[PATCHv2] x86: Add a tboot Kconfig option

[Derek Straka <derek@asterius.io>]

Allows for the conditional inclusion of tboot related functionality
via Kconfig

The default configuration for the new CONFIG_TBOOT option is 'y', so the
behavior out of the box remains unchanged.  The addition of the option allows
advanced users to disable system behaviors associated with tboot at compile
time rather than relying on the run-time detection and configuration.

The CONFIG_CRYPTO option is 'n' by default and selected by the individual users
that require the functionality.  Currently, the only user is tboot.

Signed-off-by: Derek Straka <derek@asterius.io>
---
 xen/Rules.mk                |  2 +-
 xen/arch/x86/Kconfig        | 11 +++++++++++
 xen/arch/x86/Makefile       |  2 +-
 xen/common/Kconfig          |  4 ++++
 xen/include/asm-x86/tboot.h | 16 ++++++++++++++++
 5 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/xen/Rules.mk b/xen/Rules.mk
index ebe1dc0..a190ff0 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -44,7 +44,7 @@ ALL_OBJS-y               += $(BASEDIR)/common/built_in.o
 ALL_OBJS-y               += $(BASEDIR)/drivers/built_in.o
 ALL_OBJS-y               += $(BASEDIR)/xsm/built_in.o
 ALL_OBJS-y               += $(BASEDIR)/arch/$(TARGET_ARCH)/built_in.o
-ALL_OBJS-$(CONFIG_X86)   += $(BASEDIR)/crypto/built_in.o
+ALL_OBJS-$(CONFIG_CRYPTO)   += $(BASEDIR)/crypto/built_in.o
 
 CFLAGS += -nostdinc -fno-builtin -fno-common
 CFLAGS += -Werror -Wredundant-decls -Wno-pointer-arith
diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index c1e9279..265fd79 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -76,6 +76,17 @@ config HVM_FEP
 	  for use in production.
 
 	  If unsure, say N.
+
+config TBOOT
+	def_bool y
+	prompt "Xen tboot support" if EXPERT = "y"
+	depends on X86
+	select CRYPTO
+	---help---
+	  Allows support for Trusted Boot using the Intel(R) Trusted Execution
+	  Technology (TXT)
+
+	  If unsure, say Y.
 endmenu
 
 source "common/Kconfig"
diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index b18f033..5b9e9da 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -62,7 +62,7 @@ obj-y += trace.o
 obj-y += traps.o
 obj-y += usercopy.o
 obj-y += x86_emulate.o
-obj-y += tboot.o
+obj-$(CONFIG_TBOOT) += tboot.o
 obj-y += hpet.o
 obj-y += vm_event.o
 obj-y += xstate.o
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index 51afa24..e2dd89f 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -218,6 +218,10 @@ config SCHED_DEFAULT
 
 endmenu
 
+config CRYPTO
+	bool
+	default n
+
 # Enable/Disable live patching support
 config LIVEPATCH
 	bool "Live patching support (TECH PREVIEW)"
diff --git a/xen/include/asm-x86/tboot.h b/xen/include/asm-x86/tboot.h
index d242862..59ed449 100644
--- a/xen/include/asm-x86/tboot.h
+++ b/xen/include/asm-x86/tboot.h
@@ -119,6 +119,7 @@ typedef struct __packed {
 
 extern tboot_shared_t *g_tboot_shared;
 
+#ifdef CONFIG_TBOOT
 void tboot_probe(void);
 void tboot_shutdown(uint32_t shutdown_type);
 int tboot_in_measured_env(void);
@@ -127,6 +128,21 @@ int tboot_parse_dmar_table(acpi_table_handler dmar_handler);
 int tboot_s3_resume(void);
 void tboot_s3_error(int error);
 int tboot_wake_ap(int apicid, unsigned long sipi_vec);
+#else
+static inline void tboot_probe(void) {}
+static inline void tboot_shutdown(uint32_t shutdown_type) {}
+static inline int tboot_in_measured_env(void) { return 0; }
+static inline int tboot_protect_mem_regions(void) { return 1; }
+
+static inline int tboot_parse_dmar_table(acpi_table_handler dmar_handler)
+{
+    return acpi_table_parse(ACPI_SIG_DMAR, dmar_handler);
+}
+
+static inline int tboot_s3_resume(void) { return 0; }
+static inline void tboot_s3_error(int error) {}
+static inline int tboot_wake_ap(int apicid, unsigned long sipi_vec) { return 1; }
+#endif /* CONFIG_TBOOT */
 
 #endif /* __TBOOT_H__ */
 
-- 
1.9.1


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