linux-kernel - Re: CONFIG_ARCH_SUPPORTS

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 for Android: free password hash cracker in your pocket

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

Date:   Tue, 31 Oct 2017 10:43:32 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: CONFIG_ARCH_SUPPORTS_INT128 for AArch64

On Tue, Oct 31, 2017 at 11:17:52AM +0100, Jason A. Donenfeld wrote:
> Hi folks,
> 
> Older versions of gcc are horrible for int128_t on aarch64, emitting a
> __multi3 call, which is slow and defeats the purpose. However, more
> recent versions of gcc (since 5, IIRC), do the right thing and produce
> the proper inlined instructions.
> 
> Do we have the infrastructure available to test for this, and
> conditionally set CONFIG_ARCH_SUPPORTS_INT128 if we do?

Judging by Documentation/kbuild/makefiles.txt, we could do something
like the below in the arm64 Makefile:

cflags-y += $(call cc-ifversion, -ge, 0500, -DCONFIG_ARCH_SUPPORTS_INT128)

Note that I havent tested this at all.

Thanks,