Please describe in the commit what it fixes instead of just referring to an issue.

Thanks- updated.

Would it make sense to enable PIE by default? Or rather, what's the reason we don't do this always?

Is performance the concern or breakage (or ...)?

Performance seems like a bad reason, don't other distributions enable by default? Such a trade-off seems like it should be opt-in, but regardless first it'd be good to sort out what the reason is before disagreeing with it :P.

I am thinking of just doing this for now as it avoid a mass rebuild. If someone wants to try enabling PIE globally, that would be great. It will just probably be on you to debug any of the new failures.

IIRC we tried that at first but it caused too much breakage so we didn't go that far.

I'm seeing this break musl immediately?

https://gist.github.com/dtzWill/d93dc2211fd2d134a81cd858311f42ce

nix build nixpkgs.pkgsMusl.bash, dies building bootstrap compiler

What sort of builds does this not break (and presumably improves behavior for)?

Checking behavior across branches presently...

@GrahamcOfBorg build pkgsMusl.bash

No attempt on x86_64-darwin (full log)

The following builds were skipped because they don't evaluate on x86_64-darwin: pkgsMusl.bash

Cannot nix-instantiate `pkgsMusl.bash' because:
error: Musl libc only supports Linux systems.

Unexpected error: command failed with exit code 1 on aarch64-linux (full log)

Attempted: pkgsMusl.bash

cannot build derivation '/nix/store/n51xzgr07sny7hxal9fzf8rwfbw7kkb5-mpfr-4.0.1.drv': 3 dependencies couldn't be built
cannot build derivation '/nix/store/h66rmfzfswfwgp0y4x0j83lxib1gqvd6-texinfo-6.5.drv': 5 dependencies couldn't be built
cannot build derivation '/nix/store/5k4bbhgpl7ig43ywhylqi60qxsgigbms-libelf-0.8.13.drv': 3 dependencies couldn't be built
cannot build derivation '/nix/store/c8jd9mwjpsv6vz01nkj6va5ylmk3xlq4-libmpc-1.1.0.drv': 4 dependencies couldn't be built
cannot build derivation '/nix/store/5rq674isjrhsp3hg0d0skr5ab2y4a9ar-gcc-7.3.0.drv': 15 dependencies couldn't be built
cannot build derivation '/nix/store/i7wfcp5ij0d2p05hkbbamd97b2h4hzg2-bootstrap-stage4-gcc-wrapper-7.3.0.drv': 6 dependencies couldn't be built
cannot build derivation '/nix/store/k3hlyx9wgx5ayvp9nlmnvlhrnzrx6mrv-bootstrap-stage4-stdenv-linux.drv': 5 dependencies couldn't be built
cannot build derivation '/nix/store/ida3gqjqgrjrd30453chsbvxxx6idc42-autoconf-2.69.drv': 4 dependencies couldn't be built
cannot build derivation '/nix/store/q8vnwykkhb3qczd6n9jqvy6cgwvb0bsd-bash-4.4-p23.drv': 5 dependencies couldn't be built
error: build of '/nix/store/q8vnwykkhb3qczd6n9jqvy6cgwvb0bsd-bash-4.4-p23.drv' failed

Failure on x86_64-linux (full log)

Attempted: pkgsMusl.bash

make[2]: Leaving directory '/build/build'
make[1]: *** [Makefile:21598: stage1-bubble] Error 2
make[1]: Leaving directory '/build/build'
make: *** [Makefile:22372: profiledbootstrap] Error 2
builder for '/nix/store/1757dkhp6j6j8mdp2z5qw9gda9nyzcxj-gcc-7.3.0.drv' failed with exit code 2
cannot build derivation '/nix/store/av8hqpi3za0svxcf2m7jaqc4nv0m0055-bootstrap-stage4-gcc-wrapper-7.3.0.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/6fwfwlygcz0nb8bfdk1z849db5wac1lb-bootstrap-stage4-stdenv-linux.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/2v57cyha2a6d94cis2np56r5ala5dvw6-autoconf-2.69.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/mbs1zl34blnjkfbzx79yhdh0kzc97s2i-bash-4.4-p23.drv': 3 dependencies couldn't be built
error: build of '/nix/store/mbs1zl34blnjkfbzx79yhdh0kzc97s2i-bash-4.4-p23.drv' failed

So this seems to only break things, is there a case for not reverting it? Otherwise please do so... (or I'll do so in a day or two)

That should be fixed in 2e2afa1. Hoping binutils/gcc are the only ones.

Additional failures:

• glibc
• ghc

I'm a fan of this but this looks like it was merged too eagerly and wasn't... tested at all? Including checking if the original issue was fixed since build fails long before that point AFAICT.
Unfortunately I think our testing bandwidth is thin currently, so I'm not sure how to proceed. Maybe whack-a-mole the next few failures and cross our fingers? I'd like to avoid a revert :).

FWIW here's a few packages that no one's obligated to support BUT I build regularly and so they work reasonably well as oracles, even if they're not intended to be such:

• pkgsMusl.cachix
• pkgsMusl.nix (pkgsMusl.nixUnstable)
• pkgsMusl.llvmPackages_{5,6,7}.{llvm,clang}
  Just in case that helps -- maybe we can put together a musl jobset at some point :). (and contribute builders :))

glibc is just an addition to hardeningDisable, ghc is a bit trickier. Currently testing this: dtzWill@0caf0a3 (will report back in an hour or however long ghc takes :P).

Nope, looks like problem is with bootstrap ghc not being built -fPIC -- so either new bootstrap tarball (eep) or maybe just disable PIE for ghc? Shame b/c it might be nice to use gold linker with it...

Yeah i was probably too quick with this! Sorry about that. I didn’t think pie could break so much. Feel free to revert it (but leave in the hardeningDisable flags for future reference).

I would say just disable PIE for ghc. There's some weird stuff ghc bootstrapping does that makes this stuff complex. We have to do some weird patches to get this working on Android:

https://github.com/reflex-frp/reflex-platform/blob/develop/nixpkgs-overlays/mobile-ghc/8.2.y/android-patches/force-relocation-equal-pic.patch

We do have a cross-trunk jobset with some musl jobs:

https://hydra.nixos.org/jobset/nixpkgs/cross-trunk#tabs-jobs

Maybe we should add cachix to it?

Related problem with writeup: #129247 (comment)