail:
    sclp_print("failed loading zipl: ");
    sclp_print(error);
    sclp_print("\n");
    return -1;
}