- 1 year ago
Windows x64 Assembly
Writing assembly code for the x64 architecture on Windows involves using the x86_64 instruction set and following the calling conventions specific to Windows. Here's a simple example of x64 assembly code for Windows that prints "Hello, World!" to the console:
assemblysection .data
message db 'Hello, World!', 0
section .text
global main
extern printf
main:
sub rsp, 8 ; Align stack pointer (must be 16-byte aligned)
mov rcx, message ; First argument: address of the message
call printf ; Call printf function
add rsp, 8 ; Restore stack pointer
xor eax, eax ; Return 0
ret
In the above code:
- The
.data
section defines themessage
string, terminated with a null character (0
). - The
.text
section contains themain
function. - The
sub rsp, 8
instruction aligns the stack pointer on a 16-byte boundary. - The
mov rcx, message
instruction loads the address of themessage
string into thercx
register, which is the first argument for theprintf
function. - The
call printf
instruction calls theprintf
function from the C runtime library. - The
add rsp, 8
instruction restores the stack pointer. - The
xor eax, eax
instruction clears theeax
register (return value of themain
function). - The
ret
instruction returns from the function.
To assemble and link the assembly code, you can use an assembler like NASM and a linker like GNU ld or Microsoft's linker (link.exe) with appropriate command-line options.
Keep in mind that x64 assembly programming requires a good understanding of the x86_64 instruction set, calling conventions, and system interfaces. The example above is a basic illustration, and more complex tasks will require additional instructions and considerations. It's also important to consider error handling, memory management, and other aspects depending on the specific requirements of your assembly program.