[v12,08/19] x86/boot: Place TXT MLE header in the kernel_info section

Commit Message

Ross Philipson Dec. 19, 2024, 7:42 p.m. UTC

The MLE (measured launch environment) header must be locatable by the
boot loader and TXT must be setup to do a launch with this header's
location. While the offset to the kernel_info structure does not need
to be at a fixed offset, the offsets in the header must be relative
offsets from the start of the setup kernel. The support in the linker
file achieves this.

Signed-off-by: Ross Philipson <[e-mail]>
Suggested-by: Ard Biesheuvel <[e-mail]>
Reviewed-by: Ard Biesheuvel <[e-mail]>
---
 arch/x86/boot/compressed/kernel_info.S | 50 +++++++++++++++++++++++---
 arch/x86/boot/compressed/vmlinux.lds.S |  7 ++++
 2 files changed, 53 insertions(+), 4 deletions(-)

Patch

diff --git a/arch/x86/boot/compressed/kernel_info.S b/arch/x86/boot/compressed/kernel_info.S
index f818ee8fba38..a0604a0d1756 100644
--- a/arch/x86/boot/compressed/kernel_info.S
+++ b/arch/x86/boot/compressed/kernel_info.S
@@ -1,12 +1,20 @@ 
 /* SPDX-License-Identifier: GPL-2.0 */
 
+#include <linux/linkage.h>
 #include <asm/bootparam.h>
 
-	.section ".rodata.kernel_info", "a"
+/*
+ * The kernel_info structure is not placed at a fixed offest in the
+ * kernel image. So this macro and the support in the linker file
+ * allow the relative offsets for the MLE header within the kernel
+ * image to be configured at build time.
+ */
+#define roffset(X) ((X) - kernel_info)
 
-	.global kernel_info
+	.section ".rodata.kernel_info", "a"
 
-kernel_info:
+	.balign	16
+SYM_DATA_START(kernel_info)
 	/* Header, Linux top (structure). */
 	.ascii	"LToP"
 	/* Size. */
@@ -17,6 +25,40 @@  kernel_info:
 	/* Maximal allowed type for setup_data and setup_indirect structs. */
 	.long	SETUP_TYPE_MAX
 
+	/* Offset to the MLE header structure */
+#if IS_ENABLED(CONFIG_SECURE_LAUNCH)
+	.long	roffset(mle_header_offset)
+#else
+	.long	0
+#endif
+
 kernel_info_var_len_data:
 	/* Empty for time being... */
-kernel_info_end:
+SYM_DATA_END_LABEL(kernel_info, SYM_L_LOCAL, kernel_info_end)
+
+#if IS_ENABLED(CONFIG_SECURE_LAUNCH)
+	/*
+	 * The MLE Header per the TXT Specification, section 2.1
+	 * MLE capabilities, see table 4. Capabilities set:
+	 * bit 0: Support for GETSEC[WAKEUP] for RLP wakeup
+	 * bit 1: Support for RLP wakeup using MONITOR address
+	 * bit 2: The ECX register will contain the pointer to the MLE page table
+	 * bit 5: TPM 1.2 family: Details/authorities PCR usage support
+	 * bit 9: Supported format of TPM 2.0 event log - TCG compliant
+	 */
+SYM_DATA_START(mle_header)
+	.long	0x9082ac5a  /* UUID0 */
+	.long	0x74a7476f  /* UUID1 */
+	.long	0xa2555c0f  /* UUID2 */
+	.long	0x42b651cb  /* UUID3 */
+	.long	0x00000034  /* MLE header size */
+	.long	0x00020002  /* MLE version 2.2 */
+	.long	roffset(sl_stub_entry_offset) /* Linear entry point of MLE (virt. address) */
+	.long	0x00000000  /* First valid page of MLE */
+	.long	0x00000000  /* Offset within binary of first byte of MLE */
+	.long	roffset(_edata_offset) /* Offset within binary of last byte + 1 of MLE */
+	.long	0x00000227  /* Bit vector of MLE-supported capabilities */
+	.long	0x00000000  /* Starting linear address of command line (unused) */
+	.long	0x00000000  /* Ending linear address of command line (unused) */
+SYM_DATA_END(mle_header)
+#endif
diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
index 083ec6d7722a..f82184801462 100644
--- a/arch/x86/boot/compressed/vmlinux.lds.S
+++ b/arch/x86/boot/compressed/vmlinux.lds.S
@@ -118,3 +118,10 @@  SECTIONS
 	}
 	ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations (.rela) detected!")
 }
+
+#ifdef CONFIG_SECURE_LAUNCH
+PROVIDE(kernel_info_offset      = ABSOLUTE(kernel_info - startup_32));
+PROVIDE(mle_header_offset       = kernel_info_offset + ABSOLUTE(mle_header - startup_32));
+PROVIDE(sl_stub_entry_offset    = kernel_info_offset + ABSOLUTE(sl_stub_entry - startup_32));
+PROVIDE(_edata_offset           = kernel_info_offset + ABSOLUTE(_edata - startup_32));
+#endif