linux-kernel - Re: [PATCH v2] selftests/vDSO: fix GNU hash table entry size for s390x

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Message-ID: <your-ad-here.call-01739836346-ext-7522@work.hours>
Date: Tue, 18 Feb 2025 00:52:26 +0100
From: Vasily Gorbik <gor@...ux.ibm.com>
To: Shuah Khan <shuah@...nel.org>, Shuah Khan <skhan@...uxfoundation.org>,
        Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Cc: Fangrui Song <i@...kray.me>, Xi Ruoyao <xry111@...111.site>,
        Heiko Carstens <hca@...ux.ibm.com>, Jens Remus <jremus@...ux.ibm.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] selftests/vDSO: fix GNU hash table entry size for
 s390x

On Mon, Feb 17, 2025 at 02:04:18PM +0100, Thomas Weißschuh wrote:
> Commit 14be4e6f3522 ("selftests: vDSO: fix ELF hash table entry size for s390x")
> changed the type of the ELF hash table entries to 64bit on s390x.
> However the *GNU* hash tables entries are always 32bit.
> The "bucket" pointer is shared between both hash algorithms.
--
> On s390x the GNU algorithm assigns and dereferences this pointer to a
> 64bit value as a pointer to a 32bit value, leading to compiler warnings and
> runtime crashes.

I would rephrase it as follows:

On s390, this caused the GNU hash algorithm to access its 32-bit entries as if they
were 64-bit, triggering compiler warnings (assignment between "Elf64_Xword *" and
"Elf64_Word *") and runtime crashes.

And take it via s390 tree.

Shuah, if you don't mind, may I get your Acked-by?

Thank you!

> Introduce a new dedicated "gnu_bucket" pointer which is used by the GNU hash.
> 
> Fixes: e0746bde6f82 ("selftests/vDSO: support DT_GNU_HASH")
> Reviewed-by: Jens Remus <jremus@...ux.ibm.com>
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
> ---
> Changes in v2:
> - Fix wording around the width of pointers vs the pointed-to values
> - Link to v1: https://lore.kernel.org/r/20250213-selftests-vdso-s390-gnu-hash-v1-1-ace3bcc940a3@linutronix.de
> ---
>  tools/testing/selftests/vDSO/parse_vdso.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)