Re: [PATCH] sample/tsm-mr: Use SHA-2 library APIs

[Eric Biggers <ebiggers@kernel.org>]

On Wed, Mar 18, 2026 at 08:57:01PM +0100, Arnd Bergmann wrote:
> On Wed, Mar 18, 2026, at 17:42, Eric Biggers wrote:
> > Given that tsm_mr_sample has a particular set of algorithms that it
> > wants, just use the library APIs for those algorithms rather than
> > crypto_shash.  This is more straightforward and a bit more efficient.
> >
> > This fixes an issue where this module failed to build due to the kconfig
> > options CRYPTO and CRYPTO_HASH not being selected.  Also, even if it
> > built, crypto_alloc_shash() could fail at runtime due to the needed
> > algorithms not being available.
> >
> > The library functions simply use direct linking.  So if it builds, which
> > it will due to the kconfig options being enabled, they are available.
> >
> > Fixes: f6953f1f9ec4 ("tsm-mr: Add tsm-mr sample code")
> > Fixes: 44a3873df811 ("coco/guest: Remove unneeded selection of CRYPTO")
> > Signed-off-by: Eric Biggers <ebiggers@kernel.org>
> > ---
> >
> > I'd like to take this via libcrypto-next, as that is where
> > "coco/guest: Remove unneeded selection of CRYPTO" is.
> 
> Thanks for fixing this! It is indeed nicer than the fix
> I sent earlier today.
> 
> Acked-by: Arnd Bergmann <arnd@arndb.de>

Thanks.  Additional acks from the people owning this code (Dan, Cedric?)
would be appreciated.  But since this fixes a build error and is related
to the crypto library, I went ahead and applied this to
https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=libcrypto-next

I also found that the build error is pre-existing, as CRYPTO_HASH was
not being selected.  "coco/guest: Remove unneeded selection of CRYPTO"
just made it a bit easier to encounter, by not selecting CRYPTO either.

So I updated the second paragraph of the commit message to:

    This also fixes a bug where this module failed to build if it was
    enabled without CRYPTO_HASH happening to be set elsewhere in the
    kconfig.  (With the concurrent change to make TSM_MEASUREMENTS stop
    selecting CRYPTO, this existing build error would have become easier to
    encounter, as well.)  Also, even if it built, crypto_alloc_shash() could
    fail at runtime due to the needed algorithms not being available.

I also put this commit before "coco/guest: Remove unneeded selection of
CRYPTO" and dropped the Fixes reference to that.  So now it just has:

    Fixes: f6953f1f9ec4 ("tsm-mr: Add tsm-mr sample code")

- Eric