linux-kernel - Re: [RFC V1 07/11] arm64/perf: Add BRBE driver

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: <774cac19-5907-0b35-92a4-ccfef3cc095d@arm.com>
Date:   Mon, 24 Jan 2022 18:15:30 +0000
From:   James Clark <james.clark@....com>
To:     Anshuman Khandual <anshuman.khandual@....com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-perf-users@...r.kernel.org,
        Suzuki K Poulose <suzuki.poulose@....com>,
        German Gomez <german.gomez@....com>
Subject: Re: [RFC V1 07/11] arm64/perf: Add BRBE driver



On 24/01/2022 04:30, Anshuman Khandual wrote:
> This adds a BRBE driver which implements all the required helper functions
> for struct arm_pmu. Following functions are defined by this driver which
> will configure, enable, capture, reset and disable BRBE buffer HW as and
> when requested via perf branch stack sampling framework.
> 
> - arm64_pmu_brbe_filter()
> - arm64_pmu_brbe_enable()
> - arm64_pmu_brbe_disable()
> - arm64_pmu_brbe_read()
> - arm64_pmu_brbe_probe()
> - arm64_pmu_brbe_reset()
> - arm64_pmu_brbe_supported()
> 
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-perf-users@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
[...]
> +bool arm64_pmu_brbe_supported(struct perf_event *event)
> +{
> +	struct arm_pmu *armpmu = to_arm_pmu(event->pmu);
> +	struct pmu_hw_events *hw_events = per_cpu_ptr(armpmu->hw_events, event->cpu);
> +
> +	if (event->attr.branch_sample_type & PERF_SAMPLE_BRANCH_KERNEL) {
> +		if (!perfmon_capable()) {
> +			pr_warn_once("does not have permission for kernel branch filter\n");
> +			return false;

Why not check perf_event_paranoid too? I would expect kernel sampling to be allowed for non
root users with paranoid <= 0.