| Message ID | 20210416160642.85387-3-ardb@kernel.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | relax crypto Kconfig dependencies for fsverity/fscrypt | expand |
On Fri, Apr 16, 2021 at 06:06:42PM +0200, Ard Biesheuvel wrote: > CONFIG_CRYPTO_SHA256 denotes the generic C implementation of the SHA-256 > shash algorithm, which is selected as the default crypto shash provider > for fsverity. However, fsverity has no strict link time dependency, and > the same shash could be exposed by an optimized implementation, and arm64 > has a number of those (scalar, NEON-based and one based on special crypto > instructions). In such cases, it makes little sense to require that the > generic C implementation is incorporated as well, given that it will never > be called. > > To address this, relax the 'select' clause to 'imply' so that the generic > driver can be omitted from the build if desired. > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > --- > fs/verity/Kconfig | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/fs/verity/Kconfig b/fs/verity/Kconfig > index 88fb25119899..24d1b54de807 100644 > --- a/fs/verity/Kconfig > +++ b/fs/verity/Kconfig > @@ -3,9 +3,13 @@ > config FS_VERITY > bool "FS Verity (read-only file-based authenticity protection)" > select CRYPTO > - # SHA-256 is selected as it's intended to be the default hash algorithm. > + # SHA-256 is implied as it's intended to be the default hash algorithm. > # To avoid bloat, other wanted algorithms must be selected explicitly. > - select CRYPTO_SHA256 > + # Note that CRYPTO_SHA256 denotes the generic C implementation, but > + # some architectures provided optimized implementations of the same > + # algorithm that may be used instead. In this case, CRYPTO_SHA256 may > + # be omitted even if SHA-256 is being used. > + imply CRYPTO_SHA256 > help > This option enables fs-verity. fs-verity is the dm-verity > mechanism implemented at the file level. On supported Looks fine, Acked-by: Eric Biggers <ebiggers@google.com> - Eric
diff --git a/fs/verity/Kconfig b/fs/verity/Kconfig index 88fb25119899..24d1b54de807 100644 --- a/fs/verity/Kconfig +++ b/fs/verity/Kconfig @@ -3,9 +3,13 @@ config FS_VERITY bool "FS Verity (read-only file-based authenticity protection)" select CRYPTO - # SHA-256 is selected as it's intended to be the default hash algorithm. + # SHA-256 is implied as it's intended to be the default hash algorithm. # To avoid bloat, other wanted algorithms must be selected explicitly. - select CRYPTO_SHA256 + # Note that CRYPTO_SHA256 denotes the generic C implementation, but + # some architectures provided optimized implementations of the same + # algorithm that may be used instead. In this case, CRYPTO_SHA256 may + # be omitted even if SHA-256 is being used. + imply CRYPTO_SHA256 help This option enables fs-verity. fs-verity is the dm-verity mechanism implemented at the file level. On supported
CONFIG_CRYPTO_SHA256 denotes the generic C implementation of the SHA-256 shash algorithm, which is selected as the default crypto shash provider for fsverity. However, fsverity has no strict link time dependency, and the same shash could be exposed by an optimized implementation, and arm64 has a number of those (scalar, NEON-based and one based on special crypto instructions). In such cases, it makes little sense to require that the generic C implementation is incorporated as well, given that it will never be called. To address this, relax the 'select' clause to 'imply' so that the generic driver can be omitted from the build if desired. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> --- fs/verity/Kconfig | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)