Hi,

thank you for your answer

I don't think the kernel symbols are related. I do see the segfault for the command "perf report --stdio" occurs in OpenCSD, and this is the callstack:

#0 TrcPktDecodeEtmV4I::decodePacket (this=this@entry=0x555555e9a650, Complete=@0x7fffffffbb67: true)

at /home/mike/repo/OpenCSD/decoder/source/etmv4/trc_pkt_decode_etmv4i.cpp:373

#1 0x00007ffff69b812b in TrcPktDecodeEtmV4I::processPacket (this=0x555555e9a650)

at /home/mike/repo/OpenCSD/decoder/source/etmv4/trc_pkt_decode_etmv4i.cpp:99

#2 0x00007ffff69b8b58 in TrcPktDecodeBase<EtmV4ITrcPacket, EtmV4Config>::PacketDataIn (

this=0x555555e9a650, op=OCSD_OP_DATA, index_sop=41, p_packet_in=0x555555e98cf8)

at /home/mike/repo/OpenCSD/decoder/include/common/trc_pkt_decode_base.h:247

#3 0x00007ffff69b4000 in EtmV4IPktProcImpl::processData (this=0x555555e98c70, index=<optimized out>,

dataBlockSize=15, pDataBlock=0x555555e94869 "\177\201\177\377\377",

numBytesProcessed=0x7fffffffbda4)

at /home/mike/repo/OpenCSD/decoder/source/etmv4/trc_pkt_proc_etmv4i_impl.cpp:115

#4 0x00007ffff69b036a in TrcPktProcBase<EtmV4ITrcPacket, _ocsd_etmv4_i_pkt_type, EtmV4Config>::TraceDataIn (this=0x555555e98aa0, op=<optimized out>, index=32, dataBlockSize=<optimized out>,

pDataBlock=<optimized out>, numBytesProcessed=<optimized out>)

at /home/mike/repo/OpenCSD/decoder/include/common/trc_pkt_proc_base.h:238

#5 0x00007ffff69a18bd in TraceFmtDcdImpl::outputFrame (this=this@entry=0x555555e93780)

at /home/mike/repo/OpenCSD/decoder/source/trc_frame_deformatter.cpp:700

#6 0x00007ffff69a1c24 in TraceFmtDcdImpl::processTraceData (this=0x555555e93780,

index=<optimized out>, dataBlockSize=<optimized out>, pDataBlock=<optimized out>,

numBytesProcessed=0x7fffffffbee4)

at /home/mike/repo/OpenCSD/decoder/source/trc_frame_deformatter.cpp:272

#7 0x00005555558284b6 in cs_etm_decoder__process_data_block (decoder=0x555555e8b2d0, indx=0,

buf=buf@entry=0x7ffff7ff25aa ")", len=len@entry=16640, consumed=consumed@entry=0x7fffffffbf68)

at util/cs-etm-decoder/cs-etm-decoder.c:518

#8 0x0000555555826d22 in cs_etm__run_decoder (etmq=0x555555e7b150) at util/cs-etm.c:986

#9 cs_etm__process_timeless_queues (etm=0x555555e7a070, tid=2161, time_=18446744073709551615)

This is the instruction that causes the segfault as far as i saw:

Program received signal SIGSEGV, Segmentation fault.

TrcPktDecodeEtmV4I::decodePacket (this=this@entry=0x555555e9a650, Complete=@0x7fffffffbb67: true)

at /home/mike/repo/OpenCSD/decoder/source/etmv4/trc_pkt_decode_etmv4i.cpp:373

372 std::vector<uint32_t> params;

373 params[0] = m_curr_packet_in->getCC();

This segfaults because accessing an element in a vector that doesn't exist causes undefined behavior.. this causes segfault on my system.

Any OpenCSD contributor that can help?

Thanks,

Mike.

On Mon, Mar 19, 2018 at 11:40 AM, Leo Yan <leo.yan@linaro.org> wrote:

Hi Mike,

On Mon, Mar 19, 2018 at 11:08:17AM +0200, Mike Bazov wrote:
> Greetings, i was referred to this mailing list by Mathleu Poirler.
>
> I'm recording Coresight using my Dragonboard 410c board, after compiling
> the perf-opencsd-master kernel.

I am using acme branch:
https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git

> Recording seems to work on a simple program i did which does nothing but
> print a string to the screen.
>
> Now, i use perf to hopefully decode the trace, but perf segfaults. I'll let
> you know that decoding using the sample trace given here:
> https://github.com/Linaro/OpenCSD/blob/master/HOWTO.md
>
> Does work.
>
> I dived into the cs-trace-disasm.py script to see why exactly it doesn't
> work and i noticed this command causes the segfault:
> $ ~/linux/tools/perf/perf script --show-mmap-events
>
> /lib/aarch64-linux-gnu/ld-2.26.so with build id
> 6516ef8fa13fcb739834af9e87fb5fe9df612096 not found, con>
> Segmentation fault (core dumped)
>
> This command also segfaults:
>
> $ ~/linux/tools/perf/perf report --stdio
>
> /lib/aarch64-linux-gnu/ld-2.26.so with build id
> 6516ef8fa13fcb739834af9e87fb5fe9df612096 not found, con>
> (END)Segmentation fault (core dumped)

I have not seen segmentation fault issue, but it's good to share some
my finding:

- I remembered if use kallsyms for kernel symbols, you need enable
kernel configs:

CONFIG_PROC_KCORE=y
CONFIG_PROC_VMCORE=y
CONFIG_KALLSYMS=y
CONFIG_KALLSYMS_ALL=y

Also please note that the userspace has permission to export the
complete kernel address info; IIRC, you need set '0' or '1' to below
entry:
echo 0 > /proc/sys/kernel/kptr_restrict

- If you want to specify kernel for importing kernel symbol table,
like this command './perf report -k ./vmlinux --stdio', you
might need notice this patch:
https://www.spinics.net/lists/linux-perf-users/msg05576.html

If upper two methods work, I still think it might need root cause the
segmentation fault issue and fix with extra patches.

Thanks,
Leo Yan

> But this command works:
>
> $ ~/linux/tools/perf/perf report --stdio --dump
>
> And i can see Coresight packets information when browsing the output.
>
> My .debug directory looks like this:
>
> ~/.debug/
> |-- [kernel.kallsyms]
> | `-- 1dc43d23817467d7717b19af07463af0d9a9bd83
> | `-- kallsyms
> |-- [vdso]
> | `-- 18863444e4f3e2600f53e406421b2a0edd940888
> | `-- vdso
> |-- bin
> | `-- check
> | `-- 31694f29996e06da12f63d6088ec6eb23b3079c4
> | `-- elf
> `-- lib
> `-- aarch64-linux-gnu
> |-- ld-2.26.so
> | `-- 6516ef8fa13fcb739834af9e87fb5fe9df612096
> | `-- elf
> `-- libc.so.6
> `-- 06e99d8d6acabab0643e0f525ac561cf73db6498
> `-- elf
>
>
> Now, another need i wanted to ask is where can i find the code that uses
> OpenCSD to decode the trace and output instructions? eventually, i don't
> want to use perf, but rather use OpenCSD directly in my code to decode
> traces.
>
> Not sure what to do here and how to proceed, i'll appreciate some help.
> Thank you all!

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