Re: [patch 8/8] x86/vdso: Implement __vdso_futex_robust_try_unlock()

[Thomas Weißschuh]

On Wed, Mar 18, 2026 at 05:17:38PM +0100, Thomas Gleixner wrote:
> On Tue, Mar 17 2026 at 12:17, Thomas Weißschuh wrote:
> >> Due to my pretty limited userspace DSO knowledge that was the best I
> >> came up with. If you have a better idea, please let me know.
> >
> > I would have expected GDB to be able to use the separate vDSO debugging
> > symbols to find these symbols. So far I was not able to make it work,
> > but I blame my limited GDB knowledge.
> 
> I got it "working" by manually loading vdso64.so.dbg at the right
> offset, which only took about 10 attempts to get it right. Then you can
> use actual local symbols.
> 
> vdso2c picks them up correctly too.

What also works is to have GDB look up the debug symbols through their
debug ids. At this point the load address of the vDSO is already known.

$ make vdso_install INSTALL_MOD_PATH=$SOME_DIRECTORY
$ gdb -ex "set debug-file-directory $SOME_DIRECTORY/lib/modules/$(uname -r)/vdso" $BINARY

Depending on the distribution the vDSO from the kernel package might already
be set up to be found automatically.

Maybe we could add a helper to scripts/gdb/ which uses $(vdso-install-y)
to either populate a debug-file-directory automatically or hook into the GDB
lookup process to avoid these manual steps.


Thomas