[PATCH v5 0/4] Allow guest access to EFI confidential computing secret area

[PATCH v5 0/4] Allow guest access to EFI confidential computing secret area

[Dov Murik]

Confidential computing (coco) hardware such as AMD SEV (Secure Encrypted
Virtualization) allows guest owners to inject secrets into the VMs
memory without the host/hypervisor being able to read them.  In SEV,
secret injection is performed early in the VM launch process, before the
guest starts running.

OVMF already reserves designated area for secret injection (in its
AmdSev package; see edk2 commit 01726b6d23d4 "OvmfPkg/AmdSev: Expose the
Sev Secret area using a configuration table" [1]), but the secrets were
not available in the guest kernel.

The patch series keeps the address of the EFI-provided memory for
injected secrets, and optionally exposes the secrets to userspace via
securityfs using a new efi_secret kernel module.

The first patch in EFI keeps the address of the secret area as passed in
the EFI configuration table.  The second patch is a quirk fix for older
firmwares didn't mark the secrets page as EFI_RESERVED_TYPE.  The third
patch introduces the new efi_secret module that exposes the content of
the secret entries as securityfs files, and allows clearing out secrets
with a file unlink interface.  The last patch documents the data flow of
confidential computing secret injection.

As a usage example, consider a guest performing computations on
encrypted files.  The Guest Owner provides the decryption key (= secret)
using the secret injection mechanism.  The guest application reads the
secret from the efi_secret filesystem and proceeds to decrypt the files
into memory and then performs the needed computations on the content.

In this example, the host can't read the files from the disk image
because they are encrypted.  Host can't read the decryption key because
it is passed using the secret injection mechanism (= secure channel).
Host can't read the decrypted content from memory because it's a
confidential (memory-encrypted) guest.

This has been tested with AMD SEV and SEV-ES guests, but the kernel side
of handling the secret area has no SEV-specific dependencies, and
therefore might be usable (perhaps with minor changes) for any
confidential computing hardware that can publish the secret area via the
standard EFI config table entry.

To enable this functionality, set CONFIG_EFI_SECRET=m when building the
guest kernel.

Here is a simple example for usage of the efi_secret module in a guest
to which an EFI secret area with 4 secrets was injected during launch:

# modprobe efi_secret
# ls -la /sys/kernel/security/coco/efi_secret
total 0
drwxr-xr-x 2 root root 0 Jun 28 11:54 .
drwxr-xr-x 3 root root 0 Jun 28 11:54 ..
-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

# xxd /sys/kernel/security/coco/efi_secret/e6f5a162-d67f-4750-a67c-5d065f2a9910
00000000: 7468 6573 652d 6172 652d 7468 652d 6b61  these-are-the-ka
00000010: 7461 2d73 6563 7265 7473 0001 0203 0405  ta-secrets......
00000020: 0607                                     ..

# rm /sys/kernel/security/coco/efi_secret/e6f5a162-d67f-4750-a67c-5d065f2a9910

# ls -la /sys/kernel/security/coco/efi_secret
total 0
drwxr-xr-x 2 root root 0 Jun 28 11:55 .
drwxr-xr-x 3 root root 0 Jun 28 11:54 ..
-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


[1] https://github.com/tianocore/edk2/commit/01726b6d23d4

---

v5 changes:
 - Simplify EFI code: instead of copying the secret area, the firmware
   marks the secret area as EFI_RESERVED_TYPE, and then the uefi_init()
   code just keeps the pointer as it appears in the EFI configuration
   table.  The use of reserved pages is similar to the AMD SEV-SNP
   patches for handling SNP-Secrets and SNP-CPUID pages.
 - In order to handle OVMF releases out there which mark the
   confidential computing secrets page as EFI_BOOT_SERVICES_DATA, add
   efi/libstub code that detects this and fixes the E820 map to reserve
   this page.
 - In the efi_secret module code, map the secrets page using
   ioremap_encrypted (again, similar to the AMD SEV-SNP guest patches
   for accessing SNP-Secrets and SNP-CPUID pages).
 - Add documentation in Documentation/security/coco/efi_secret.

v4: https://lore.kernel.org/linux-coco/20211020061408.3447533-1-dovmurik@linux.ibm.com/
v4 changes:
 - Guard all the new EFI and efi-stub code (patches 1+2) with #ifdef
   CONFIG_EFI_COCO_SECRET (thanks Greg KH).  Selecting
   CONFIG_EFI_SECRET=m (patch 3) will enable the EFI parts as well.
 - Guard call to clflush_cache_range() with #ifdef CONFIG_X86
   (Reported-by: kernel test robot <lkp@intel.com>)

v3: https://lore.kernel.org/linux-coco/20211014130848.592611-1-dovmurik@linux.ibm.com/
v3 changes:
 - Rename the module to efi_secret
 - Remove the exporting of clean_cache_range
 - Use clflush_cache_range in wipe_memory
 - Document function wipe_memory
 - Initialize efi.coco_secret to EFI_INVALID_TABLE_ADDR to correctly detect
   when there's no secret area published in the EFI configuration tables

v2: https://lore.kernel.org/linux-coco/20211007061838.1381129-1-dovmurik@linux.ibm.com
v2 changes:
 - Export clean_cache_range()
 - When deleteing a secret, call clean_cache_range() after explicit_memzero
 - Add Documentation/ABI/testing/securityfs-coco-sev_secret

v1: https://lore.kernel.org/linux-coco/20210809190157.279332-1-dovmurik@linux.ibm.com/

RFC: https://lore.kernel.org/linux-coco/20210628183431.953934-1-dovmurik@linux.ibm.com/




Dov Murik (4):
  efi: Save location of EFI confidential computing area
  efi/libstub: Reserve confidential computing secret area
  virt: Add efi_secret module to expose confidential computing secrets
  docs: security: Add coco/efi_secret documentation

 .../ABI/testing/securityfs-coco-efi_secret    |  50 +++
 Documentation/security/coco/efi_secret.rst    | 103 ++++++
 Documentation/security/coco/index.rst         |   9 +
 Documentation/security/index.rst              |   1 +
 arch/x86/platform/efi/efi.c                   |   3 +
 drivers/firmware/efi/Kconfig                  |  16 +
 drivers/firmware/efi/efi.c                    |   6 +
 drivers/firmware/efi/libstub/x86-stub.c       |  28 ++
 drivers/virt/Kconfig                          |   3 +
 drivers/virt/Makefile                         |   1 +
 drivers/virt/coco/efi_secret/Kconfig          |  11 +
 drivers/virt/coco/efi_secret/Makefile         |   2 +
 drivers/virt/coco/efi_secret/efi_secret.c     | 341 ++++++++++++++++++
 include/linux/efi.h                           |   7 +
 14 files changed, 581 insertions(+)
 create mode 100644 Documentation/ABI/testing/securityfs-coco-efi_secret
 create mode 100644 Documentation/security/coco/efi_secret.rst
 create mode 100644 Documentation/security/coco/index.rst
 create mode 100644 drivers/virt/coco/efi_secret/Kconfig
 create mode 100644 drivers/virt/coco/efi_secret/Makefile
 create mode 100644 drivers/virt/coco/efi_secret/efi_secret.c


base-commit: 42eb8fdac2fc5d62392dcfcf0253753e821a97b0
-- 
2.25.1

[PATCH v5 1/4] efi: Save location of EFI confidential computing area

[Dov Murik]

Confidential computing (coco) hardware such as AMD SEV (Secure Encrypted
Virtualization) allows a guest owner to inject secrets into the VMs
memory without the host/hypervisor being able to read them.

Firmware support for secret injection is available in OVMF, which
reserves a memory area for secret injection and includes a pointer to it
the in EFI config table entry LINUX_EFI_COCO_SECRET_TABLE_GUID.

If EFI exposes such a table entry, uefi_init() will keep a pointer to
the EFI config table entry in efi.coco_secret, so it can be used later
by the kernel (specifically drivers/virt/coco/efi_secret).  It will also
appear in the kernel log as "CocoSecret=ADDRESS"; for example:

    [    0.000000] efi: EFI v2.70 by EDK II
    [    0.000000] efi: CocoSecret=0x7f22e680 SMBIOS=0x7f541000 ACPI=0x7f77e000 ACPI 2.0=0x7f77e014 MEMATTR=0x7ea0c018

The new functionality can be enabled with CONFIG_EFI_COCO_SECRET=y.

Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
 arch/x86/platform/efi/efi.c  |  3 +++
 drivers/firmware/efi/Kconfig | 16 ++++++++++++++++
 drivers/firmware/efi/efi.c   |  6 ++++++
 include/linux/efi.h          |  7 +++++++
 4 files changed, 32 insertions(+)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 147c30a81f15..1591d67e0bcd 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -93,6 +93,9 @@ static const unsigned long * const efi_tables[] = {
 #ifdef CONFIG_LOAD_UEFI_KEYS
 	&efi.mokvar_table,
 #endif
+#ifdef CONFIG_EFI_COCO_SECRET
+	&efi.coco_secret,
+#endif
 };
 
 u64 efi_setup;		/* efi setup_data physical address */
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index 2c3dac5ecb36..6fa251b3709f 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -284,3 +284,19 @@ config EFI_CUSTOM_SSDT_OVERLAYS
 
 	  See Documentation/admin-guide/acpi/ssdt-overlays.rst for more
 	  information.
+
+config EFI_COCO_SECRET
+	bool "EFI Confidential Computing Secret Area Support"
+	depends on EFI
+	help
+	  Confidential Computing platforms (such as AMD SEV) allow the
+	  Guest Owner to securely inject secrets during guest VM launch.
+	  The secrets are placed in a designated EFI reserved memory area.
+
+	  In order to use the secrets in the kernel, the location of the secret
+	  area (as published in the EFI config table) must be kept.
+
+	  If you say Y here, the address of the EFI secret area will be kept
+	  for usage inside the kernel.  This will allow the
+	  virt/coco/efi_secret module to access the secrets, which in turn
+	  allows userspace programs to access the injected secrets.
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index ae79c3300129..3cc3a7449c64 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -46,6 +46,9 @@ struct efi __read_mostly efi = {
 #ifdef CONFIG_LOAD_UEFI_KEYS
 	.mokvar_table		= EFI_INVALID_TABLE_ADDR,
 #endif
+#ifdef CONFIG_EFI_COCO_SECRET
+	.coco_secret		= EFI_INVALID_TABLE_ADDR,
+#endif
 };
 EXPORT_SYMBOL(efi);
 
@@ -528,6 +531,9 @@ static const efi_config_table_type_t common_tables[] __initconst = {
 #endif
 #ifdef CONFIG_LOAD_UEFI_KEYS
 	{LINUX_EFI_MOK_VARIABLE_TABLE_GUID,	&efi.mokvar_table,	"MOKvar"	},
+#endif
+#ifdef CONFIG_EFI_COCO_SECRET
+	{LINUX_EFI_COCO_SECRET_AREA_GUID,	&efi.coco_secret,	"CocoSecret"	},
 #endif
 	{},
 };
diff --git a/include/linux/efi.h b/include/linux/efi.h
index dbd39b20e034..f8d2150a2dc4 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -359,6 +359,7 @@ void efi_native_runtime_setup(void);
 #define LINUX_EFI_MEMRESERVE_TABLE_GUID		EFI_GUID(0x888eb0c6, 0x8ede, 0x4ff5,  0xa8, 0xf0, 0x9a, 0xee, 0x5c, 0xb9, 0x77, 0xc2)
 #define LINUX_EFI_INITRD_MEDIA_GUID		EFI_GUID(0x5568e427, 0x68fc, 0x4f3d,  0xac, 0x74, 0xca, 0x55, 0x52, 0x31, 0xcc, 0x68)
 #define LINUX_EFI_MOK_VARIABLE_TABLE_GUID	EFI_GUID(0xc451ed2b, 0x9694, 0x45d3,  0xba, 0xba, 0xed, 0x9f, 0x89, 0x88, 0xa3, 0x89)
+#define LINUX_EFI_COCO_SECRET_AREA_GUID		EFI_GUID(0xadf956ad, 0xe98c, 0x484c,  0xae, 0x11, 0xb5, 0x1c, 0x7d, 0x33, 0x64, 0x47)
 
 /* OEM GUIDs */
 #define DELLEMC_EFI_RCI2_TABLE_GUID		EFI_GUID(0x2d9f28a2, 0xa886, 0x456a,  0x97, 0xa8, 0xf1, 0x1e, 0xf2, 0x4f, 0xf4, 0x55)
@@ -550,6 +551,7 @@ extern struct efi {
 	unsigned long			tpm_log;		/* TPM2 Event Log table */
 	unsigned long			tpm_final_log;		/* TPM2 Final Events Log table */
 	unsigned long			mokvar_table;		/* MOK variable config table */
+	unsigned long			coco_secret;		/* Confidential computing secret table */
 
 	efi_get_time_t			*get_time;
 	efi_set_time_t			*set_time;
@@ -1283,4 +1285,9 @@ static inline struct efi_mokvar_table_entry *efi_mokvar_entry_find(
 }
 #endif
 
+struct linux_efi_coco_secret_area {
+	u64	base_pa;
+	u64	size;
+};
+
 #endif /* _LINUX_EFI_H */
-- 
2.25.1

[PATCH v5 2/4] efi/libstub: Reserve confidential computing secret area

[Dov Murik]

Some older firmware declare the confidential computing secret area as
EFI_BOOT_SERVICES_DATA region.  Fix this up by treating this memory
region as EFI_RESERVED_TYPE, as it should be.

If that memory region is already EFI_RESERVED_TYPE then this has no
effect on the E820 map.

Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
 drivers/firmware/efi/libstub/x86-stub.c | 28 +++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index f14c4ff5839f..dabfa33ae2b3 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -24,6 +24,7 @@
 const efi_system_table_t *efi_system_table;
 extern u32 image_offset;
 static efi_loaded_image_t *image = NULL;
+static u64 efi_coco_secret_phys_addr = U64_MAX;
 
 static efi_status_t
 preserve_pci_rom_image(efi_pci_io_protocol_t *pci, struct pci_setup_rom **__rom)
@@ -443,6 +444,21 @@ static void add_e820ext(struct boot_params *params,
 		params->hdr.setup_data = (unsigned long)e820ext;
 }
 
+#ifdef CONFIG_EFI_COCO_SECRET
+static void efi_set_coco_secret_phys_addr(void)
+{
+	struct linux_efi_coco_secret_area *secret_area =
+		get_efi_config_table(LINUX_EFI_COCO_SECRET_AREA_GUID);
+
+	if (!secret_area || secret_area->size == 0 || secret_area->size >= SZ_4G)
+		return;
+
+	efi_coco_secret_phys_addr = secret_area->base_pa;
+}
+#else
+static void efi_set_coco_secret_phys_addr(void) {}
+#endif
+
 static efi_status_t
 setup_e820(struct boot_params *params, struct setup_data *e820ext, u32 e820ext_size)
 {
@@ -494,6 +510,16 @@ setup_e820(struct boot_params *params, struct setup_data *e820ext, u32 e820ext_s
 				e820_type = E820_TYPE_SOFT_RESERVED;
 			else
 				e820_type = E820_TYPE_RAM;
+#ifdef CONFIG_EFI_COCO_SECRET
+			if (d->phys_addr == efi_coco_secret_phys_addr)
+				/*
+				 * Fix a quirk in firmwares which don't mark
+				 * the EFI confidential computing area as
+				 * EFI_RESERVED_TYPE, but instead as
+				 * EFI_BOOT_SERVICES_DATA.
+				 */
+				e820_type = E820_TYPE_RESERVED;
+#endif
 			break;
 
 		case EFI_ACPI_MEMORY_NVS:
@@ -793,6 +819,8 @@ unsigned long efi_main(efi_handle_t handle,
 
 	efi_retrieve_tpm2_eventlog();
 
+	efi_set_coco_secret_phys_addr();
+
 	setup_graphics(boot_params);
 
 	setup_efi_pci(boot_params);
-- 
2.25.1

[PATCH v5 3/4] virt: Add efi_secret module to expose confidential computing secrets

[Dov Murik]

The new efi_secret module exposes the confidential computing (coco)
EFI secret area via securityfs interface.

When the module is loaded (and securityfs is mounted, typically under
/sys/kernel/security), a "coco/efi_secret" directory is created in
securityfs.  In it, a file is created for each secret entry.  The name
of each such file is the GUID of the secret entry, and its content is
the secret data.

This allows applications running in a confidential computing setting to
read secrets provided by the guest owner via a secure secret injection
mechanism (such as AMD SEV's LAUNCH_SECRET command).

Removing (unlinking) files in the "coco/efi_secret" directory will zero
out the secret in memory, and remove the filesystem entry.  If the
module is removed and loaded again, that secret will not appear in the
filesystem.

Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
 .../ABI/testing/securityfs-coco-efi_secret    |  50 +++
 drivers/virt/Kconfig                          |   3 +
 drivers/virt/Makefile                         |   1 +
 drivers/virt/coco/efi_secret/Kconfig          |  11 +
 drivers/virt/coco/efi_secret/Makefile         |   2 +
 drivers/virt/coco/efi_secret/efi_secret.c     | 341 ++++++++++++++++++
 6 files changed, 408 insertions(+)
 create mode 100644 Documentation/ABI/testing/securityfs-coco-efi_secret
 create mode 100644 drivers/virt/coco/efi_secret/Kconfig
 create mode 100644 drivers/virt/coco/efi_secret/Makefile
 create mode 100644 drivers/virt/coco/efi_secret/efi_secret.c

diff --git a/Documentation/ABI/testing/securityfs-coco-efi_secret b/Documentation/ABI/testing/securityfs-coco-efi_secret
new file mode 100644
index 000000000000..ae56976db1bc
--- /dev/null
+++ b/Documentation/ABI/testing/securityfs-coco-efi_secret
@@ -0,0 +1,50 @@
+What:		security/coco/efi_secret
+Date:		October 2021
+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>/coco/efi_secret,
+		where the filename is the GUID of the entry in the secrets
+		table.
+
+		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/coco/efi_secret
+		  -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/coco/efi_secret/e6f5a162-d67f-4750-a67c-5d065f2a9910
+		  the-content-of-the-secret-data
+
+		Wiping a secret by unlinking a file::
+
+		  # rm /sys/kernel/security/coco/efi_secret/e6f5a162-d67f-4750-a67c-5d065f2a9910
+		  # ls -l /sys/kernel/security/coco/efi_secret
+		  -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".
diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
index 8061e8ef449f..fe7a6579b974 100644
--- a/drivers/virt/Kconfig
+++ b/drivers/virt/Kconfig
@@ -36,4 +36,7 @@ source "drivers/virt/vboxguest/Kconfig"
 source "drivers/virt/nitro_enclaves/Kconfig"
 
 source "drivers/virt/acrn/Kconfig"
+
+source "drivers/virt/coco/efi_secret/Kconfig"
+
 endif
diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile
index 3e272ea60cd9..efdb015783f9 100644
--- a/drivers/virt/Makefile
+++ b/drivers/virt/Makefile
@@ -8,3 +8,4 @@ obj-y				+= vboxguest/
 
 obj-$(CONFIG_NITRO_ENCLAVES)	+= nitro_enclaves/
 obj-$(CONFIG_ACRN_HSM)		+= acrn/
+obj-$(CONFIG_EFI_SECRET)	+= coco/efi_secret/
diff --git a/drivers/virt/coco/efi_secret/Kconfig b/drivers/virt/coco/efi_secret/Kconfig
new file mode 100644
index 000000000000..a39a5a90a1e5
--- /dev/null
+++ b/drivers/virt/coco/efi_secret/Kconfig
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config EFI_SECRET
+	tristate "EFI secret area securityfs support"
+	depends on EFI
+	select EFI_COCO_SECRET
+	select SECURITYFS
+	help
+	  This is a driver for accessing the EFI secret area via securityfs.
+
+	  To compile this driver as a module, choose M here.
+	  The module will be called efi_secret.
diff --git a/drivers/virt/coco/efi_secret/Makefile b/drivers/virt/coco/efi_secret/Makefile
new file mode 100644
index 000000000000..c7047ce804f7
--- /dev/null
+++ b/drivers/virt/coco/efi_secret/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_EFI_SECRET) += efi_secret.o
diff --git a/drivers/virt/coco/efi_secret/efi_secret.c b/drivers/virt/coco/efi_secret/efi_secret.c
new file mode 100644
index 000000000000..c0eaf63bc85a
--- /dev/null
+++ b/drivers/virt/coco/efi_secret/efi_secret.c
@@ -0,0 +1,341 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * efi_secret module
+ *
+ * Copyright (C) 2021 IBM Corporation
+ * Author: Dov Murik <dovmurik@linux.ibm.com>
+ */
+
+/**
+ * DOC: efi_secret: Allow reading EFI confidential computing (coco) secret area
+ * via securityfs interface.
+ *
+ * When the module is loaded (and securityfs is mounted, typically under
+ * /sys/kernel/security), a "coco/efi_secret" directory is created in
+ * securityfs.  In it, a file is created for each secret entry.  The name of
+ * each such file is the GUID of the secret entry, and its content is the
+ * secret data.
+ */
+
+#include <linux/seq_file.h>
+#include <linux/fs.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/io.h>
+#include <linux/security.h>
+#include <linux/efi.h>
+#include <asm/cacheflush.h>
+
+#define EFI_SECRET_NUM_FILES 64
+
+#define EFI_SECRET_TABLE_HEADER_GUID \
+	EFI_GUID(0x1e74f542, 0x71dd, 0x4d66, 0x96, 0x3e, 0xef, 0x42, 0x87, 0xff, 0x17, 0x3b)
+
+struct efi_secret {
+	struct dentry *coco_dir;
+	struct dentry *fs_dir;
+	struct dentry *fs_files[EFI_SECRET_NUM_FILES];
+	void __iomem *secret_data;
+	u64 secret_data_len;
+};
+
+/*
+ * Structure of the EFI secret area
+ *
+ * Offset   Length
+ * (bytes)  (bytes)  Usage
+ * -------  -------  -----
+ *       0       16  Secret table header GUID (must be 1e74f542-71dd-4d66-963e-ef4287ff173b)
+ *      16        4  Length of bytes of the entire secret area
+ *
+ *      20       16  First secret entry's GUID
+ *      36        4  First secret entry's length in bytes (= 16 + 4 + x)
+ *      40        x  First secret entry's data
+ *
+ *    40+x       16  Second secret entry's GUID
+ *    56+x        4  Second secret entry's length in bytes (= 16 + 4 + y)
+ *    60+x        y  Second secret entry's data
+ *
+ * (... and so on for additional entries)
+ *
+ * The GUID of each secret entry designates the usage of the secret data.
+ */
+
+/**
+ * struct secret_header - Header of entire secret area; this should be followed
+ * by instances of struct secret_entry.
+ * @guid:	Must be EFI_SECRET_TABLE_HEADER_GUID
+ * @len:	Length in bytes of entire secret area, including header
+ */
+struct secret_header {
+	efi_guid_t guid;
+	u32 len;
+} __attribute((packed));
+
+/**
+ * struct secret_entry - Holds one secret entry
+ * @guid:	Secret-specific GUID (or NULL_GUID if this secret entry was deleted)
+ * @len:	Length of secret entry, including its guid and len fields
+ * @data:	The secret data (full of zeros if this secret entry was deleted)
+ */
+struct secret_entry {
+	efi_guid_t guid;
+	u32 len;
+	u8 data[];
+} __attribute((packed));
+
+static size_t secret_entry_data_len(struct secret_entry *e)
+{
+	return e->len - sizeof(*e);
+}
+
+static struct efi_secret the_efi_secret;
+
+static inline struct efi_secret *efi_secret_get(void)
+{
+	return &the_efi_secret;
+}
+
+static int efi_secret_bin_file_show(struct seq_file *file, void *data)
+{
+	struct secret_entry *e = file->private;
+
+	if (e)
+		seq_write(file, e->data, secret_entry_data_len(e));
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(efi_secret_bin_file);
+
+/*
+ * Overwrite memory content with zeroes, and ensure that dirty cache lines are
+ * actually written back to memory, to clear out the secret.
+ */
+static void wipe_memory(void *addr, size_t size)
+{
+	memzero_explicit(addr, size);
+#ifdef CONFIG_X86
+	clflush_cache_range(addr, size);
+#endif
+}
+
+static int efi_secret_unlink(struct inode *dir, struct dentry *dentry)
+{
+	struct efi_secret *s = efi_secret_get();
+	struct inode *inode = d_inode(dentry);
+	struct secret_entry *e = (struct secret_entry *)inode->i_private;
+	int i;
+
+	if (e) {
+		/* Zero out the secret data */
+		wipe_memory(e->data, secret_entry_data_len(e));
+		e->guid = NULL_GUID;
+	}
+
+	inode->i_private = NULL;
+
+	for (i = 0; i < EFI_SECRET_NUM_FILES; i++)
+		if (s->fs_files[i] == dentry)
+			s->fs_files[i] = NULL;
+
+	/*
+	 * securityfs_remove tries to lock the directory's inode, but we reach
+	 * the unlink callback when it's already locked
+	 */
+	inode_unlock(dir);
+	securityfs_remove(dentry);
+	inode_lock(dir);
+
+	return 0;
+}
+
+static const struct inode_operations efi_secret_dir_inode_operations = {
+	.lookup         = simple_lookup,
+	.unlink         = efi_secret_unlink,
+};
+
+static int efi_secret_map_area(void)
+{
+	int ret;
+	struct efi_secret *s = efi_secret_get();
+	struct linux_efi_coco_secret_area *secret_area;
+
+	if (efi.coco_secret == EFI_INVALID_TABLE_ADDR) {
+		pr_err("Secret area address is not available\n");
+		return -EINVAL;
+	}
+
+	secret_area = memremap(efi.coco_secret, sizeof(*secret_area), MEMREMAP_WB);
+	if (secret_area == NULL) {
+		pr_err("Could not map secret area EFI config entry\n");
+		return -ENOMEM;
+	}
+	if (!secret_area->base_pa || secret_area->size < sizeof(struct secret_header)) {
+		pr_err("Invalid secret area memory location (base_pa=0x%llx size=0x%llx)\n",
+		       secret_area->base_pa, secret_area->size);
+		ret = -EINVAL;
+		goto unmap;
+	}
+
+	s->secret_data = ioremap_encrypted(secret_area->base_pa, secret_area->size);
+	if (s->secret_data == NULL) {
+		pr_err("Could not map secret area\n");
+		ret = -ENOMEM;
+		goto unmap;
+	}
+
+	s->secret_data_len = secret_area->size;
+	ret = 0;
+
+unmap:
+	memunmap(secret_area);
+	return ret;
+}
+
+static void efi_secret_securityfs_teardown(void)
+{
+	struct efi_secret *s = efi_secret_get();
+	int i;
+
+	for (i = (EFI_SECRET_NUM_FILES - 1); i >= 0; i--) {
+		securityfs_remove(s->fs_files[i]);
+		s->fs_files[i] = NULL;
+	}
+
+	securityfs_remove(s->fs_dir);
+	s->fs_dir = NULL;
+
+	securityfs_remove(s->coco_dir);
+	s->coco_dir = NULL;
+
+	pr_debug("Removed efi_secret securityfs entries\n");
+}
+
+static int efi_secret_securityfs_setup(void)
+{
+	efi_guid_t tableheader_guid = EFI_SECRET_TABLE_HEADER_GUID;
+	struct efi_secret *s = efi_secret_get();
+	int ret = 0, i = 0, bytes_left;
+	unsigned char *ptr;
+	struct secret_header *h;
+	struct secret_entry *e;
+	struct dentry *dent;
+	char guid_str[EFI_VARIABLE_GUID_LEN + 1];
+
+	s->coco_dir = NULL;
+	s->fs_dir = NULL;
+	memset(s->fs_files, 0, sizeof(s->fs_files));
+
+	dent = securityfs_create_dir("coco", NULL);
+	if (IS_ERR(dent)) {
+		pr_err("Error creating coco securityfs directory entry err=%ld\n", PTR_ERR(dent));
+		return PTR_ERR(dent);
+	}
+	s->coco_dir = dent;
+
+	dent = securityfs_create_dir("efi_secret", s->coco_dir);
+	if (IS_ERR(dent)) {
+		pr_err("Error creating efi_secret securityfs directory entry err=%ld\n",
+		       PTR_ERR(dent));
+		return PTR_ERR(dent);
+	}
+	d_inode(dent)->i_op = &efi_secret_dir_inode_operations;
+	s->fs_dir = dent;
+
+	ptr = s->secret_data;
+	h = (struct secret_header *)ptr;
+	if (memcmp(&h->guid, &tableheader_guid, sizeof(h->guid))) {
+		pr_err("EFI secret area does not start with correct GUID\n");
+		ret = -EINVAL;
+		goto err_cleanup;
+	}
+	if (h->len < sizeof(*h)) {
+		pr_err("EFI secret area reported length is too small\n");
+		ret = -EINVAL;
+		goto err_cleanup;
+	}
+	if (h->len > s->secret_data_len) {
+		pr_err("EFI secret area reported length is too big\n");
+		ret = -EINVAL;
+		goto err_cleanup;
+	}
+
+	bytes_left = h->len - sizeof(*h);
+	ptr += sizeof(*h);
+	while (bytes_left >= (int)sizeof(*e) && i < EFI_SECRET_NUM_FILES) {
+		e = (struct secret_entry *)ptr;
+		if (e->len < sizeof(*e) || e->len > (unsigned int)bytes_left) {
+			pr_err("EFI secret area is corrupted\n");
+			ret = -EINVAL;
+			goto err_cleanup;
+		}
+
+		/* Skip deleted entries (which will have NULL_GUID) */
+		if (efi_guidcmp(e->guid, NULL_GUID)) {
+			efi_guid_to_str(&e->guid, guid_str);
+
+			dent = securityfs_create_file(guid_str, 0440, s->fs_dir, (void *)e,
+						      &efi_secret_bin_file_fops);
+			if (IS_ERR(dent)) {
+				pr_err("Error creating efi_secret securityfs entry\n");
+				ret = PTR_ERR(dent);
+				goto err_cleanup;
+			}
+
+			s->fs_files[i++] = dent;
+		}
+		ptr += e->len;
+		bytes_left -= e->len;
+	}
+
+	pr_debug("Created %d entries in efi_secret securityfs\n", i);
+	return 0;
+
+err_cleanup:
+	efi_secret_securityfs_teardown();
+	return ret;
+}
+
+static void efi_secret_unmap_area(void)
+{
+	struct efi_secret *s = efi_secret_get();
+
+	if (s->secret_data) {
+		iounmap(s->secret_data);
+		s->secret_data = NULL;
+		s->secret_data_len = 0;
+	}
+}
+
+static int __init efi_secret_init(void)
+{
+	int ret;
+
+	ret = efi_secret_map_area();
+	if (ret)
+		return ret;
+
+	ret = efi_secret_securityfs_setup();
+	if (ret)
+		goto err_unmap;
+
+	return ret;
+
+err_unmap:
+	efi_secret_unmap_area();
+	return ret;
+}
+
+static void __exit efi_secret_exit(void)
+{
+	efi_secret_securityfs_teardown();
+	efi_secret_unmap_area();
+}
+
+module_init(efi_secret_init);
+module_exit(efi_secret_exit);
+
+MODULE_DESCRIPTION("Confidential computing EFI secret area access");
+MODULE_AUTHOR("IBM");
+MODULE_LICENSE("GPL");
-- 
2.25.1

[PATCH v5 4/4] docs: security: Add coco/efi_secret documentation

[Dov Murik]

Add documentation for the efi_secret module which allows access
to Confidential Computing injected secrets.

Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
 Documentation/security/coco/efi_secret.rst | 103 +++++++++++++++++++++
 Documentation/security/coco/index.rst      |   9 ++
 Documentation/security/index.rst           |   1 +
 3 files changed, 113 insertions(+)
 create mode 100644 Documentation/security/coco/efi_secret.rst
 create mode 100644 Documentation/security/coco/index.rst

diff --git a/Documentation/security/coco/efi_secret.rst b/Documentation/security/coco/efi_secret.rst
new file mode 100644
index 000000000000..bb7acae22e90
--- /dev/null
+++ b/Documentation/security/coco/efi_secret.rst
@@ -0,0 +1,103 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==========
+efi_secret
+==========
+
+This document describes how Confidential Computing secret injection is handled
+from the firmware to the operating system.
+
+
+Introduction
+============
+
+Confidential Computing (coco) hardware such as AMD SEV (Secure Encrypted
+Virtualization) allows guest owners to inject secrets into the VMs
+memory without the host/hypervisor being able to read them.  In SEV,
+secret injection is performed early in the VM launch process, before the
+guest starts running.
+
+The efi_secret kernel module allows userspace applications to access these
+secrets via securityfs.
+
+
+Secret data flow
+================
+
+The guest firmware may reserve a designated memory area for secret injection,
+and publish its location (base GPA and length) in the EFI configuration table
+under a ``LINUX_EFI_COCO_SECRET_AREA_GUID`` entry
+(``adf956ad-e98c-484c-ae11-b51c7d336447``).  This memory area should be marked
+by the firmware as ``EFI_RESERVED_TYPE``, and therefore the kernel should not
+be use it for its own purposes.
+
+During the VM's launch, the virtual machine manager may inject a secret to that
+area.  In AMD SEV and SEV-ES this is performed using the
+``KVM_SEV_LAUNCH_SECRET`` command (see [amd-mem-enc]_).  The strucutre of the
+injected Guest Owner secret data should be a GUIDed table of secret values; the
+binary format is described in ``drivers/virt/coco/efi_secret/efi_secret.c``
+under "Structure of the EFI secret area".
+
+On kernel start, the kernel's EFI driver saves the location of the secret
+memory (taken from the EFI configuration table) in the ``efi.coco_secret``
+field.
+
+When a userspace application needs to access the secrets inside the guest VM,
+it loads the efi_secret kernel module (``CONFIG_EFI_SECRET=m``) which exposes
+the secrets via securityfs.  The details of the efi_secret filesystem interface
+are in [efi-secret-abi]_.
+
+
+
+Application usage example
+=========================
+
+Consider a guest performing computations on encrypted files.  The Guest Owner
+provides the decryption key (= secret) using the secret injection mechanism.
+The guest application reads the secret from the efi_secret filesystem and
+proceeds to decrypt the files into memory and then performs the needed
+computations on the content.
+
+In this example, the host can't read the files from the disk image
+because they are encrypted.  Host can't read the decryption key because
+it is passed using the secret injection mechanism (= secure channel).
+Host can't read the decrypted content from memory because it's a
+confidential (memory-encrypted) guest.
+
+Here is a simple example for usage of the efi_secret module in a guest
+to which an EFI secret area with 4 secrets was injected during launch::
+
+	# modprobe efi_secret
+	# ls -la /sys/kernel/security/coco/efi_secret
+	total 0
+	drwxr-xr-x 2 root root 0 Jun 28 11:54 .
+	drwxr-xr-x 3 root root 0 Jun 28 11:54 ..
+	-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
+
+	# xxd /sys/kernel/security/coco/efi_secret/e6f5a162-d67f-4750-a67c-5d065f2a9910
+	00000000: 7468 6573 652d 6172 652d 7468 652d 6b61  these-are-the-ka
+	00000010: 7461 2d73 6563 7265 7473 0001 0203 0405  ta-secrets......
+	00000020: 0607                                     ..
+
+	# rm /sys/kernel/security/coco/efi_secret/e6f5a162-d67f-4750-a67c-5d065f2a9910
+
+	# ls -la /sys/kernel/security/coco/efi_secret
+	total 0
+	drwxr-xr-x 2 root root 0 Jun 28 11:55 .
+	drwxr-xr-x 3 root root 0 Jun 28 11:54 ..
+	-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
+
+
+References
+==========
+
+See [sev-api-spec]_ for more info regarding SEV ``LAUNCH_SECRET`` operation.
+
+.. [amd-mem-enc] :ref:`Documentation/virt/kvm/amd-memory-encryption <amdmemenc>`
+.. [efi-secret-abi] :ref:`Documentation/ABI/testing/securityfs-coco-efi_secret <efisecret>`
+.. [sev-api-spec] https://www.amd.com/system/files/TechDocs/55766_SEV-KM_API_Specification.pdf
diff --git a/Documentation/security/coco/index.rst b/Documentation/security/coco/index.rst
new file mode 100644
index 000000000000..56b803d4b33e
--- /dev/null
+++ b/Documentation/security/coco/index.rst
@@ -0,0 +1,9 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+====================================
+Confidential Computing documentation
+====================================
+
+.. toctree::
+
+   efi_secret
diff --git a/Documentation/security/index.rst b/Documentation/security/index.rst
index 16335de04e8c..d4ef543825a7 100644
--- a/Documentation/security/index.rst
+++ b/Documentation/security/index.rst
@@ -17,3 +17,4 @@ Security Documentation
    tpm/index
    digsig
    landlock
+   coco
-- 
2.25.1

Re: [PATCH v5 3/4] virt: Add efi_secret module to expose confidential computing secrets

[Greg KH]

On Thu, Nov 18, 2021 at 11:33:58AM +0000, Dov Murik wrote:
> The new efi_secret module exposes the confidential computing (coco)
> EFI secret area via securityfs interface.
> 
> When the module is loaded (and securityfs is mounted, typically under
> /sys/kernel/security), a "coco/efi_secret" directory is created in
> securityfs.  In it, a file is created for each secret entry.  The name
> of each such file is the GUID of the secret entry, and its content is
> the secret data.
> 
> This allows applications running in a confidential computing setting to
> read secrets provided by the guest owner via a secure secret injection
> mechanism (such as AMD SEV's LAUNCH_SECRET command).
> 
> Removing (unlinking) files in the "coco/efi_secret" directory will zero
> out the secret in memory, and remove the filesystem entry.  If the
> module is removed and loaded again, that secret will not appear in the
> filesystem.
> 
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
> ---
>  .../ABI/testing/securityfs-coco-efi_secret    |  50 +++
>  drivers/virt/Kconfig                          |   3 +
>  drivers/virt/Makefile                         |   1 +
>  drivers/virt/coco/efi_secret/Kconfig          |  11 +
>  drivers/virt/coco/efi_secret/Makefile         |   2 +
>  drivers/virt/coco/efi_secret/efi_secret.c     | 341 ++++++++++++++++++
>  6 files changed, 408 insertions(+)
>  create mode 100644 Documentation/ABI/testing/securityfs-coco-efi_secret
>  create mode 100644 drivers/virt/coco/efi_secret/Kconfig
>  create mode 100644 drivers/virt/coco/efi_secret/Makefile
>  create mode 100644 drivers/virt/coco/efi_secret/efi_secret.c
> 
> diff --git a/Documentation/ABI/testing/securityfs-coco-efi_secret b/Documentation/ABI/testing/securityfs-coco-efi_secret
> new file mode 100644
> index 000000000000..ae56976db1bc
> --- /dev/null
> +++ b/Documentation/ABI/testing/securityfs-coco-efi_secret
> @@ -0,0 +1,50 @@
> +What:		security/coco/efi_secret
> +Date:		October 2021
> +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>/coco/efi_secret,
> +		where the filename is the GUID of the entry in the secrets
> +		table.
> +
> +		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/coco/efi_secret
> +		  -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/coco/efi_secret/e6f5a162-d67f-4750-a67c-5d065f2a9910
> +		  the-content-of-the-secret-data
> +
> +		Wiping a secret by unlinking a file::
> +
> +		  # rm /sys/kernel/security/coco/efi_secret/e6f5a162-d67f-4750-a67c-5d065f2a9910
> +		  # ls -l /sys/kernel/security/coco/efi_secret
> +		  -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".
> diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
> index 8061e8ef449f..fe7a6579b974 100644
> --- a/drivers/virt/Kconfig
> +++ b/drivers/virt/Kconfig
> @@ -36,4 +36,7 @@ source "drivers/virt/vboxguest/Kconfig"
>  source "drivers/virt/nitro_enclaves/Kconfig"
>  
>  source "drivers/virt/acrn/Kconfig"
> +
> +source "drivers/virt/coco/efi_secret/Kconfig"
> +
>  endif
> diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile
> index 3e272ea60cd9..efdb015783f9 100644
> --- a/drivers/virt/Makefile
> +++ b/drivers/virt/Makefile
> @@ -8,3 +8,4 @@ obj-y				+= vboxguest/
>  
>  obj-$(CONFIG_NITRO_ENCLAVES)	+= nitro_enclaves/
>  obj-$(CONFIG_ACRN_HSM)		+= acrn/
> +obj-$(CONFIG_EFI_SECRET)	+= coco/efi_secret/
> diff --git a/drivers/virt/coco/efi_secret/Kconfig b/drivers/virt/coco/efi_secret/Kconfig
> new file mode 100644
> index 000000000000..a39a5a90a1e5
> --- /dev/null
> +++ b/drivers/virt/coco/efi_secret/Kconfig
> @@ -0,0 +1,11 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +config EFI_SECRET
> +	tristate "EFI secret area securityfs support"
> +	depends on EFI
> +	select EFI_COCO_SECRET
> +	select SECURITYFS
> +	help
> +	  This is a driver for accessing the EFI secret area via securityfs.
> +
> +	  To compile this driver as a module, choose M here.
> +	  The module will be called efi_secret.


Shouldn't this module auto-load only if the efi secret area is present?

What is going to cause the module to be loaded by a distro if it does
not have some sort of way to tell userspace what resources it belongs
to?  Can you trigger off of a DMI or EFI attribute somehow for this?

Otherwise you are going to force distros to modify their init scripts
for this functionality, how is that going to happen?

thanks,

greg k-h

Re: [PATCH v5 3/4] virt: Add efi_secret module to expose confidential computing secrets

[kernel test robot]

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Hi Dov,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on 42eb8fdac2fc5d62392dcfcf0253753e821a97b0]

url:    https://github.com/0day-ci/linux/commits/Dov-Murik/Allow-guest-access-to-EFI-confidential-computing-secret-area/20211118-193724
base:   42eb8fdac2fc5d62392dcfcf0253753e821a97b0
config: riscv-allyesconfig (attached as .config)
compiler: riscv64-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/547e54014b34e24cd885e941dd66e3fdece3c0c6
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Dov-Murik/Allow-guest-access-to-EFI-confidential-computing-secret-area/20211118-193724
        git checkout 547e54014b34e24cd885e941dd66e3fdece3c0c6
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=riscv 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   drivers/virt/coco/efi_secret/efi_secret.c: In function 'efi_secret_map_area':
   drivers/virt/coco/efi_secret/efi_secret.c:181:26: error: implicit declaration of function 'ioremap_encrypted' [-Werror=implicit-function-declaration]
     181 |         s->secret_data = ioremap_encrypted(secret_area->base_pa, secret_area->size);
         |                          ^~~~~~~~~~~~~~~~~
>> drivers/virt/coco/efi_secret/efi_secret.c:181:24: warning: assignment to 'void *' from 'int' makes pointer from integer without a cast [-Wint-conversion]
     181 |         s->secret_data = ioremap_encrypted(secret_area->base_pa, secret_area->size);
         |                        ^
   cc1: some warnings being treated as errors


vim +181 drivers/virt/coco/efi_secret/efi_secret.c

   157	
   158	static int efi_secret_map_area(void)
   159	{
   160		int ret;
   161		struct efi_secret *s = efi_secret_get();
   162		struct linux_efi_coco_secret_area *secret_area;
   163	
   164		if (efi.coco_secret == EFI_INVALID_TABLE_ADDR) {
   165			pr_err("Secret area address is not available\n");
   166			return -EINVAL;
   167		}
   168	
   169		secret_area = memremap(efi.coco_secret, sizeof(*secret_area), MEMREMAP_WB);
   170		if (secret_area == NULL) {
   171			pr_err("Could not map secret area EFI config entry\n");
   172			return -ENOMEM;
   173		}
   174		if (!secret_area->base_pa || secret_area->size < sizeof(struct secret_header)) {
   175			pr_err("Invalid secret area memory location (base_pa=0x%llx size=0x%llx)\n",
   176			       secret_area->base_pa, secret_area->size);
   177			ret = -EINVAL;
   178			goto unmap;
   179		}
   180	
 > 181		s->secret_data = ioremap_encrypted(secret_area->base_pa, secret_area->size);
   182		if (s->secret_data == NULL) {
   183			pr_err("Could not map secret area\n");
   184			ret = -ENOMEM;
   185			goto unmap;
   186		}
   187	
   188		s->secret_data_len = secret_area->size;
   189		ret = 0;
   190	
   191	unmap:
   192		memunmap(secret_area);
   193		return ret;
   194	}
   195	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

[-- Attachment #2: config.gz --]
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Re: [PATCH v5 3/4] virt: Add efi_secret module to expose confidential computing secrets

[kernel test robot]

[-- Attachment #1: Type: text/plain, Size: 3461 bytes --]

Hi Dov,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on 42eb8fdac2fc5d62392dcfcf0253753e821a97b0]

url:    https://github.com/0day-ci/linux/commits/Dov-Murik/Allow-guest-access-to-EFI-confidential-computing-secret-area/20211118-193724
base:   42eb8fdac2fc5d62392dcfcf0253753e821a97b0
config: riscv-allyesconfig (attached as .config)
compiler: riscv64-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/547e54014b34e24cd885e941dd66e3fdece3c0c6
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Dov-Murik/Allow-guest-access-to-EFI-confidential-computing-secret-area/20211118-193724
        git checkout 547e54014b34e24cd885e941dd66e3fdece3c0c6
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=riscv 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/virt/coco/efi_secret/efi_secret.c: In function 'efi_secret_map_area':
>> drivers/virt/coco/efi_secret/efi_secret.c:181:26: error: implicit declaration of function 'ioremap_encrypted' [-Werror=implicit-function-declaration]
     181 |         s->secret_data = ioremap_encrypted(secret_area->base_pa, secret_area->size);
         |                          ^~~~~~~~~~~~~~~~~
   drivers/virt/coco/efi_secret/efi_secret.c:181:24: warning: assignment to 'void *' from 'int' makes pointer from integer without a cast [-Wint-conversion]
     181 |         s->secret_data = ioremap_encrypted(secret_area->base_pa, secret_area->size);
         |                        ^
   cc1: some warnings being treated as errors


vim +/ioremap_encrypted +181 drivers/virt/coco/efi_secret/efi_secret.c

   157	
   158	static int efi_secret_map_area(void)
   159	{
   160		int ret;
   161		struct efi_secret *s = efi_secret_get();
   162		struct linux_efi_coco_secret_area *secret_area;
   163	
   164		if (efi.coco_secret == EFI_INVALID_TABLE_ADDR) {
   165			pr_err("Secret area address is not available\n");
   166			return -EINVAL;
   167		}
   168	
   169		secret_area = memremap(efi.coco_secret, sizeof(*secret_area), MEMREMAP_WB);
   170		if (secret_area == NULL) {
   171			pr_err("Could not map secret area EFI config entry\n");
   172			return -ENOMEM;
   173		}
   174		if (!secret_area->base_pa || secret_area->size < sizeof(struct secret_header)) {
   175			pr_err("Invalid secret area memory location (base_pa=0x%llx size=0x%llx)\n",
   176			       secret_area->base_pa, secret_area->size);
   177			ret = -EINVAL;
   178			goto unmap;
   179		}
   180	
 > 181		s->secret_data = ioremap_encrypted(secret_area->base_pa, secret_area->size);
   182		if (s->secret_data == NULL) {
   183			pr_err("Could not map secret area\n");
   184			ret = -ENOMEM;
   185			goto unmap;
   186		}
   187	
   188		s->secret_data_len = secret_area->size;
   189		ret = 0;
   190	
   191	unmap:
   192		memunmap(secret_area);
   193		return ret;
   194	}
   195	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

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