[mythtv] Gdb Woes

David Engel david at istwok.net
Sun Jul 1 04:28:37 UTC 2018


On Sun, Jul 01, 2018 at 02:02:25PM +1000, Mark Spieth wrote:
> On 7/1/2018 12:53 PM, David Engel wrote:
> > On Sun, Jul 01, 2018 at 10:55:17AM +1000, Mark Spieth wrote:
> > > On 7/1/2018 2:20 AM, David Engel wrote:
> > > > Mark,
> > > > 
> > > > I'm still having issues trying to get gdb to run.  Attached are two
> > > > log files.  Can you make any sense of them?
> > > > 
> > > > gdb.log is from running "bash -x ./gdb.sh | tee gdb.log".  The "Can't
> > > > open socket: Permission denied." look suspicious.
> > > > 
> > > > logcat.log is from running "adb logcat |& tee logcat.log".  The
> > > > "Debugger is no longer active" looks suspicious here.
> > > > 
> > > > David
> > > did a quick search for "oreo gdbserver" and found this good info
> > > https://github.com/android-ndk/ndk/issues/447
> > > 
> > > They found your copy trick (a bit different)
> > > adb push .../gdbserver /data/local/tmp
> > > adb shell
> > > $ cat /data/local/tmp/gdbserver | run-as |org.mythtv.mythfrontend| sh -c
> > > 'cat > /data/data/|org.mythtv.mythfrontend|/gdbserver'
> > > 
> > > or do it your way is also fine with dd or the sh -c cat trick. no middle
> > > man. will also work on any version of android (I think).
> > > chmod like normal of course is still required.
> > Using cat with quoted redirection was going to be my next attempt.
> > 
> > > Key log lines
> > > 
> > > 06-30 11:10:35.093 27145 27145 W gdbserver: type=1400 audit(0.0:4016): avc: denied { read } for name="stat" dev="proc" ino=4026540912 scontext=u:r:untrusted_app_25:s0:c512,c768 tcontext=u:object_r:proc_stat:s0 tclass=file permissive=0
> > > 
> > > + /home/david/android/android-ndk/my-android-toolchain64/bin/gdb -n -x
> > > so/gdb.setup
> > > Can't open socket: Permission denied.
> > > 
> > > Easy way to fix #2 is change USE_IP=0 in gdb.sh and it should work
> > > (hopefully).
> > The actual error is different (Connection reset by peer instead of
> > Permission denied), but still no go.  gdb2.log file attached.
> looks like mfe was not even started.
> cant see any mention of gdbserver in logcat output.

I get a popup stating that mfe is waiting for the debugger to attach.

Might this log be relevant?

06-30 21:29:05.194 10886 10886 W gdbserver: type=1400 audit(0.0:5110): avc: denied { read } for name="stat" dev="proc" ino=4026540912 scontext=u:r:untrusted_app_25:s0:c512,c768 tcontext=u:object_r:proc_stat:s0 tclass=file permissive=0

> Try to reorder the adb forward and the gdbserver start, may be important to
> have the "adb forward" done first.
> if that fails,
> Try changing to target remote to explicitly use localhost
> Try netstat -tan | grep 5089 to see if adb forward is actually listening on
> the host.
> Also check netstat on the shield too after gdbserver is running to make sure
> its listening on the domain socket.
> put them in the script to make it easy.

Tomorrow.

David

> Other than that I have no more good ideas.
> 
> > > #1 probably requires gdbserver from the latest ndk (and maybe gdb as well)
> > > see discussion on this.
> > > You don't need to build with the latest ndk (stick with 13b) but there may
> > > be libc issues perhaps that affect us too.
> > I installed NDK 17.whatever using Android Studio and used the
> > gdbserver that was installed in
> > /home/david/android/android-sdk-linux/ndk-bundle/prebuilt/android-arm64/gdbserver/gdbserver,
> > but it didn't make a difference.  logcat2.log file attached.
> > 
> > > Other tricks to try
> > > adb shell -t
> > > * not sure what this would help with.
> > Which invocation of adb shell?
> Dont know. Just something they tried.
> > > It would be interesting to know what release of oreo nvidia used. prerelease
> > > 3 is not good apparently.
> > The reported version is 8.0.0 and the security patch level is from May
> > 5 2018, so it looks to be current, at least for 8.0.
> Bugger. definitely release with many patches.
> 
> This problem cant be debugged by rooting the device either as that would
> change everything. selinux is our main enemy here and it looks like oreo has
> tightened everything.
> 
> Mark

-- 
David Engel
david at istwok.net


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