linux-kernel - RE: [PATCH v8 02/14] perf: Add AUX area to ring buffer for raw data streams

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: <A78C989F6D9628469189715575E55B231E676088@IRSMSX104.ger.corp.intel.com>
Date:	Mon, 17 Nov 2014 09:33:00 +0000
From:	"Metzger, Markus T" <markus.t.metzger@...el.com>
To:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Ingo Molnar <mingo@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Robert Richter <rric@...nel.org>,
	"Frederic Weisbecker" <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	"Paul Mackerras" <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	"Andi Kleen" <ak@...ux.intel.com>,
	"Liang, Kan" <kan.liang@...el.com>,
	"Hunter, Adrian" <adrian.hunter@...el.com>,
	"mathieu.poirier@...aro.org" <mathieu.poirier@...aro.org>,
	"acme@...radead.org" <acme@...radead.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: RE: [PATCH v8 02/14] perf: Add AUX area to ring buffer for raw data
 streams

> -----Original Message-----
> From: Alexander Shishkin [mailto:alexander.shishkin@...ux.intel.com]
> Sent: Friday, November 14, 2014 2:44 PM
> To: Peter Zijlstra
> Cc: Ingo Molnar; linux-kernel@...r.kernel.org; Robert Richter; Frederic
> Weisbecker; Mike Galbraith; Paul Mackerras; Stephane Eranian; Andi Kleen;
> Liang, Kan; Hunter, Adrian; Metzger, Markus T; mathieu.poirier@...aro.org;
> acme@...radead.org; Peter Zijlstra; Alexander Shishkin
> Subject: [PATCH v8 02/14] perf: Add AUX area to ring buffer for raw data
> streams
> 
> From: Peter Zijlstra <peterz@...radead.org>
> 
> This patch introduces "AUX space" in the perf mmap buffer, intended for
> exporting high bandwidth data streams to userspace, such as instruction
> flow traces.
> 
> AUX space is a ring buffer, defined by aux_{offset,size} fields in the
> user_page structure, and read/write pointers aux_{head,tail}, which abide
> by the same rules as data_* counterparts of the main perf buffer.
> 
> In order to allocate/mmap AUX, userspace needs to set up aux_offset to
> such an offset that will be greater than data_offset+data_size and
> aux_size to be the desired buffer size. Both need to be page aligned.
> Then, same aux_offset and aux_size should be passed to mmap() call and
> if everything adds up, you should have an AUX buffer as a result.

Why would userspace need to fill in aux_offset and aux_size?  Can't the kernel
do this when userspace mmaps the aux buffer like it does for the respective
data_* fields?

How would userspace fill in those fields if it mapped the data buffer read-only?

Regards,
Markus.

Intel GmbH
Dornacher Strasse 1
85622 Feldkirchen/Muenchen, Deutschland
Sitz der Gesellschaft: Feldkirchen bei Muenchen
Geschaeftsfuehrer: Christian Lamprechter, Hannes Schwaderer, Douglas Lusk
Registergericht: Muenchen HRB 47456
Ust.-IdNr./VAT Registration No.: DE129385895
Citibank Frankfurt a.M. (BLZ 502 109 00) 600119052

--
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/