Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[H. Peter Anvin]

On October 27, 2026 1:22:44 PM PDT, Nicolas Schier <nsc@xxxxxxxxxx> wrote:
>On 2026-07-08 15:56 +0200, Thomas Weißschuh wrote:
>> Finding the debug version of the vDSO is not trivial as there is no common
>> scheme where it is placed. That's especially problematic for CI testing.
>> 
>> The vDSO futex unlock mechanism requires for testing to have access to the
>> inner labels of the unlock assembly, which are only accessible via the
>> debug so.
>> 
>> Also for general debugging purposes it's convenient to have access to the
>> debug vDSO at a well defined place.
>> 
>> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
>> regular 'make vdso_install' layout, including build-id symlinks to find
>> the correct file for each process.
>> 
>> The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.
>> 
>> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
>> explicit dependency to avoid errors due to concurrent builds.
>> 
>> Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxx>
>> Link: https://lore.kernel.org/lkml/20260602090536.045586688@xxxxxxxxxx/
>> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
>> ---
>>  Makefile            | 33 ++++++++++++++++++++++++++++++++-
>>  arch/x86/Makefile   |  3 +++
>>  init/Kconfig        | 10 ++++++++++
>>  kernel/Makefile     |  1 +
>>  kernel/vdso_debug.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>>  5 files changed, 89 insertions(+), 1 deletion(-)
>> 
>
>This seems to have fallen through the cracks; shall it be considered for
>kbuild-7.5?
>

A thought: most tools support compressed separate debug information. Would it make more sense to have the vdso images with separate, compressed debug data in a subdirectory?