Re: Eclipse GDB setup issues; can't determine cause for SIGSEGV


Bryan Evenson
 

All,

-----Original Message-----
From: yocto@... <yocto@...> On
Behalf Of Bryan Evenson via lists.yoctoproject.org
Sent: Monday, June 1, 2020 4:46 PM
To: Bryan Evenson <bevenson@...>;
yocto@...
Subject: Re: [yocto] Eclipse GDB setup issues; can't determine cause for
SIGSEGV

All,

-----Original Message-----
From: yocto@... <yocto@...> On
Behalf Of Bryan Evenson via lists.yoctoproject.org
Sent: Monday, June 1, 2020 11:16 AM
To: yocto@...
Subject: [yocto] Eclipse GDB setup issues; can't determine cause for
SIGSEGV

All,

I have a AT91SAM9G25 system that has been idle for a couple years
(running
morty, yocto version 2.2.1) and I am working on updating to the latest
Yocto
production branch. Before I get there, I'm trying to confirm the old setup
and I'm having problems with remote debugging. I know there have been
changes since yocto version 2.7 for debugging support, so I want to make
sure I can get the old setup to work first prior to changing everything. I'm
looking for assistance in tracking down my debug issues.

My stable production image is based off of core-image-minimal, with a few
additional packages for our proprietary applications (proprietary
applications
are written in C). I also have a development image, based off of our
production image, with the following additions:

IMAGE_FEATURES += "package-management dev-pkgs eclipse-debug
allow-
empty-password empty-root-password"

IMAGE_INSTALL += " \
#same additional packages as production image \
#"-dbg" version of proprietary applications \
gdbserver \
"
# Strip python from the image to reduce the image size
PACKAGE_EXCLUDE = "python"

I have the Eclipse Yocto plugin installed and it is setup to use the SDK that I
have built based on the development image. I've confirmed that I can start
a
debug session on one of our proprietary applications. I can set breakpoints
and run the debugger. However, the debugger always stops at the first call
to uuid_compare with a SIGSEGV. The last line in the call stack states
"<symbol is not available> 0x00000000". From my understanding, the stack
pointer is getting set to NULL when uuid_compare is getting called. If I stop
the debugger and just run the application on the hardware, the application
runs without errors. I have confirmed with syslog messages that I do not
have the same NULL stack pointer issue when I run the application outside
of
the debugger.

Any suggestions on where to start looking? I don't see any obvious
possible
causes and I don't know where to start looking for the problem.
On a whim, I changed in my code:
if(uuid_compare(uuid1, uuid2) == 0)

To:
If(memcmp(uuid1, uuid2, 16) == 0)

After this change the problematic line of code worked just fine. The
debugger worked fine until I got to the next spot in my code that called
uuid_compare. At the next call to uuid_compare I got the same SIGSEGV
error I had before. Something is clearly a problem with calling uuid_compare.
However, I'm using several other functions from the uuid library
(uuid_is_null, uuid_parse, uuid_unparse for a few) and none of them are
causing problems. I don't think it's a problem with the input parameters
because I'm passing the same UUIDs to memcomp as I did to uuid_compare.
Has anyone ever seen only one function from a library cause problems like
this?
I don't know if this is related, but I noticed that the debugger cannot step into any library functions. For example, I tried stepping into strncpy, and the debugger stepped over the function call. I switched to assembly instruction stepping mode, then when I stepped into strncpy I received the message "No source available for strncpy@plt". I continued single stepping and was able to step through all the assembly code for strncpy. I then instruction single stepped into uuid_compare, and I was able to single step without issue until I got to the following instruction:
bx r12
When this instruction is called, r12 is 0. I'm a little confused why this library function call is failing in this manner (when all the input parameters to uuid_compare are valid), and I'm not sure why I can't source step through any library functions. If anyone has any suggestions on either issue, please let me know.

Thanks,
Bryan


Thanks,
Bryan

Join yocto@lists.yoctoproject.org to automatically receive all group messages.