linux-kernel - Re: [PATCH v7 02/26] x86/mm: Relocate page fault error codes to traps.h

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Date:   Fri, 26 May 2017 20:40:26 -0700
From:   Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To:     Borislav Petkov <bp@...e.de>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brian Gerst <brgerst@...il.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Liang Z Li <liang.z.li@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Huang Rui <ray.huang@....com>, Jiri Slaby <jslaby@...e.cz>,
        Jonathan Corbet <corbet@....net>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Chen Yucong <slaoub@...il.com>,
        Alexandre Julliard <julliard@...ehq.org>,
        Stas Sergeev <stsp@...t.ru>, Fenghua Yu <fenghua.yu@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-msdos@...r.kernel.org, wine-devel@...ehq.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH v7 02/26] x86/mm: Relocate page fault error codes to
 traps.h

On Sun, 2017-05-21 at 16:23 +0200, Borislav Petkov wrote:
> On Fri, May 05, 2017 at 11:17:00AM -0700, Ricardo Neri wrote:
> > Up to this point, only fault.c used the definitions of the page fault error
> > codes. Thus, it made sense to keep them within such file. Other portions of
> > code might be interested in those definitions too. For instance, the User-
> > Mode Instruction Prevention emulation code will use such definitions to
> > emulate a page fault when it is unable to successfully copy the results
> > of the emulated instructions to user space.
> > 
> > While relocating the error code enumeration, the prefix X86_ is used to
> > make it consistent with the rest of the definitions in traps.h. Of course,
> > code using the enumeration had to be updated as well. No functional changes
> > were performed.
> > 
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Ingo Molnar <mingo@...hat.com>
> > Cc: "H. Peter Anvin" <hpa@...or.com>
> > Cc: Andy Lutomirski <luto@...nel.org>
> > Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> > Cc: Josh Poimboeuf <jpoimboe@...hat.com>
> > Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> > Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
> > Cc: x86@...nel.org
> > Reviewed-by: Andy Lutomirski <luto@...nel.org>
> > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> > ---
> >  arch/x86/include/asm/traps.h | 18 +++++++++
> >  arch/x86/mm/fault.c          | 88 +++++++++++++++++---------------------------
> >  2 files changed, 52 insertions(+), 54 deletions(-)
> 
> ...
> 
> > @@ -1382,7 +1362,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
> >  	 * space check, thus avoiding the deadlock:
> >  	 */
> >  	if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
> > -		if ((error_code & PF_USER) == 0 &&
> > +		if ((error_code & X86_PF_USER) == 0 &&
> 
> 	if (!(error_code & X86_PF_USER))

This change was initially intended to only rename the error codes,
without functional changes. Would making change be considered a change
in functionality? The behavior would be preserved, though.

Thanks and BR,
Ricardo


> 
> With that fixed:
> 
> Reviewed-by: Borislav Petkov <bp@...e.de>

Thank you for your review!

BR,
Ricardo
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)