linux-kernel - Re: [PATCH v2 16/22] arm64/debug: Make use of the system wide safe value

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: <561659EC.7030508@arm.com>
Date:	Thu, 8 Oct 2015 12:56:28 +0100
From:	"Suzuki K. Poulose" <Suzuki.Poulose@....com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	linux-arm-kernel@...ts.infradead.org, mark.rutland@....com,
	Vladimir.Murzin@....com, steve.capper@...aro.org,
	ard.biesheuvel@...aro.org, marc.zyngier@....com,
	will.deacon@....com, linux-kernel@...r.kernel.org,
	edward.nevill@...aro.org, aph@...hat.com, james.morse@....com,
	andre.przywara@....com, dave.martin@....com
Subject: Re: [PATCH v2 16/22] arm64/debug: Make use of the system wide safe
 value

On 08/10/15 12:11, Catalin Marinas wrote:
> On Mon, Oct 05, 2015 at 06:02:05PM +0100, Suzuki K. Poulose wrote:
>> @@ -137,13 +138,17 @@ extern struct pmu perf_ops_bp;
>>   /* Determine number of BRP registers available. */
>>   static inline int get_num_brps(void)
>>   {
>> -	return ((read_cpuid(ID_AA64DFR0_EL1) >> 12) & 0xf) + 1;
>> +	return 1 +
>> +		cpuid_feature_extract_field(read_system_reg(SYS_ID_AA64DFR0_EL1),
>> +						ID_AA64DFR0_BRPS_SHIFT);
>>   }
>
> cpuid_feature_extract_field() is fine but we should we bother with
> read_system_reg vs just read_cpuid?
> Similar question for patch 17/22.

Well, we would have already TAINTed the kernel, if these fields are different.
It is just the matter of, whether we want to provide the safer value on a tainted
kernel or not. I am open to suggestions.


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/