[PATCH v10 08/20] x86/boot: Place TXT MLE header in the kernel_info section

[Ard Biesheuvel]

On Tue, 27 Aug 2024 at 00:42, Ross Philipson <ross.philipson at oracle.com> wrote:
>
> 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 <ross.philipson at oracle.com>
> Suggested-by: Ard Biesheuvel <ardb at kernel.org>

Reviewed-by: Ard Biesheuvel <ardb at kernel.org>

> ---
>  arch/x86/boot/compressed/kernel_info.S | 50 +++++++++++++++++++++++---
>  arch/x86/boot/compressed/vmlinux.lds.S |  7 ++++
>  2 files changed, 53 insertions(+), 4 deletions(-)
>
> 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
> --
> 2.39.3
>