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Added geometry-guessing code based on the partition table

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This commit is contained in:
Michael Brown 2006-09-08 22:22:03 +00:00
parent 21bc2015f2
commit 0566ab2a2f
2 changed files with 94 additions and 14 deletions
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39
src/arch/i386/include/int13.h
View File

@ -201,6 +201,45 @@ struct int13_disk_parameters {
/** @} */
/** A C/H/S address within a partition table entry */
struct partition_chs {
/** Head number */
uint8_t head;
/** Sector number, plus high 2 bits of cylinder number */
uint8_t cyl_sector;
/** Low 8 bits of cylinder number */
uint8_t cyl;
} __attribute__ (( packed ));
#define PART_HEAD(chs) ( (chs).head )
#define PART_SECTOR(chs) ( (chs).cyl_sector & 0x3f )
#define PART_CYLINDER(chs) ( (chs).cyl | ( ( (chs).cyl_sector & 0xc0 ) << 2 ) )
/** A partition table entry within the MBR */
struct partition_table_entry {
/** Bootable flag */
uint8_t bootable;
/** C/H/S start address */
struct partition_chs chs_start;
/** System indicator (partition type) */
uint8_t type;
/** C/H/S end address */
struct partition_chs chs_end;
/** Linear start address */
uint32_t start;
/** Linear length */
uint32_t length;
} __attribute__ (( packed ));
/** A Master Boot Record */
struct master_boot_record {
uint8_t pad[446];
/** Partition table */
struct partition_table_entry partitions[4];
/** 0x55aa MBR signature */
uint16_t signature;
} __attribute__ (( packed ));
extern void register_int13_drive ( struct int13_drive *drive );
extern void unregister_int13_drive ( struct int13_drive *drive );
extern int int13_boot ( unsigned int drive );

69
src/arch/i386/interface/pcbios/int13.c
View File

@ -437,6 +437,60 @@ static void unhook_int13 ( void ) {
&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;
/* Scan through partition table and modify guesses for heads
* and sectors_per_track if we find any used partitions.
*/
if ( drive->blockdev->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
*
@ -450,22 +504,9 @@ static void unhook_int13 ( void ) {
*/
void register_int13_drive ( struct int13_drive *drive ) {
uint8_t num_drives;
unsigned long blocks;
unsigned long blocks_per_cyl;
/* Give drive a default geometry if none specified */
if ( ! drive->heads )
drive->heads = 255;
if ( ! drive->sectors_per_track )
drive->sectors_per_track = 63;
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 );
}
guess_int13_geometry ( drive );
/* Assign drive number if none specified, update BIOS drive count */
get_real ( num_drives, BDA_SEG, BDA_NUM_DRIVES );