From: Jan Beulich <jbeulich@suse.com>
To: Fangrui Song <maskray@google.com>
Cc: binutils@sourceware.org
Subject: Re: [PATCH v2] ld: Allow R_386_GOT32 for call *__tls_get_addr@GOT(%reg)
Date: Fri, 10 Mar 2023 10:10:50 +0100 [thread overview]
Message-ID: <efa93d8d-fab3-7fe7-bfa1-eafa9ae1abd5@suse.com> (raw)
In-Reply-To: <20230302201722.1304941-1-maskray@google.com>
On 02.03.2023 21:17, Fangrui Song via Binutils wrote:
> Similar to
> https://sourceware.org/pipermail/binutils/2023-March/126434.html (x86_64).
>
> _Thread_local int a;
> int main() { return a; }
>
> % gcc -m32 -fno-plt -fpic a.c -fuse-ld=bfd -Wa,-mrelax-relocations=no
> /usr/bin/ld.bfd: /tmp/ccR8Yexy.o: TLS transition from R_386_TLS_GD to R_386_TLS_IE_32 against `a' at 0x15 in section `.text' failed
> /usr/bin/ld.bfd: failed to set dynamic section sizes: bad value
> collect2: error: ld returned 1 exit status
>
> This commit fixes the issue.
>
> There is an argument that the -fno-plt TLS sequence was added after
> R_386_GOT32X was required for call *func@GOT(%ebx), so R_386_GOT32 was
> intended to be unsupported.
>
> Unfortunately this standpoint has caused interop difficulty: some
> projects specify -mrelax-relocations=no to build relocatable object
> files compatible with older linkers (e.g.
> https://github.com/IHaskell/IHaskell/issues/636) or do so by accident
> (e.g. https://github.com/rust-lang/rust/pull/106511 not addressed as of
> today). Many uses have not been cleaned up in practice, and compiling
> with -fno-plt will lead to the `TLS transition from R_386_TLS_GD ...`
> error which is hard to reason about.
>
> It seems easier to apply this simple change to prevent the footgun.
>
> PR ld/24784
> * bfd/elf32-i386.c (elf_i386_check_tls_transition): Allow R_386_GOT32.
> ---
> Changes from v1:
> * Update description as suggested by Jan (https://sourceware.org/pipermail/binutils/2023-March/126430.html)
Same here: Okay.
Jan
prev parent reply other threads:[~2023-03-10 9:10 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-02 20:17 Fangrui Song
2023-03-10 9:10 ` Jan Beulich [this message]
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