Updated notes on Mach-O

docs/macho.md

@@ -2,11 +2,21 @@
 
 ## Notes
 
-- Headers must be included in the __TEXT segment.
+- The start of the file must be loaded in some segment.
+- The start of the file must be marked as readable + executable.
 - Load command size must be divisible by 8.
+- Segments must be page-aligned in the file[^1].
+
+Due to the page alignment requirement on disk[^1] instead of just memory,
+MacOS is the only OS that forces you to write bloated executables on disk.
+
+Until this check is removed, we cannot produce smaller executables.
+
+[^1]: https://github.com/apple-oss-distributions/xnu/blob/main/bsd/kern/mach_loader.c#L2021-L2027
 
 ## Links
 
+- https://github.com/apple-oss-distributions/xnu/blob/main/bsd/kern/mach_loader.c
 - https://github.com/apple-oss-distributions/xnu/blob/main/EXTERNAL_HEADERS/mach-o/loader.h
 - https://en.wikipedia.org/wiki/Mach-O
 - https://github.com/aidansteele/osx-abi-macho-file-format-reference