Use more LFS functions.

[mikebenfield]

On Linux, use mmap64, open64, openat64, and sendfile64 in place of their non-LFS counterparts.

This is relevant to #94173.

With these changes (together with rust-lang/backtrace-rs#501), the simple binaries I produce with rustc seem to have no non-LFS functions, so maybe #94173 is fixed. But I can't be sure if I've missed something and maybe some non-LFS functions could sneak in somehow.

[rustbot]

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[rustbot]

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[thomcc]

Looks like this is still WIP. Please fix the CI failures, and use \at rustbot ready when you're done to push it back into my queue

@rustbot author

[mikebenfield]

@rustbot ready

[mikebenfield]

oh whoops, I picked up some extra commits into this PR somehow. Hold on I'll get rid of them.

[thomcc]

Just to check, have you verified that these are present in the version of Linux and glibc we support? It seems to be the case, but some evidence would speed up a review a bit (sorry!)

[mikebenfield]

I'm not sure precisely what you're asking, but does this answer it? Non-LFS symbols are usually present in the Rust compiler; with my patch (+lfs) they are not.

~/lfs  [ mbenfield ]
% rustc +lfs main.rs -o mainlfs
~/lfs  [ mbenfield ]
% nm mainlfs | rg 'U (open|openat|sendfile|mmap)'
                 U mmap64@GLIBC_2.2.5
                 U open64@GLIBC_2.2.5
                 U openat64@GLIBC_2.4
                 U sendfile64@GLIBC_2.3
~/lfs  [ mbenfield ]
% rustc main.rs -o main
~/lfs  [ mbenfield ]
% nm main | rg 'U (open|openat|sendfile|mmap)'
                 U mmap@GLIBC_2.2.5
                 U open64@GLIBC_2.2.5
                 U openat@GLIBC_2.4
                 U open@GLIBC_2.2.5
                 U sendfile@GLIBC_2.2.5
~/lfs  [ mbenfield ]
% uname -rv
5.18.16-1rodete4-amd64 #1 SMP PREEMPT_DYNAMIC Debian 5.18.16-1rodete4 (2022-10-21)
~/lfs  [ mbenfield ]
% cat main.rs
fn main() {
    ::std::fs::remove_dir_all("/some/fake/directory").unwrap();
    let mut f1 = ::std::fs::File::open("filename1").unwrap();
    let mut f2 = ::std::fs::File::create("filename2").unwrap();
    ::std::io::copy(&mut f2, &mut f1).unwrap();
}

[thomcc]

I more meant if any of these functions need to be conditionally loaded due to being unavailable in Linux 3.2/glibc 2.17

[thomcc]

That said, the versions are listed in your comment.

[thomcc]

@bors r+

[bors]

📌 Commit 27011b4 has been approved by thomcc

It is now in the queue for this repository.