CoreSight

coresight@lists.linaro.org

4 participants
2500 discussions

[PATCH] MAINTAINERS: Remove myself as a Arm CoreSight reviewer

by Leo Yan

I haven't done any meaningful work for a long while on Arm CoreSight and it's unlikely I'll be able to do related work in the future. Remove myself from the Arm CoreSight "Reviewers" list. Signed-off-by: Leo Yan <leo.yan(a)linaro.org> --- MAINTAINERS | 1 - 1 file changed, 1 deletion(-) diff --git a/MAINTAINERS b/MAINTAINERS index e0ad886d3163..342b8a3e19e3 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2102,7 +2102,6 @@ N: digicolor ARM/CORESIGHT FRAMEWORK AND DRIVERS M: Suzuki K Poulose <suzuki.poulose(a)arm.com> R: Mike Leach <mike.leach(a)linaro.org> -R: Leo Yan <leo.yan(a)linaro.org> L: coresight(a)lists.linaro.org (moderated for non-subscribers) L: linux-arm-kernel(a)lists.infradead.org (moderated for non-subscribers) S: Maintained -- 2.39.2

2 years, 1 month

[RESEND PATCH] MAINTAINERS: Remove myself as a Arm CoreSight reviewer

by Leo Yan

I haven't done any meaningful work for a long while on Arm CoreSight and it's unlikely I'll be able to do related work in the future. Remove myself from the Arm CoreSight "Reviewers" list. Signed-off-by: Leo Yan <leo.yan(a)linaro.org> --- Rebased on Linux kernel 6.5. MAINTAINERS | 1 - 1 file changed, 1 deletion(-) diff --git a/MAINTAINERS b/MAINTAINERS index 1cc0be8ea75a..f72a275c8ea1 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2044,7 +2044,6 @@ ARM/CORESIGHT FRAMEWORK AND DRIVERS M: Suzuki K Poulose <suzuki.poulose(a)arm.com> R: Mike Leach <mike.leach(a)linaro.org> R: James Clark <james.clark(a)arm.com> -R: Leo Yan <leo.yan(a)linaro.org> L: coresight(a)lists.linaro.org (moderated for non-subscribers) L: linux-arm-kernel(a)lists.infradead.org (moderated for non-subscribers) S: Maintained -- 2.34.1

2 years, 1 month

[RFC 0/7] coresight: Move remaining AMBA ACPI devices into platform driver

by Anshuman Khandual

This moves remaining AMBA ACPI devices into respective platform drivers for enabling ACPI based power management support. This might still require some further changes but presented here just for some initial review & feedback. This series applies on coresight/next coresight-next-v6.6 and has been built tested. This series has also been boot tested on a DT based coresight device platform. Although it still requires testing on ACPI platform. Cc: Suzuki Poulose <suzuki.poulose(a)arm.com> Cc: James Clark <james.clark(a)arm.com> Cc: Mike Leach <mike.leach(a)linaro.org> Cc: coresight(a)lists.linaro.org Cc: linux-arm-kernel(a)lists.infradead.org Cc: linux-kernel(a)vger.kernel.org Anshuman Khandual (7): coresight: replicator: Move ACPI support from AMBA driver to platform driver coresight: funnel: Move ACPI support from AMBA driver to platform driver coresight: catu: Move ACPI support from AMBA driver to platform driver coresight: tpiu: Move ACPI support from AMBA driver to platform driver coresight: tmc: Move ACPI support from AMBA driver to platform driver coresight: stm: Move ACPI support from AMBA driver to platform driver coresight: debug: Move ACPI support from AMBA driver to platform driver drivers/acpi/acpi_amba.c | 8 -- drivers/hwtracing/coresight/coresight-catu.c | 136 ++++++++++++++++-- drivers/hwtracing/coresight/coresight-catu.h | 1 + .../hwtracing/coresight/coresight-cpu-debug.c | 130 +++++++++++++++-- .../hwtracing/coresight/coresight-funnel.c | 49 ++++--- .../coresight/coresight-replicator.c | 44 +++--- drivers/hwtracing/coresight/coresight-stm.c | 80 +++++++++-- .../hwtracing/coresight/coresight-tmc-core.c | 127 ++++++++++++++-- drivers/hwtracing/coresight/coresight-tmc.h | 1 + drivers/hwtracing/coresight/coresight-tpiu.c | 76 +++++++++- 10 files changed, 549 insertions(+), 103 deletions(-) -- 2.25.1

2 years, 1 month

Re: Merge conflict resolution for CoreSight ACPI TRBE support

by Suzuki K Poulose

On 01/09/2023 20:23, Greg Kroah-Hartman wrote: > On Fri, Sep 01, 2023 at 06:38:14PM +0100, Suzuki K Poulose wrote: >> On 01/09/2023 16:47, Greg Kroah-Hartman wrote: >>> On Fri, Sep 01, 2023 at 12:15:51PM +0100, Suzuki K Poulose wrote: >>>> Hi Greg >>>> >>>> I have a question for you w.r.t pushing this series [0]. This >>>> involved some changes to the ARM PMU ACPI stub code, for parsing >>>> the ACPI tables to detect TRBE (managed via CoreSight drivers). >>>> >>>> The ARM PMU ACPI stub is maintained by Will and he tried to queue this >>>> in, but there was a conflict [1] with the CoreSight branch and >>>> hence he dropped the coresight changes, keeping the base changes. >>>> >>>> His questions in the thread above were clariried [2] and Anshuman has >>>> posted the "coresight" changes alone [3]. >>>> >>>> Now, I have already sent a pull request for v6.6. Do you think >>>> I can send a pull request with the remaining changes from Anshuman ? >>> >>> Has any of this been in linux-next yet? If not, then 6.6 is not going >>> to happen, sorry. >> >> As mentioned they were in shortly, but dropped due to the conflict with >> CoreSight tree. > > Then the code can't be merged into 6.6-rc1. > >>> If it has been in linux-next, then what's the issue? >>> >>>> If so, what do you recommend ? The dependent patches are already queued >>>> via Will's tree and merged by Linus [4] >>>> >>>> I am happy to wait for the next cycle, if this is inconvenient for you. >>> >>> I can't take anything new for my trees until after 6.6-rc1 is out, >>> neither can anyone else. >>> >>> And if the dependancies are going to go in for 6.6-rc1, then what's the >>> issue? >> >> It is just that the functionality was split and there is something in >> in 6.6-rc1, which nobody is consuming, unless these two patches come in. >> Do you recommend sending them for v6.6 ? Or queue them for v6.7 ? > > Queue for 6.7 please. Thanks, will do. Suzuki

2 years, 1 month

Re: Merge conflict resolution for CoreSight ACPI TRBE support

by Suzuki K Poulose

On 01/09/2023 16:47, Greg Kroah-Hartman wrote: > On Fri, Sep 01, 2023 at 12:15:51PM +0100, Suzuki K Poulose wrote: >> Hi Greg >> >> I have a question for you w.r.t pushing this series [0]. This >> involved some changes to the ARM PMU ACPI stub code, for parsing >> the ACPI tables to detect TRBE (managed via CoreSight drivers). >> >> The ARM PMU ACPI stub is maintained by Will and he tried to queue this >> in, but there was a conflict [1] with the CoreSight branch and >> hence he dropped the coresight changes, keeping the base changes. >> >> His questions in the thread above were clariried [2] and Anshuman has >> posted the "coresight" changes alone [3]. >> >> Now, I have already sent a pull request for v6.6. Do you think >> I can send a pull request with the remaining changes from Anshuman ? > > Has any of this been in linux-next yet? If not, then 6.6 is not going > to happen, sorry. As mentioned they were in shortly, but dropped due to the conflict with CoreSight tree. > > If it has been in linux-next, then what's the issue? > >> If so, what do you recommend ? The dependent patches are already queued >> via Will's tree and merged by Linus [4] >> >> I am happy to wait for the next cycle, if this is inconvenient for you. > > I can't take anything new for my trees until after 6.6-rc1 is out, > neither can anyone else. > > And if the dependancies are going to go in for 6.6-rc1, then what's the > issue? It is just that the functionality was split and there is something in in 6.6-rc1, which nobody is consuming, unless these two patches come in. Do you recommend sending them for v6.6 ? Or queue them for v6.7 ? Kind regards Suzuki > > confused, > > greg k-h

2 years, 1 month

Re: [PATCH V2] coresight: tmc: Make etr buffer mode user configurable from sysfs

by Suzuki K Poulose

Cc: Sudeep Hi Steve On 28/08/2023 17:35, Steve Clevenger wrote: > > Hi Suzuki, > > On 8/27/2023 2:35 PM, Suzuki K Poulose wrote: >> Hi Steve >> >> On 26/08/2023 01:14, Steve Clevenger wrote: >>> >>> Unfortunately, I tested with the original patch not [PATCH V2]. I've >>> remedied this. My results below: >>> >>> [root@sut01sys-b212 linux]# cat >>> /sys/devices/system/cpu/cpu123/ARMHC501\:23/tmc_etr35/buf_modes_available >>> auto flat catu >>> [root@sut01sys-b212 linux]# cat >>> /sys/devices/system/cpu/cpu123/ARMHC501\:23/tmc_etr35/buf_mode_preferred >>> auto >>> [root@sut01sys-b212 linux]# echo "catu" > >>> /sys/devices/system/cpu/cpu123/ARMHC501\:23/tmc_etr35/buf_mode_preferred >>> [root@sut01sys-b212 linux]# cat >>> /sys/devices/system/cpu/cpu123/ARMHC501\:23/tmc_etr35/buf_mode_preferred >>> catu >>> >>> As with the V1 patch, auto defaults to catu. >>> >>> I expected to see tmc-sg (former default) as an available mode, but do >>> not. As I recall, the buffer mode defaulted to ETR scatter-gather prior >>> to this patch. Must this capability now be explicitly advertised? I've >>> seen this done as "arm,scatter-gather" in device trees, but not used by >>> Ampere. Perhaps someone can enlighten me. >> >> Yes, you must add that property to the TMC-ETR node (for both DT and >> ACPI). In the past, almost all of the TMC-ETRs (except Juno board) >> locked up the system while using the SG mode (due to the interconnect >> issues, something to do with the transaction). Thus, we decided to >> add a property explicitly enabling this for a given platform. >> >> When you mentioned, it was using TMC-ETR SG mode, how did you verify >> this ? Please be aware that the table allocation code etc are shared >> by both TMC-SG and CATU. >> > > You might recall how this started. I had no way to test the CATU due to > the order the ETR modes defaulted (Flat, ETR-SG, CATU). For test > purposes, I programmatically swapped the ETR-SG/CATU order and could > then verify CATU operation by the driver calling into CATU code. This So, were you using the DT based boot for the above runs ? > suggests Flat mode was bypassed, and the driver defaulted to ETR-SG > prior to this hack. This didn't offer the user any control, hence my > feature request. Note that most of the early Ampere self-hosted trace > collection used ETR-SG. Now I can't select it. > > How is this property described in the ACPI? The "ACPI for CoreSight™ 1.1 > Platform Design Document" (DEN0067) doesn't describe this. This is not specified in the ACPI platform design document. I can get it fixed. Ideally we need a property describing that the scatter-gather mode is safe to use. DT uses "arm,scatter-gather" property [0] and this is what we now expect in the ACPI based systems too. https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bin… Does it sound fine ? Suzuki > > Thanks, > Steve > > >> Kind regards >> Suzuki >> >>> >>> Steve C. >>> >>> On 8/23/2023 4:10 PM, Steve Clevenger wrote: >>>> >>>> Here's some quick feedback. My system shows two modes available; auto >>>> catu >>>> >>>> etr_buf_mode_current is writable. I expected to see tmc-sg (former >>>> default) listed in etr_buf_modes_available but it doesn't show up. >>>> >>>> Note that both the auto and catu etr_buf_mode_current settings default >>>> to catu. My understanding is auto should revert to the default behavior. >>>> On my system the default was tmc-sg. >>>> >>>> More later. >>>> >>>> [root@sut01sys-b212 kernel]# cat >>>> /sys/devices/system/cpu/cpu20/ARMHC501\:60/tmc_etr96/etr_buf_modes_available >>>> >>>> auto catu >>>> [root@sut01sys-b212 kernel]# cat >>>> /sys/devices/system/cpu/cpu20/ARMHC501\:60/tmc_etr96/etr_buf_mode_current >>>> catu >>>> [root@sut01sys-b212 kernel]# echo "catu" > >>>> /sys/devices/system/cpu/cpu20/ARMHC501\:60/tmc_etr96/etr_buf_mode_current >>>> [root@sut01sys-b212 kernel]# cat >>>> /sys/devices/system/cpu/cpu20/ARMHC501\:60/tmc_etr96/etr_buf_mode_current >>>> catu >>>> >>>> Steve C. >>>> >>>> >>>> On 8/21/2023 12:40 PM, Steve Clevenger wrote: >>>>> >>>>> Hi Suzuki, >>>>> >>>>> I may be able to test it this week. You've already pointed me at the >>>>> patch thread(s). The main holdup is I need to merge the 6.6 pending >>>>> platform work in order to use the Ampere ACPI. I couldn't get these >>>>> patches to apply directly to 6.4 last I tried. >>>>> >>>>> Steve C. >>>>> >>>>> On 8/18/2023 2:39 AM, Suzuki K Poulose wrote: >>>>>> Cc: Steve >>>>>> >>>>>> Steve, >>>>>> >>>>>> Are you able to test this with CATU ? >>>>>> >>>>>> >>>>>> On 18/08/2023 09:21, Anshuman Khandual wrote: >>>>>>> Currently TMC-ETR automatically selects the buffer mode from all >>>>>>> available >>>>>>> methods in the following sequentially fallback manner - also in that >>>>>>> order. >>>>>>> >>>>>>> 1. FLAT mode with or without IOMMU >>>>>>> 2. TMC-ETR-SG (scatter gather) mode when available >>>>>>> 3. CATU mode when available >>>>>>> >>>>>>> But this order might not be ideal for all situations. For example if >>>>>>> there >>>>>>> is a CATU connected to ETR, it may be better to use TMC-ETR scatter >>>>>>> gather >>>>>>> method, rather than CATU. But hard coding such order changes will >>>>>>> prevent >>>>>>> us from testing or using a particular mode. This change provides >>>>>>> following >>>>>>> new sysfs tunables for the user to control TMC-ETR buffer mode >>>>>>> explicitly, >>>>>>> if required. This adds following new sysfs files for buffer mode >>>>>>> selection >>>>>>> purpose explicitly in the user space. >>>>>>> >>>>>>> /sys/bus/coresight/devices/tmc_etr<N>/buf_modes_available >>>>>>> /sys/bus/coresight/devices/tmc_etr<N>/buf_mode_preferred >>>>>>> >>>>>>> $ cat buf_modes_available >>>>>>> auto flat tmc-sg catu ------------------> Supported TMC-ETR buffer >>>>>>> modes >>>>>>> >>>>>>> $ echo catu > buf_mode_preferred -------> Explicit buffer mode >>>>>>> request >>>>>>> >>>>>>> But explicit user request has to be within supported ETR buffer modes >>>>>>> only. >>>>>>> These sysfs interface files are exclussive to ETR, and hence these >>>>>>> are >>>>>>> not >>>>>>> available for other TMC devices such as ETB or ETF etc. >>>>>>> >>>>>>> A new auto' mode (i.e ETR_MODE_AUTO) has been added to help fallback >>>>>>> to the >>>>>>> existing default behaviour, when user provided preferred buffer mode >>>>>>> fails. >>>>>>> ETR_MODE_FLAT and ETR_MODE_AUTO are always available as preferred >>>>>>> modes. >>>>>>> >>>>>>> Cc: Suzuki K Poulose <suzuki.poulose(a)arm.com> >>>>>>> Cc: Mike Leach <mike.leach(a)linaro.org> >>>>>>> Cc: James Clark <james.clark(a)arm.com> >>>>>>> Cc: Leo Yan <leo.yan(a)linaro.org> >>>>>>> Cc: Alexander Shishkin <alexander.shishkin(a)linux.intel.com> >>>>>>> Cc: coresight(a)lists.linaro.org >>>>>>> Cc: linux-arm-kernel(a)lists.infradead.org >>>>>>> Cc: linux-kernel(a)vger.kernel.org >>>>>>> Signed-off-by: Anshuman Khandual <anshuman.khandual(a)arm.com> >>>>>>> --- >>>>>>> This applies on v6.5-rc6 >>>>>>> >>>>>>> Changes in V2: >>>>>>> >>>>>>> - Renamed sysfs file etr_buf_modes_available as buf_modes_available >>>>>>> - Renamed sysfs file buf_mode_current as buf_mode_preferred >>>>>>> - Renamed etr_supports_flat_mode() as etr_can_use_flat_mode() >>>>>>> - Renamed coresight_tmc_groups[] as coresight_etf_groups[] >>>>>>> - Reused coresight_tmc_group[] for trigger_cntr and buffer_size >>>>>>> - Fallback trying ETR_MODE_AUTO when user preferred mode fails >>>>>>> - Moved ETR sysfs details into coresight-tmc-etr.c >>>>>>> - Dropped etr_can_use_flat_mode() check while offering ETR_MODE_FLAT >>>>>>> in sysfs >>>>>>> - Moved struct etr_buf_hw inside coresight-tmc-etr.c >>>>>>> - Moved get_etr_buf_hw() and etr_can_use_flat_mode() inside >>>>>>> coresight-tmc-etr.c >>>>>>> - Updated month in >>>>>>> Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc >>>>>>> >>>>>>> Changes in V1: >>>>>>> >>>>>>> https://lore.kernel.org/all/20230728084837.276551-1-anshuman.khandual@arm.c… >>>>>>> >>>>>>> .../testing/sysfs-bus-coresight-devices-tmc | 16 +++ >>>>>>> .../hwtracing/coresight/coresight-tmc-core.c | 15 ++- >>>>>>> .../hwtracing/coresight/coresight-tmc-etr.c | 111 >>>>>>> ++++++++++++++++-- >>>>>>> drivers/hwtracing/coresight/coresight-tmc.h | 3 + >>>>>>> 4 files changed, 131 insertions(+), 14 deletions(-) >>>>>> >>>>>> >>>>>> Looks good to me. >>>>>> >>>>>> Suzuki >>>>>> >>>>>> >>

2 years, 1 month

Merge conflict resolution for CoreSight ACPI TRBE support

by Suzuki K Poulose

Hi Greg I have a question for you w.r.t pushing this series [0]. This involved some changes to the ARM PMU ACPI stub code, for parsing the ACPI tables to detect TRBE (managed via CoreSight drivers). The ARM PMU ACPI stub is maintained by Will and he tried to queue this in, but there was a conflict [1] with the CoreSight branch and hence he dropped the coresight changes, keeping the base changes. His questions in the thread above were clariried [2] and Anshuman has posted the "coresight" changes alone [3]. Now, I have already sent a pull request for v6.6. Do you think I can send a pull request with the remaining changes from Anshuman ? If so, what do you recommend ? The dependent patches are already queued via Will's tree and merged by Linus [4] I am happy to wait for the next cycle, if this is inconvenient for you. Kind regards Suzuki [0] https://lkml.kernel.org/r/20230817055405.249630-1-anshuman.khandual@arm.com [1] https://lkml.kernel.org/r/20230821144030.52ab1357@canb.auug.org.au [2] https://lore.kernel.org/all/96d41d86-bfa2-f4d4-49ea-449c3471d036@arm.com/ [3] https://lkml.kernel.org/r/20230829135405.1159449-1-anshuman.khandual@arm.com [4] https://git.kernel.org/torvalds/c/1aa3d0274a4a

2 years, 1 month

[PATCH V6 0/2] coresight: trbe: Enable ACPI based devices

by Anshuman Khandual

These are remaining coresight patches after fixing the merge conflict which applies on coresight/next coresight-next-v6.6. Changes in V6: - Fixed te merge conflict Changes in V5: https://lore.kernel.org/all/20230817055405.249630-1-anshuman.khandual@arm.c… - Detected zeroed parsed GSI as a mismatch but handled all zero scenario - Changed condition check from 'if (ret < 0)' into a 'if (ret)' - Dropped pr_warn() message after platform_device_register() Changes in V4: https://lore.kernel.org/all/20230808082247.383405-1-anshuman.khandual@arm.c… - Added in-code comment for arm_trbe_device_probe() - Reverted back using IS_ENABLED() for SPE PMU platform device - Replaced #ifdef with IS_ENABLED() for TRBE platform device - Protected arm_trbe_acpi_match with ACPI_PTR() - preventing a build failure when CONFIG_ACPI is not enabled - Added __maybe_unused for arm_acpi_register_pmu_device() and dropped config checks with IS_ENABLED() Changes in V3: https://lore.kernel.org/all/20230803055652.1322801-1-anshuman.khandual@arm.… - Changed ARMV8_TRBE_PDEV_NAME from "arm-trbe-acpi" into "arm,trbe" - Dropped local variable 'matched' - Replaced 'matched' with 'valid gsi' as being already matched once - Moved find_acpi_cpu_topology_hetero_id() outside conditional check Changes in V2: https://lore.kernel.org/all/20230801094052.750416-1-anshuman.khandual@arm.c… - Refactored arm_spe_acpi_register_device() in a separate patch - Renamed trbe_acpi_resources as trbe_resources - Renamed trbe_acpi_dev as trbe_dev Changes in V1: https://lore.kernel.org/all/20230728112733.359620-1-anshuman.khandual@arm.c… Cc: Sami Mujawar <sami.mujawar(a)arm.com> Cc: Catalin Marinas <catalin.marinas(a)arm.com> Cc: Will Deacon <will(a)kernel.org> Cc: Mark Rutland <mark.rutland(a)arm.com> Cc: Suzuki K Poulose <suzuki.poulose(a)arm.com> Cc: Mike Leach <mike.leach(a)linaro.org> Cc: Leo Yan <leo.yan(a)linaro.org> Cc: Alexander Shishkin <alexander.shishkin(a)linux.intel.com> Cc: James Clark <james.clark(a)arm.com> Cc: coresight(a)lists.linaro.org Cc: linux-arm-kernel(a)lists.infradead.org Cc: linux-kernel(a)vger.kernel.org Anshuman Khandual (2): coresight: trbe: Add a representative coresight_platform_data for TRBE coresight: trbe: Enable ACPI based TRBE devices drivers/hwtracing/coresight/coresight-trbe.c | 23 ++++++++++++++++++-- drivers/hwtracing/coresight/coresight-trbe.h | 2 ++ 2 files changed, 23 insertions(+), 2 deletions(-) -- 2.25.1

2 years, 1 month

Re: [PATCH] coresight: tmc-etr: Don't fail probe when non-secure access is disabled

by Suzuki K Poulose

Hi Yabin On 29/08/2023 22:16, Yabin Cui wrote: >> How can this be enabled ? Why not enable it before probing the ETR ? > How can a user know if this has been done or not ? > > Pixel devices (like Pixel 6, 7) support enabling some debugging features > (including granting non-secure access to ETM/ETR) even on devices with > secure boot. It is only used internally and has strict requirements, > needing to connect to a server to verify identification after booting. > So it can't be established when probing ETR at device boot time. Are you not able to build the coresight drivers as modules and load them after the device has been authenticated and NS access enabled ? Running a trace session without NS access enabled on a normal device would be asking for trouble in the "normal world". Suzuki > > > On Sun, Aug 27, 2023 at 2:37 PM Suzuki K Poulose <suzuki.poulose(a)arm.com> wrote: >> >> On 26/08/2023 00:39, Yabin Cui wrote: >>> Because the non-secure access can be enabled later on some devices. >> >> How can this be enabled ? Why not enable it before probing the ETR ? >> How can a user know if this has been done or not ? It is asking for >> trouble to continue without this. >> >> Suzuki >> >>> >>> Signed-off-by: Yabin Cui <yabinc(a)google.com> >>> --- >>> drivers/hwtracing/coresight/coresight-tmc-core.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c >>> index c106d142e632..5ebfd12b627b 100644 >>> --- a/drivers/hwtracing/coresight/coresight-tmc-core.c >>> +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c >>> @@ -370,7 +370,7 @@ static int tmc_etr_setup_caps(struct device *parent, u32 devid, void *dev_caps) >>> struct tmc_drvdata *drvdata = dev_get_drvdata(parent); >>> >>> if (!tmc_etr_has_non_secure_access(drvdata)) >>> - return -EACCES; >>> + dev_warn(parent, "TMC ETR doesn't have non-secure access\n"); >>> >>> /* Set the unadvertised capabilities */ >>> tmc_etr_init_caps(drvdata, (u32)(unsigned long)dev_caps); >>

2 years, 1 month

Re: About ARM64 Kernel Instruction Trace

by James Clark

On 29/08/2023 05:44, Steve Clevenger wrote: > > Ampere has been using the following command sequence to generate a 'perf > record' kernel instruction trace on an AmpereOne AARCH64 based systems > using a 6.3.0 Fedora distribution with CoreSight related patches. > > > [root@sut01sys-b212 kernel]# uname -a > Linux sut01sys-b212.scc-lab.amperecomputing.com 6.3.0-coresight-enabled+ > #9 SMP PREEMPT_DYNAMIC Fri Jun 30 12:54:14 PDT 2023 aarch64 aarch64 > aarch64 GNU/Linux > [root@sut01sys-b212 kernel]# > [root@sut01sys-b212 kernel]# timeout 45s perf record --kcore -o kcore -e > cs_etm/@tmc_etr63/k --per-thread taskset --cpu-list 15 dd if=/dev/zero > of=/dev/null > [ perf record: Woken up 41 times to write data ] > [ perf record: Captured and wrote 144.056 MB kcore ] > [root@sut01sys-b212 kernel]# > [root@sut01sys-b212 kernel]# ls -l ~/linux/vmlinux > -rwxr-xr-x. 1 root root 390426912 Jun 30 12:54 /home/stevec/linux/vmlinux* > [root@sut01sys-b212 kernel]# > [root@sut01sys-b212 kernel]# timeout 45s perf script --input > ./kcore/data -s ../../scripts/arm-cs-trace-disasm.py -F > cpu,event,ip,addr,sym – -d objdump -k ~/linux/vmlinux > ./perf.itrace > [root@sut01sys-b212 kernel]# > [root@sut01sys-b212 kernel]# ls -l perf.itrace > -rw-r--r--. 1 root root 485834744 Jul 17 14:18 perf.itrace > > > The executive summary is the code sections in vmlinux do not match the > actual code executing on the target due to self-modifying code > (alternate code sequences) in the kernel image. These sequences are > typically applied over nop place-holder instructions. This was verified > by comparing a location in the ./drivers/char/mem.c read_zero objdump > instruction stream to the memory resident instructions captured with the > TRACE32 ETM instruction trace feature. This particular instruction trace > example shows a disconnect. It displays a ‘b ffff800008ab8a70 > <read_zero+0x168>’ instruction at address 0xffff800008ab89e8 which did > not branch. The actual instruction present at 0xffff800008ab89e8 is a ‘nop’. > . > . > ffff800008ab89a8: 1400000d b ffff800008ab89dc > <read_zero+0xd4> > dd 8774/8774 [0015] 0.000000000 read_zero+0xa0 > ffff800008ab89dc <read_zero+0xd4>: > ffff800008ab89dc: 9248f840 and x0, x2, > #0xff7fffffffffffff > ffff800008ab89e0: aa1403e1 mov x1, x20 > ffff800008ab89e4: 9418b6fb bl ffff8000090e65d0 > <__arch_clear_user> > dd 8774/8774 [0015] 0.000000000 read_zero+0xdc > ffff8000090e65d0 <__arch_clear_user>: > ffff8000090e65d0: d503245f bti c > ffff8000090e65d4: 8b010002 add x2, x0, x1 > ffff8000090e65d8: f1002021 subs x1, x1, #0x8 > ffff8000090e65dc: 54000104 b.mi ffff8000090e65fc > <__arch_clear_user+0x2c> // b.first > ffff8000090e65e0: f800081f sttr xzr, [x0] > ffff8000090e65e4: 91002000 add x0, x0, #0x8 > ffff8000090e65e8: f1002021 subs x1, x1, #0x8 > ffff8000090e65ec: 54ffffa8 b.hi ffff8000090e65e0 > <__arch_clear_user+0x10> // b.pmore > dd 8774/8774 [0015] 0.000000000 > __arch_clear_user+0x1c > ...vec/linux/arch/arm64/lib/clear_user.S 31 b.hi 1b > ffff8000090e65e0 <__arch_clear_user+0x10>: > ffff8000090e65e0: f800081f sttr xzr, [x0] > ffff8000090e65e4: 91002000 add x0, x0, #0x8 > ffff8000090e65e8: f1002021 subs x1, x1, #0x8 > ffff8000090e65ec: 54ffffa8 b.hi ffff8000090e65e0 > <__arch_clear_user+0x10> // b.pmore > . > . > ffff8000090e65f0: f81f885f sttr xzr, [x2, #-8] > ffff8000090e65f4: d2800000 mov x0, #0x0 > // #0 > ffff8000090e65f8: d65f03c0 ret > dd 8774/8774 [0015] 0.000000000 > __arch_clear_user+0x28 > ...vec/linux/arch/arm64/lib/clear_user.S 34 ret > ffff800008ab89e8 <read_zero+0xe0>: > ffff800008ab89e8: 14000022 b ffff800008ab8a70 > <read_zero+0x168> > ffff800008ab89ec: d503201f nop > dd 8774/8774 [0015] 0.000000000 read_zero+0xe4 > /home/stevec/linux/drivers/char/mem.c 521 > left = clear_user(buf + cleared, chunk); > ffff800008ab8a18 <read_zero+0x110>: > ffff800008ab8a18: 8b14035a add x26, x26, x20 > ffff800008ab8a1c: b5000360 cbnz x0, > ffff800008ab8a88 <read_zero+0x180> > ffff800008ab8a20: f9400320 ldr x0, [x25] > ffff800008ab8a24: cb140273 sub x19, x19, x20 > . > . > > Ostensibly, the ‘perf record –kcore’ option produces a representative > image of the kernel. But this option does not produce suitable output to > generate ARM64 kernel instruction trace. perf doesn’t disassemble ARM64, > so the arm-cs-trace-disasm.py python script is used with the native > objdump utility to provide ARM64 disassembly from CoreSight trace > capture. objdump itself requires an ELF/DWARF file image + symbols to > generate the symbolic (+ line information for mixed source) disassembly. > The linux vmlinux image + symbols file is typically used for this > purpose. The kallsyms file is not formatted for objdump use. As an > experiment, I patched the executable code sections in a local copy of > vmlinux with the corresponding executable code segments extracted from > the kcore image using an Ampere internal ELF patch utility. > > This patch utility leverages the (MIT Licensed) ELFIO open source > library API. These were the commands. > > > [root@sut01sys-b212 kernel]# timeout 30s perf record --kcore -o kcore -e > cs_etm/@tmc_etr63/k --per-thread taskset --cpu-list 15 dd if=/dev/zero > of=/dev/null > [ perf record: Woken up 25 times to write data ] > [ perf record: Captured and wrote 88.053 MB kcore ] > [root@sut01sys-b212 kernel]# > [root@sut01sys-b212 kernel]# ls -l ~/linux/vmlinux > -rwxr-xr-x. 1 root root 390426912 Jun 30 12:54 /home/stevec/linux/vmlinux* > [root@sut01sys-b212 kernel]# cp ~/linux/vmlinux . > [root@sut01sys-b212 kernel]# patch-elf --help > > patch-elf overlays the kernel image from a local copy of > '/proc/kcore' to the corresponding (by address) ELF sections > in a local copy of the vmlinux ELF file. > A local '/proc/kcore' is created by: > 'perf report --kcore -e cs_etm/@tmc_etr1/k ...' > The local (patched) vmlinux copy is used by: > 'perf script -s arm-cs-trace-disasm.py ...' > See the CoreSight Hardware-Assisted Trace Application Note for > use of the 'perf report' and 'perf script' commands. > > Usage: patch-elf <--verbose> kcore_file vmlinux_file > [root@sut01sys-b212 kernel]# > [root@sut01sys-b212 kernel]# patch-elf kcore/kcore_dir/kcore ./vmlinux > ELF File kcore Properties > ELF file class: ELF64 > ELF file encoding: Little endian > Machine: ARM AArch64 > Type: Core file > Number of segments: 3 > Number of sections: 0 > > ELF File vmlinux Properties > ELF file class: ELF64 > ELF file encoding: Little endian > Machine: ARM AArch64 > Type: Shared object file > Number of segments: 3 > Number of sections: 43 > > Patching section[ 2] ffff800008010000 17997936 bytes > > Patching section[15] ffff800009a31000 20480 bytes > > Patching section[16] ffff800009a40000 612372 bytes > > Patching section[17] ffff800009ad5818 24752 bytes > > [root@sut01sys-b212 kernel]# ls -l ./vmlinux > -rwxr-xr-x. 1 root root 390426908 Jul 19 11:14 ./vmlinux* > [root@sut01sys-b212 kernel]# > [root@sut01sys-b212 kernel]# timeout 45s perf script --input > ./kcore/data -s ../../scripts/arm-cs-trace-disasm.py -F > cpu,event,ip,addr,sym – -d objdump -k ./vmlinux > ./perf.itrace > [root@sut01sys-b212 kernel]# > [root@sut01sys-b212 kernel]# ls -l perf.itrace > -rw-r--r--. 1 root root 32142060 Jul 19 11:18 perf.itrace > > Here is the representative kernel instruction trace using a patched vmlinux. > > . > . > ffff800008ab89a8: 1400000d b ffff800008ab89dc > <read_zero+0xd4> > dd 8774/8774 [0015] 0.000000000 read_zero+0xa0 > ffff800008ab89dc <read_zero+0xd4>: > ffff800008ab89dc: 9248f840 and x0, x2, > #0xff7fffffffffffff > ffff800008ab89e0: aa1403e1 mov x1, x20 > ffff800008ab89e4: 9418b6fb bl ffff8000090e65d0 > <__arch_clear_user> > dd 8774/8774 [0015] 0.000000000 read_zero+0xdc > ffff8000090e65d0 <__arch_clear_user>: > ffff8000090e65d0: d503245f bti c > ffff8000090e65d4: 8b010002 add x2, x0, x1 > ffff8000090e65d8: f1002021 subs x1, x1, #0x8 > ffff8000090e65dc: 54000104 b.mi ffff8000090e65fc > <__arch_clear_user+0x2c> // b.first > ffff8000090e65e0: f800081f sttr xzr, [x0] > ffff8000090e65e4: 91002000 add x0, x0, #0x8 > ffff8000090e65e8: f1002021 subs x1, x1, #0x8 > ffff8000090e65ec: 54ffffa8 b.hi ffff8000090e65e0 > <__arch_clear_user+0x10> // b.pmore > dd 8774/8774 [0015] 0.000000000 > __arch_clear_user+0x1c > ffff8000090e65e0 <__arch_clear_user+0x10>: > ffff8000090e65e0: f800081f sttr xzr, [x0] > ffff8000090e65e4: 91002000 add x0, x0, #0x8 > ffff8000090e65e8: f1002021 subs x1, x1, #0x8 > ffff8000090e65ec: 54ffffa8 b.hi ffff8000090e65e0 > <__arch_clear_user+0x10> // b.pmore > . > . > ffff8000090e65f0: f81f885f sttr xzr, [x2, #-8] > ffff8000090e65f4: d2800000 mov x0, #0x0 > // #0 > ffff8000090e65f8: d65f03c0 ret > dd 8774/8774 [0015] 0.000000000 > __arch_clear_user+0x28 > ...vec/linux/arch/arm64/lib/clear_user.S 34 ret > ffff800008ab89e8 <read_zero+0xe0>: > ffff800008ab89e8: d503201f nop > ffff800008ab89ec: 1400000b b ffff800008ab8a18 > <read_zero+0x110> > dd 8774/8774 [0015] 0.000000000 read_zero+0xe4 > /home/stevec/linux/drivers/char/mem.c 521 > left = clear_user(buf + cleared, chunk); > ffff800008ab8a18 <read_zero+0x110>: > ffff800008ab8a18: 8b14035a add x26, x26, x20 > ffff800008ab8a1c: b5000360 cbnz x0, > ffff800008ab8a88 <read_zero+0x180> > ffff800008ab8a20: f9400320 ldr x0, [x25] > ffff800008ab8a24: cb140273 sub x19, x19, x20 > . > . > . > > This begs the question what perf enhancements could be added to make > ARM64 kernel instruction trace easier to use? The process I’ve followed > is cumbersome, but could be done behind the scenes by perf. The caveat > is it requires a vmlinux which might not be available to an end user. > Here are 2 options. > > 1. 'perf report -kcore'could use the process I’ve used here > transparently in the background. The plus side is the objdump feature of > mixed disassembly is available based on the current vmlinux. > Hi Steve, What you're saying makes sense to me. I think #1 sounds best, I'm not sure of the use-case where you wanted to make actionable decisions from the trace but wouldn't have vmlinux available? Maybe an end-user could be missing it, but I can only imagine use cases where you are actively building and developing the kernel. > 2. 'perf report -kcore' generates an ELF + symbols file based on > kallsyms (and/or System.map). No vmlinux patching, so intermixed source > and disassembly wouldn’t be available. It’s a reasonable alternative > without relying on vmlinux. > > It makes sense performance-wise to use an ARM64 disassembler directly > through perf. perf-script use of the arm-cs-trace-disasm.py python > script can be slow. I’m unfamiliar with the Intel implementation, but > perf-annotate uses objdump. Unfortunately, I can't seem to get annotate > to work for me. A patch operation is still be required if vmlinux is used. > We have had other reports about arm-cs-trace-disasm.py being slow. I had a plan to make it work with disassembly directly from Perf as that is available in other modes. For example the annotate mode in perf already works on Arm. What error are you getting with it exactly? It might require installation of the aarch64 objdump tool if you are running on x86, or provide the --objdump option? > I suspect the CoreSight/perf communities are aware of these issues. > Is there any ongoing work not known to the outside world? > > Thanks and regards, > Steve C.

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