linux-kernel - Re: [PATCH v9 02/10] Makefile: Prepare for using macros for inline asm

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: <192946CF-8543-4CF5-B2A3-93674FCD07E2@vmware.com>
Date:   Wed, 7 Nov 2018 18:56:52 +0000
From:   Nadav Amit <namit@...are.com>
To:     Logan Gunthorpe <logang@...tatee.com>,
        Ingo Molnar <mingo@...hat.com>
CC:     LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Stephen Bates <sbates@...thlin.com>
Subject: Re: [PATCH v9 02/10] Makefile: Prepare for using macros for inline
 asm

From: Logan Gunthorpe
Sent: November 7, 2018 at 6:53:02 PM GMT
> Subject: Re: [PATCH v9 02/10] Makefile: Prepare for using macros for inline asm
> 
> 
> 
> 
> On 2018-11-07 11:01 a.m., Nadav Amit wrote:
>> Ideas? Do people care about it?
> 
> Just spit balling, but is there a reason we didn't just put the macros
> for inline assembly directly in the header? Something like this:
> 
> asm(".macro ANNOTATE_UNREACHABLE counter:req\n\t"
>    "\\counter:\n\t"
>        ".pushsection .discard.unreachable\n\t"
>        ".long \\counter\\()b -.\n\t"
>        ".popsection\n\t"
>    ".endm\n");
> 
> #define annotate_unreachable() ({                   \
>    asm volatile("ANNOTATE_UNREACHABLE counter=%c0" \
>                 : : "i" (__COUNTER__));            \
> })
> 
> It does mean the macros won't be usable in non-inline assembly, without
> duplicating them, but do we care about that?

HPA indicated more than once that this is wrong (and that was indeed my
initial solution), since it is not guaranteed that the compiler would put
the macro assembly before its use.