41 lines
1.4 KiB
ArmAsm
41 lines
1.4 KiB
ArmAsm
; Definition of the MBR (Master Boot Record). This is basically our bootloader and
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; is located in the first 512 bytes of the drive we're booting from. From here, we
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; do some basic setup and then call into the kernel
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[org 0x7c00] ; Address where the code expects to be loaded in. The BIOS always loads us here
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[bits 16] ; All x86 CPUs start in 16 bit (aka "real") mode, so we tell nasm to emit 16-bit code
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; We print a simple startup message using the ISRs
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; from the BIOS
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mov si, startup_msg
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call print
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; Now we setup the stack by setting the
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; base pointer to address 0x8000. The
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; address itself doesn't matter as long
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; as it's far enough away from memory already
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; in use by the BIOS
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mov bp, 0x8000
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mov sp, bp ; The stack starts out empty, so sp == bp
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jmp $ ; Keeps jumping at the current address (loops forever)
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; These two lines never execute (for now), but they might once
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; we jump into the kernel, so we disable interrupts and halt the
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; CPU, just in case
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cli
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hlt
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; Now we include our "function definitions" (after the halting, so
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; they're never executed unless explicitly called)
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%include "src/bootloader/util/tty.s"
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; Here we define our variables: They need to be defined after the
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; halting because otherwise they will be executed as code!
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startup_msg: db "TSOS - Bootloader: Starting up", 0xA, 0xD, 0x0
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; padding and magic number
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times 510 - ($-$$) db 0
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dw 0xaa55 |