linux-kernel - Re: GCC bug ? Re: [PATCH v2 10/10] powerpc/32s: Implement Kernel Userspace Access Protection

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <8501a33e-6c76-b6bd-9d8e-985313f94579@c-s.fr>
Date:   Wed, 22 Jan 2020 07:57:15 +0100
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Segher Boessenkool <segher@...nel.crashing.org>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>, ruscur@...sell.cc,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: GCC bug ? Re: [PATCH v2 10/10] powerpc/32s: Implement Kernel
 Userspace Access Protection



Le 21/01/2020 à 20:55, Segher Boessenkool a écrit :
> On Tue, Jan 21, 2020 at 05:22:32PM +0000, Christophe Leroy wrote:
>> g1() should return 3, not 5.
> 
> What makes you say that?
> 
> "A return of 0 does not indicate that the
>   value is _not_ a constant, but merely that GCC cannot prove it is a
>   constant with the specified value of the '-O' option."
> 

GCC doc also says:

"if you use it in an inlined function and pass an argument of the 
function as the argument to the built-in, GCC never returns 1 when you 
call the inline function with a string constant"

Does GCC considers (void*)0 as a string constant ?

Christophe