Re: [musl] Accessing Thread-Local-Storage in GDB

[Rich Felker <dalias@libc.org>]

On Wed, Feb 09, 2022 at 09:32:10AM +0200, Yehuda Yitchak wrote:
> Hello
> 
> one of the applications i am debugging is compiled using MUSL libc
> (aarch64) Version 1.1.19
> when i inspect a core-dump and try to view TLS variables with "print
> __percpu_dev" gdb (v8.3) complains:
> 
> Cannot find thread-local storage for LWP 22873, executable file
> <core-dump-file>
> Cannot find thread-local variables on this target
> 
> Any idea how I can overcome this?
> Appreciate if you could CC me since i'm not subscribed.

I think this is a consequence of gdb wanting to have a libthread_db (a
GNU- and Solaris-ism) to tell it how to interact with the threads
implementation of the process being debugged rather than just doing
things in a libpthread-agnostic way like musl wants it to do. I think
it should be fixable on the gdb side without too much headache, but I
don't know how.

As a workaround, if the program is dynamic-linked, you can do
something like print *(int *)dlsym(0, "foo") from the relevant thread
context and it should work.

Rich