Summary: Generating Raw Machine Code for m68k with Clang
Here’s the step-by-step process we followed to produce raw machine code for the m68k architecture without relying on any libraries or system headers:
1. Write Minimal C Code
Write a simple C program without standard library dependencies. For example:
main.c:
void _start() {
while (1) {}
}
- Avoid standard headers like
<stdio.h>since they depend on system libraries.
2. Compile with Clang
Use Clang to compile for the m68k target, in freestanding mode, and without linking:
/mnt/Texas/3rd-party/llvm-project/build/bin/clang --target=m68k-unknown-elf -c -ffreestanding -nostdlib -o output.o main.c
Key Flags:
--target=m68k-unknown-elf: Specifies the m68k architecture.-c: Generates an object file (.o) without linking.-ffreestanding: Disables assumptions about standard libraries.-nostdlib: Ensures no standard library functions are linked.
3. Extract Raw Machine Code
Use llvm-objcopy to strip away metadata and leave only the raw machine code:
/mnt/Texas/3rd-party/llvm-project/build/bin/llvm-objcopy -O binary output.o output.bin
Explanation:
-O binary: Outputs a raw binary file containing only machine code.
4. Verify the Raw Binary
Check the contents of the resulting binary file:
hexdump -C output.bin
Example Output:
00000000 4e 56 00 00 60 00 00 02 60 fe |NV..`...`.|
This is the raw machine code for your program.
5. Tools Overview
- Clang: Compiles the source code to an ELF object file.
- llvm-objcopy: Extracts raw machine code from the ELF object file.
Recap of Commands:
# Step 1: Compile to an object file
/mnt/Texas/3rd-party/llvm-project/build/bin/clang --target=m68k-unknown-elf -c -ffreestanding -nostdlib -o output.o main.c
# Step 2: Extract raw binary
/mnt/Texas/3rd-party/llvm-project/build/bin/llvm-objcopy -O binary output.o output.bin
# Step 3: Verify the raw binary
hexdump -C output.bin
You now have a minimal workflow for generating raw machine code for the m68k architecture using Clang. If you have more questions or need additional help, feel free to ask! :blush: