[Crash-utility] Extensions: Dump log buffer of Intel Processor Trace
Dave Anderson
anderson at redhat.com
Wed Jan 6 21:27:42 UTC 2016
----- 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
Thanks,
Dave
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