linux-kernel - Re: [PATCH v3 1/3] syscalls,x86 Expose arch

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Date:   Fri, 16 Sep 2016 08:56:30 -0700
From:   Kyle Huey <me@...ehuey.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     "Robert O'Callahan" <robert@...llahan.org>,
        open list <linux-kernel@...r.kernel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...capital.net>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Borislav Petkov <bp@...e.de>,
        Linux API <linux-api@...r.kernel.org>,
        "moderated list:XEN HYPERVISOR INTERFACE" 
        <xen-devel@...ts.xenproject.org>, Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Jeff Dike <jdike@...toit.com>,
        Richard Weinberger <richard@....at>,
        Al Viro <viro@...iv.linux.org.uk>,
        David Howells <dhowells@...hat.com>,
        Anna Schumaker <Anna.Schumaker@...app.com>,
        Andy Lutomirski <luto@...nel.org>, Zach Brown <zab@...hat.com>,
        Eric B Munson <emunson@...mai.com>,
        "Dmitry V. Levin" <ldv@...linux.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Jan Beulich <JBeulich@...e.com>,
        Mateusz Guzik <mguzik@...hat.com>,
        Chuck Ebbert <cebbert.lkml@...il.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Dmitry Safonov <dsafonov@...tuozzo.com>,
        "chengang@...ndsoft.com.cn" <chengang@...ndsoft.com.cn>,
        Jeff Moyer <jmoyer@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jiri Kosina <jkosina@...e.cz>,
        Milosz Tanski <milosz@...in.com>,
        "open list:USER-MODE LINUX (UML)" 
        <user-mode-linux-devel@...ts.sourceforge.net>,
        "open list:USER-MODE LINUX (UML)" 
        <user-mode-linux-user@...ts.sourceforge.net>
Subject: Re: [PATCH v3 1/3] syscalls,x86 Expose arch_prctl on x86-32.

On Fri, Sep 16, 2016 at 12:50 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Thu, 15 Sep 2016, Kyle Huey wrote:
>
> First of all, please add a cover letter [PATCH 0/N] to your patch series
> and send it with something which provides proper mail threading.
> See: git-send-email, quilt

I did ... seems like using git-send-email with
--cc-cmd=scripts/get_maintainer.pl is not a good idea since people get
CCd to some parts of the thread and not others.

https://lkml.org/lkml/2016/9/15/811

>> arch_prctl is currently 64-bit only. Wire it up for 32-bits, as a no-op for
>> now. Rename the second arg to a more generic name.
>
> This changelog is useless.
>
> - it does not provide any rationale for this change, i.e. why this is
>   required. Just because its 64bit only is not a reason.
>
> - "Rename the second arg to a more generic name" does not give
>   any useful information.
>
> Misleading information is worse than no information.
>
> Further your patch does 5 things at once. It wants to be split into parts:
>
> 1) Rename do_arch_prctl() and change the argument name,
>
>> -long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
>> +long do_arch_prctl_64(struct task_struct *task, int code, unsigned long arg2)
>
> 2) Provide do_arch_prctl_common() and hook it up to the arch_prctl syscall
>
>> -long sys_arch_prctl(int code, unsigned long addr)
>> +SYSCALL_DEFINE2(arch_prctl, int, code, unsigned long, arg2)
>>  {
>> -     return do_arch_prctl(current, code, addr);
>> +     long ret;
>> +
>> +     ret = do_arch_prctl_64(current, code, arg2);
>> +     if (ret == -EINVAL)
>> +             ret = do_arch_prctl_common(current, code, arg2);
>> +
>> +     return ret;
>>  }
>
> 3) Implement the compat version

Ok.

- Kyle