I have two different version of a library let's say
libxyz.so
at two different location
1) /home/maverick/dev/libxyz.so ( development Version)
2) /home/maverick/prod/libxyz.so ( Production Version )
I have a setup that compile my program and link with appropriate version of the library depending on LD_LIBRARY_PATH. for example If I want to link my program with dev version of libxyz.so i change my LD_LIBRARY_PATH to add /home/maverick/dev and if I want to link with prod version I change LD_LIBRARY_PATH to add /home/maverick/prod instead.
I compiled my program by linking with dev version and the output of
ldd MyProg
is
libxyz.so => /home/maverick/dev/libxyz.so
If i run the program it loads the libxyz.so from
/home/maverick/dev/libxyz.so
and runs fine.
it this point my LD_LIBRARY_PATH includes /home/maverick/dev not /home/maverick/prod
but when I try to debug this program through GDB
gdb MyProg
it loads the libxyz.so from location
/home/maverick/prod/libxyz.so
I have trouble making GDB load the correct version of the library during debug. So till now what I am doing is first launch the program (that load the dev version) and attach gdb to that PID this way its works fine. but if it run like
gdb MyProg
it dosen't
I tried every thing to fix this like setting up sysroot, solib-search-path in GDB but nothing is working.
if fact when I set up sysroot to point to the debug version of the library gdb gave some message like
.dynamic section for XXX is not at the expected address
any suggestion would be appreciated.
I have trouble making GDB load the correct version of the library during debug.
Let me guess: you are using tcsh, right?
The problem most likely comes from yoour ~/.cshrc resetting LD_LIBRARY_PATH to /home/maverick/prod.
When you run the program in GDB, it executes $SHELL -c your-program [args...] (so as to allow you to use I/O redirection).
Solution: don't touch environment in your .cshrc for non-interactive shell, e.g. start it with:
if ($?prompt == 0) exit
Related
Main question:
In Ubuntu trying to debug an embedded application running in QNX, I am getting the following error message from gdb:
warning: Shared object "$SOLIB_PATH/libc.so.4" could not be validated and will be ignored.,
Q: What is the "validation" operation going on ?
After some research I found that the information reported by readelf -n libfoo.so contains a build-id and that this is compared against something and there could be a mismatch causing gdb to refuse to load the library. If that's the case what ELF file's build-id is the shared object's build-id compared against ? Can I find this information parsing the executable file ?
More context:
I have a .core file for this executable. I am using a version of gdb provided by QNX and making sure I use set sysroot and set solib-search-path to where I installed the QNX toolchain.
My full command to launch gdb in Ubuntu is :
$QNX_TOOLCHAIN_PATH/ntox86_64-gdb --init-eval-command 'set sysroot $SYSROOT_PATH' --init-eval-command 'set solib-search-path $SOLIB_PATH --init-eval-command 'python sys.path.append("/usr/share/gcc-8/python");' -c path-to-exe.core path-to-executable-bin
Gdb is complaining that it cannot load shared objects :
warning: Shared object "$SOLIB_PATH/libc.so.4" could not be validated and will be ignored.
The big thing here is to make sure you're using the exact same binary that is on the target (that the program runs over). This is often quite difficult with libc, especially because libc/ldqnx are sometimes "the same thing" and it confuses gdb.
The easiest way to do this is to log your mkifs output (on the linux host):
make 2>&1 | tee build-out.txt
and read through that, search for libc.so.4, and copy the binary that's being pulled onto the target into . (wherever you're running gdb) so you don't need to mess with SOLIB paths (the lazy solution).
Alternatively, scp/ftp a new libc (one that you want to use, and ideally one that you have associated symbols for) into /tmp and use LD_LIBRARY_PATH to pull that one (and DL_DEBUG=libs to confirm, if you need). Use that same libc to debug
source: I work at QNX and even we struggle with gdb + libc sometimes
I have an embedded ARM application which is bundled with all the so-libraries stripped, including the libpthread.so. Sometimes the application gets stuck in some part of code and I want to be able to attach to it with gdb and see what's going on. The problem is that gdb refuses to load the needed threading support library, with the following messages:
Trying host libthread_db library: /home/me/debug_libs/libthread_db.so.1.
td_ta_new failed: application not linked with libthread
thread_db_load_search returning 0
warning: Unable to find libthread_db matching inferior's thread
library, thread debugging will not be available.
Because of this I cannot debug the application, e.g. I cannot see current call stacks for all threads.
After some investigation I suspect that the td_ta_new failing with the application not linked with libthread is caused by the stripped version of libpthread, which lacks the nptl_version symbol. Is there any way to bypass the error?
The gdb is compiled for ARM and being run on the device itself. I have unstripped versions of the libraries, but the application is already running with the stripped libraries.
Is there any way to bypass the error?
A few ways that come to mind:
Use add-symbol-file to override the stripped libpthread.so.0 with un-stripped one:
(gdb) info shared libpthread.so
# shows the path and memory address where stripped libpthread.so.0 is loaded
(gdb) add-symbol-file /path/to/unstripped/libpthread.so.0 $address
# should override with new symbols, and attempt to re-load libthread_db.so.1
Run gdb -ex 'set sysroot /path/to/unstripped' ... where /path/to/unstripped is the path that mirrors installed tree (that is, if you are using /lib/libpthread.so.0, there should be /path/to/unstripped/lib/libpthread.so.0.
I have not tested this, but I believe it should work.
You could comment out the version check in GDB and rebuild it.
I've configured and built gpreftools. however, I can't seem to find the generated profile file of my program to display it.
I took the following actions:
Adding the -lprofiler linker flag to my .pro, building the program and the flag is added correctly at the linking stage.
QMAKE_LFLAGS += -lprofiler
Running with:
$ CPUPROFILE=/tmp/prof.out /path/to/executable
Executing:
$ pprof --gv /path/to/MyExe /tmp/prof.out
Then I get the following:
Failed to get profile: curl -s --max-time 90 'http:///pprof/profile?seconds=30' > /home/eslam/pprof/.tmp.MyExe.1509005857.: No such file or directory.
Anyone has a resolve on this?
Check that your program actually links to libprofiler.so. Some OSes (e.g. AFAIK some versions of ubuntu) do not actually add .so if none of it's symbols are actually used. E.g. ldd ./yourprogram should list libprofiler.so. If this does not happen, then you should prepend something like -Wl,--no-as-needed to your linker flags.
LD_PRELOAD method without rebuild
Besides passing -Wl,--no-as-needed,-lprofiler,--as-needed at build time mentioned by Eslam, you can also get it to work without modifying the build by passing the LD_PRELOAD option at runtime as:
LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libprofiler.so CPUPROFILE=prof.out ./main.out
You can find libprofiler.so easily with locate libprofiler.so.
See also: How can I profile C++ code running on Linux?
Tested in Ubuntu 18.04.
I'm trying to debug a CUDA program, but when I'm launching gdb like so:
$ gdb -i=mi <program name>
$ r <program arguments>
I'm getting:
/home/wvxvw/Projects/cuda/exercise-1-udacity/cs344/HW2/hw:
error while loading shared libraries: libcudart.so.5.0:
cannot open shared object file: No such file or directory
Process gdb-inferior killed
(formatted for readability)
(I'm running gdb using M-xgdb) If that matters, then CUDA libraries are in the .bashrc
export PATH="/usr/local/cuda/bin:$PATH"
export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/usr/local/cuda/lib64"
error while loading shared libraries: libcudart.so.5.0
This error has nothing to do with GDB: your executable, when run from inside GDB, can't find the library it needs.
export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/usr/local/cuda/lib64"
GDB runs your program in a new $SHELL, so that should have worked. I wonder if there is some interaction with emacs.
In any case, this:
(gdb) set env LD_LIBRARY_PATH /usr/local/cuda/lib64
(gdb) run
should fix this problem.
Update:
as I've mentioned it before, ld path is set properly
No, it isn't. If it was, you wouldn't have the problem.
Now, I don't know why it isn't set properly. If you really want to find out, start by running GDB outside emacs (to exclude possible emacs interactions).
If the problem is still present, gdb show env, shell env, adding echo "Here" to your ~/.basrc, etc. should help you find where things are not working as you expect them.
I've had this problem as well. One way to look at it is that even if the LD_LIBRARY_PATH variable is correct when you enter show env into gdb, it may not be correct when you actually execute the program because gdb executes $SHELL -c <program> to run the program. Try this as a test, run $SHELL from the command line and then echo $LD_LIBRARY_PATH. Is it correct? If not, then you probably need to add it to your rc (.tcshrc in my case).
I had a similar problem when trying to run gdb on windows 7. I use MobaXterm to access a Linux toolbox. I installed gdb separately from http://www.gnu.org/software/gdb/ . I got it to work by making sure gdb could find the correct .dll files as mentioned by Employed Russian. If you have MobaXterm installed the .dll files should appear in your home directory in MobaXterm/slash/bin.
gdb however did not recognize the LD_LIBRARY_PATH variable. For me, it worked when I used the PATH variable instead:
(gdb) set env PATH C:\Users\Joshua\Documents\MobaXterm\slash\bin
(gdb) run
I would think using PATH instead of LD_LIBRARY_PATH might work for you provided you put the correct path to your library.
gdb is looking for a library, so why are you concerned with the include path? You may want to try to set the gdb option "solib-search-path" to point to the location of the libcudart.so.5.0 library.
I'm working on RHEL WS 4.5.
I've obtained the glibc source rpm matching this system, opened it to get its contents using rpm2cpio.
Working in that tree, I've created a patch to mtrace.c (i want to add more stack backtrace levels) and incorporated it in the spec file and created a new set of RPMs including the debuginfo rpms.
I installed all of these on a test vm (created from the same RH base image) and can confirm that my changes are included.
But with more complex executions, I crash in mtrace.c ... but gdb can't find the debug information so I don't get line number info and I can't actually debug the failure.
Based on dates, I think I can confirm that the debug information is installed on the test system in /usr/src/debug/glibc-2.3.6/
I tried
sharedlibrary libc*
in gdb and it tells me the symbols are already loaded.
My test includes a locally built python and full symbols are found for python.
My sense is that perhaps glibc isn't being built under rpmbuild with debug enabled. I've reviewed the glibc.spec file and even built with
_enable_debug_packages
defined as 1 which looked like it might influence the result. My review of the configure scripts invoked during the rpmbuild build step didn't give me any hints.
Hmmmm .. just found /usr/lib/debug/lib/libc-2.3.4.so.debug
and /usr/lib/debug/lib/tls/i486/libc-2.3.4.so.debug
but both of these are reported as stripped by the file command.
It appears that you are installing non-matching RPMs:
/usr/src/debug/glibc-2.3.6
just found /usr/lib/debug/lib/libc-2.3.4.so.debug
There are not for the same version; there is no way they came from the same -debuginfo RPM.
both of these are reported as stripped by the file command.
These should not show as stripped. Either they were not built correctly, or your strip is busted.
Also note that you don't actually have to get all of this working to debug your problem. In the RPMBUILD directory, you should be able to find the glibc build directory, with full-debug libc.so.6. Just copy that library into your VM, and you wouldn't have to worry about the debuginfo RPM.
Try verifying that debug info for mtrace.c is indeed present. First see if the separate debug info for GLIBC knows about a compilation unit called mtrace.c:
$ eu-readelf -w /usr/lib/debug/lib64/libc-2.15.so.debug > t
$ grep mtrace t
name (strp) "mtrace.c"
name (strp) "mtrace"
1 0 0 0 mtrace.c
[10480] "mtrace.c"
[104bb] "mtrace"
[5052] symbol: mtrace, CUs: 446
Then see if GDB actually finds the source file from the glibc-debuginfo RPM:
(gdb) set pagination off
(gdb) start # pause your test program right after main()
(gdb) set logging on
Copying output to gdb.txt.
(gdb) info sources
Quit GDB then grep for mtrace in gdb.txt and you should find something like /usr/src/debug/glibc-2.15-a316c1f/malloc/mtrace.c
This works with GDB 7.4. I'm not sure the GDB version shipped with RHEL 4.5 supports all the command used above. Building upstream GDB from source is in fact easier than Python though.
When trying to add strack traces to mtrace, make sure you don't call malloc() directly or indirectly in the GLIBC malloc hooks.