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Message-ID: <00fac24c-d664-4ebb-8c60-f4697b7f76c1@linaro.org>
Date: Mon, 5 Aug 2024 14:59:27 +0100
From: James Clark <james.clark@...aro.org>
To: Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
Cc: acme@...hat.com, coresight@...ts.linaro.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
darren@...amperecomputing.com, scclevenger@...amperecomputing.com,
james.clark@....com, suzuki.poulose@....com, Leo Yan <leo.yan@....com>,
Al.Grant@....com, Mike Leach <mike.leach@...aro.org>
Subject: Re: [PATCH] perf scripts python arm-cs-trace-disasm.py: Skip disasm
if address continuity is broken
On 05/08/2024 1:22 pm, Ganapatrao Kulkarni wrote:
>
>
> On 01-08-2024 03:30 pm, James Clark wrote:
>>
>>
>> On 24/07/2024 3:45 pm, James Clark wrote:
>>>
>>>
>>> On 24/07/2024 7:38 am, Ganapatrao Kulkarni wrote:
>>>>
>>>>
>>>> On 23-07-2024 09:16 pm, James Clark wrote:
>>>>>
>>>>>
>>>>> On 23/07/2024 4:26 pm, Ganapatrao Kulkarni wrote:
>>>>>>
>>>>>>
>>>>>> On 23-07-2024 06:40 pm, James Clark wrote:
>>>>>>>
>>>>>>>
>>>>>>> On 22/07/2024 11:02 am, Ganapatrao Kulkarni wrote:
>>>>>>>>
>>>>>>>> Hi James,
>>>>>>>>
>>>>>>>> On 19-07-2024 08:09 pm, James Clark wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On 19/07/2024 10:26 am, Ganapatrao Kulkarni wrote:
>>>>>>>>>> To generate the instruction tracing, script uses 2 contiguous
>>>>>>>>>> packets
>>>>>>>>>> address range. If there a continuity brake due to
>>>>>>>>>> discontiguous branch
>>>>>>>>>> address, it is required to reset the tracing and start tracing
>>>>>>>>>> with the
>>>>>>>>>> new set of contiguous packets.
>>>>>>>>>>
>>>>>>>>>> Adding change to identify the break and complete the remaining
>>>>>>>>>> tracing
>>>>>>>>>> of current packets and restart tracing from new set of
>>>>>>>>>> packets, if
>>>>>>>>>> continuity is established.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Hi Ganapatrao,
>>>>>>>>>
>>>>>>>>> Can you add a before and after example of what's changed to the
>>>>>>>>> commit message? It wasn't immediately obvious to me if this is
>>>>>>>>> adding missing output, or it was correcting the tail end of the
>>>>>>>>> output that was previously wrong.
>>>>>>>>
>>>>>>>> It is adding tail end of the trace as well avoiding the segfault
>>>>>>>> of the perf application. With out this change the perf segfaults
>>>>>>>> with as below log
>>>>>>>>
>>>>>>>>
>>>>>>>> ./perf script
>>>>>>>> --script=python:./scripts/python/arm-cs-trace-disasm.py -- -d
>>>>>>>> objdump -k ../../vmlinux -v $* > dump
>>>>>>>> objdump: error: the stop address should be after the start address
>>>>>>>> Traceback (most recent call last):
>>>>>>>> File "./scripts/python/arm-cs-trace-disasm.py", line 271, in
>>>>>>>> process_event
>>>>>>>> print_disam(dso_fname, dso_vm_start, start_addr, stop_addr)
>>>>>>>> File "./scripts/python/arm-cs-trace-disasm.py", line 105, in
>>>>>>>> print_disam
>>>>>>>> for line in read_disam(dso_fname, dso_start, start_addr,
>>>>>>>> stop_addr):
>>>>>>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>>>>>> File "./scripts/python/arm-cs-trace-disasm.py", line 99, in
>>>>>>>> read_disam
>>>>>>>> disasm_output =
>>>>>>>> check_output(disasm).decode('utf-8').split('\n')
>>>>>>>> ^^^^^^^^^^^^^^^^^^^^
>>>>>>>> File "/usr/lib64/python3.12/subprocess.py", line 466, in
>>>>>>>> check_output
>>>>>>>> return run(*popenargs, stdout=PIPE, timeout=timeout,
>>>>>>>> check=True,
>>>>>>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>>>>>> File "/usr/lib64/python3.12/subprocess.py", line 571, in run
>>>>>>>> raise CalledProcessError(retcode, process.args,
>>>>>>>> subprocess.CalledProcessError: Command '['objdump', '-d', '-z',
>>>>>>>> '--start-address=0xffff80008125b758',
>>>>>>>> '--stop-address=0xffff80008125a934', '../../vmlinux']' returned
>>>>>>>> non-zero exit status 1.
>>>>>>>> Fatal Python error: handler_call_die: problem in Python trace
>>>>>>>> event handler
>>>>>>>> Python runtime state: initialized
>>>>>>>>
>>>>>>>> Current thread 0x0000ffffb05054e0 (most recent call first):
>>>>>>>> <no Python frame>
>>>>>>>>
>>>>>>>> Extension modules: perf_trace_context, systemd._journal,
>>>>>>>> systemd._reader, systemd.id128, report._py3report,
>>>>>>>> _dbus_bindings, problem._py3abrt (total: 7)
>>>>>>>> Aborted (core dumped)
>>>>>>>>
>>>>>>>>>
>>>>>>>>>> Signed-off-by: Ganapatrao Kulkarni
>>>>>>>>>> <gankulkarni@...amperecomputing.com>
>>>>>>>>>> ---
>>>>>>>>>> tools/perf/scripts/python/arm-cs-trace-disasm.py | 10
>>>>>>>>>> ++++++++++
>>>>>>>>>> 1 file changed, 10 insertions(+)
>>>>>>>>>>
>>>>>>>>>> diff --git a/tools/perf/scripts/python/arm-cs-trace-disasm.py
>>>>>>>>>> b/tools/perf/scripts/python/arm-cs-trace-disasm.py
>>>>>>>>>> index d973c2baed1c..ad10cee2c35e 100755
>>>>>>>>>> --- a/tools/perf/scripts/python/arm-cs-trace-disasm.py
>>>>>>>>>> +++ b/tools/perf/scripts/python/arm-cs-trace-disasm.py
>>>>>>>>>> @@ -198,6 +198,10 @@ def process_event(param_dict):
>>>>>>>>>> cpu_data[str(cpu) + 'addr'] = addr
>>>>>>>>>> return
>>>>>>>>>> + if (cpu_data.get(str(cpu) + 'ip') == None):
>>>>>>>>>> + cpu_data[str(cpu) + 'ip'] = ip
>>>>>>>>>> +
>>>>>>>>>
>>>>>>>>> Do you need to write into the global cpu_data here? Doesn't it
>>>>>>>>> get overwritten after you load it back into 'prev_ip'
>>>>>>>>
>>>>>>>> No, the logic is same as holding the addr of previous packet.
>>>>>>>> Saving the previous packet saved ip in to prev_ip before
>>>>>>>> overwriting with the current packet.
>>>>>>>
>>>>>>> It's not exactly the same logic as holding the addr of the
>>>>>>> previous sample. For addr, we return on the first None, with your
>>>>>>> change we now "pretend" that the second one is also the previous
>>>>>>> one:
>>>>>>>
>>>>>>> if (cpu_data.get(str(cpu) + 'addr') == None):
>>>>>>> cpu_data[str(cpu) + 'addr'] = addr
>>>>>>> return <----------------------------sample 0 return
>>>>>>>
>>>>>>> if (cpu_data.get(str(cpu) + 'ip') == None):
>>>>>>> cpu_data[str(cpu) + 'ip'] = ip <---- sample 1 save but no
>>>>>>> return
>>>>>>>
>>>>>>> Then for sample 1 'prev_ip' is actually now the 'current' IP:
>>>>>>
>>>>>> Yes, it is dummy for first packet. Added anticipating that we wont
>>>>>> hit the discontinuity for the first packet itself.
>>>>>>
>>>>>> Can this be changed to more intuitive like below?
>>>>>>
>>>>>> diff --git a/tools/perf/scripts/python/arm-cs-trace-disasm.py
>>>>>> b/tools/perf/scripts/python/arm-cs-trace-disasm.py
>>>>>> index d973c2baed1c..d49f5090059f 100755
>>>>>> --- a/tools/perf/scripts/python/arm-cs-trace-disasm.py
>>>>>> +++ b/tools/perf/scripts/python/arm-cs-trace-disasm.py
>>>>>> @@ -198,6 +198,8 @@ def process_event(param_dict):
>>>>>> cpu_data[str(cpu) + 'addr'] = addr
>>>>>> return
>>>>>>
>>>>>> + if (cpu_data.get(str(cpu) + 'ip') != None):
>>>>>> + prev_ip = cpu_data[str(cpu) + 'ip']
>>>>>>
>>>>>> if (options.verbose == True):
>>>>>> print("Event type: %s" % name)
>>>>>> @@ -243,12 +245,18 @@ def process_event(param_dict):
>>>>>>
>>>>>> # Record for previous sample packet
>>>>>> cpu_data[str(cpu) + 'addr'] = addr
>>>>>> + cpu_data[str(cpu) + 'ip'] = stop_addr
>>>>>>
>>>>>> # Handle CS_ETM_TRACE_ON packet if start_addr=0 and
>>>>>> stop_addr=4
>>>>>> if (start_addr == 0 and stop_addr == 4):
>>>>>> print("CPU%d: CS_ETM_TRACE_ON packet is inserted"
>>>>>> % cpu)
>>>>>> return
>>>>>>
>>>>>> + if (stop_addr < start_addr and prev_ip != 0):
>>>>>> + # Continuity of the Packets broken, set start_addr
>>>>>> to previous
>>>>>> + # packet ip to complete the remaining tracing of
>>>>>> the address range.
>>>>>> + start_addr = prev_ip
>>>>>> +
>>>>>> if (start_addr < int(dso_start) or start_addr >
>>>>>> int(dso_end)):
>>>>>> print("Start address 0x%x is out of range [ 0x%x
>>>>>> .. 0x%x ] for dso %s" % (start_addr, int(dso_start), int(dso_end),
>>>>>> dso))
>>>>>> return
>>>>>>
>>>>>> Without this patch below is the failure log(with segfault) for
>>>>>> reference.
>>>>>>
>>>>>> [root@...01sys-r214 perf]# timeout 4s ./perf record -e cs_etm// -C
>>>>>> 1 dd if=/dev/zero of=/dev/null
>>>>>> [ perf record: Woken up 1 times to write data ]
>>>>>> [ perf record: Captured and wrote 1.087 MB perf.data ]
>>>>>> [root@...01sys-r214 perf]# ./perf script
>>>>>> --script=python:./scripts/python/arm-cs-trace-disasm.py -- -d
>>>>>> objdump -k ../../vmlinux -v $* > dump
>>>>>> objdump: error: the stop address should be after the start address
>>>>>> Traceback (most recent call last):
>>>>>> File "./scripts/python/arm-cs-trace-disasm.py", line 271, in
>>>>>> process_event
>>>>>> print_disam(dso_fname, dso_vm_start, start_addr, stop_addr)
>>>>>> File "./scripts/python/arm-cs-trace-disasm.py", line 105, in
>>>>>> print_disam
>>>>>> for line in read_disam(dso_fname, dso_start, start_addr,
>>>>>> stop_addr):
>>>>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>>>> File "./scripts/python/arm-cs-trace-disasm.py", line 99, in
>>>>>> read_disam
>>>>>> disasm_output = check_output(disasm).decode('utf-8').split('\n')
>>>>>> ^^^^^^^^^^^^^^^^^^^^
>>>>>> File "/usr/lib64/python3.12/subprocess.py", line 466, in
>>>>>> check_output
>>>>>> return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
>>>>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>>>> File "/usr/lib64/python3.12/subprocess.py", line 571, in run
>>>>>> raise CalledProcessError(retcode, process.args,
>>>>>> subprocess.CalledProcessError: Command '['objdump', '-d', '-z',
>>>>>> '--start-address=0xffff80008125b758',
>>>>>> '--stop-address=0xffff80008125a934', '../../vmlinux']' returned
>>>>>> non-zero exit status 1.
>>>>>> Fatal Python error: handler_call_die: problem in Python trace
>>>>>> event handler
>>>>>> Python runtime state: initialized
>>>>>>
>>>>>> Current thread 0x0000ffffb90d54e0 (most recent call first):
>>>>>> <no Python frame>
>>>>>>
>>>>>> Extension modules: perf_trace_context, systemd._journal,
>>>>>> systemd._reader, systemd.id128, report._py3report, _dbus_bindings,
>>>>>> problem._py3abrt (total: 7)
>>>>>> Aborted (core dumped)
>>>>>>
>>>>>>
>>>>>> dump snippet:
>>>>>> ============
>>>>>> Event type: branches
>>>>>> Sample = { cpu: 0001 addr: 0xffff80008030cb00 phys_addr:
>>>>>> 0x0000000000000000 ip: 0xffff800080313f0c pid: 12720 tid: 12720
>>>>>> period: 1 time: 5986372298040 }
>>>>>> ffff800080313f04 <__perf_event_header__init_id+0x4c>:
>>>>>> ffff800080313f04: 36100094 tbz w20, #2,
>>>>>> ffff800080313f14 <__perf_event_header__init_id+0x5c>
>>>>>> ffff800080313f08: f941e6a0 ldr x0, [x21,
>>>>>> #968]
>>>>>> ffff800080313f0c: d63f0000 blr x0
>>>>>> perf 12720/12720 [0001] 5986.372298040
>>>>>> __perf_event_header__init_id+0x54
>>>>>> .../coresight/linux/kernel/events/core.c 586 return
>>>>>> event->clock();
>>>>>> Event type: branches
>>>>>> Sample = { cpu: 0001 addr: 0xffff8000801bb4a8 phys_addr:
>>>>>> 0x0000000000000000 ip: 0xffff80008030cb0c pid: 12720 tid: 12720
>>>>>> period: 1 time: 5986372298040 }
>>>>>> ffff80008030cb00 <local_clock>:
>>>>>> ffff80008030cb00: d503233f paciasp
>>>>>> ffff80008030cb04: a9bf7bfd stp x29, x30,
>>>>>> [sp, #-16]!
>>>>>> ffff80008030cb08: 910003fd mov x29, sp
>>>>>> ffff80008030cb0c: 97faba67 bl
>>>>>> ffff8000801bb4a8 <sched_clock>
>>>>>> perf 12720/12720 [0001] 5986.372298040
>>>>>> local_clock+0xc ...t/linux/./include/linux/sched/clock.h 64
>>>>>> return sched_clock();
>>>>>> Event type: branches
>>>>>> Sample = { cpu: 0001 addr: 0xffff80008125a8a8 phys_addr:
>>>>>> 0x0000000000000000 ip: 0xffff8000801bb4c8 pid: 12720 tid: 12720
>>>>>> period: 1 time: 5986372298040 }
>>>>>> ffff8000801bb4a8 <sched_clock>:
>>>>>> ffff8000801bb4a8: d503233f paciasp
>>>>>> ffff8000801bb4ac: a9be7bfd stp x29, x30,
>>>>>> [sp, #-32]!
>>>>>> ffff8000801bb4b0: 910003fd mov x29, sp
>>>>>> ffff8000801bb4b4: a90153f3 stp x19, x20,
>>>>>> [sp, #16]
>>>>>> ffff8000801bb4b8: d5384113 mrs x19, sp_el0
>>>>>> ffff8000801bb4bc: b9401260 ldr w0, [x19,
>>>>>> #16]
>>>>>> ffff8000801bb4c0: 11000400 add w0, w0, #0x1
>>>>>> ffff8000801bb4c4: b9001260 str w0, [x19,
>>>>>> #16]
>>>>>> ffff8000801bb4c8: 94427cf8 bl
>>>>>> ffff80008125a8a8 <sched_clock_noinstr>
>>>>>> perf 12720/12720 [0001] 5986.372298040
>>>>>> sched_clock+0x20 ...sight/linux/kernel/time/sched_clock.c 105 ns
>>>>>> = sched_clock_noinstr();
>>>>>> Event type: branches
>>>>>> Sample = { cpu: 0001 addr: 0xffff80008125b758 phys_addr:
>>>>>> 0x0000000000000000 ip: 0xffff80008125a8e4 pid: 12720 tid: 12720
>>>>>> period: 1 time: 5986372298040 }
>>>>>> ffff80008125a8a8 <sched_clock_noinstr>:
>>>>>> ffff80008125a8a8: d503233f paciasp
>>>>>> ffff80008125a8ac: a9bc7bfd stp x29, x30,
>>>>>> [sp, #-64]!
>>>>>> ffff80008125a8b0: 910003fd mov x29, sp
>>>>>> ffff80008125a8b4: a90153f3 stp x19, x20,
>>>>>> [sp, #16]
>>>>>> ffff80008125a8b8: b000e354 adrp x20,
>>>>>> ffff800082ec3000 <tick_bc_dev+0x140>
>>>>>> ffff80008125a8bc: 910d0294 add x20, x20,
>>>>>> #0x340
>>>>>> ffff80008125a8c0: a90363f7 stp x23, x24,
>>>>>> [sp, #48]
>>>>>> ffff80008125a8c4: 91002297 add x23, x20,
>>>>>> #0x8
>>>>>> ffff80008125a8c8: 52800518 mov w24,
>>>>>> #0x28 // #40
>>>>>> ffff80008125a8cc: a9025bf5 stp x21, x22,
>>>>>> [sp, #32]
>>>>>> ffff80008125a8d0: b9400296 ldr w22, [x20]
>>>>>> ffff80008125a8d4: 120002d5 and w21, w22,
>>>>>> #0x1
>>>>>> ffff80008125a8d8: 9bb87eb5 umull x21, w21,
>>>>>> w24
>>>>>> ffff80008125a8dc: 8b1502f3 add x19, x23,
>>>>>> x21
>>>>>> ffff80008125a8e0: f9400e60 ldr x0, [x19,
>>>>>> #24]
>>>>>> ffff80008125a8e4: d63f0000 blr x0
>>>>>> perf 12720/12720 [0001] 5986.372298040
>>>>>> sched_clock_noinstr+0x3c ...sight/linux/kernel/time/sched_clock.c
>>>>>> 93 cyc = (rd->read_sched_clock() - rd->epoch_cyc) &
>>>>>> Event type: branches
>>>>>> Sample = { cpu: 0001 addr: 0xffff8000801bb4cc phys_addr:
>>>>>> 0x0000000000000000 ip: 0xffff80008125a930 pid: 12720 tid: 12720
>>>>>> period: 1 time: 5986372298040 }
>>>>>>
>>>>>>
>>>>>> With fix:
>>>>>> =========
>>>>>>
>>>>>> Event type: branches
>>>>>> Sample = { cpu: 0001 addr: 0xffff80008030cb00 phys_addr:
>>>>>> 0x0000000000000000 ip: 0xffff800080313f0c pid: 12720 tid: 12720
>>>>>> period: 1 time: 5986372298040 }
>>>>>> ffff800080313f04 <__perf_event_header__init_id+0x4c>:
>>>>>> ffff800080313f04: 36100094 tbz w20, #2,
>>>>>> ffff800080313f14 <__perf_event_header__init_id+0x5c>
>>>>>> ffff800080313f08: f941e6a0 ldr x0, [x21,
>>>>>> #968]
>>>>>> ffff800080313f0c: d63f0000 blr x0
>>>>>> perf 12720/12720 [0001] 5986.372298040
>>>>>> __perf_event_header__init_id+0x54
>>>>>> .../coresight/linux/kernel/events/core.c 586 return
>>>>>> event->clock();
>>>>>> Event type: branches
>>>>>> Sample = { cpu: 0001 addr: 0xffff8000801bb4a8 phys_addr:
>>>>>> 0x0000000000000000 ip: 0xffff80008030cb0c pid: 12720 tid: 12720
>>>>>> period: 1 time: 5986372298040 }
>>>>>> ffff80008030cb00 <local_clock>:
>>>>>> ffff80008030cb00: d503233f paciasp
>>>>>> ffff80008030cb04: a9bf7bfd stp x29, x30,
>>>>>> [sp, #-16]!
>>>>>> ffff80008030cb08: 910003fd mov x29, sp
>>>>>> ffff80008030cb0c: 97faba67 bl
>>>>>> ffff8000801bb4a8 <sched_clock>
>>>>>> perf 12720/12720 [0001] 5986.372298040
>>>>>> local_clock+0xc ...t/linux/./include/linux/sched/clock.h 64
>>>>>> return sched_clock();
>>>>>> Event type: branches
>>>>>> Sample = { cpu: 0001 addr: 0xffff80008125a8a8 phys_addr:
>>>>>> 0x0000000000000000 ip: 0xffff8000801bb4c8 pid: 12720 tid: 12720
>>>>>> period: 1 time: 5986372298040 }
>>>>>> ffff8000801bb4a8 <sched_clock>:
>>>>>> ffff8000801bb4a8: d503233f paciasp
>>>>>> ffff8000801bb4ac: a9be7bfd stp x29, x30,
>>>>>> [sp, #-32]!
>>>>>> ffff8000801bb4b0: 910003fd mov x29, sp
>>>>>> ffff8000801bb4b4: a90153f3 stp x19, x20,
>>>>>> [sp, #16]
>>>>>> ffff8000801bb4b8: d5384113 mrs x19, sp_el0
>>>>>> ffff8000801bb4bc: b9401260 ldr w0, [x19,
>>>>>> #16]
>>>>>> ffff8000801bb4c0: 11000400 add w0, w0, #0x1
>>>>>> ffff8000801bb4c4: b9001260 str w0, [x19,
>>>>>> #16]
>>>>>> ffff8000801bb4c8: 94427cf8 bl
>>>>>> ffff80008125a8a8 <sched_clock_noinstr>
>>>>>> perf 12720/12720 [0001] 5986.372298040
>>>>>> sched_clock+0x20 ...sight/linux/kernel/time/sched_clock.c 105 ns
>>>>>> = sched_clock_noinstr();
>>>>>> Event type: branches
>>>>>> Sample = { cpu: 0001 addr: 0xffff80008125b758 phys_addr:
>>>>>> 0x0000000000000000 ip: 0xffff80008125a8e4 pid: 12720 tid: 12720
>>>>>> period: 1 time: 5986372298040 }
>>>>>> ffff80008125a8a8 <sched_clock_noinstr>:
>>>>>> ffff80008125a8a8: d503233f paciasp
>>>>>> ffff80008125a8ac: a9bc7bfd stp x29, x30,
>>>>>> [sp, #-64]!
>>>>>> ffff80008125a8b0: 910003fd mov x29, sp
>>>>>> ffff80008125a8b4: a90153f3 stp x19, x20,
>>>>>> [sp, #16]
>>>>>> ffff80008125a8b8: b000e354 adrp x20,
>>>>>> ffff800082ec3000 <tick_bc_dev+0x140>
>>>>>> ffff80008125a8bc: 910d0294 add x20, x20,
>>>>>> #0x340
>>>>>> ffff80008125a8c0: a90363f7 stp x23, x24,
>>>>>> [sp, #48]
>>>>>> ffff80008125a8c4: 91002297 add x23, x20,
>>>>>> #0x8
>>>>>> ffff80008125a8c8: 52800518 mov w24,
>>>>>> #0x28 // #40
>>>>>> ffff80008125a8cc: a9025bf5 stp x21, x22,
>>>>>> [sp, #32]
>>>>>> ffff80008125a8d0: b9400296 ldr w22, [x20]
>>>>>> ffff80008125a8d4: 120002d5 and w21, w22,
>>>>>> #0x1
>>>>>> ffff80008125a8d8: 9bb87eb5 umull x21, w21,
>>>>>> w24
>>>>>> ffff80008125a8dc: 8b1502f3 add x19, x23,
>>>>>> x21
>>>>>> ffff80008125a8e0: f9400e60 ldr x0, [x19,
>>>>>> #24]
>>>>>> ffff80008125a8e4: d63f0000 blr x0
>>>>>
>>>>> It looks like the disassembly now assumes this BLR wasn't taken. We
>>>>> go from ffff80008125a8e4 straight through to ...
>>>>>
>>>>>> perf 12720/12720 [0001] 5986.372298040
>>>>>> sched_clock_noinstr+0x3c ...sight/linux/kernel/time/sched_clock.c
>>>>>> 93 cyc = (rd->read_sched_clock() - rd->epoch_cyc) &
>>>>>> Event type: branches
>>>>>> Sample = { cpu: 0001 addr: 0xffff8000801bb4cc phys_addr:
>>>>>> 0x0000000000000000 ip: 0xffff80008125a930 pid: 12720 tid: 12720
>>>>>> period: 1 time: 5986372298040 }
>>>>>> ffff80008125a8e8 <sched_clock_noinstr+0x40>:
>>>>>> ffff80008125a8e8: f8756ae3 ldr x3, [x23,
>>>>>> x21]
>>>>>
>>>>> ffff80008125a8e4 which is just the previous one +4. Isn't your
>>>>> issue actually a decode issue in Perf itself? Why is there a
>>>>> discontinuity without branch samples being generated where either
>>>>> the source or destination address is 0?
>>>>>
>>>>> What are your record options to create this issue? As I mentioned
>>>>> in the previous reply I haven't been able to reproduce it.
>>>>
>>>> I am using below perf record command.
>>>>
>>>> timeout 4s ./perf record -e cs_etm// -C 1 dd if=/dev/zero of=/dev/null
>>>>
>>>
>>> Thanks I managed to reproduce it. I'll take a look to see if I think
>>> the issue is somewhere else.
>>>
>>
>> At least for the failures I encountered, the issue is due to the
>> alternatives runtime instruction patching mechanism. vmlinux ends up
>> being the wrong image to decode with because a load of branches are
>> actually turned into nops.
>>
>> Can you confirm if you use --kcore instead of vmlinux that you still
>> get failures:
>>
>> sudo perf record -e cs_etm// -C 1 --kcore -o <output-folder.data> -- \
>> dd if=/dev/zero of=/dev/null
>>
>> perf script -i <output-folder.data> \
>> tools/perf/scripts/python/arm-cs-trace-disasm.py -d llvm-objdump \
>> -k <output-folder.data>/kcore_dir/kcore
>>
>
> With below command combination with kcore also the issue is seen, as
> reported in this email chain.
>
> timeout 8s ./perf record -e cs_etm// -C 1 --kcore -o kcore \
> dd if=/dev/zero of=/dev/null
>
> ./perf script -i kcore/data \
> --script=python:./scripts/python/arm-cs-trace-disasm.py -- \
> -d objdump -k kcore/kcore_dir/kcore
>
>
> However, with below sequence(same as your command) the issue is *not* seen.
>
> timeout 8s ./perf record -e cs_etm// -C 1 --kcore -o kcore \
> dd if=/dev/zero of=/dev/null
>
> ./perf script -i kcore/data ./scripts/python/arm-cs-trace-disasm.py \
> -- -d objdump -k kcore/kcore_dir/kcore
>
> Do you see any issue with the command, which is showing the problem?
> Also the output log produced by these both commands is different.
>
Double check the command I gave. "-i" needs to be the same as "-o" (it's
the folder, not the data file). I think this could be causing your
issue. Unless you give it the folder it doesn't open kcore along with
the data file.
> The below diff that you have shared has no effect on the failing case.
>
>> But I still think bad decode detection should be moved as much as
>> possible into OpenCSD and Perf rather than this script. Otherwise
>> every tool will have to re-implement it, and OpenCSD has a lot more
>> info to make decisions with.
>>
>> One change we can make is to desynchronize when an N atom is an
>> unconditional branch:
>>
>> diff --git a/decoder/source/etmv4/trc_pkt_decode_etmv4i.cpp
>> b/decoder/source/etmv4/trc_pkt_decode_etmv4i.cpp
>> index c557998..3eefd5d 100644
>> --- a/decoder/source/etmv4/trc_pkt_decode_etmv4i.cpp
>> +++ b/decoder/source/etmv4/trc_pkt_decode_etmv4i.cpp
>> @@ -1341,6 +1341,14 @@ ocsd_err_t
>> TrcPktDecodeEtmV4I::processAtom(const ocsd_atm_val atom)
>> // save recorded next instuction address
>> ocsd_vaddr_t nextAddr = m_instr_info.instr_addr;
>>
>> + // must have lost sync if an unconditional branch wasn't taken
>> + if (atom == ATOM_N && !m_instr_info.is_conditional) {
>> + m_need_addr = true;
>> + m_out_elem.addElemType(m_index_curr_pkt,
>> OCSD_GEN_TRC_ELEM_NO_SYNC);
>> + // wait for next address
>> + return OCSD_OK;
>> + }
>> +
>>
>> Another one we can spot is when a new address comes that is before the
>> current decode address (basically the backwards check that you added).
>>
>> There are probably others that can be spotted like an address
>> appearing after a direct branch that doesn't match the branch target.
>>
>> I think at that point, desynchronising should cause the disassembly
>> script to throw away the last bit, rather than force it to be printed
>> as in this patch. As I mentioned above in the thread, it leads to
>> printing disassembly that's implausible and misleading (where an
>> unconditional branch wasn't taken).
>
> Thanks,
> Ganapat
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