Jas is a minimal, fast and simple zero-dependency assembler for the x64 family of processors, jas not only aims to be fast and simple when using it but also aims to be a learning reasource for others to learn about low-level system programming and the x64 instruction set. Useful for implementing into compilers, operating systems and JIT interpreters and other types of utilites that need compilation to ELF or just a plain enocded buffer.

⚡Quick start

First of all, install/link against the binary releases here or build it from source with following the instructions below. Jas takes instructions in an array in a struct form defined in instruction.h and passes it to a codegen() function which generates the the actual buffer of an array of uint8_t for you to process.

#include <jas.h>
#include <stdint.h>
#include <stdlib.h>

int main(void) {
  instruction_t instr[] = (instruction_t[]) {
      (instruction_t){
          .instr = INSTR_MOV,
          .operands = (operand_t[]){
              (operand_t){.type = OP_R64, .data = &(enum registers){REG_RAX}},
              (operand_t){.type = OP_IMM64, .data = &(uint64_t){0}},
              OP_NONE,
              OP_NONE,
          },
      },
  };

  buffer_t buf = codegen(MODE_LONG, instr, sizeof(instr), CODEGEN_RAW);

  /* Do something to `buf.data` - The uint8_t array */

  free(buf.data);
  return 0;
}

Yeah! that's it! Seriously! It's that simple, this little snippet of code generates and encodes a mov rax, 0 instruction.

Since the returned buffer is in the form of a dynamically allocated pointer, care must be taken to free and manage the block of memory.

🏗️ Build and install

The very first step in doing anything with jas is to build and link the library against your application code, since jas is a library. Ensure you have a C99 and C++17 compiler installed (Anything will do, preferably clang), and GNU make or something to run makefile while buidling.

To obtain the Jas source files, run:

git clone https://github.com/cheng-alvin/jas/

Now, you should have a folder named jas in your current directory, now you can just simply run make within that directory like so: (Some directories and folders can be missing, you must run make clean before you actually build the library.)

cd jas # Change into the cloned directory
make clean # Clean directory and setup
make # Build source code

Voila! Now you have a built copy of Jas in the build folder, just simply copy and link against the archive to start building your dream compiler or assembler frontend!

📝 Licensing

All the code under the Jas assembler project repository is licensed under the MIT license which is a popular open-source license for projects like this! Please see LICENSE for the details.

No warranty of any kind is provided, please double check offical sources before deploying code to production

❤️ Contributing / Security issues

No software is perfect, nor is Jas. As the assembler is written in C, many secuity issues may arise, causing issues across the program. It's a shared responsibility to safeguard Jas of all developers, contributers and users alike. Please report all secuity concerns in a timely manner via email or the means provided here.

However, for developers interested and passionate about assemblers and low-level programming, please see the contributing guide in the home directory for more information on how to contribute code to the repository!

All changes and reports are welcome, no matter how big or small your changes are :-)

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Made with love by Alvin / the Jas crew and contributors ❤️ .