On Tue, Sep 08, 2026 at 09:19:11AM +0200, Peter Zijlstra wrote:
> On Tue, Sep 08, 2026 at 08:33:46AM +0200, Thomas Weißschuh wrote:
> > All vDSO code needs to be completely position independent. Symbol
> > references are marked as hidden so the compiler emits PC-relative
> > relocations. However there are cases where the compiler may still
> > emit absolute relocations, as they are valid in regular PIC DSO code.
> > These would be resolved by the linker and will break at runtime.
> > This has been observed on arm64, see commit 0c314cda9325 ("arm64: vdso:
> > Work around invalid absolute relocations from GCC")
> >
> > Introduce a tool to check for absolute relocations during the build,
> > as the current inline-shell logic is not expressive enough.
> > The check is done on the object files as the relocations will not exist
> > anymore in the final DSO. As there is no extension point for the
> > compilation of each object file, perform the validation in vdso_check.
> >
> > Signed-off-by: Thomas Weißschuh <[email protected]>
> > ---
> > Makefile | 19 ++
> > lib/vdso/Kconfig | 5 +
> > lib/vdso/Makefile | 2 +
> > lib/vdso/Makefile.include | 14 ++
> > lib/vdso/check/.gitignore | 3 +
> > lib/vdso/check/Makefile | 34 +++
> > lib/vdso/check/elf.rs | 498
> > ++++++++++++++++++++++++++++++++++++++++++++
> > lib/vdso/check/vdsocheck.rs | 154 ++++++++++++++
> > 8 files changed, 729 insertions(+)
>
> Urgh, does this mean I have to have rust installed just to build a
> kernel now?
No.
If you don't have rust installed the build will instead use the existing shell
script for a less thorough check. We only need one build machine at some point
to have rust installed to report issues and this check to be useful.
Thomas
