[PATCH] Unconditionally define __stack_chk_guard [BZ #26817]

[Fāng-ruì Sòng]

On Mon, Jan 11, 2021 at 1:39 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * Fangrui Song via Libc-alpha:
>
> > This makes -mstack-protector-guard=global work even if
> > -mstack-protector-guard=tls is the default.
>
> It's unclear how you intend this to work.  Is it just for building
> glibc?  Or also for user code?

It is for user applications.

gcc -fstack-protector -mstack-protector-guard=global a.c
or
clang -fstack-protector -mstack-protector-guard=global a.c (clang 12)

Currently there is an undefined symbol error. This patch fixes the problem.

> In the latter case, we either need to provide a way to initialize a
> hidden __stack_chk_guard symbol (probably with new relocations), or
> export __stack_chk_guard from glibc, under a GLIBC_2.33 symbol version
> for architectures that were missing it before.

In elf/Versions, __stack_chk_guard is already exported as
__stack_chk_guard@@GLIBC_2.4


> Thanks,
> Florian
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