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

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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



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