Re: [PATCH v2 23/33] s390/boot: Add the KMSAN runtime stub

[Alexander Potapenko]

On Tue, Nov 21, 2023 at 11:02 PM Ilya Leoshkevich <iii@xxxxxxxxxxxxx> wrote:
>
> It should be possible to have inline functions in the s390 header
> files, which call kmsan_unpoison_memory(). The problem is that these
> header files might be included by the decompressor, which does not
> contain KMSAN runtime, causing linker errors.
>
> Not compiling these calls if __SANITIZE_MEMORY__ is not defined -
> either by changing kmsan-checks.h or at the call sites - may cause
> unintended side effects, since calling these functions from an
> uninstrumented code that is linked into the kernel is valid use case.
>
> One might want to explicitly distinguish between the kernel and the
> decompressor. Checking for a decompressor-specific #define is quite
> heavy-handed, and will have to be done at all call sites.
>
> A more generic approach is to provide a dummy kmsan_unpoison_memory()
> definition. This produces some runtime overhead, but only when building
> with CONFIG_KMSAN. The benefit is that it does not disturb the existing
> KMSAN build logic and call sites don't need to be changed.
>
> Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>