[2.43 PATCH] LoongArch: Fix broken DESC => IE transition for 2.43 branch

[Xi Ruoyao]

On Thu, 2024-12-19 at 17:04 +0800, Icenowy Zheng wrote:
> 在 2024-12-19星期四的 13:23 +0800，Xi Ruoyao写道：
> > If code compiled with -fPIC -mtls-dialect=desc is linked into a PDE
> > or
> > PIE, and the code refers to external DSO symbols, we can produce
> > broken
> > link unit as check_relocs expects DESC => IE transition to happen and
> > emits a TLS IE entry in the GOT, but a too early "continue" in
> > relax_section actually jumps over the DESC => IE transition so the
> > code
> > sequence is unchanged and still expecting a TLS descriptor (instead
> > of
> > an IE entry) in the GOT.
> > 
> > The bug is already fixed in master branch by commit 5c3d09c1855b
> > ("LoongArch: Optimize the relaxation process") so this fix is only
> > needed for the 2.43 branch.
> > 
> > Reported-by: Icenowy Zheng <uwu@icenowy.me>
> 
> My original case (which is compiling a full-featured Mesa) fails in
> another way after applying this patch -- originally it fails because
> intel_clc gets segfault (which uses std::call_once to initialize LLVM),
> now it fails when linking some .so files (including libgallium).
> 
> Here's the backtrace:
> 
> ```
> #0  loongarch_can_trans_tls (input_bfd=<optimized out>,
> info=0x555558f60b78 <link_info>, h=0x0, r_symndx=<optimized out>,
> r_type=<optimized out>)
>     at /var/cache/acbs/build/acbs._4a9gw_q/binutils-2.43.1/bfd/elfnn-
> loongarch.c:787

I guess (not sure) it's fixed by

commit 28489a70d4660d67e71d75e82286a6e1a7003b93
Author: Xin Wang <yw987194828@gmail.com>
Date:   Fri Sep 6 09:00:12 2024 +0800

    LoongArch: Add elfNN_loongarch_mkobject to initialize LoongArch tdata

This is already backported to 2.43 branch as commit
c40337b1784d81c615a5dd9fd391f6677e52c6d8.

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University