From: Michael Ellerman <mpe@ellerman.id.au>
To: Fangrui Song <maskray@google.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Christophe Leroy <christophe.leroy@c-s.fr>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
clang-built-linux@googlegroups.com,
Fangrui Song <maskray@google.com>
Subject: Re: [PATCH] powerpc/vdso32: mark __kernel_datapage_offset as STV_PROTECTED
Date: Mon, 10 Feb 2020 22:01:37 +1100 [thread overview]
Message-ID: <87pnemzoxa.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <20200205005054.k72fuikf6rwrgfe4@google.com>
Fangrui Song <maskray@google.com> writes:
> A PC-relative relocation (R_PPC_REL16_LO in this case) referencing a
> preemptible symbol in a -shared link is not allowed. GNU ld's powerpc
> port is permissive and allows it [1], but lld will report an error after
> https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?id=ec0895f08f99515194e9fcfe1338becf6f759d38
>
> Make the symbol protected so that it is non-preemptible but still
> exported.
"preemptible" means something different to me, and I assume we're not
using it to mean the same thing.
Can you explain it using small words that a kernel developer can
understand? :)
cheers
> [1]: https://sourceware.org/bugzilla/show_bug.cgi?id=25500
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/851
> Signed-off-by: Fangrui Song <maskray@google.com>
> ---
> arch/powerpc/kernel/vdso32/datapage.S | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/vdso32/datapage.S b/arch/powerpc/kernel/vdso32/datapage.S
> index 217bb630f8f9..2831a8676365 100644
> --- a/arch/powerpc/kernel/vdso32/datapage.S
> +++ b/arch/powerpc/kernel/vdso32/datapage.S
> @@ -13,7 +13,8 @@
> #include <asm/vdso_datapage.h>
>
> .text
> - .global __kernel_datapage_offset;
> + .global __kernel_datapage_offset
> + .protected __kernel_datapage_offset
> __kernel_datapage_offset:
> .long 0
>
> --
> 2.25.0.341.g760bfbb309-goog
next prev parent reply other threads:[~2020-02-10 11:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-05 0:50 [PATCH] powerpc/vdso32: mark __kernel_datapage_offset as STV_PROTECTED Fangrui Song
2020-02-05 6:25 ` Christophe Leroy
2020-02-07 6:42 ` Nathan Chancellor
2020-06-03 23:50 ` Nick Desaulniers
2020-02-10 11:01 ` Michael Ellerman [this message]
2020-02-10 18:41 ` Fāng-ruì Sòng
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87pnemzoxa.fsf@mpe.ellerman.id.au \
--to=mpe@ellerman.id.au \
--cc=benh@kernel.crashing.org \
--cc=christophe.leroy@c-s.fr \
--cc=clang-built-linux@googlegroups.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=maskray@google.com \
--cc=paulus@samba.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).