/* * Copyright (C) 2006 Michael Brown . * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation; either version 2 of the * License, or any later version. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ FILE_LICENCE ( GPL2_OR_LATER ); #include #include #include #include #include #include #include #include #include #include #include #include #include /** @file * * INT 13 emulation * * This module provides a mechanism for exporting block devices via * the BIOS INT 13 disk interrupt interface. * */ /** Vector for chaining to other INT 13 handlers */ static struct segoff __text16 ( int13_vector ); #define int13_vector __use_text16 ( int13_vector ) /** Assembly wrapper */ extern void int13_wrapper ( void ); /** List of registered emulated drives */ static LIST_HEAD ( drives ); /** * Number of BIOS drives * * Note that this is the number of drives in the system as a whole * (i.e. a mirror of the counter at 40:75), rather than a count of the * number of emulated drives. */ static uint8_t num_drives; /** * Update BIOS drive count */ static void int13_set_num_drives ( void ) { struct int13_drive *drive; /* Get current drive count */ get_real ( num_drives, BDA_SEG, BDA_NUM_DRIVES ); /* Ensure count is large enough to cover all of our emulated drives */ list_for_each_entry ( drive, &drives, list ) { if ( num_drives <= ( drive->drive & 0x7f ) ) num_drives = ( ( drive->drive & 0x7f ) + 1 ); } /* Update current drive count */ put_real ( num_drives, BDA_SEG, BDA_NUM_DRIVES ); } /** * Check number of drives */ static void int13_check_num_drives ( void ) { uint8_t check_num_drives; get_real ( check_num_drives, BDA_SEG, BDA_NUM_DRIVES ); if ( check_num_drives != num_drives ) { int13_set_num_drives(); DBG ( "INT13 fixing up number of drives from %d to %d\n", check_num_drives, num_drives ); } } /** * INT 13, 00 - Reset disk system * * @v drive Emulated drive * @ret status Status code */ static int int13_reset ( struct int13_drive *drive __unused, struct i386_all_regs *ix86 __unused ) { DBG ( "Reset drive\n" ); return 0; } /** * INT 13, 01 - Get status of last operation * * @v drive Emulated drive * @ret status Status code */ static int int13_get_last_status ( struct int13_drive *drive, struct i386_all_regs *ix86 __unused ) { DBG ( "Get status of last operation\n" ); return drive->last_status; } /** * Read / write sectors * * @v drive Emulated drive * @v al Number of sectors to read or write (must be nonzero) * @v ch Low bits of cylinder number * @v cl (bits 7:6) High bits of cylinder number * @v cl (bits 5:0) Sector number * @v dh Head number * @v es:bx Data buffer * @v io Read / write method * @ret status Status code * @ret al Number of sectors read or written */ static int int13_rw_sectors ( struct int13_drive *drive, struct i386_all_regs *ix86, int ( * io ) ( struct block_device *blockdev, uint64_t block, unsigned long count, userptr_t buffer ) ) { struct block_device *blockdev = drive->blockdev; unsigned int cylinder, head, sector; unsigned long lba; unsigned int count; userptr_t buffer; int rc; /* Validate blocksize */ if ( blockdev->blksize != INT13_BLKSIZE ) { DBG ( "Invalid blocksize (%zd) for non-extended read/write\n", blockdev->blksize ); return -INT13_STATUS_INVALID; } /* Calculate parameters */ cylinder = ( ( ( ix86->regs.cl & 0xc0 ) << 2 ) | ix86->regs.ch ); assert ( cylinder < drive->cylinders ); head = ix86->regs.dh; assert ( head < drive->heads ); sector = ( ix86->regs.cl & 0x3f ); assert ( ( sector >= 1 ) && ( sector <= drive->sectors_per_track ) ); lba = ( ( ( ( cylinder * drive->heads ) + head ) * drive->sectors_per_track ) + sector - 1 ); count = ix86->regs.al; buffer = real_to_user ( ix86->segs.es, ix86->regs.bx ); DBG ( "C/H/S %d/%d/%d = LBA %#lx <-> %04x:%04x (count %d)\n", cylinder, head, sector, lba, ix86->segs.es, ix86->regs.bx, count ); /* Read from / write to block device */ if ( ( rc = io ( blockdev, lba, count, buffer ) ) != 0 ) { DBG ( "INT 13 failed: %s\n", strerror ( rc ) ); return -INT13_STATUS_READ_ERROR; } return 0; } /** * INT 13, 02 - Read sectors * * @v drive Emulated drive * @v al Number of sectors to read (must be nonzero) * @v ch Low bits of cylinder number * @v cl (bits 7:6) High bits of cylinder number * @v cl (bits 5:0) Sector number * @v dh Head number * @v es:bx Data buffer * @ret status Status code * @ret al Number of sectors read */ static int int13_read_sectors ( struct int13_drive *drive, struct i386_all_regs *ix86 ) { DBG ( "Read: " ); return int13_rw_sectors ( drive, ix86, drive->blockdev->op->read ); } /** * INT 13, 03 - Write sectors * * @v drive Emulated drive * @v al Number of sectors to write (must be nonzero) * @v ch Low bits of cylinder number * @v cl (bits 7:6) High bits of cylinder number * @v cl (bits 5:0) Sector number * @v dh Head number * @v es:bx Data buffer * @ret status Status code * @ret al Number of sectors written */ static int int13_write_sectors ( struct int13_drive *drive, struct i386_all_regs *ix86 ) { DBG ( "Write: " ); return int13_rw_sectors ( drive, ix86, drive->blockdev->op->write ); } /** * INT 13, 08 - Get drive parameters * * @v drive Emulated drive * @ret status Status code * @ret ch Low bits of maximum cylinder number * @ret cl (bits 7:6) High bits of maximum cylinder number * @ret cl (bits 5:0) Maximum sector number * @ret dh Maximum head number * @ret dl Number of drives */ static int int13_get_parameters ( struct int13_drive *drive, struct i386_all_regs *ix86 ) { unsigned int max_cylinder = drive->cylinders - 1; unsigned int max_head = drive->heads - 1; unsigned int max_sector = drive->sectors_per_track; /* sic */ DBG ( "Get drive parameters\n" ); ix86->regs.ch = ( max_cylinder & 0xff ); ix86->regs.cl = ( ( ( max_cylinder >> 8 ) << 6 ) | max_sector ); ix86->regs.dh = max_head; get_real ( ix86->regs.dl, BDA_SEG, BDA_NUM_DRIVES ); return 0; } /** * INT 13, 15 - Get disk type * * @v drive Emulated drive * @ret ah Type code * @ret cx:dx Sector count * @ret status Status code / disk type */ static int int13_get_disk_type ( struct int13_drive *drive, struct i386_all_regs *ix86 ) { uint32_t blocks; DBG ( "Get disk type\n" ); blocks = ( ( drive->blockdev->blocks <= 0xffffffffUL ) ? drive->blockdev->blocks : 0xffffffffUL ); ix86->regs.cx = ( blocks >> 16 ); ix86->regs.dx = ( blocks & 0xffff ); return INT13_DISK_TYPE_HDD; } /** * INT 13, 41 - Extensions installation check * * @v drive Emulated drive * @v bx 0x55aa * @ret bx 0xaa55 * @ret cx Extensions API support bitmap * @ret status Status code / API version */ static int int13_extension_check ( struct int13_drive *drive __unused, struct i386_all_regs *ix86 ) { if ( ix86->regs.bx == 0x55aa ) { DBG ( "INT 13 extensions installation check\n" ); ix86->regs.bx = 0xaa55; ix86->regs.cx = INT13_EXTENSION_LINEAR; return INT13_EXTENSION_VER_1_X; } else { return -INT13_STATUS_INVALID; } } /** * Extended read / write * * @v drive Emulated drive * @v ds:si Disk address packet * @v io Read / write method * @ret status Status code */ static int int13_extended_rw ( struct int13_drive *drive, struct i386_all_regs *ix86, int ( * io ) ( struct block_device *blockdev, uint64_t block, unsigned long count, userptr_t buffer ) ) { struct block_device *blockdev = drive->blockdev; struct int13_disk_address addr; uint64_t lba; unsigned long count; userptr_t buffer; int rc; /* Read parameters from disk address structure */ copy_from_real ( &addr, ix86->segs.ds, ix86->regs.si, sizeof ( addr )); lba = addr.lba; count = addr.count; buffer = real_to_user ( addr.buffer.segment, addr.buffer.offset ); DBG ( "LBA %#llx <-> %04x:%04x (count %ld)\n", (unsigned long long)lba, addr.buffer.segment, addr.buffer.offset, count ); /* Read from / write to block device */ if ( ( rc = io ( blockdev, lba, count, buffer ) ) != 0 ) { DBG ( "INT 13 failed: %s\n", strerror ( rc ) ); return -INT13_STATUS_READ_ERROR; } return 0; } /** * INT 13, 42 - Extended read * * @v drive Emulated drive * @v ds:si Disk address packet * @ret status Status code */ static int int13_extended_read ( struct int13_drive *drive, struct i386_all_regs *ix86 ) { DBG ( "Extended read: " ); return int13_extended_rw ( drive, ix86, drive->blockdev->op->read ); } /** * INT 13, 43 - Extended write * * @v drive Emulated drive * @v ds:si Disk address packet * @ret status Status code */ static int int13_extended_write ( struct int13_drive *drive, struct i386_all_regs *ix86 ) { DBG ( "Extended write: " ); return int13_extended_rw ( drive, ix86, drive->blockdev->op->write ); } /** * INT 13, 48 - Get extended parameters * * @v drive Emulated drive * @v ds:si Drive parameter table * @ret status Status code */ static int int13_get_extended_parameters ( struct int13_drive *drive, struct i386_all_regs *ix86 ) { struct int13_disk_parameters params = { .bufsize = sizeof ( params ), .flags = INT13_FL_DMA_TRANSPARENT, .cylinders = drive->cylinders, .heads = drive->heads, .sectors_per_track = drive->sectors_per_track, .sectors = drive->blockdev->blocks, .sector_size = drive->blockdev->blksize, }; DBG ( "Get extended drive parameters to %04x:%04x\n", ix86->segs.ds, ix86->regs.si ); copy_to_real ( ix86->segs.ds, ix86->regs.si, ¶ms, sizeof ( params ) ); return 0; } /** * INT 13 handler * */ static __asmcall void int13 ( struct i386_all_regs *ix86 ) { int command = ix86->regs.ah; unsigned int bios_drive = ix86->regs.dl; struct int13_drive *drive; int status; /* Check BIOS hasn't killed off our drive */ int13_check_num_drives(); list_for_each_entry ( drive, &drives, list ) { if ( bios_drive != drive->drive ) { /* Remap any accesses to this drive's natural number */ if ( bios_drive == drive->natural_drive ) { DBG ( "INT 13,%04x (%02x) remapped to " "(%02x)\n", ix86->regs.ax, bios_drive, drive->drive ); ix86->regs.dl = drive->drive; return; } continue; } DBG ( "INT 13,%04x (%02x): ", ix86->regs.ax, drive->drive ); switch ( command ) { case INT13_RESET: status = int13_reset ( drive, ix86 ); break; case INT13_GET_LAST_STATUS: status = int13_get_last_status ( drive, ix86 ); break; case INT13_READ_SECTORS: status = int13_read_sectors ( drive, ix86 ); break; case INT13_WRITE_SECTORS: status = int13_write_sectors ( drive, ix86 ); break; case INT13_GET_PARAMETERS: status = int13_get_parameters ( drive, ix86 ); break; case INT13_GET_DISK_TYPE: status = int13_get_disk_type ( drive, ix86 ); break; case INT13_EXTENSION_CHECK: status = int13_extension_check ( drive, ix86 ); break; case INT13_EXTENDED_READ: status = int13_extended_read ( drive, ix86 ); break; case INT13_EXTENDED_WRITE: status = int13_extended_write ( drive, ix86 ); break; case INT13_GET_EXTENDED_PARAMETERS: status = int13_get_extended_parameters ( drive, ix86 ); break; default: DBG ( "*** Unrecognised INT 13 ***\n" ); status = -INT13_STATUS_INVALID; break; } /* Store status for INT 13,01 */ drive->last_status = status; /* Negative status indicates an error */ if ( status < 0 ) { status = -status; DBG ( "INT 13 returning failure status %x\n", status ); } else { ix86->flags &= ~CF; } ix86->regs.ah = status; /* Set OF to indicate to wrapper not to chain this call */ ix86->flags |= OF; return; } } /** * Hook INT 13 handler * */ static void hook_int13 ( void ) { /* Assembly wrapper to call int13(). int13() sets OF if we * should not chain to the previous handler. (The wrapper * clears CF and OF before calling int13()). */ __asm__ __volatile__ ( TEXT16_CODE ( "\nint13_wrapper:\n\t" /* Preserve %ax and %dx for future reference */ "pushw %%bp\n\t" "movw %%sp, %%bp\n\t" "pushw %%ax\n\t" "pushw %%dx\n\t" /* Clear OF, set CF, call int13() */ "orb $0, %%al\n\t" "stc\n\t" "pushl %0\n\t" "pushw %%cs\n\t" "call prot_call\n\t" /* Chain if OF not set */ "jo 1f\n\t" "pushfw\n\t" "lcall *%%cs:int13_vector\n\t" "\n1:\n\t" /* Overwrite flags for iret */ "pushfw\n\t" "popw 6(%%bp)\n\t" /* Fix up %dl: * * INT 13,15 : do nothing * INT 13,08 : load with number of drives * all others: restore original value */ "cmpb $0x15, -1(%%bp)\n\t" "je 2f\n\t" "movb -4(%%bp), %%dl\n\t" "cmpb $0x08, -1(%%bp)\n\t" "jne 2f\n\t" "pushw %%ds\n\t" "pushw %1\n\t" "popw %%ds\n\t" "movb %c2, %%dl\n\t" "popw %%ds\n\t" /* Return */ "\n2:\n\t" "movw %%bp, %%sp\n\t" "popw %%bp\n\t" "iret\n\t" ) : : "i" ( int13 ), "i" ( BDA_SEG ), "i" ( BDA_NUM_DRIVES ) ); hook_bios_interrupt ( 0x13, ( unsigned int ) int13_wrapper, &int13_vector ); } /** * Unhook INT 13 handler */ static void unhook_int13 ( void ) { unhook_bios_interrupt ( 0x13, ( unsigned int ) int13_wrapper, &int13_vector ); } /** * Guess INT 13 drive geometry * * @v drive Emulated drive * * Guesses the drive geometry by inspecting the partition table. */ static void guess_int13_geometry ( struct int13_drive *drive ) { struct master_boot_record mbr; struct partition_table_entry *partition; unsigned int guessed_heads = 255; unsigned int guessed_sectors_per_track = 63; unsigned long blocks; unsigned long blocks_per_cyl; unsigned int i; /* Don't even try when the blksize is invalid for C/H/S access */ if ( drive->blockdev->blksize != INT13_BLKSIZE ) return; /* Scan through partition table and modify guesses for heads * and sectors_per_track if we find any used partitions. */ if ( drive->blockdev->op->read ( drive->blockdev, 0, 1, virt_to_user ( &mbr ) ) == 0 ) { for ( i = 0 ; i < 4 ; i++ ) { partition = &mbr.partitions[i]; if ( ! partition->type ) continue; guessed_heads = ( PART_HEAD ( partition->chs_end ) + 1 ); guessed_sectors_per_track = PART_SECTOR ( partition->chs_end ); DBG ( "Guessing C/H/S xx/%d/%d based on partition " "%d\n", guessed_heads, guessed_sectors_per_track, ( i + 1 ) ); } } else { DBG ( "Could not read partition table to guess geometry\n" ); } /* Apply guesses if no geometry already specified */ if ( ! drive->heads ) drive->heads = guessed_heads; if ( ! drive->sectors_per_track ) drive->sectors_per_track = guessed_sectors_per_track; if ( ! drive->cylinders ) { /* Avoid attempting a 64-bit divide on a 32-bit system */ blocks = ( ( drive->blockdev->blocks <= ULONG_MAX ) ? drive->blockdev->blocks : ULONG_MAX ); blocks_per_cyl = ( drive->heads * drive->sectors_per_track ); assert ( blocks_per_cyl != 0 ); drive->cylinders = ( blocks / blocks_per_cyl ); if ( drive->cylinders > 1024 ) drive->cylinders = 1024; } } /** * Register INT 13 emulated drive * * @v drive Emulated drive * * Registers the drive with the INT 13 emulation subsystem, and hooks * the INT 13 interrupt vector (if not already hooked). * * The underlying block device must be valid. A drive number and * geometry will be assigned if left blank. */ void register_int13_drive ( struct int13_drive *drive ) { uint8_t num_drives; /* Give drive a default geometry if none specified */ guess_int13_geometry ( drive ); /* Assign natural drive number */ get_real ( num_drives, BDA_SEG, BDA_NUM_DRIVES ); drive->natural_drive = ( num_drives | 0x80 ); /* Assign drive number */ if ( ( drive->drive & 0xff ) == 0xff ) { /* Drive number == -1 => use natural drive number */ drive->drive = drive->natural_drive; } else { /* Use specified drive number (+0x80 if necessary) */ drive->drive |= 0x80; } DBG ( "Registered INT13 drive %02x (naturally %02x) with C/H/S " "geometry %d/%d/%d\n", drive->drive, drive->natural_drive, drive->cylinders, drive->heads, drive->sectors_per_track ); /* Hook INT 13 vector if not already hooked */ if ( list_empty ( &drives ) ) hook_int13(); /* Add to list of emulated drives */ list_add ( &drive->list, &drives ); /* Update BIOS drive count */ int13_set_num_drives(); } /** * Unregister INT 13 emulated drive * * @v drive Emulated drive * * Unregisters the drive from the INT 13 emulation subsystem. If this * is the last emulated drive, the INT 13 vector is unhooked (if * possible). */ void unregister_int13_drive ( struct int13_drive *drive ) { /* Remove from list of emulated drives */ list_del ( &drive->list ); /* Should adjust BIOS drive count, but it's difficult to do so * reliably. */ DBG ( "Unregistered INT13 drive %02x\n", drive->drive ); /* Unhook INT 13 vector if no more drives */ if ( list_empty ( &drives ) ) unhook_int13(); } /** * Attempt to boot from an INT 13 drive * * @v drive Drive number * @ret rc Return status code * * This boots from the specified INT 13 drive by loading the Master * Boot Record to 0000:7c00 and jumping to it. INT 18 is hooked to * capture an attempt by the MBR to boot the next device. (This is * the closest thing to a return path from an MBR). * * Note that this function can never return success, by definition. */ int int13_boot ( unsigned int drive ) { struct memory_map memmap; int status, signature; int discard_c, discard_d; int rc; DBG ( "Booting from INT 13 drive %02x\n", drive ); /* Use INT 13 to read the boot sector */ __asm__ __volatile__ ( REAL_CODE ( "pushw %%es\n\t" "pushw $0\n\t" "popw %%es\n\t" "stc\n\t" "sti\n\t" "int $0x13\n\t" "sti\n\t" /* BIOS bugs */ "jc 1f\n\t" "xorl %%eax, %%eax\n\t" "\n1:\n\t" "movzwl %%es:0x7dfe, %%ebx\n\t" "popw %%es\n\t" ) : "=a" ( status ), "=b" ( signature ), "=c" ( discard_c ), "=d" ( discard_d ) : "a" ( 0x0201 ), "b" ( 0x7c00 ), "c" ( 1 ), "d" ( drive ) ); if ( status ) return -EIO; /* Check signature is correct */ if ( signature != be16_to_cpu ( 0x55aa ) ) { DBG ( "Invalid disk signature %#04x (should be 0x55aa)\n", cpu_to_be16 ( signature ) ); return -ENOEXEC; } /* Dump out memory map prior to boot, if memmap debugging is * enabled. Not required for program flow, but we have so * many problems that turn out to be memory-map related that * it's worth doing. */ get_memmap ( &memmap ); /* Jump to boot sector */ if ( ( rc = call_bootsector ( 0x0, 0x7c00, drive ) ) != 0 ) { DBG ( "INT 13 drive %02x boot returned: %s\n", drive, strerror ( rc ) ); return rc; } return -ECANCELED; /* -EIMPOSSIBLE */ }