linux-kernel - Re: [PATCH] x86/asm/64: do not clear high 32 bits of syscall number when CONFIG_X86

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Date:   Thu, 14 Sep 2017 23:24:30 +0300
From:   "Dmitry V. Levin" <ldv@...linux.org>
To:     Eugene Syromyatnikov <evgsyr@...il.com>
Cc:     Oleg Nesterov <oleg@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/asm/64: do not clear high 32 bits of syscall number
 when CONFIG_X86_X32=y

On Thu, Sep 14, 2017 at 07:40:43PM +0000, Eugene Syromyatnikov wrote:
> On Wed, Sep 13, 2017 at 4:49 PM, Oleg Nesterov <oleg@...hat.com> wrote:
> > IOW, why do we want to silently ignore the upper bits in $rax ?
> 
> By the way, they are ignored elsewhere, in audit[1] or seccomp[2], for example.
> 
> [1] include/linux/audit.h
> [2] include/uapi/linux/seccomp.h, definition of struct seccomp_data

Yes, unfortunately, they are ignored later, but that is another story.


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