[PATCH] arm64: efi: Force the use of SetVirtualAddressMap() on Altra machines

Ard Biesheuvel
2022-11-10T09:50:02Z

Ampere Altra machines are reported to misbehave when the SetTime() EFI
runtime service is called after ExitBootServices() but before calling
SetVirtualAddressMap(). Given that the latter is horrid, pointless and
explicitly documented as optional by the EFI spec, we no longer invoke
it at boot if the configured size of the VA space guarantees that the
EFI runtime memory regions can remain mapped 1:1 like they are at boot
time.

This means that SetTime() calls on Ampere Altra machines issued by the
rtc-efi driver now trigger a synchronous exception during boot. We can
now recover from those without bringing down the system entirely, due to
commit 23715a26c8d81291 ("arm64: efi: Recover from synchronous
exceptions occurring in firmware"). However, it would be better to avoid
this completely, given that the firmware appears to remain in a funny
state after this.

So attempt to identify these machines based on the 'family' field in the
type #1 SMBIOS record, and call SetVirtualAddressMap() unconditionally
in that case.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
drivers/firmware/efi/libstub/Makefile | 2 +-
drivers/firmware/efi/libstub/arm64-stub.c | 17 ++++++-
drivers/firmware/efi/libstub/efistub.h | 28 ++++++++++
drivers/firmware/efi/libstub/smbios.c | 62 +++++++++++++++++++++++
include/linux/efi.h | 1 +
5 files changed, 108 insertions(+), 2 deletions(-)
create mode 100644 drivers/firmware/efi/libstub/smbios.c

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index b1601aad7e1a8d66..ef5045a53ce09653 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -82,7 +82,7 @@ $(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o

lib-$(CONFIG_ARM) += arm32-stub.o
-lib-$(CONFIG_ARM64) += arm64-stub.o
+lib-$(CONFIG_ARM64) += arm64-stub.o smbios.o
lib-$(CONFIG_X86) += x86-stub.o
lib-$(CONFIG_RISCV) += riscv-stub.o
lib-$(CONFIG_LOONGARCH) += loongarch-stub.o
diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
index 259e4b852d63276d..f9de5217ea65ed93 100644
--- a/drivers/firmware/efi/libstub/arm64-stub.c
+++ b/drivers/firmware/efi/libstub/arm64-stub.c
@@ -15,6 +15,21 @@

#include "efistub.h"

+static bool system_needs_vamap(void)
+{
+ const u8 *type1_family = efi_get_smbios_string(1, family);
+
+ /*
+ * Ampere Altra machines crash in SetTime() if SetVirtualAddressMap()
+ * has not been called prior.
+ */
+ if (!type1_family || strcmp(type1_family, "Altra"))
+ return false;
+
+ efi_warn("Working around broken SetVirtualAddressMap()\n");
+ return true;
+}
+
efi_status_t check_platform_features(void)
{
u64 tg;
@@ -24,7 +39,7 @@ efi_status_t check_platform_features(void)
* UEFI runtime regions 1:1 and so calling SetVirtualAddressMap() is
* unnecessary.
*/
- if (VA_BITS_MIN >= 48)
+ if (VA_BITS_MIN >= 48 && !system_needs_vamap())
efi_novamap = true;

/* UEFI mandates support for 4 KB granularity, no need to check */
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index a30fb5d8ef05ae9c..eb03d5a9aac88e84 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -975,4 +975,32 @@ efi_enable_reset_attack_mitigation(void) { }

void efi_retrieve_tpm2_eventlog(void);

+struct efi_smbios_record {
+ u8 type;
+ u8 length;
+ u16 handle;
+};
+
+struct efi_smbios_type1_record {
+ struct efi_smbios_record header;
+
+ u8 manufacturer;
+ u8 product_name;
+ u8 version;
+ u8 serial_number;
+ efi_guid_t uuid;
+ u8 wakeup_type;
+ u8 sku_number;
+ u8 family;
+};
+
+#define efi_get_smbios_string(__type, __name) ({ \
+ int size = sizeof(struct efi_smbios_type ## __type ## _record); \
+ int off = offsetof(struct efi_smbios_type ## __type ## _record, \
+ __name); \
+ __efi_get_smbios_string(__type, off, size); \
+})
+
+const u8 *__efi_get_smbios_string(u8 type, int offset, int recsize);
+
#endif
diff --git a/drivers/firmware/efi/libstub/smbios.c b/drivers/firmware/efi/libstub/smbios.c
new file mode 100644
index 0000000000000000..0b7fbd85cc2f6b4b
--- /dev/null
+++ b/drivers/firmware/efi/libstub/smbios.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright 2022 Google LLC
+// Author: Ard Biesheuvel <ardb@google.com>
+
+#include <linux/efi.h>
+
+#include "efistub.h"
+
+typedef union efi_smbios_protocol efi_smbios_protocol_t;
+
+union efi_smbios_protocol {
+ struct {
+ efi_status_t (__efiapi *add)(efi_smbios_protocol_t *,
+ efi_handle_t, u16 *,
+ struct efi_smbios_record *);
+ efi_status_t (__efiapi *update_string)(efi_smbios_protocol_t *,
+ u16 *, unsigned long *,
+ u8 *);
+ efi_status_t (__efiapi *remove)(efi_smbios_protocol_t *, u16);
+ efi_status_t (__efiapi *get_next)(efi_smbios_protocol_t *,
+ u16 *, u8 *,
+ struct efi_smbios_record **,
+ efi_handle_t *);
+
+ u8 major_version;
+ u8 minor_version;
+ };
+ struct {
+ u32 add;
+ u32 update_string;
+ u32 remove;
+ u32 get_next;
+
+ u8 major_version;
+ u8 minor_version;
+ } mixed_mode;
+};
+
+const u8 *__efi_get_smbios_string(u8 type, int offset, int recsize)
+{
+ struct efi_smbios_record *record;
+ efi_smbios_protocol_t *smbios;
+ efi_status_t status;
+ u16 handle = 0xfffe;
+ const u8 *strtable;
+
+ status = efi_bs_call(locate_protocol, &EFI_SMBIOS_PROTOCOL_GUID, NULL,
+ (void **)&smbios) ?:
+ efi_call_proto(smbios, get_next, &handle, &type, &record, NULL);
+ if (status != EFI_SUCCESS)
+ return NULL;
+
+ strtable = (u8 *)record + recsize;
+ for (int i = 1; i < ((u8 *)record)[offset]; i++) {
+ int len = strlen(strtable);
+
+ if (!len)
+ return NULL;
+ strtable += len + 1;
+ }
+ return strtable;
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 61b252386d61cc4d..cf88dda630649f87 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -389,6 +389,7 @@ void efi_native_runtime_setup(void);
#define EFI_LOAD_FILE2_PROTOCOL_GUID EFI_GUID(0x4006c0c1, 0xfcb3, 0x403e, 0x99, 0x6d, 0x4a, 0x6c, 0x87, 0x24, 0xe0, 0x6d)
#define EFI_RT_PROPERTIES_TABLE_GUID EFI_GUID(0xeb66918a, 0x7eef, 0x402a, 0x84, 0x2e, 0x93, 0x1d, 0x21, 0xc3, 0x8a, 0xe9)
#define EFI_DXE_SERVICES_TABLE_GUID EFI_GUID(0x05ad34ba, 0x6f02, 0x4214, 0x95, 0x2e, 0x4d, 0xa0, 0x39, 0x8e, 0x2b, 0xb9)
+#define EFI_SMBIOS_PROTOCOL_GUID EFI_GUID(0x03583ff6, 0xcb36, 0x4940, 0x94, 0x7e, 0xb9, 0xb3, 0x9f, 0x4a, 0xfa, 0xf7)

#define EFI_IMAGE_SECURITY_DATABASE_GUID EFI_GUID(0xd719b2cb, 0x3d3a, 0x4596, 0xa3, 0xbc, 0xda, 0xd0, 0x0e, 0x67, 0x65, 0x6f)
#define EFI_SHIM_LOCK_GUID EFI_GUID(0x605dab50, 0xe046, 0x4300, 0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 0x23)
--
2.35.1