diff mbox series

[RFC,v2,2/3] efi: Reserve confidential computing secret area

Message ID 20210628183431.953934-3-dovmurik@linux.ibm.com (mailing list archive)
State New, archived
Headers show
Series Allow access to confidential computing secret area | expand

Commit Message

Dov Murik June 28, 2021, 6:34 p.m. UTC 
When efi-stub copies an EFI-provided confidential computing secret area,
reserve that memory block for future use within the kernel.

Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
 drivers/firmware/efi/Makefile                 |  2 +-
 drivers/firmware/efi/confidential-computing.c | 41 +++++++++++++++++++
 drivers/firmware/efi/efi.c                    |  5 +++
 include/linux/efi.h                           |  4 ++
 4 files changed, 51 insertions(+), 1 deletion(-)
 create mode 100644 drivers/firmware/efi/confidential-computing.c

Comments

Tom Lendacky June 28, 2021, 8:40 p.m. UTC | #1 
On 6/28/21 1:34 PM, Dov Murik wrote:
> When efi-stub copies an EFI-provided confidential computing secret area,
> reserve that memory block for future use within the kernel.
> 
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
> ---
>  drivers/firmware/efi/Makefile                 |  2 +-
>  drivers/firmware/efi/confidential-computing.c | 41 +++++++++++++++++++
>  drivers/firmware/efi/efi.c                    |  5 +++
>  include/linux/efi.h                           |  4 ++
>  4 files changed, 51 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/firmware/efi/confidential-computing.c
> 
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index 4f647f1ee298..e9740bd16db0 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -551,6 +551,8 @@ 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			confidential_computing_secret;	/* Confidential computing */
> +									/* secret table           */

If there is any possibility that someone could reuse a form of this
confidential computing secret table in a bare metal system, then this
table needs to be added to the efi_tables[] array in
arch/x86/platform/efi/efi.c. Otherwise, it will be mapped improperly on a
system with SME active.

Thanks,
Tom

>  
>  	efi_get_time_t			*get_time;
>  	efi_set_time_t			*set_time;
> @@ -1190,6 +1192,8 @@ extern int efi_tpm_final_log_size;
>  
>  extern unsigned long rci2_table_phys;
>  
> +extern int efi_confidential_computing_secret_area_reserve(void);
> +
>  /*
>   * efi_runtime_service() function identifiers.
>   * "NONE" is used by efi_recover_from_page_fault() to check if the page
>
Dov Murik June 29, 2021, 6:04 a.m. UTC | #2 
Hi Tom,

On 28/06/2021 23:40, Tom Lendacky wrote:
> On 6/28/21 1:34 PM, Dov Murik wrote:
>> When efi-stub copies an EFI-provided confidential computing secret area,
>> reserve that memory block for future use within the kernel.
>>
>> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
>> ---
>>  drivers/firmware/efi/Makefile                 |  2 +-
>>  drivers/firmware/efi/confidential-computing.c | 41 +++++++++++++++++++
>>  drivers/firmware/efi/efi.c                    |  5 +++
>>  include/linux/efi.h                           |  4 ++
>>  4 files changed, 51 insertions(+), 1 deletion(-)
>>  create mode 100644 drivers/firmware/efi/confidential-computing.c
>>
>> diff --git a/include/linux/efi.h b/include/linux/efi.h
>> index 4f647f1ee298..e9740bd16db0 100644
>> --- a/include/linux/efi.h
>> +++ b/include/linux/efi.h
>> @@ -551,6 +551,8 @@ 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			confidential_computing_secret;	/* Confidential computing */
>> +									/* secret table           */
> 
> If there is any possibility that someone could reuse a form of this
> confidential computing secret table in a bare metal system, then this
> table needs to be added to the efi_tables[] array in
> arch/x86/platform/efi/efi.c. Otherwise, it will be mapped improperly on a
> system with SME active.

Good catch, thanks.  I see that all existing table addresses from
struct efi are added to the efi_tables[] array, so for completeness it
makes sense to add efi.confidential_computing_secret as well (even
though currently bare metal firmware doesn't have this table).

Thanks,
-Dov


> 
> Thanks,
> Tom
> 
>>  
>>  	efi_get_time_t			*get_time;
>>  	efi_set_time_t			*set_time;
>> @@ -1190,6 +1192,8 @@ extern int efi_tpm_final_log_size;
>>  
>>  extern unsigned long rci2_table_phys;
>>  
>> +extern int efi_confidential_computing_secret_area_reserve(void);
>> +
>>  /*
>>   * efi_runtime_service() function identifiers.
>>   * "NONE" is used by efi_recover_from_page_fault() to check if the page
>>
diff mbox series

Patch

diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
index 467e94259679..63f21f7351da 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -12,7 +12,7 @@  KASAN_SANITIZE_runtime-wrappers.o	:= n
 
 obj-$(CONFIG_ACPI_BGRT) 		+= efi-bgrt.o
 obj-$(CONFIG_EFI)			+= efi.o vars.o reboot.o memattr.o tpm.o
-obj-$(CONFIG_EFI)			+= memmap.o
+obj-$(CONFIG_EFI)			+= memmap.o confidential-computing.o
 ifneq ($(CONFIG_EFI_CAPSULE_LOADER),)
 obj-$(CONFIG_EFI)			+= capsule.o
 endif
diff --git a/drivers/firmware/efi/confidential-computing.c b/drivers/firmware/efi/confidential-computing.c
new file mode 100644
index 000000000000..e6bb4d1e8f17
--- /dev/null
+++ b/drivers/firmware/efi/confidential-computing.c
@@ -0,0 +1,41 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Confidential computing secret area handling
+ *
+ * Copyright (C) 2021 IBM Corporation
+ * Author: Dov Murik <dovmurik@linux.ibm.com>
+ */
+
+#define pr_fmt(fmt) "efi: " fmt
+
+#include <linux/efi.h>
+#include <linux/init.h>
+#include <linux/memblock.h>
+#include <asm/early_ioremap.h>
+
+/*
+ * Reserve the confidential computing secret area memory
+ */
+int __init efi_confidential_computing_secret_area_reserve(void)
+{
+	struct linux_efi_confidential_computing_secret_area *secret_area;
+	unsigned long secret_area_size;
+
+	if (efi.confidential_computing_secret == EFI_INVALID_TABLE_ADDR)
+		return 0;
+
+	secret_area = early_memremap(efi.confidential_computing_secret, sizeof(*secret_area));
+	if (!secret_area) {
+		pr_err("Failed to map confidential computing secret area\n");
+		efi.confidential_computing_secret = EFI_INVALID_TABLE_ADDR;
+		return -ENOMEM;
+	}
+
+	secret_area_size = sizeof(*secret_area) + secret_area->size;
+	memblock_reserve(efi.confidential_computing_secret, secret_area_size);
+
+	pr_info("Reserved memory of EFI-provided confidential computing secret area");
+
+	early_memunmap(secret_area, sizeof(*secret_area));
+	return 0;
+}
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 4b7ee3fa9224..da36333e5c9f 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -526,6 +526,9 @@  static const efi_config_table_type_t common_tables[] __initconst = {
 #ifdef CONFIG_LOAD_UEFI_KEYS
 	{LINUX_EFI_MOK_VARIABLE_TABLE_GUID,	&efi.mokvar_table,	"MOKvar"	},
 #endif
+	{LINUX_EFI_CONFIDENTIAL_COMPUTING_SECRET_AREA_GUID,
+						&efi.confidential_computing_secret,
+									"ConfCompSecret"},
 	{},
 };
 
@@ -613,6 +616,8 @@  int __init efi_config_parse_tables(const efi_config_table_t *config_tables,
 
 	efi_tpm_eventlog_init();
 
+	efi_confidential_computing_secret_area_reserve();
+
 	if (mem_reserve != EFI_INVALID_TABLE_ADDR) {
 		unsigned long prsv = mem_reserve;
 
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 4f647f1ee298..e9740bd16db0 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -551,6 +551,8 @@  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			confidential_computing_secret;	/* Confidential computing */
+									/* secret table           */
 
 	efi_get_time_t			*get_time;
 	efi_set_time_t			*set_time;
@@ -1190,6 +1192,8 @@  extern int efi_tpm_final_log_size;
 
 extern unsigned long rci2_table_phys;
 
+extern int efi_confidential_computing_secret_area_reserve(void);
+
 /*
  * efi_runtime_service() function identifiers.
  * "NONE" is used by efi_recover_from_page_fault() to check if the page