[jchw]

I like this idea. I have an idea for something that would be cool, if impractical: Imagine a GCC wrapper that doesn't actually link, but produces a bundle that performs the linking in randomized order in realtime and then runs.

I think that you could do this quite well on NixOS, and I'm now intrigued to try to rig up a proof-of-concept when I can find the time.

Side-effect: Does not work for libraries without a significantly more complex wrapper that certainly could not work for all libraries. Though, you could re-order the objects within a static library fairly easily.

[xxpor]

That'd make process startup EXTREMELY slow

[jchw]

It's pretty much what OpenBSD is doing at bootup.

Truthfully though you're right, using typical linkers, this would be pretty slow; at least a few seconds for large binaries, to minutes for things as large as web browsers. However, for many binaries, linking can be done much faster; mold claims to be only 50% the runtime of using `cp` on the object files, which is fast enough to even re-link Firefox on-the-fly without it being unusable.

You could imagine writing a linker specifically for this case, that encodes information about the object files directly into the resulting bundle.

[blibble]

I thought openbsd did it after boot?

[dfox]

OpenBSD relinks sshd. Which is relatively small thing that is linked from relatively large objects (ie. it is the typical modern C code). Relinking thing like glibc on demand is going to be problematic, because it is structured as to allow small binary sizes for static linking and thus almost every function that is part of glibc API is a separate compilation unit and object file. Linking that into .so is slow, no mater what kind of optimalization tricks you implement in the linker.

[blibble]

doesn't matter how long it takes if you don't block the boot process doing it

you can link in the background at idle priority, and if you don't complete before reboot: no big deal

[saagarjha]

Relinking glibc would block the boot process.

[jchw]

Yeah. That said, I'm suggesting that if it was really too slow, though, it'd probably be infeasible to relink libc, the kernel, etc. at bootup. It's not a direct comparison to be sure.

[speed_spread]

Not that bad if you link with a custom mold fork.