Merge tag 'efi-next-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi

Pull EFI updates from Ard Biesheuvel:

 - Allow runtime services to be re-enabled at boot on RT kernels.

 - Provide access to secrets injected into the boot image by CoCo
   hypervisors (COnfidential COmputing)

 - Use DXE services on x86 to make the boot image executable after
   relocation, if needed.

 - Prefer mirrored memory for randomized allocations.

 - Only randomize the placement of the kernel image on arm64 if the
   loader has not already done so.

 - Add support for obtaining the boot hartid from EFI on RISC-V.

* tag 'efi-next-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi:
  riscv/efi_stub: Add support for RISCV_EFI_BOOT_PROTOCOL
  efi: stub: prefer mirrored memory for randomized allocations
  efi/arm64: libstub: run image in place if randomized by the loader
  efi: libstub: pass image handle to handle_kernel_image()
  efi: x86: Set the NX-compatibility flag in the PE header
  efi: libstub: ensure allocated memory to be executable
  efi: libstub: declare DXE services table
  efi: Add missing prototype for efi_capsule_setup_info
  docs: security: Add secrets/coco documentation
  efi: Register efi_secret platform device if EFI secret area is declared
  virt: Add efi_secret module to expose confidential computing secrets
  efi: Save location of EFI confidential computing area
  efi: Allow to enable EFI runtime services by default on RT

1 files changed, 51 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/securityfs-secrets-coco b/Documentation/ABI/testing/securityfs-secrets-coco
new file mode 100644
index 000000000000..f2b6909155f9
--- /dev/null
+++ b/Documentation/ABI/testing/securityfs-secrets-coco
@@ -0,0 +1,51 @@
+What:		security/secrets/coco
+Date:		February 2022
+Contact:	Dov Murik <dovmurik@linux.ibm.com>
+Description:
+		Exposes confidential computing (coco) EFI secrets to
+		userspace via securityfs.
+
+		EFI can declare memory area used by confidential computing
+		platforms (such as AMD SEV and SEV-ES) for secret injection by
+		the Guest Owner during VM's launch.  The secrets are encrypted
+		by the Guest Owner and decrypted inside the trusted enclave,
+		and therefore are not readable by the untrusted host.
+
+		The efi_secret module exposes the secrets to userspace.  Each
+		secret appears as a file under <securityfs>/secrets/coco,
+		where the filename is the GUID of the entry in the secrets
+		table.  This module is loaded automatically by the EFI driver
+		if the EFI secret area is populated.
+
+		Two operations are supported for the files: read and unlink.
+		Reading the file returns the content of secret entry.
+		Unlinking the file overwrites the secret data with zeroes and
+		removes the entry from the filesystem.  A secret cannot be read
+		after it has been unlinked.
+
+		For example, listing the available secrets::
+
+		  # modprobe efi_secret
+		  # ls -l /sys/kernel/security/secrets/coco
+		  -r--r----- 1 root root 0 Jun 28 11:54 736870e5-84f0-4973-92ec-06879ce3da0b
+		  -r--r----- 1 root root 0 Jun 28 11:54 83c83f7f-1356-4975-8b7e-d3a0b54312c6
+		  -r--r----- 1 root root 0 Jun 28 11:54 9553f55d-3da2-43ee-ab5d-ff17f78864d2
+		  -r--r----- 1 root root 0 Jun 28 11:54 e6f5a162-d67f-4750-a67c-5d065f2a9910
+
+		Reading the secret data by reading a file::
+
+		  # cat /sys/kernel/security/secrets/coco/e6f5a162-d67f-4750-a67c-5d065f2a9910
+		  the-content-of-the-secret-data
+
+		Wiping a secret by unlinking a file::
+
+		  # rm /sys/kernel/security/secrets/coco/e6f5a162-d67f-4750-a67c-5d065f2a9910
+		  # ls -l /sys/kernel/security/secrets/coco
+		  -r--r----- 1 root root 0 Jun 28 11:54 736870e5-84f0-4973-92ec-06879ce3da0b
+		  -r--r----- 1 root root 0 Jun 28 11:54 83c83f7f-1356-4975-8b7e-d3a0b54312c6
+		  -r--r----- 1 root root 0 Jun 28 11:54 9553f55d-3da2-43ee-ab5d-ff17f78864d2
+
+		Note: The binary format of the secrets table injected by the
+		Guest Owner is described in
+		drivers/virt/coco/efi_secret/efi_secret.c under "Structure of
+		the EFI secret area".