48 lines
1.6 KiB
ArmAsm
48 lines
1.6 KiB
ArmAsm
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;; Hello World Program #1
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;; Compile with: nasm -f elf hello.s
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;; Link with: ld -m elf_i386 -o hello hello.o
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;; Run with: ./hello
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;; sys/unistd_32.h
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%define SYS_write 4
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%define SYS_exit 1
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;; unistd.h
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%define STDOUT 1
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section .data
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msg db "Hello You Beautiful Human, You're Looking Fine Today!", 0Ah, 00h
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section .text
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global _start
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_start:
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mov ebx, msg ; Move the address of the message into ebx
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mov eax, ebx ; Move the address of the message into eax (Register-to-register copying is faster that a constant!)
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nextchar:
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cmp byte [eax], 0 ; Compare the byte pointed to by eax with zero.
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;; Small detail: cmp and sub use the same internal architecture,
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;; except cmp doesn't copy the results into the first operand and
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;; sub does. cmp sets flags; does sub? This is why 'jz' works,
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;; because if they're equal the result of subtraction is zero.
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jz counted ; Jump if the zero flag set
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inc eax
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jmp nextchar
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counted:
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sub eax, ebx ; Subtract the end from the start, and the result goes into the start
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mov edx, eax ; syswrite needs that register for something else! Man, picking registers is hard.
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mov ecx, msg ; Address of the message (not the content)
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mov ebx, STDOUT ; using STDOUT (see definition above)
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mov eax, SYS_write ; Using WRITE in 32-bit mode?
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int 80h ; Interrupt target. The 'h' means 'hexidecimal'
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mov ebx, 0
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mov eax, SYS_exit
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int 80h
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