Add smaller ASM version and Makefile clean target

[acd407]

By adjusting the compilation and linking parameters, tiny_asm_opt can be as small as tiny.

$ LC_ALL=C ls -la tiny tiny_asm_opt
-rwxr-xr-x 1 acd407 acd407 127 Mar  8 15:10 tiny
-rwxr-xr-x 1 acd407 acd407 127 Mar  8 15:10 tiny_asm_opt

This is the commands:

clang -s -Wl,--build-id=none -z noseparate-code -nostartfiles -nostdlib -static tiny.s -o tiny_asm_opt
objcopy --strip-section-headers tiny_asm_opt tiny_asm_opt

• -s: Strips all symbol tables (.symtab and .strtab).
• -Wl,--build-id=none: Directs the linker (ld) to omit the .note.gnu.build-id section, which normally contains a build hash.
• -z noseparate-code: A linker option that disables the "separate code" feature. This prevents enforcement of separate, non-writable segments for code and data. Critically, it allows the ELF header, program headers, and code to reside in the same loadable segment, enabling extreme size reduction.
• objcopy: A GNU Binutils tool for copying and transforming object files.
• --strip-section-headers: Removes the Section Header Table and all associated section name strings.

Resulting ELF Structure

The final binary (tiny_asm_opt) consists of:

• ELF Header: Defines file type, entry point (0x400078), and program header table location.
• Program Header Table: Contains two LOAD segments:
  1. A minimal segment (likely for alignment/placeholder).
  2. The key segment: A read-only, executable PT_LOAD segment that starts at file offset 0 but declares a size of 0x4000 bytes. Since the actual file is only 0x7F bytes, the loader maps the entire file (including its own headers) to virtual address 0x400000 and zero-fills the remainder. This segment contains the entry point code.
• Code: The 7-byte machine code at file offset 0x78.

Key Optimization

By declaring a segment much larger than the file, the ELF avoids trailing zero-padding for alignment. Combining the ELF header, program headers, and code into a single executable segment—and then stripping non-essential section headers—achieves the minimal possible size while remaining a valid, executable ELF file.

[tchajed]

Thanks, this is cool!