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Subject[PATCH v4 2/3] efi: Reserve confidential computing secret area
Date
When efi-stub copies an EFI-provided confidential computing (coco)
secret area, reserve that memory block for future use within the kernel.

Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
arch/x86/platform/efi/efi.c | 3 +++
drivers/firmware/efi/Makefile | 1 +
drivers/firmware/efi/coco.c | 41 +++++++++++++++++++++++++++++++++++
drivers/firmware/efi/efi.c | 8 +++++++
include/linux/efi.h | 10 +++++++++
5 files changed, 63 insertions(+)
create mode 100644 drivers/firmware/efi/coco.c

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/Makefile b/drivers/firmware/efi/Makefile
index c02ff25dd477..49c4a8c0bfc4 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -32,6 +32,7 @@ obj-$(CONFIG_APPLE_PROPERTIES) += apple-properties.o
obj-$(CONFIG_EFI_RCI2_TABLE) += rci2-table.o
obj-$(CONFIG_EFI_EMBEDDED_FIRMWARE) += embedded-firmware.o
obj-$(CONFIG_LOAD_UEFI_KEYS) += mokvar-table.o
+obj-$(CONFIG_EFI_COCO_SECRET) += coco.o

fake_map-y += fake_mem.o
fake_map-$(CONFIG_X86) += x86_fake_mem.o
diff --git a/drivers/firmware/efi/coco.c b/drivers/firmware/efi/coco.c
new file mode 100644
index 000000000000..42f477d6188c
--- /dev/null
+++ b/drivers/firmware/efi/coco.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Confidential computing (coco) 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_coco_secret_area_reserve(void)
+{
+ struct linux_efi_coco_secret_area *secret_area;
+ unsigned long secret_area_size;
+
+ if (efi.coco_secret == EFI_INVALID_TABLE_ADDR)
+ return 0;
+
+ secret_area = early_memremap(efi.coco_secret, sizeof(*secret_area));
+ if (!secret_area) {
+ pr_err("Failed to map confidential computing secret area\n");
+ efi.coco_secret = EFI_INVALID_TABLE_ADDR;
+ return -ENOMEM;
+ }
+
+ secret_area_size = sizeof(*secret_area) + secret_area->size;
+ memblock_reserve(efi.coco_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 847f33ffc4ae..31bdae2afc47 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);

@@ -525,6 +528,9 @@ 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
{},
};
@@ -613,6 +619,8 @@ int __init efi_config_parse_tables(const efi_config_table_t *config_tables,

efi_tpm_eventlog_init();

+ efi_coco_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 9021dd521302..6e57dd083e25 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -550,6 +550,7 @@ 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;
@@ -1288,4 +1289,13 @@ struct linux_efi_coco_secret_area {
u8 area[];
};

+#ifdef CONFIG_EFI_COCO_SECRET
+extern int efi_coco_secret_area_reserve(void);
+#else
+static inline int efi_coco_secret_area_reserve(void)
+{
+ return 0;
+}
+#endif
+
#endif /* _LINUX_EFI_H */
--
2.25.1
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