linux-kernel - Re: [PATCH] x86/mm/dump_pagetables: Change to use DEFINE_SHOW

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Message-ID: <CAGXu5jJuHQOi3C7_xH7Fo2H-=EmzKkwAPWmWPOUNb0WWMTLnJQ@mail.gmail.com>
Date:   Tue, 27 Nov 2018 14:50:24 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Yangtao Li <tiny.windzz@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/mm/dump_pagetables: Change to use DEFINE_SHOW_ATTRIBUTE
 macro

On Mon, Nov 19, 2018 at 9:06 AM, Dave Hansen <dave.hansen@...el.com> wrote:
> On 11/19/18 7:43 AM, Yangtao Li wrote:
>> -static const struct file_operations ptdump_curusr_fops = {
>> -     .owner          = THIS_MODULE,
>> -     .open           = ptdump_open_curusr,
>> -     .read           = seq_read,
>> -     .llseek         = seq_lseek,
>> -     .release        = single_release,
>> -};
>> +DEFINE_SHOW_ATTRIBUTE(ptdump_curusr);
>
> FWIW, I rather dislike this conversion and the DEFINE_SHOW_ATTRIBUTE()
> approach in general.  It makes it basically impossible to go from
> ptdump_curusr to ptdump_open_curusr without opening up the macro and
> reverse-engineering it.
>
> My test is that for these macros to be sane, I need to be able to find
> "ptdump_open_curusr" by grepping for "ptdump_curusr".  This fails the test.

Er, "ptdump_curusr" matches the generated name "ptdump_curusr_show",
is that what you mean?

> I don't think saving a few lines of code is worth the obfuscation.

This is the standard boilerplate for attributes, though. I'd be nice
to drop all the copy/pasted code...

-- 
Kees Cook