OSDev.org

Code: Select all

//harddisk.h
typedef struct __attribute__((packed))
{
	// Use the LBA values. The CHS isn't read correctly for some reason.
	uint_8 active;
	uint_8 start_head;
	uint_8 start_sector;
	uint_8 start_cylinder;
	uint_8 partition_type;
	uint_8 end_head;
	uint_8 end_sector;
	uint_8 end_cylinder;
	uint_32 start_lba;
	uint_32 end_lba;
} partition;

typedef struct __attribute__((packed))
{
	uint_8 useless_data[446];
	partition partitions[4];
	uint_16 signature;
} partition_table;

typedef struct
{
	partition part;
	uint_8 drive;
} partition_info;

Code: Select all

#include <harddisk.h>
#include <types.h>

#define CMD_READ	0x20
#define CMD_WRITE	0x30
// NR = no retry
#define CMD_READ_NR	0x21
#define CMD_WRITE_NR	0x31

void read_sector(uint_8 drivenum, uint_16 cylinder, uint_8 sector, uint_8 head, uint_8 *buffer)
{
	uint_8 drive;
	uint_16 port_base;
	switch (drivenum)
	{
		case 0:
		case 1:
			port_base = 0x1f0;
			break;
		case 2:
		case 3:
			port_base = 0x170;
			break;
		// If I ever get bored enough to add them, 0x1e8 for
		// ide2 and 0x168 for ide3.
	}

	drive = 0xA0;
	if (drivenum % 2) drive |= 0x10;
	drive |= head;
	
	// send some info to the IDE controller
	// drive to read from
	outportb(port_base + 6, drive);
	// just one sector
	outportb(port_base + 2, 1);
	// sector
	outportb(port_base + 3, sector);
	// extract low and high bytes from cylinder number
	uint_8 cyl_low = cylinder & 0xFF;
	uint_8 cyl_high = (cylinder & 0xFF00) >> 8;
	// ...then send them to the IDE controller
	outportb(port_base + 4, cyl_low);
	outportb(port_base + 5, cyl_high);
	// and now send the command
	outportb(port_base + 7, CMD_READ);

	// wait for it to finish reading
	while (inportb(port_base + 7) & 0x80) printf("waiting\n");

	// now read the data in from the buffer
	int i;
	for (i = 0; i < 256; i++)
	{
		// No, I don't have the slightest clue what this does.
		*(uint_16 *)(buffer + 2 * i) = inportw(port_base);
	}
}

partition_info find_boot_partition(uint_8 ptype)
{
	int boot_drive = -1;
	int boot_partition = -1;
	partition bp;
	int i, j;
	for (i = 0; i < 4; i++)
	{
		partition_table mbr;
		read_sector(i, 0, 1, 0, &mbr);
		for(j = 0; j < 4; j++)
		{
			if (mbr.partitions[i].partition_type == ptype)
			{
				printf("Found Popcorn partition on /device/hd%d/%d\n", i, j);
				boot_drive = i;
				boot_partition = j;
				bp = mbr.partitions[j];
				break;
			}
		}
		// if we already found a partition, stop looking
		if (boot_partition != -1)
			break;
	}
	if (boot_partition == -1)
		panic("Couldn't find a Popcorn partition!");

	partition_info pi;
	pi.part = bp;
	pi.drive = boot_drive;
	return pi;
}