linux-kernel - Re: [PATCH v4] arm64: run-time detection for aarch32 support

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] [day] [month] [year] [list]

Message-ID: <56748437.2040905@arm.com>
Date:	Fri, 18 Dec 2015 22:09:59 +0000
From:	"Suzuki K. Poulose" <Suzuki.Poulose@....com>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Yury Norov <ynorov@...iumnetworks.com>, Catalin.Marinas@....com,
	klimov.linux@...il.com, ddaney.cavm@...il.com,
	ard.biesheuvel@...aro.org, will.deacon@....com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] arm64: run-time detection for aarch32 support

On 18/12/15 17:46, Mark Rutland wrote:
> On Fri, Dec 18, 2015 at 05:03:11PM +0000, Suzuki K. Poulose wrote:
>> On 18/12/15 16:00, Yury Norov wrote:
>>> Kernel option COMPAT defines the ability of executing aarch32 binaries.
>> As per ARM ARM, AArch32 only ID register values are unknown if AArch32 is
>> not implemented. So I think we need to skip accessing the AArch32 ID registers
>> everywhere (feature tracking), if the CPU doesn't supports it, to avoid
>> unnecessary SANITY failures and TAINTing the kernel.
>
> That all sounds good to me.
>
> After boot-time we should also fail hotplug of a CPU that doesn't
> support AArch32, if we decided at boot-time that AArch32 was supported
> accross the system. That should probably be added to your early cpu
> feature verification [1].

You are right. I think we could add this as system capability to arm64_feautres
which would make the check automatic. Also, the compat_elf_arch() check won't
have to always to read_system_reg(), something like ARM64_HAS_32BIT_EL0.

Thanks
Suzuki

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/