On Wed, Dec 14, 2016 at 12:10 PM, Mark Greer <mgreer@xxxxxxxxxxxxxxx> wrote: > On Wed, Dec 14, 2016 at 11:17:33AM -0500, Geoff Lansberry wrote: >> On Wed, Dec 14, 2016 at 10:57 AM, Mark Greer <mgreer@xxxxxxxxxxxxxxx> wrote: >> > >> > On Tue, Dec 13, 2016 at 08:50:04PM -0500, Geoff Lansberry wrote: >> > > Hi Mark - Thanks for getting back to me. It's funny that you ask, >> > > because we are currently chasing a segfault that is happening in neard, but >> > > may end up back in the trf7970a driver. Have you ever heard on anyone >> > > having segfault problems related to the trf7970a hardware drivers? >> > >> > No. Mind sharing more info on that segfault? >> > >> > > I'll get you an update later tonight or tomorrow. >> > >> > Okay, thanks. >> > >> > Mark >> > -- >> >> Mark - The segfault issue is only happening on writing, The work on >> the segfault is being done by a consultant, but here is his statement >> on how to recreate it on our build: >> >> I am able to reliably force neard to segfault by flooding it with >> write requests. I have attached a python script called flood.py that >> can be used to do this. The script uses utilities that ship with >> neard. >> >> The segfault does not appear deterministic. It usually happens within >> 1000 writes, but the time can varying greatly. The logs output from >> neard are inconsistent between crashes, which suggests this may be a >> timing or race condition related issue. >> >> I have been running neard manually to obtain the log information and a >> core file for debugging (attached). I run neard as, >> >> $ /usr/lib/neard/nfc/neard -d -n >> >> In a separate terminal I run, >> >> $ python flood.py >> >> And the resulting core file provides the following backtrace, >> >> (gdb) bt >> #0 0xb6caed64 in ?? () >> #1 0x0001ed7c in data_recv (resp=0x5bd90 "", length=17, data=0x58348) >> at plugins/nfctype2.c:156 >> #2 0x00024ecc in execute_recv_cb (user_data=0x5bd88) at src/adapter.c:979 >> #3 0xb6e70d60 in ?? () >> Backtrace stopped: previous frame identical to this frame (corrupt stack?) >> (gdb) >> >> The line at nfctype2.c:156 contains a memcpy operation. > > Thanks Geoff. > > What are the values of the arguments to memcpy()? > > I will look at it later today/tomorrow but if you have another NFC device > to test with, it would help isolate whether it is neard or the trf7970a > driver. The driver shouldn't be able to make neard crash like this but > who knows. > > You could also try testing older versions of neard to see if they also > fail and if not, start bisecting from there. Maybe test a different > tag type too. > > Mark > -- Mark - We can't seem to get gdb to run on our board, so we can't see the exact arguments. Here is what our consultant has to say about your question: The backtrace seems to indicate that the error is occurring in neard, not the driver. Since the driver is built as a module, your kernel won't crash if there is a problem in it, but you should be told that the error is originating in the module. It is also possible that the NFC driver does have a non-fatal problem in it (such as returning unexpected data) that is propagating to neard and causing the error there. Of course, it is also worth noting: Backtrace stopped: previous frame identical to this frame (corrupt stack?) and the same address appearing twice -- what I would assume to be your memcpy address, since that is the last call made on a given source line. If the stack is corrupt, then the error could very well originate in the driver and not neard.
