From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: Chris Metcalf <cmetcalf@mellanox.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
linuxppc-dev@lists.ozlabs.org, Mike Frysinger <vapier@gentoo.org>
Subject: Re: possible bug in powerpc LE compat syscalls with 64-bit args
Date: Thu, 16 Jun 2016 12:56:57 -0300 [thread overview]
Message-ID: <5762CC49.6090400@linaro.org> (raw)
In-Reply-To: <28c367c1-0f60-cd1d-b443-d3876798a627@mellanox.com>
On 16/06/2016 12:36, Chris Metcalf wrote:
> Adhemerval Zanella is cleaning up the preadv/pwritev implementation in glibc
> and came across an issue with the tilepro/tilegx32 implementation of argument
> passing for 64-bit arguments in split register pairs.
>
> The glibc code base uses __LONG_LONG_PAIR to split 64-bit arguments,
> passing "hi, lo" for BE systems and "lo, hi" for LE systems. Tile is almost uniformly
> LE, but we do support BE for specific customers. The 32-bit compat mode on
> tilegx was getting passed "hi, lo" arguments by glibc but looking for them to
> be "lo, hi" arguments on the kernel side. I fixed this here:
>
> https://lkml.kernel.org/g/1466019219-10462-1-git-send-email-cmetcalf@mellanox.com
>
> Reviewing what other platforms do, it seems like powerpc compat mode may
> have the opposite problem in little-endian mode, since arguments are passed
> in "hi, lo" order unconditionally in arch/powerpc/kernel/sys_ppc32.c. You may
> want to adopt the solution in the patch cited above, or similar solutions
> elsewhere, eg regs_to_64 in arch/arm64/include/asm/assembler.h, or
> merge_64 in arch/mips/kernel/linux32.c.
>
> Here's the email thread from libc-alpha:
>
> https://sourceware.org/ml/libc-alpha/2016-06/msg00638.html
>
I am not fully familiar with kernel policy regarding ABI so is this considered
an ABI breakage or a real defect?
next prev parent reply other threads:[~2016-06-16 15:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-16 15:36 possible bug in powerpc LE compat syscalls with 64-bit args Chris Metcalf
2016-06-16 15:56 ` Adhemerval Zanella [this message]
2016-06-17 1:52 ` Michael Ellerman
[not found] <28c367c1-0f60-cd1d-b443-d3876798a627__12262.0927206755$1466112970$gmane$org@mellanox.com>
2016-06-16 21:42 ` Andreas Schwab
2016-06-17 20:46 ` Chris Metcalf
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