Add qemu 2.4.0

Change-Id: Ic99cbad4b61f8b127b7dc74d04576c0bcbaaf4f5
Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>

1 files changed, 748 insertions, 0 deletions

diff --git a/qemu/roms/seabios/src/disk.c b/qemu/roms/seabios/src/disk.c
new file mode 100644
index 000000000..0e0af24b3
--- /dev/null
+++ b/qemu/roms/seabios/src/disk.c
@@ -0,0 +1,748 @@
+// 16bit code to access hard drives.
+//
+// Copyright (C) 2008  Kevin O'Connor <kevin@koconnor.net>
+// Copyright (C) 2002  MandrakeSoft S.A.
+//
+// This file may be distributed under the terms of the GNU LGPLv3 license.
+
+#include "biosvar.h" // SET_BDA
+#include "bregs.h" // struct bregs
+#include "config.h" // CONFIG_*
+#include "hw/ata.h" // ATA_CB_DC
+#include "hw/pic.h" // pic_eoi2
+#include "output.h" // debug_enter
+#include "stacks.h" // call16_int
+#include "std/disk.h" // DISK_RET_SUCCESS
+#include "string.h" // memset
+#include "util.h" // CDRom_locks
+
+
+/****************************************************************
+ * Return status functions
+ ****************************************************************/
+
+static void
+__disk_ret(struct bregs *regs, u32 linecode, const char *fname)
+{
+    u8 code = linecode;
+    if (regs->dl < EXTSTART_HD)
+        SET_BDA(floppy_last_status, code);
+    else
+        SET_BDA(disk_last_status, code);
+    if (code)
+        __set_code_invalid(regs, linecode, fname);
+    else
+        set_code_success(regs);
+}
+
+static void
+__disk_ret_unimplemented(struct bregs *regs, u32 linecode, const char *fname)
+{
+    u8 code = linecode;
+    if (regs->dl < EXTSTART_HD)
+        SET_BDA(floppy_last_status, code);
+    else
+        SET_BDA(disk_last_status, code);
+    __set_code_unimplemented(regs, linecode, fname);
+}
+
+static void
+__disk_stub(struct bregs *regs, int lineno, const char *fname)
+{
+    __warn_unimplemented(regs, lineno, fname);
+    __disk_ret(regs, DISK_RET_SUCCESS | (lineno << 8), fname);
+}
+
+#define disk_ret(regs, code) \
+    __disk_ret((regs), (code) | (__LINE__ << 8), __func__)
+#define disk_ret_unimplemented(regs, code) \
+    __disk_ret_unimplemented((regs), (code) | (__LINE__ << 8), __func__)
+#define DISK_STUB(regs)                         \
+    __disk_stub((regs), __LINE__, __func__)
+
+
+/****************************************************************
+ * Helper functions
+ ****************************************************************/
+
+// Get the cylinders/heads/sectors for the given drive.
+static struct chs_s
+getLCHS(struct drive_s *drive_gf)
+{
+    struct chs_s res = { };
+    if (CONFIG_CDROM_EMU && drive_gf == GET_GLOBAL(cdemu_drive_gf)) {
+        // Emulated drive - get info from CDEmu.  (It's not possible to
+        // populate the geometry directly in the driveid because the
+        // geometry is only known after the bios segment is made
+        // read-only).
+        u8 sptcyl = GET_LOW(CDEmu.chs.sptcyl);
+        res.cylinder = GET_LOW(CDEmu.chs.cyllow) + ((sptcyl << 2) & 0x300) + 1;
+        res.head = GET_LOW(CDEmu.chs.heads) + 1;
+        res.sector = sptcyl & 0x3f;
+        return res;
+    }
+    res.cylinder = GET_GLOBALFLAT(drive_gf->lchs.cylinder);
+    res.head = GET_GLOBALFLAT(drive_gf->lchs.head);
+    res.sector = GET_GLOBALFLAT(drive_gf->lchs.sector);
+    return res;
+}
+
+// Perform read/write/verify using old-style chs accesses
+static void noinline
+basic_access(struct bregs *regs, struct drive_s *drive_gf, u16 command)
+{
+    struct disk_op_s dop;
+    dop.drive_gf = drive_gf;
+    dop.command = command;
+
+    u8 count = regs->al;
+    u16 cylinder = regs->ch | ((((u16)regs->cl) << 2) & 0x300);
+    u16 sector = regs->cl & 0x3f;
+    u16 head = regs->dh;
+
+    if (count > 128 || count == 0 || sector == 0) {
+        warn_invalid(regs);
+        disk_ret(regs, DISK_RET_EPARAM);
+        return;
+    }
+    dop.count = count;
+
+    struct chs_s chs = getLCHS(drive_gf);
+    u16 nlc=chs.cylinder, nlh=chs.head, nls=chs.sector;
+
+    // sanity check on cyl heads, sec
+    if (cylinder >= nlc || head >= nlh || sector > nls) {
+        warn_invalid(regs);
+        disk_ret(regs, DISK_RET_EPARAM);
+        return;
+    }
+
+    // translate lchs to lba
+    dop.lba = (((((u32)cylinder * (u32)nlh) + (u32)head) * (u32)nls)
+               + (u32)sector - 1);
+
+    dop.buf_fl = MAKE_FLATPTR(regs->es, regs->bx);
+
+    int status = send_disk_op(&dop);
+
+    regs->al = dop.count;
+
+    disk_ret(regs, status);
+}
+
+// Perform read/write/verify using new-style "int13ext" accesses.
+static void noinline
+extended_access(struct bregs *regs, struct drive_s *drive_gf, u16 command)
+{
+    struct disk_op_s dop;
+    struct int13ext_s *param_far = (struct int13ext_s*)(regs->si+0);
+    // Get lba and check.
+    dop.lba = GET_FARVAR(regs->ds, param_far->lba);
+    dop.command = command;
+    dop.drive_gf = drive_gf;
+    if (dop.lba >= GET_GLOBALFLAT(drive_gf->sectors)) {
+        warn_invalid(regs);
+        disk_ret(regs, DISK_RET_EPARAM);
+        return;
+    }
+
+    dop.buf_fl = SEGOFF_TO_FLATPTR(GET_FARVAR(regs->ds, param_far->data));
+    dop.count = GET_FARVAR(regs->ds, param_far->count);
+    if (! dop.count) {
+        // Nothing to do.
+        disk_ret(regs, DISK_RET_SUCCESS);
+        return;
+    }
+
+    int status = send_disk_op(&dop);
+
+    SET_FARVAR(regs->ds, param_far->count, dop.count);
+
+    disk_ret(regs, status);
+}
+
+
+/****************************************************************
+ * Hard Drive functions
+ ****************************************************************/
+
+// disk controller reset
+static void
+disk_1300(struct bregs *regs, struct drive_s *drive_gf)
+{
+    struct disk_op_s dop;
+    dop.drive_gf = drive_gf;
+    dop.command = CMD_RESET;
+    dop.count = 0;
+    int status = send_disk_op(&dop);
+    disk_ret(regs, status);
+}
+
+// read disk status
+static void
+disk_1301(struct bregs *regs, struct drive_s *drive_gf)
+{
+    u8 v;
+    if (regs->dl < EXTSTART_HD)
+        // Floppy
+        v = GET_BDA(floppy_last_status);
+    else
+        v = GET_BDA(disk_last_status);
+    regs->ah = v;
+    set_cf(regs, v);
+    // XXX - clear disk_last_status?
+}
+
+// read disk sectors
+static void
+disk_1302(struct bregs *regs, struct drive_s *drive_gf)
+{
+    basic_access(regs, drive_gf, CMD_READ);
+}
+
+// write disk sectors
+static void
+disk_1303(struct bregs *regs, struct drive_s *drive_gf)
+{
+    basic_access(regs, drive_gf, CMD_WRITE);
+}
+
+// verify disk sectors
+static void
+disk_1304(struct bregs *regs, struct drive_s *drive_gf)
+{
+    basic_access(regs, drive_gf, CMD_VERIFY);
+}
+
+// format disk track
+static void noinline
+disk_1305(struct bregs *regs, struct drive_s *drive_gf)
+{
+    debug_stub(regs);
+
+    struct chs_s chs = getLCHS(drive_gf);
+    u16 nlc=chs.cylinder, nlh=chs.head, nls=chs.sector;
+
+    u8 count = regs->al;
+    u8 cylinder = regs->ch;
+    u8 head = regs->dh;
+
+    if (cylinder >= nlc || head >= nlh || count == 0 || count > nls) {
+        disk_ret(regs, DISK_RET_EPARAM);
+        return;
+    }
+
+    struct disk_op_s dop;
+    dop.drive_gf = drive_gf;
+    dop.command = CMD_FORMAT;
+    dop.lba = (((u32)cylinder * (u32)nlh) + (u32)head) * (u32)nls;
+    dop.count = count;
+    dop.buf_fl = MAKE_FLATPTR(regs->es, regs->bx);
+    int status = send_disk_op(&dop);
+    disk_ret(regs, status);
+}
+
+// read disk drive parameters
+static void noinline
+disk_1308(struct bregs *regs, struct drive_s *drive_gf)
+{
+    // Get logical geometry from table
+    struct chs_s chs = getLCHS(drive_gf);
+    u16 nlc=chs.cylinder, nlh=chs.head, nls=chs.sector;
+    nlc--;
+    nlh--;
+    u8 count;
+    if (regs->dl < EXTSTART_HD) {
+        // Floppy
+        count = GET_GLOBAL(FloppyCount);
+
+        if (CONFIG_CDROM_EMU && drive_gf == GET_GLOBAL(cdemu_drive_gf))
+            regs->bx = GET_LOW(CDEmu.media) * 2;
+        else
+            regs->bx = GET_GLOBALFLAT(drive_gf->floppy_type);
+
+        // set es & di to point to 11 byte diskette param table in ROM
+        regs->es = SEG_BIOS;
+        regs->di = (u32)&diskette_param_table2;
+    } else if (regs->dl < EXTSTART_CD) {
+        // Hard drive
+        count = GET_BDA(hdcount);
+        nlc--;  // last sector reserved
+    } else {
+        // Not supported on CDROM
+        disk_ret(regs, DISK_RET_EPARAM);
+        return;
+    }
+
+    if (CONFIG_CDROM_EMU && GET_LOW(CDEmu.media)) {
+        u8 emudrive = GET_LOW(CDEmu.emulated_drive);
+        if (((emudrive ^ regs->dl) & 0x80) == 0)
+            // Note extra drive due to emulation.
+            count++;
+        if (regs->dl < EXTSTART_HD && count > 2)
+            // Max of two floppy drives.
+            count = 2;
+    }
+
+    regs->al = 0;
+    regs->ch = nlc & 0xff;
+    regs->cl = ((nlc >> 2) & 0xc0) | (nls & 0x3f);
+    regs->dh = nlh;
+
+    disk_ret(regs, DISK_RET_SUCCESS);
+    regs->dl = count;
+}
+
+// initialize drive parameters
+static void
+disk_1309(struct bregs *regs, struct drive_s *drive_gf)
+{
+    DISK_STUB(regs);
+}
+
+// seek to specified cylinder
+static void
+disk_130c(struct bregs *regs, struct drive_s *drive_gf)
+{
+    DISK_STUB(regs);
+}
+
+// alternate disk reset
+static void
+disk_130d(struct bregs *regs, struct drive_s *drive_gf)
+{
+    DISK_STUB(regs);
+}
+
+// check drive ready
+static void
+disk_1310(struct bregs *regs, struct drive_s *drive_gf)
+{
+    // should look at 40:8E also???
+
+    struct disk_op_s dop;
+    dop.drive_gf = drive_gf;
+    dop.command = CMD_ISREADY;
+    dop.count = 0;
+    int status = send_disk_op(&dop);
+    disk_ret(regs, status);
+}
+
+// recalibrate
+static void
+disk_1311(struct bregs *regs, struct drive_s *drive_gf)
+{
+    DISK_STUB(regs);
+}
+
+// controller internal diagnostic
+static void
+disk_1314(struct bregs *regs, struct drive_s *drive_gf)
+{
+    DISK_STUB(regs);
+}
+
+// read disk drive size
+static void noinline
+disk_1315(struct bregs *regs, struct drive_s *drive_gf)
+{
+    disk_ret(regs, DISK_RET_SUCCESS);
+    if (regs->dl < EXTSTART_HD || regs->dl >= EXTSTART_CD) {
+        // Floppy or cdrom
+        regs->ah = 1;
+        return;
+    }
+    // Hard drive
+
+    // Get logical geometry from table
+    struct chs_s chs = getLCHS(drive_gf);
+    u16 nlc=chs.cylinder, nlh=chs.head, nls=chs.sector;
+
+    // Compute sector count seen by int13
+    u32 lba = (u32)(nlc - 1) * (u32)nlh * (u32)nls;
+    regs->cx = lba >> 16;
+    regs->dx = lba & 0xffff;
+    regs->ah = 3; // hard disk accessible
+}
+
+static void
+disk_1316(struct bregs *regs, struct drive_s *drive_gf)
+{
+    if (regs->dl >= EXTSTART_HD) {
+        // Hard drive
+        disk_ret(regs, DISK_RET_EPARAM);
+        return;
+    }
+    disk_ret(regs, DISK_RET_ECHANGED);
+}
+
+// IBM/MS installation check
+static void
+disk_1341(struct bregs *regs, struct drive_s *drive_gf)
+{
+    regs->bx = 0xaa55;  // install check
+    regs->cx = 0x0007;  // ext disk access and edd, removable supported
+    disk_ret(regs, DISK_RET_SUCCESS);
+    regs->ah = 0x30;    // EDD 3.0
+}
+
+// IBM/MS extended read
+static void
+disk_1342(struct bregs *regs, struct drive_s *drive_gf)
+{
+    extended_access(regs, drive_gf, CMD_READ);
+}
+
+// IBM/MS extended write
+static void
+disk_1343(struct bregs *regs, struct drive_s *drive_gf)
+{
+    extended_access(regs, drive_gf, CMD_WRITE);
+}
+
+// IBM/MS verify
+static void
+disk_1344(struct bregs *regs, struct drive_s *drive_gf)
+{
+    extended_access(regs, drive_gf, CMD_VERIFY);
+}
+
+// lock
+static void
+disk_134500(struct bregs *regs, struct drive_s *drive_gf)
+{
+    int cdid = regs->dl - EXTSTART_CD;
+    u8 locks = GET_LOW(CDRom_locks[cdid]);
+    if (locks == 0xff) {
+        regs->al = 1;
+        disk_ret(regs, DISK_RET_ETOOMANYLOCKS);
+        return;
+    }
+    SET_LOW(CDRom_locks[cdid], locks + 1);
+    regs->al = 1;
+    disk_ret(regs, DISK_RET_SUCCESS);
+}
+
+// unlock
+static void
+disk_134501(struct bregs *regs, struct drive_s *drive_gf)
+{
+    int cdid = regs->dl - EXTSTART_CD;
+    u8 locks = GET_LOW(CDRom_locks[cdid]);
+    if (locks == 0x00) {
+        regs->al = 0;
+        disk_ret(regs, DISK_RET_ENOTLOCKED);
+        return;
+    }
+    locks--;
+    SET_LOW(CDRom_locks[cdid], locks);
+    regs->al = (locks ? 1 : 0);
+    disk_ret(regs, DISK_RET_SUCCESS);
+}
+
+// status
+static void
+disk_134502(struct bregs *regs, struct drive_s *drive_gf)
+{
+    int cdid = regs->dl - EXTSTART_CD;
+    u8 locks = GET_LOW(CDRom_locks[cdid]);
+    regs->al = (locks ? 1 : 0);
+    disk_ret(regs, DISK_RET_SUCCESS);
+}
+
+static void
+disk_1345XX(struct bregs *regs, struct drive_s *drive_gf)
+{
+    disk_ret_unimplemented(regs, DISK_RET_EPARAM);
+}
+
+// IBM/MS lock/unlock drive
+static void
+disk_1345(struct bregs *regs, struct drive_s *drive_gf)
+{
+    if (regs->dl < EXTSTART_CD) {
+        // Always success for HD
+        disk_ret(regs, DISK_RET_SUCCESS);
+        return;
+    }
+
+    switch (regs->al) {
+    case 0x00: disk_134500(regs, drive_gf); break;
+    case 0x01: disk_134501(regs, drive_gf); break;
+    case 0x02: disk_134502(regs, drive_gf); break;
+    default:   disk_1345XX(regs, drive_gf); break;
+    }
+}
+
+// IBM/MS eject media
+static void noinline
+disk_1346(struct bregs *regs, struct drive_s *drive_gf)
+{
+    if (regs->dl < EXTSTART_CD) {
+        // Volume Not Removable
+        disk_ret(regs, DISK_RET_ENOTREMOVABLE);
+        return;
+    }
+
+    int cdid = regs->dl - EXTSTART_CD;
+    u8 locks = GET_LOW(CDRom_locks[cdid]);
+    if (locks != 0) {
+        disk_ret(regs, DISK_RET_ELOCKED);
+        return;
+    }
+
+    // FIXME should handle 0x31 no media in device
+    // FIXME should handle 0xb5 valid request failed
+
+    // Call removable media eject
+    struct bregs br;
+    memset(&br, 0, sizeof(br));
+    br.ah = 0x52;
+    br.dl = regs->dl;
+    call16_int(0x15, &br);
+
+    if (br.ah || br.flags & F_CF) {
+        disk_ret(regs, DISK_RET_ELOCKED);
+        return;
+    }
+    disk_ret(regs, DISK_RET_SUCCESS);
+}
+
+// IBM/MS extended seek
+static void
+disk_1347(struct bregs *regs, struct drive_s *drive_gf)
+{
+    extended_access(regs, drive_gf, CMD_SEEK);
+}
+
+// IBM/MS get drive parameters
+static void
+disk_1348(struct bregs *regs, struct drive_s *drive_gf)
+{
+    int ret = fill_edd(regs->ds, (void*)(regs->si+0), drive_gf);
+    disk_ret(regs, ret);
+}
+
+// IBM/MS extended media change
+static void
+disk_1349(struct bregs *regs, struct drive_s *drive_gf)
+{
+    if (regs->dl < EXTSTART_CD) {
+        // Always success for HD
+        disk_ret(regs, DISK_RET_SUCCESS);
+        return;
+    }
+    set_invalid(regs);
+    // always send changed ??
+    regs->ah = DISK_RET_ECHANGED;
+}
+
+static void
+disk_134e01(struct bregs *regs, struct drive_s *drive_gf)
+{
+    disk_ret(regs, DISK_RET_SUCCESS);
+}
+
+static void
+disk_134e03(struct bregs *regs, struct drive_s *drive_gf)
+{
+    disk_ret(regs, DISK_RET_SUCCESS);
+}
+
+static void
+disk_134e04(struct bregs *regs, struct drive_s *drive_gf)
+{
+    disk_ret(regs, DISK_RET_SUCCESS);
+}
+
+static void
+disk_134e06(struct bregs *regs, struct drive_s *drive_gf)
+{
+    disk_ret(regs, DISK_RET_SUCCESS);
+}
+
+static void
+disk_134eXX(struct bregs *regs, struct drive_s *drive_gf)
+{
+    disk_ret(regs, DISK_RET_EPARAM);
+}
+
+// IBM/MS set hardware configuration
+static void
+disk_134e(struct bregs *regs, struct drive_s *drive_gf)
+{
+    switch (regs->al) {
+    case 0x01: disk_134e01(regs, drive_gf); break;
+    case 0x03: disk_134e03(regs, drive_gf); break;
+    case 0x04: disk_134e04(regs, drive_gf); break;
+    case 0x06: disk_134e06(regs, drive_gf); break;
+    default:   disk_134eXX(regs, drive_gf); break;
+    }
+}
+
+static void
+disk_13XX(struct bregs *regs, struct drive_s *drive_gf)
+{
+    disk_ret_unimplemented(regs, DISK_RET_EPARAM);
+}
+
+static void
+disk_13(struct bregs *regs, struct drive_s *drive_gf)
+{
+    //debug_stub(regs);
+
+    // clear completion flag
+    SET_BDA(disk_interrupt_flag, 0);
+
+    switch (regs->ah) {
+    case 0x00: disk_1300(regs, drive_gf); break;
+    case 0x01: disk_1301(regs, drive_gf); break;
+    case 0x02: disk_1302(regs, drive_gf); break;
+    case 0x03: disk_1303(regs, drive_gf); break;
+    case 0x04: disk_1304(regs, drive_gf); break;
+    case 0x05: disk_1305(regs, drive_gf); break;
+    case 0x08: disk_1308(regs, drive_gf); break;
+    case 0x09: disk_1309(regs, drive_gf); break;
+    case 0x0c: disk_130c(regs, drive_gf); break;
+    case 0x0d: disk_130d(regs, drive_gf); break;
+    case 0x10: disk_1310(regs, drive_gf); break;
+    case 0x11: disk_1311(regs, drive_gf); break;
+    case 0x14: disk_1314(regs, drive_gf); break;
+    case 0x15: disk_1315(regs, drive_gf); break;
+    case 0x16: disk_1316(regs, drive_gf); break;
+    case 0x41: disk_1341(regs, drive_gf); break;
+    case 0x42: disk_1342(regs, drive_gf); break;
+    case 0x43: disk_1343(regs, drive_gf); break;
+    case 0x44: disk_1344(regs, drive_gf); break;
+    case 0x45: disk_1345(regs, drive_gf); break;
+    case 0x46: disk_1346(regs, drive_gf); break;
+    case 0x47: disk_1347(regs, drive_gf); break;
+    case 0x48: disk_1348(regs, drive_gf); break;
+    case 0x49: disk_1349(regs, drive_gf); break;
+    case 0x4e: disk_134e(regs, drive_gf); break;
+    default:   disk_13XX(regs, drive_gf); break;
+    }
+}
+
+static void
+floppy_13(struct bregs *regs, struct drive_s *drive_gf)
+{
+    // Only limited commands are supported on floppies.
+    switch (regs->ah) {
+    case 0x00:
+    case 0x01:
+    case 0x02:
+    case 0x03:
+    case 0x04:
+    case 0x05:
+    case 0x08:
+    case 0x15:
+    case 0x16:
+        disk_13(regs, drive_gf);
+        break;
+    default:   disk_13XX(regs, drive_gf); break;
+    }
+}
+
+// ElTorito - Terminate disk emu
+static void
+cdemu_134b(struct bregs *regs)
+{
+    memcpy_far(regs->ds, (void*)(regs->si+0), SEG_LOW, &CDEmu, sizeof(CDEmu));
+
+    // If we have to terminate emulation
+    if (regs->al == 0x00) {
+        // FIXME ElTorito Various. Should be handled accordingly to spec
+        SET_LOW(CDEmu.media, 0x00); // bye bye
+
+        // XXX - update floppy/hd count.
+    }
+
+    disk_ret(regs, DISK_RET_SUCCESS);
+}
+
+
+/****************************************************************
+ * Entry points
+ ****************************************************************/
+
+static void
+handle_legacy_disk(struct bregs *regs, u8 extdrive)
+{
+    if (! CONFIG_DRIVES) {
+        // XXX - support handle_1301 anyway?
+        disk_ret(regs, DISK_RET_EPARAM);
+        return;
+    }
+
+    if (extdrive < EXTSTART_HD) {
+        struct drive_s *drive_gf = getDrive(EXTTYPE_FLOPPY, extdrive);
+        if (!drive_gf)
+            goto fail;
+        floppy_13(regs, drive_gf);
+        return;
+    }
+
+    struct drive_s *drive_gf;
+    if (extdrive >= EXTSTART_CD)
+        drive_gf = getDrive(EXTTYPE_CD, extdrive - EXTSTART_CD);
+    else
+        drive_gf = getDrive(EXTTYPE_HD, extdrive - EXTSTART_HD);
+    if (!drive_gf)
+        goto fail;
+    disk_13(regs, drive_gf);
+    return;
+
+fail:
+    // XXX - support 1301/1308/1315 anyway?
+    disk_ret(regs, DISK_RET_EPARAM);
+}
+
+void VISIBLE16
+handle_40(struct bregs *regs)
+{
+    debug_enter(regs, DEBUG_HDL_40);
+    handle_legacy_disk(regs, regs->dl);
+}
+
+// INT 13h Fixed Disk Services Entry Point
+void VISIBLE16
+handle_13(struct bregs *regs)
+{
+    debug_enter(regs, DEBUG_HDL_13);
+    u8 extdrive = regs->dl;
+
+    if (CONFIG_CDROM_EMU) {
+        if (regs->ah == 0x4b) {
+            cdemu_134b(regs);
+            return;
+        }
+        if (GET_LOW(CDEmu.media)) {
+            u8 emudrive = GET_LOW(CDEmu.emulated_drive);
+            if (extdrive == emudrive) {
+                // Access to an emulated drive.
+                struct drive_s *cdemu_gf = GET_GLOBAL(cdemu_drive_gf);
+                if (regs->ah > 0x16) {
+                    // Only old-style commands supported.
+                    disk_13XX(regs, cdemu_gf);
+                    return;
+                }
+                disk_13(regs, cdemu_gf);
+                return;
+            }
+            if (extdrive < EXTSTART_CD && ((emudrive ^ extdrive) & 0x80) == 0)
+                // Adjust id to make room for emulated drive.
+                extdrive--;
+        }
+    }
+    handle_legacy_disk(regs, extdrive);
+}
+
+// record completion in BIOS task complete flag
+void VISIBLE16
+handle_76(void)
+{
+    debug_isr(DEBUG_ISR_76);
+    SET_BDA(disk_interrupt_flag, 0xff);
+    pic_eoi2();
+}