Rust musl build segfaults on startup when linked with LLD 12

[rocallahan]

Steps to reproduce:

$ git clone https://github.com/rocallahan/rust-musl-segfault.git
$ cd rust-musl-segfault
$ cargo +nightly build --target x86_64-unknown-linux-musl
...
$ target/x86_64-unknown-linux-musl/debug/test_crate
Segmentation fault (core dumped)

Since the code is literally

use nix::sys::stat::Mode;

fn main() {
}

I expected it to not segfault.

[rocallahan]

$ ld --version
LLD 12.0.0 (compatible with GNU linkers)

If I actually use ld.bfd the problem goes away, so this is quite possibly an LLD bug, though it might not be.

[rocallahan]

The segfault is in musl's __libc_sigaction. The segfault is at this instruction:

=> 0x00007f844d139e29 <+142>:	mov    %eax,-0x4be2f(%rip)        # 0x7f844d0ee000

0x7f844d0ee000 is unmapped memory. Looks like a linker relocation points somewhere wild.

[rocallahan]

If I remove the use statement the problem goes away.

[12101111]

I can reproduce this issue, the output will segfault when

1. use x86_64-unknown-linux-musl target
2. crt-static is enabled -C target-feature=+crt-static (It enabled by default on musl )
3. Use lld as linker ( Either use ld.lld directly -Clink-self-contained=yes -Clinker=ld.lld or use clang and linker args -Clink-self-contained=no -Clinker=clang -Clink-arg=-fuse-ld=bfd)
4. In debug mode ( no --release or -Copt-level > 0 )

The bisect command is

export RUSTFLAGS="-Ctarget-feature=+crt-static -Clinker=clang -Clink-arg=-fuse-ld=lld"
cargo bisect-rustc --start 2020-08-07 --end 2020-08-09 -- run

The bisect result is:

get_commits_between returning commits, len: 13
  commit[0] 2020-08-07UTC: Auto merge of #75255 - davidtwco:polymorphisation-symbol-mangling-v0-upvar-closures, r=lcnr
  commit[1] 2020-08-07UTC: Auto merge of #75071 - ssomers:btree_cleanup_5, r=Mark-Simulacrum
  commit[2] 2020-08-08UTC: Auto merge of #75048 - eggyal:force-no-tco-start-backtrace-frame, r=Mark-Simulacrum
  commit[3] 2020-08-08UTC: Auto merge of #74877 - lcnr:min_const_generics, r=oli-obk
  commit[4] 2020-08-08UTC: Auto merge of #75276 - JohnTitor:rollup-rz4hs0w, r=JohnTitor
  commit[5] 2020-08-08UTC: Auto merge of #74932 - nnethercote:rm-ast-session-globals, r=petrochenkov
  commit[6] 2020-08-08UTC: Auto merge of #75257 - ssomers:btree_74762_again, r=Mark-Simulacrum
  commit[7] 2020-08-08UTC: Auto merge of #75282 - RalfJung:miri-black-box, r=oli-obk
  commit[8] 2020-08-08UTC: Auto merge of #74289 - lzutao:unroll, r=LukasKalbertodt
  commit[9] 2020-08-08UTC: Auto merge of #74533 - nikic:issue-74425, r=eddyb
  commit[10] 2020-08-08UTC: Auto merge of #75260 - davidtwco:polymorphization-promoted-substs, r=lcnr
  commit[11] 2020-08-08UTC: Auto merge of #75163 - canova:map_into_keys_values, r=dtolnay
  commit[12] 2020-08-08UTC: Auto merge of #75271 - cuviper:array-iter, r=LukasKalbertodt
ERROR: no CI builds available between 09f4c9f5082f78b0adcee83d3ab4337e000cd28e and ceedf1d5febd65b012b8bcd513d70a0a6a091210 within last 167 days

My environment:

> clang -v
clang version 12.0.0
Target: x86_64-gentoo-linux-musl
Thread model: posix
InstalledDir: /usr/lib/llvm/12/bin
> ld.lld --version
LLD 12.0.0 (compatible with GNU linkers)

@rustbot label: +A-linkage +O-musl +regression-from-stable-to-stable

[apiraino]

thanks @12101111 for the additional information. Assigning priority as discussed in the Zulip thread of the Prioritization Working Group.

@rustbot label -I-prioritize +P-high +T-compiler

[wesleywiser]

Testing with our build of lld 15 on nightly and this seems to work fine now:

$ rustc +nightly --version -v
rustc 1.67.0-nightly (77e57db38 2022-10-30)
binary: rustc
commit-hash: 77e57db384aca99444c3b5f6a9c86bc58a804d89
commit-date: 2022-10-30
host: x86_64-unknown-linux-gnu
release: 1.67.0-nightly
LLVM version: 15.0.4
$ git clone https://github.com/rocallahan/rust-musl-segfault.git
$ cd rust-musl-segfault/
$ RUSTFLAGS="-Ctarget-feature=+crt-static -Clinker=rust-lld" cargo +nightly build --target x86_64-unknown-linux-musl
$ ./target/x86_64-unknown-linux-musl/debug/test_crate
$ echo $?
0