59 lines
1.5 KiB
ArmAsm
59 lines
1.5 KiB
ArmAsm
/* https://github.com/cirosantilli/x86-bare-metal-examples#bios-disk-load */
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#include "common.h"
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BEGIN
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CLEAR
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/* Reset disk. TODO is this really needed?
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* Was suggested in one tutorial.
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*/
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/*mov $0, %ah
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*mov $0x80, %dl
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*int $0x13
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*/
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/* Read sectors into memory */
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mov $2, %ah
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/* Number of sectors to read. */
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mov $1, %al
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/* Drive number. Starts at 0x80, second one is 0x81. TODO why not from 0?
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*
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* The BIOS stores the right number on dl as an initial state,
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* but we may be destroying it before, and are lazy to properly store it somewhere.
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* http://stackoverflow.com/a/19387093/895245
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*/
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mov $0x80, %dl
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/* cylinder number */
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mov $0, %ch
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/* Head number */
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mov $0, %dh
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/* Starting sector number. 2 because 1 was already loaded. */
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mov $2, %cl
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/* Where to load to.
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* Must coincide with our stage2 for the linking to work.
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*
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* The address is calculated as:
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*
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* ....
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* 16 * ES + BX
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* ....
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*/
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mov $stage2, %bx
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int $0x13
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jmp stage2
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/* Our linker script will put this section on the right place in memory:
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* just after the magic bytes.
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*/
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.section .stage2
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stage2:
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PUTC $'a
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hlt
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/* We could use `.org` here to fill up the second sector to a multiple of 512 bytes.
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* But the linker does that beautifully with `. = ALIGN(512)` for any size of stage2,
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* so we use that instead.
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*/
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/*.org 512*/
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