| 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
| ||
|
Date: Thu, 21 Jul 2022 11:27:47 +0100
From: James Clark <james.clark@....com>
To: Mike Leach <mike.leach@...aro.org>
Cc: mathieu.poirier@...aro.org, peterz@...radead.org, mingo@...hat.com,
acme@...nel.org, linux-perf-users@...r.kernel.org,
quic_jinlmao@...cinc.com, suzuki.poulose@....com,
coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 00/13] coresight: Add new API to allocate trace source
ID values
On 04/07/2022 09:11, Mike Leach wrote:
> The current method for allocating trace source ID values to sources is
> to use a fixed algorithm for CPU based sources of (cpu_num * 2 + 0x10).
> The STM is allocated ID 0x1.
>
> This fixed algorithm is used in both the CoreSight driver code, and by
> perf when writing the trace metadata in the AUXTRACE_INFO record.
>
> The method needs replacing as currently:-
> 1. It is inefficient in using available IDs.
> 2. Does not scale to larger systems with many cores and the algorithm
> has no limits so will generate invalid trace IDs for cpu number > 44.
>
> Additionally requirements to allocate additional system IDs on some
> systems have been seen.
>
> This patch set introduces an API that allows the allocation of trace IDs
> in a dynamic manner.
I've tested this with various commands like with per-thread mode, attaching,
running the tests and also Carsten's new tests. Apart from the possible
backwards compatibility issue and the minor code comments it looks good to
me.
>
> Architecturally reserved IDs are never allocated, and the system is
> limited to allocating only valid IDs.
>
> Each of the current trace sources ETM3.x, ETM4.x and STM is updated to use
> the new API.
>
> For the ETMx.x devices IDs are allocated on certain events
> a) When using sysfs, an ID will be allocated on hardware enable, or a read of
> sysfs TRCTRACEID register and freed when the sysfs reset is written.
>
> b) When using perf, ID is allocated on hardware enable, and freed on
> hardware disable. IDs are communicated using the AUX_OUTPUT_HW_ID packet.
> The ID allocator is notified when perf sessions start and stop
> so CPU based IDs are kept constant throughout any perf session.
>
>
> Note: This patchset breaks backward compatibility for perf record and
> perf report.
>
> Because the method for generating the AUXTRACE_INFO meta data has
> changed, using an older perf record will result in metadata that
> does not match the trace IDs used in the recorded trace data.
> This mismatch will cause subsequent decode to fail.
>
> The version of the AUXTRACE_INFO has been updated to reflect the fact that
> the trace source IDs are no longer present in the metadata. This will
> mean older versions of perf report cannot decode the file.
>
> Applies to coresight/next [c06475910b52]
> Tested on DB410c
>
> Changes since v1:
> (after feedback & discussion with Mathieu & Suzuki).
>
> 1) API has changed. The global trace ID map is managed internally, so it
> is no longer passed in to the API functions.
>
> 2) perf record does not use sysfs to find the trace IDs. These are now
> output as AUX_OUTPUT_HW_ID events. The drivers, perf record, and perf report
> have been updated accordingly to generate and handle these events.
>
> Mike Leach (13):
> coresight: trace-id: Add API to dynamically assign Trace ID values
> coresight: trace-id: update CoreSight core to use Trace ID API
> coresight: stm: Update STM driver to use Trace ID API
> coresight: etm4x: Update ETM4 driver to use Trace ID API
> coresight: etm3x: Update ETM3 driver to use Trace ID API
> coresight: etmX.X: stm: Remove unused legacy source Trace ID ops
> coresight: perf: traceid: Add perf notifiers for Trace ID
> perf: cs-etm: Move mapping of Trace ID and cpu into helper function
> perf: cs-etm: Update record event to use new Trace ID protocol
> kernel: events: Export perf_report_aux_output_id()
> perf: cs-etm: Handle PERF_RECORD_AUX_OUTPUT_HW_ID packet
> coresight: events: PERF_RECORD_AUX_OUTPUT_HW_ID used for Trace ID
> coresight: trace-id: Add debug & test macros to Trace ID allocation
>
> drivers/hwtracing/coresight/Makefile | 2 +-
> drivers/hwtracing/coresight/coresight-core.c | 49 +---
> .../hwtracing/coresight/coresight-etm-perf.c | 17 ++
> drivers/hwtracing/coresight/coresight-etm.h | 3 +-
> .../coresight/coresight-etm3x-core.c | 85 +++---
> .../coresight/coresight-etm3x-sysfs.c | 28 +-
> .../coresight/coresight-etm4x-core.c | 65 ++++-
> .../coresight/coresight-etm4x-sysfs.c | 32 ++-
> drivers/hwtracing/coresight/coresight-etm4x.h | 3 +
> drivers/hwtracing/coresight/coresight-stm.c | 49 +---
> .../hwtracing/coresight/coresight-trace-id.c | 263 ++++++++++++++++++
> .../hwtracing/coresight/coresight-trace-id.h | 65 +++++
> include/linux/coresight-pmu.h | 31 ++-
> include/linux/coresight.h | 3 -
> kernel/events/core.c | 1 +
> tools/include/linux/coresight-pmu.h | 31 ++-
> tools/perf/arch/arm/util/cs-etm.c | 21 +-
> .../perf/util/cs-etm-decoder/cs-etm-decoder.c | 9 +
> tools/perf/util/cs-etm.c | 220 +++++++++++++--
> tools/perf/util/cs-etm.h | 14 +-
> 20 files changed, 784 insertions(+), 207 deletions(-)
> create mode 100644 drivers/hwtracing/coresight/coresight-trace-id.c
> create mode 100644 drivers/hwtracing/coresight/coresight-trace-id.h
>
Powered by blists - more mailing lists