Linux System Call – 0x2B|~0x2B

The HelloWorld application is much simpler than the Windows one. Just put parameters into registers from %eax to %edx, and trigger a 0x80 interrupt.

# gcc -nostdlib syscall_linux.s -o syscall_linux
.global _start

.text

_start:
    # write(1, message, 13)
    mov     $4, %eax            # system call 4 is write
    mov     $1, %ebx            # file handle 1 is stdout
    mov     $message, %ecx      # address of string to output
    mov     $13, %edx           # number of bytes to write
    int     $0x80               # invoke system call  
    # exit(0)
    mov     $1, %eax            # system call 1 is exit
    xor     %ebx, %ebx          # return 0
    int     $0x80               # invoke system call
message:
    .ascii  "Hello World!\n"

# gcc -nostdlib syscall_linux.s -o syscall_linux

.global _start

.text

_start:

# write(1, message, 13)

mov $4, %eax # system call 4 is write

mov $1, %ebx # file handle 1 is stdout

mov $message, %ecx # address of string to output

mov $13, %edx # number of bytes to write

int $0x80 # invoke system call

# exit(0)

mov $1, %eax # system call 1 is exit

xor %ebx, %ebx # return 0

int $0x80 # invoke system call

message:

.ascii "Hello World!\n"

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