[PATCH v3 1/3] efi: generalize efi_get_secureboot

Chester Lin
2020-10-30T06:09:28Z

Generalize the efi_get_secureboot() function so not only efistub but also
other subsystems can use it.

Signed-off-by: Chester Lin <clin@suse.com>
---
drivers/firmware/efi/libstub/Makefile | 2 +-
drivers/firmware/efi/libstub/efi-stub.c | 2 +-
drivers/firmware/efi/libstub/efistub.h | 22 ++++---
drivers/firmware/efi/libstub/secureboot.c | 76 -----------------------
drivers/firmware/efi/libstub/x86-stub.c | 2 +-
include/linux/efi.h | 41 +++++++++++-
6 files changed, 57 insertions(+), 88 deletions(-)
delete mode 100644 drivers/firmware/efi/libstub/secureboot.c

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 8a94388e38b3..88e47b0ca09d 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -49,7 +49,7 @@ OBJECT_FILES_NON_STANDARD := y
# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
KCOV_INSTRUMENT := n

-lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \
+lib-y := efi-stub-helper.o gop.o tpm.o \
file.o mem.o random.o randomalloc.o pci.o \
skip_spaces.o lib-cmdline.o lib-ctype.o \
alignedmem.o relocate.o vsprintf.o
diff --git a/drivers/firmware/efi/libstub/efi-stub.c b/drivers/firmware/efi/libstub/efi-stub.c
index 914a343c7785..ad96f1d786a9 100644
--- a/drivers/firmware/efi/libstub/efi-stub.c
+++ b/drivers/firmware/efi/libstub/efi-stub.c
@@ -196,7 +196,7 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
/* Ask the firmware to clear memory on unclean shutdown */
efi_enable_reset_attack_mitigation();

- secure_boot = efi_get_secureboot();
+ secure_boot = efi_get_secureboot(get_efi_var);

/*
* Unauthenticated device tree data is a security hazard, so ignore
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index 2d7abcd99de9..b1833b51e6d6 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -91,14 +91,6 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
fdt_setprop((fdt), (node_offset), (name), &(var), sizeof(var))
#endif

-#define get_efi_var(name, vendor, ...) \
- efi_rt_call(get_variable, (efi_char16_t *)(name), \
- (efi_guid_t *)(vendor), __VA_ARGS__)
-
-#define set_efi_var(name, vendor, ...) \
- efi_rt_call(set_variable, (efi_char16_t *)(name), \
- (efi_guid_t *)(vendor), __VA_ARGS__)
-
#define efi_get_handle_at(array, idx) \
(efi_is_native() ? (array)[idx] \
: (efi_handle_t)(unsigned long)((u32 *)(array))[idx])
@@ -112,6 +104,20 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
((handle = efi_get_handle_at((array), i)) || true); \
i++)

+static inline
+efi_status_t get_efi_var(efi_char16_t *name, efi_guid_t *vendor, u32 *attr,
+ unsigned long *size, void *data)
+{
+ return efi_rt_call(get_variable, name, vendor, attr, size, data);
+}
+
+static inline
+efi_status_t set_efi_var(efi_char16_t *name, efi_guid_t *vendor, u32 attr,
+ unsigned long size, void *data)
+{
+ return efi_rt_call(set_variable, name, vendor, attr, size, data);
+}
+
static inline
void efi_set_u64_split(u64 data, u32 *lo, u32 *hi)
{
diff --git a/drivers/firmware/efi/libstub/secureboot.c b/drivers/firmware/efi/libstub/secureboot.c
deleted file mode 100644
index 5efc524b14be..000000000000
--- a/drivers/firmware/efi/libstub/secureboot.c
+++ /dev/null
@@ -1,76 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Secure boot handling.
- *
- * Copyright (C) 2013,2014 Linaro Limited
- * Roy Franz <roy.franz@linaro.org
- * Copyright (C) 2013 Red Hat, Inc.
- * Mark Salter <msalter@redhat.com>
- */
-#include <linux/efi.h>
-#include <asm/efi.h>
-
-#include "efistub.h"
-
-/* BIOS variables */
-static const efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
-static const efi_char16_t efi_SecureBoot_name[] = L"SecureBoot";
-static const efi_char16_t efi_SetupMode_name[] = L"SetupMode";
-
-/* SHIM variables */
-static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
-static const efi_char16_t shim_MokSBState_name[] = L"MokSBState";
-
-/*
- * Determine whether we're in secure boot mode.
- *
- * Please keep the logic in sync with
- * arch/x86/xen/efi.c:xen_efi_get_secureboot().
- */
-enum efi_secureboot_mode efi_get_secureboot(void)
-{
- u32 attr;
- u8 secboot, setupmode, moksbstate;
- unsigned long size;
- efi_status_t status;
-
- size = sizeof(secboot);
- status = get_efi_var(efi_SecureBoot_name, &efi_variable_guid,
- NULL, &size, &secboot);
- if (status == EFI_NOT_FOUND)
- return efi_secureboot_mode_disabled;
- if (status != EFI_SUCCESS)
- goto out_efi_err;
-
- size = sizeof(setupmode);
- status = get_efi_var(efi_SetupMode_name, &efi_variable_guid,
- NULL, &size, &setupmode);
- if (status != EFI_SUCCESS)
- goto out_efi_err;
-
- if (secboot == 0 || setupmode == 1)
- return efi_secureboot_mode_disabled;
-
- /*
- * See if a user has put the shim into insecure mode. If so, and if the
- * variable doesn't have the runtime attribute set, we might as well
- * honor that.
- */
- size = sizeof(moksbstate);
- status = get_efi_var(shim_MokSBState_name, &shim_guid,
- &attr, &size, &moksbstate);
-
- /* If it fails, we don't care why. Default to secure */
- if (status != EFI_SUCCESS)
- goto secure_boot_enabled;
- if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS) && moksbstate == 1)
- return efi_secureboot_mode_disabled;
-
-secure_boot_enabled:
- efi_info("UEFI Secure Boot is enabled.\n");
- return efi_secureboot_mode_enabled;
-
-out_efi_err:
- efi_err("Could not determine UEFI Secure Boot status.\n");
- return efi_secureboot_mode_unknown;
-}
diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index 3672539cb96e..3f9b492c566b 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -781,7 +781,7 @@ unsigned long efi_main(efi_handle_t handle,
* otherwise we ask the BIOS.
*/
if (boot_params->secure_boot == efi_secureboot_mode_unset)
- boot_params->secure_boot = efi_get_secureboot();
+ boot_params->secure_boot = efi_get_secureboot(get_efi_var);

/* Ask the firmware to clear memory on unclean shutdown */
efi_enable_reset_attack_mitigation();
diff --git a/include/linux/efi.h b/include/linux/efi.h
index d7c0e73af2b9..cc2d3de39031 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1089,7 +1089,46 @@ enum efi_secureboot_mode {
efi_secureboot_mode_disabled,
efi_secureboot_mode_enabled,
};
-enum efi_secureboot_mode efi_get_secureboot(void);
+
+static inline enum efi_secureboot_mode efi_get_secureboot(efi_get_variable_t *get_var)
+{
+ efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID;
+ efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
+ efi_status_t status;
+ unsigned long size;
+ u8 secboot, setupmode, moksbstate;
+ u32 attr;
+
+ size = sizeof(secboot);
+ status = get_var(L"SecureBoot", &var_guid, NULL, &size, &secboot);
+
+ if (status == EFI_NOT_FOUND)
+ return efi_secureboot_mode_disabled;
+ if (status != EFI_SUCCESS)
+ return efi_secureboot_mode_unknown;
+
+ size = sizeof(setupmode);
+ status = get_var(L"SetupMode", &var_guid, NULL, &size, &setupmode);
+
+ if (status != EFI_SUCCESS)
+ return efi_secureboot_mode_unknown;
+ if (secboot == 0 || setupmode == 1)
+ return efi_secureboot_mode_disabled;
+
+ /*
+ * See if a user has put the shim into insecure mode. If so, and if the
+ * variable doesn't have the runtime attribute set, we might as well
+ * honor that.
+ */
+ size = sizeof(moksbstate);
+ status = get_var(L"MokSBState", &shim_guid, &attr, &size, &moksbstate);
+ /* If it fails, we don't care why. Default to secure */
+ if (status == EFI_SUCCESS && moksbstate == 1
+ && !(attr & EFI_VARIABLE_RUNTIME_ACCESS))
+ return efi_secureboot_mode_disabled;
+
+ return efi_secureboot_mode_enabled;
+}

#ifdef CONFIG_RESET_ATTACK_MITIGATION
void efi_enable_reset_attack_mitigation(void);
--
2.28.0