README.md

Asmiov

x86 386 assembler with support for source file parsing (NASM-like Intel syntax) and JIT code generation using the build-in C++ API with syntax closely matching the source format. The project consists of a tasml CLI assembler and a test unit test runner.

The code unique to the CLI utility is separated from the rest of the library and located in the /src/tasml. The /src/file contains binary file IO, and /src/asm implements the assembler itself.

Utility

The example of the syntax used by tasml utility, the API version of the exact same code can be seen below.

text:
	byte "Hello!", 0

strlen:
	mov ecx, /* inline comments! */ eax
	dec eax

l_strlen_next:
		inc eax
		cmp byte [eax], 0
	jne @l_strlen_next

	sub eax, ecx
	ret

_start:
	lea eax, @text
	call @strlen
	mov ebx, eax // exit code
	mov eax, 1 // sys_exit
	int 0x80; ret // multi-statement lines

To assemble this code the following command can be used, assuming the code is saved in file test.s

# TASML generates an executable ELF file
tasml -o a.out test.s

Library

#include "asm/x86/writer.hpp"
#include "asm/x86/emitter.hpp"
#include "file/elf/buffer.hpp"

int main() {

	using namespace asmio::elf;

	BufferWriter writer;

	writer.label("text");
	writer.put_ascii("Hello!");

	writer.label("strlen");
	writer.put_mov(ECX, EAX);
	writer.put_dec(EAX);
	
	writer.label("l_strlen_next");
	writer.put_inc(EAX);
	writer.put_cmp(cast<BYTE>(ref(EAX)), 0);
	writer.put_jne("l_strlen_next");
	writer.put_sub(EAX, ECX);
	writer.put_ret();

	writer.label("_start");
	writer.put_lea(EAX, "text");
	writer.put_call("strlen");
	writer.put_mov(EBX, EAX); // exit code
	writer.put_mov(EAX, 1); // sys_exit
	writer.put_int(0x80);
	writer.put_ret();

	ElfBuffer file = writer.bake_elf(nullptr);

	int status;
	RunResult result = file.execute("memfd-elf-1", &status);

	return status;
	
}