ld: provide /PASSTHRU/ section rule to avoid orphan warnings?

[Kees Cook <keescook@chromium.org>]

Hi!

The Linux kernel would like to have a way for the linker to emit sections
without changing their section name, using wildcards. (This is needed
for our efforts towards Function-Granular Kernel Address Space Layout
Randomization[1].) Normally this happens automatically if a section
doesn't match an existing rule, but then the --orphan-handling=warn
option will report it. There is currently no way to silence these
"expected sections".

e.g. if we had something like:

	/PASSTHRU/ : {
		*(.text.*)
	}

Then stuff like ".text.func1" and ".text.func2" will pass through as-is,
but something unexpected, like ".other" would still get correctly
reported by --orphan-handling=warn.

I've opened issues in both binutils[2] and LLVM[3] for this and was
hoping to get some feedback on what's needed to see this implemented.  :)

Thanks!

-Kees

[1] https://github.com/KSPP/linux/issues/132
[2] https://sourceware.org/bugzilla/show_bug.cgi?id=28772
[3] https://github.com/llvm/llvm-project/issues/65087

-- 
Kees Cook