diff options
Diffstat (limited to 'contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/bootpart.S')
| -rw-r--r-- | contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/bootpart.S | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/bootpart.S b/contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/bootpart.S new file mode 100644 index 0000000..968da1a --- /dev/null +++ b/contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/bootpart.S @@ -0,0 +1,218 @@ +FILE_LICENCE ( GPL2_OR_LATER ) + +#define BOOT_SEG 0x07c0 +#define EXEC_SEG 0x0100 +#define STACK_SEG 0x0200 +#define STACK_SIZE 0x2000 + + .text + .arch i386 + .section ".prefix", "awx", @progbits + .code16 + +/* + * Find active partition + * + * Parameters: + * %dl : BIOS drive number + * %bp : Active partition handler routine + */ +find_active_partition: + /* Set up stack at STACK_SEG:STACK_SIZE */ + movw $STACK_SEG, %ax + movw %ax, %ss + movw $STACK_SIZE, %sp + + /* Relocate self to EXEC_SEG */ + pushw $BOOT_SEG + popw %ds + pushw $EXEC_SEG + popw %es + xorw %si, %si + xorw %di, %di + movw $0x200, %cx + rep movsb + ljmp $EXEC_SEG, $1f +1: pushw %ds + popw %es + pushw %cs + popw %ds + + /* Check for LBA extensions */ + movb $0x41, %ah + movw $0x55aa, %bx + stc + int $0x13 + jc 1f + cmpw $0xaa55, %bx + jne 1f + movw $read_lba, read_sectors +1: + /* Read and process root partition table */ + xorb %dh, %dh + movw $0x0001, %cx + xorl %esi, %esi + xorl %edi, %edi + call process_table + + /* Print failure message */ + movw $10f, %si + jmp boot_error +10: .asciz "Could not locate active partition\r\n" + +/* + * Print failure message and boot next device + * + * Parameters: + * %si : Failure string + */ +boot_error: + cld + movw $0x0007, %bx + movb $0x0e, %ah +1: lodsb + testb %al, %al + je 99f + int $0x10 + jmp 1b +99: /* Boot next device */ + int $0x18 + +/* + * Process partition table + * + * Parameters: + * %dl : BIOS drive number + * %dh : Head + * %cl : Sector (bits 0-5), high two bits of cylinder (bits 6-7) + * %ch : Low eight bits of cylinder + * %esi:%edi : LBA address + * %bp : Active partition handler routine + * + * Returns: + * CF set on error + */ +process_table: + pushal + call read_boot_sector + jc 99f + movw $446, %bx +1: call process_partition + addw $16, %bx + cmpw $510, %bx + jne 1b +99: popal + ret + +/* + * Process partition + * + * Parameters: + * %dl : BIOS drive number + * %dh : Head + * %cl : Sector (bits 0-5), high two bits of cylinder (bits 6-7) + * %ch : Low eight bits of cylinder + * %esi:%edi : LBA address + * %bx : Offset within partition table + * %bp : Active partition handler routine + */ +process_partition: + pushal + /* Load C/H/S values from partition entry */ + movb %es:1(%bx), %dh + movw %es:2(%bx), %cx + /* Update LBA address from partition entry */ + addl %es:8(%bx), %edi + adcl $0, %esi + /* Check active flag */ + testb $0x80, %es:(%bx) + jz 1f + call read_boot_sector + jc 99f + jmp *%bp +1: /* Check for extended partition */ + movb %es:4(%bx), %al + cmpb $0x05, %al + je 2f + cmpb $0x0f, %al + je 2f + cmpb $0x85, %al + jne 99f +2: call process_table +99: popal + /* Reload original partition table */ + call read_boot_sector + ret + +/* + * Read single sector to %es:0000 and verify 0x55aa signature + * + * Parameters: + * %dl : BIOS drive number + * %dh : Head + * %cl : Sector (bits 0-5), high two bits of cylinder (bits 6-7) + * %ch : Low eight bits of cylinder + * %esi:%edi : LBA address + * + * Returns: + * CF set on error + */ +read_boot_sector: + pushw %ax + movw $1, %ax + call *read_sectors + jc 99f + cmpw $0xaa55, %es:(510) + je 99f + stc +99: popw %ax + ret + +/* + * Read sectors to %es:0000 + * + * Parameters: + * %dl : BIOS drive number + * %dh : Head + * %cl : Sector (bits 0-5), high two bits of cylinder (bits 6-7) + * %ch : Low eight bits of cylinder + * %esi:%edi : LBA address + * %ax : Number of sectors (max 127) + * + * Returns: + * CF set on error + */ +read_sectors: .word read_chs + +read_chs: + /* Read sectors using C/H/S address */ + pushal + xorw %bx, %bx + movb $0x02, %ah + stc + int $0x13 + sti + popal + ret + +read_lba: + /* Read sectors using LBA address */ + pushal + movw %ax, (lba_desc + 2) + pushw %es + popw (lba_desc + 6) + movl %edi, (lba_desc + 8) + movl %esi, (lba_desc + 12) + movw $lba_desc, %si + movb $0x42, %ah + int $0x13 + popal + ret + +lba_desc: + .byte 0x10 + .byte 0 + .word 1 + .word 0x0000 + .word 0x0000 + .long 0, 0 |