[Crash-utility] Extensions: Dump log buffer of Intel Processor Trace
Takao Indoh
indou.takao at jp.fujitsu.com
Thu Jan 7 00:03:03 UTC 2016
On 2016/01/07 6:27, Dave Anderson wrote:
>
>
> ----- Original Message -----
>> On 2016/01/06 12:32, Dave Anderson wrote:
>>>
>>>
>>> ----- Original Message -----
>>>> On 2016/01/06 1:42, Dave Anderson wrote:
>>>>>
>>>>>
>>>>> ----- Original Message -----
>>>>>>
>>>>>>
>>>>>> ----- Original Message -----
>>>>>>> Hi Dave,
>>>>>>>
>>>>>>> The attached files are extension module to dump log buffer of Intel
>>>>>>> Processor Trace from vmcore. Please consider placing this in the
>>>>>>> extensions page.
>>>>>>>
>>>>>>> [Overview of PT]
>>>>>>> PT(Processor Trace) is a new feature of Intel CPU "Broadwell", it
>>>>>>> captures information about program execution flow.[1]
>>>>>>>
>>>>>>> Once Intel PT is enabled, the events which change program flow, like
>>>>>>> branch instructions, exceptions, interruptions, traps and so on are
>>>>>>> logged in the memory. This is very useful for debugging because we can
>>>>>>> know the detailed behavior of software.
>>>>>>>
>>>>>>>
>>>>>>> [About extension]
>>>>>>> This extension retrieves log buff of PT from vmcore and saves it as a
>>>>>>> file. 'ptdump' command can be used once this extension is loaded.
>>>>>>>
>>>>>>> crash> extend extensions/ptdump.so
>>>>>>> ./extensions/ptdump.so: shared object loaded
>>>>>>> crash> ptdump output_dir
>>>>>>> [0] buffer dump: dump.0
>>>>>>> [0] packet decode: decode.0
>>>>>>> [1] buffer dump: dump.1
>>>>>>> [1] packet decode: decode.1
>>>>>>> (snipped)
>>>>>>>
>>>>>>> In this case, output_dir directory is created, and then dump.N and
>>>>>>> decode.N files are created in the directory for each cpus(N is cpu
>>>>>>> number).
>>>>>>>
>>>>>>> dump.N: raw data of PT
>>>>>>> decode.N: result of PT packet decoder
>>>>>>>
>>>>>>> dump.N is binary data and it is not human readable. decode.N is
>>>>>>> generated by fastdecode[2], which is PT packet dumper created by Andi
>>>>>>> Kleen. It's useful for checking what kinds of packets are included in
>>>>>>> dump.N. I'll update extension using PT library(libipt[3]) to generate
>>>>>>> more useful file for investigation.
>>>>>>>
>>>>>>> [Build extension]
>>>>>>> To build the module from the top-level crash-<version> directory,
>>>>>>> enter:
>>>>>>>
>>>>>>> $ tar xvf ptdump-1.0.0.tar.gz
>>>>>>> $ mv ptdump-1.0.0/* extensions
>>>>>>> $ make extensions
>>>>>>>
>>>>>>> [1] https://software.intel.com/en-us/blogs/2013/09/18/processor-tracing
>>>>>>> [2] https://github.com/andikleen/simple-pt
>>>>>>> [3] https://github.com/01org/processor-trace
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Takao Indoh
>>>>>>
>>>>>> Hi Takao,
>>>>>>
>>>>>> I certainly can add this to the extensions subdirectory. However
>>>>>> I do have a couple suggestions with respect to the build procedure:
>>>>>>
>>>>>> $ tar xvf $dl/ptdump-1.0.0.tar.gz
>>>>>> ptdump-1.0.0/
>>>>>> ptdump-1.0.0/fastdecode.c
>>>>>> ptdump-1.0.0/map.c
>>>>>> ptdump-1.0.0/map.h
>>>>>> ptdump-1.0.0/ptdump.c
>>>>>> ptdump-1.0.0/ptdump.mk
>>>>>> $ mv ptdump-1.0.0/* extensions
>>>>>> $ make extensions
>>>>>> gcc -Wall -g -nostartfiles -shared -rdynamic -o fastdecode.so
>>>>>> fastdecode.c
>>>>>> -fPIC -DX86_64 -DLZO -DSNAPPY -DGDB_7_6
>>>>>> gcc -DLZO -DSNAPPY -Wall -I.. -fPIC -DX86_64 -c -o ptdump.o
>>>>>> ptdump.c
>>>>>> gcc -DLZO -DSNAPPY -Wall -I.. -fPIC -DX86_64 -c -o fastdecode.o
>>>>>> fastdecode.c
>>>>>> gcc -DLZO -DSNAPPY -Wall -I.. -fPIC -DX86_64 -c -o map.o map.c
>>>>>> gcc -Wall -g -shared -rdynamic -o map.so map.c -fPIC -DX86_64 -DLZO
>>>>>> -DSNAPPY -DGDB_7_6
>>>>>> $ ls -ltr extensions/*.so
>>>>>> -rwxrwxr-x 1 anderson anderson 17613 Jan 5 10:51
>>>>>> extensions/echo.so*
>>>>>> -rwxrwxr-x 1 anderson anderson 851633 Jan 5 10:51
>>>>>> extensions/eppic.so*
>>>>>> -rwxrwxr-x 1 anderson anderson 100465 Jan 5 10:51
>>>>>> extensions/trace.so*
>>>>>> -rwxrwxr-x 1 anderson anderson 112373 Jan 5 10:51
>>>>>> extensions/dminfo.so*
>>>>>> -rwxrwxr-x 1 anderson anderson 42358 Jan 5 10:51
>>>>>> extensions/snap.so*
>>>>>> -rwxrwxr-x 1 anderson anderson 15539 Jan 5 10:57
>>>>>> extensions/fastdecode.so*
>>>>>> -rwxrwxr-x 1 anderson anderson 21136 Jan 5 10:57
>>>>>> extensions/ptdump.so*
>>>>>> -rwxrwxr-x 1 anderson anderson 14880 Jan 5 10:57
>>>>>> extensions/map.so*
>>>>>> $
>>>>>>
>>>>>> The build procedure shows the creation of the "map.so" and
>>>>>> "fastdecode.so"
>>>>>> shared objects, but does not show the creation of "ptdump.so", which is
>>>>>> the
>>>>>> only object that actually gets loaded into a crash session, correct?
>>>>>> That build line gets hidden because of the "@if" clause:
>>>>>>
>>>>>> @if [ $(ARCH) = "UNSUPPORTED" ]; then \
>>>>>> echo "ptdump: architecture not supported"; \
>>>>>> else \
>>>>>> gcc $(CFLAGS) $(TARGET_CFLAGS) $(COMMON_CFLAGS)
>>>>>> -nostartfiles
>>>>>> -shared -rdynamic -o $@ $^ ; \
>>>>>> fi;
>>>>>>
>>>>>> Can you fix that so that a user can actually see the build of ptdump.so?
>>>>
>>>> Ok, I'll fix it.
>>>>
>>>>
>>>>>> Also, unlike the other extension modules, the ptdump files and build
>>>>>> procedure clutter up the extensions subdirectory. Since you do
>>>>>> not have a single ptdump.mk and ptdump.c file, would it be possible
>>>>>> for you to do the same kind of thing that the "eppic" module does,
>>>>>> where there would be an extensions/ptdump.mk file, which would reference
>>>>>> the sources in a "ptdump" subdirectory where all of the files can be
>>>>>> cleanly kept in one place?
>>>>>>
>>>>>> Thanks,
>>>>>> Dave
>>>>>
>>>>>
>>>>> Hi Takao,
>>>>>
>>>>> Can you explain what fastdecode.so and map.so are used for?
>>>>>
>>>>> crash> extend ptdump.so
>>>>> ./extensions/ptdump.so: shared object loaded
>>>>> crash> extend fastdecode.so
>>>>> extend: ./extensions/fastdecode.so: no commands registered: shared
>>>>> object unloaded
>>>>> crash> extend map.so
>>>>> extend: ./extensions/map.so: no commands registered: shared object
>>>>> unloaded
>>>>> crash>
>>>>>
>>>>> I see fastdecode.o and map.o being included in the ptdump.so compile
>>>>> line,
>>>>> but
>>>>> don't see where fastdecode.so and map.so fit into the picture?
>>>>
>>>> fastdecode.so and map.so is not generated. Everything is included in
>>>> ptdump.so.
>>
>> I mean, fastdecode.so and map.so was created by mistake. They are not
>> needed. This bug is fixed in new version.
>>
>>>>
>>>> I'll change ptdump.mk like this so that unnecessary *.o file is not
>>>> generated.
>>>>
>>>> gcc -Wall -I. -fPIC -DX86_64 -nostartfiles -shared -rdynamic \
>>>> -o ptdump.so *.c
>>>>
>>>>
>>>>>
>>>>> In any case, to clarify my request again, after installation, there
>>>>> should
>>>>> be
>>>>> these files:
>>>>>
>>>>> extensions/ptdump.mk
>>>>> extensions/ptdump/ptdump.c
>>>>> extensions/ptdump/fastdecode.c
>>>>> extensions/ptdump/map.c
>>>>> extensions/ptdump/map.h
>>>>>
>>>>> And after the build:
>>>>>
>>>>> extensions/ptdump.so
>>>>>
>>>>> All of the other .o and .so files should only exist in the
>>>>> extensions/ptdump
>>>>> subdirectory.
>>>>
>>>> I see, I'll fix them and post updated version soon.
>>>> I have one question.
>>>>
>>>>> extensions/ptdump.mk
>>>>> extensions/ptdump/ptdump.c
>>>>
>>>> ptdump.c should be also placed in extensions/ptdump?
>>>> In the case of eppic, the files seems to be placed like this:
>>>>
>>>> extensions/eppic.mk
>>>> extensions/eppic.c
>>>> extensions/eppic/*
>>>>
>>>> Therefore if I should do in the same manner, the files should be like
>>>> this?
>>>>
>>>> extensions/ptdump.mk
>>>> extensions/ptdump.c
>>>> extensions/ptdump/fastdecode.c
>>>> extensions/ptdump/map.c
>>>> extensions/ptdump/map.h
>>>
>>> The extensions/eppic.c file is only there so that the extensions/Makefile
>>> will initiate
>>> the build of eppic.mk:
>>>
>>> $ cat extensions/eppic.c
>>> /*
>>> Place holder for proper working of the extension Makefile.
>>> Eppic crash application file is in eppic/applications/crash/eppic.c
>>> */
>>> $
>>>
>>> But you can put your actual ptdump.c file in the extensions subdirectory if
>>> you'd like.
>>
>> I noticed that ptdump.so was not built if all *.c files are in
>> extensions/ptdump directory. See extensions/Makefile for details.
>>
>> So, I place files like this.
>>
>> extensions/ptdump.mk
>> extensions/ptdump.c
>> extensions/ptdump/fastdecode.c
>> extensions/ptdump/map.c
>> extensions/ptdump/map.h
>>
>> I attach new version.
>>
>> Thanks,
>> Takao Indoh
>>
>
> Hi Takao,
>
> Nicely done! The module has been added to the extensions page:
>
> http://people.redhat.com/anderson/extensions.html#PTDUMP
I confirmed, thank you so much!
Thanks,
Takao Indoh
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