Re: [PATCH v6 06/14] x86: Add early SHA support for Secure Launch early measurements

[Daniel P. Smith]

On 5/5/23 12:34, Simon Horman wrote:
> On Thu, May 04, 2023 at 02:50:15PM +0000, Ross Philipson wrote:
> > From: "Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>
> >
> > The SHA algorithms are necessary to measure configuration information into
> > the TPM as early as possible before using the values. This implementation
> > uses the established approach of #including the SHA libraries directly in
> > the code since the compressed kernel is not uncompressed at this point.
> >
> > The SHA code here has its origins in the code from the main kernel:
> >
> > commit c4d5b9ffa31f ("crypto: sha1 - implement base layer for SHA-1")
> >
> > That code could not be pulled directly into the setup portion of the
> > compressed kernel because of other dependencies it pulls in. The result
> > is this is a modified copy of that code that still leverages the core
> > SHA algorithms.
> >
> > Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Ross Philipson <ross.philipson@xxxxxxxxxx>
> > ---
> >   arch/x86/boot/compressed/Makefile       |  2 +
> >   arch/x86/boot/compressed/early_sha1.c   | 97 +++++++++++++++++++++++++++++++++
> >   arch/x86/boot/compressed/early_sha1.h   | 17 ++++++
> >   arch/x86/boot/compressed/early_sha256.c |  7 +++
> >   lib/crypto/sha1.c                       |  4 ++
> >   lib/crypto/sha256.c                     |  8 +++
> >   6 files changed, 135 insertions(+)
> >   create mode 100644 arch/x86/boot/compressed/early_sha1.c
> >   create mode 100644 arch/x86/boot/compressed/early_sha1.h
> >   create mode 100644 arch/x86/boot/compressed/early_sha256.c
> >
> > diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> > index 6b6cfe6..1d327d4 100644
> > --- a/arch/x86/boot/compressed/Makefile
> > +++ b/arch/x86/boot/compressed/Makefile
> > @@ -112,6 +112,8 @@ vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi.o
> >   vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_mixed.o
> >   vmlinux-objs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
> >   
> > +vmlinux-objs-$(CONFIG_SECURE_LAUNCH) += $(obj)/early_sha1.o $(obj)/early_sha256.o
> > +
> >   $(obj)/vmlinux: $(vmlinux-objs-y) FORCE
> >   	$(call if_changed,ld)
> >   
> > diff --git a/arch/x86/boot/compressed/early_sha1.c b/arch/x86/boot/compressed/early_sha1.c
> > new file mode 100644
> > index 0000000..524ec23
> > --- /dev/null
> > +++ b/arch/x86/boot/compressed/early_sha1.c
> > @@ -0,0 +1,97 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (c) 2022 Apertus Solutions, LLC.
> > + */
> > +
> > +#include <linux/init.h>
> > +#include <linux/linkage.h>
> > +#include <linux/string.h>
> > +#include <asm/boot.h>
> > +#include <asm/unaligned.h>
> > +
> > +#include "early_sha1.h"
> > +
> > +#define SHA1_DISABLE_EXPORT
>
> Hi Ross,
>
> I could be mistaken, but it seems to me that *_DISABLE_EXPORT
> is a mechanism of this patch to disable exporting symbols
> (use of EXPORT_SYMBOL), at compile time.
>
> If so, this doesn't strike me as something that should be part of upstream
> kernel code.  Could you consider dropping this part of the patch?

Greetings Simon,

This was patterned after the move of sha256 to /lib. Upon re-inspection, 
it appears this has since been updated to use the __DISABLE_EXPORTS 
CFLAG mechanism of EXPORT_SYMBOL as a conditionally included rule in the 
Makefile where the desire to disable exporting is wanted. We will update 
this patch to follow the same pattern.

V/r,
Daniel P. Smith