efi: call get_event_log before ExitBootServices

With TPM 2.0 specification, the event logs may only be accessible by
calling an EFI Boot Service. Modify the EFI stub to copy the log area to
a new Linux-specific EFI configuration table so it remains accessible
once booted.

When calling this service, it is possible to specify the expected format
of the logs: TPM 1.2 (SHA1) or TPM 2.0 ("Crypto Agile"). For now, only the
first format is retrieved.

Signed-off-by: Thiebaud Weksteen <tweek@google.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: Jarkko Sakkinen  <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen  <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen  <jarkko.sakkinen@linux.intel.com>

5 files changed, 127 insertions, 3 deletions

diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
index 269501dfba53..1d7226fb7d2f 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -11,7 +11,7 @@
 KASAN_SANITIZE_runtime-wrappers.o	:= n
 
 obj-$(CONFIG_ACPI_BGRT) 		+= efi-bgrt.o
-obj-$(CONFIG_EFI)			+= efi.o vars.o reboot.o memattr.o
+obj-$(CONFIG_EFI)			+= efi.o vars.o reboot.o memattr.o tpm.o
 obj-$(CONFIG_EFI)			+= capsule.o memmap.o
 obj-$(CONFIG_EFI_VARS)			+= efivars.o
 obj-$(CONFIG_EFI_ESRT)			+= esrt.o
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 557a47829d03..cfa6fe786ab6 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -52,6 +52,7 @@ struct efi __read_mostly efi = {
 	.properties_table	= EFI_INVALID_TABLE_ADDR,
 	.mem_attr_table		= EFI_INVALID_TABLE_ADDR,
 	.rng_seed		= EFI_INVALID_TABLE_ADDR,
+	.tpm_log		= EFI_INVALID_TABLE_ADDR
 };
 EXPORT_SYMBOL(efi);
 
@@ -464,6 +465,7 @@ static __initdata efi_config_table_type_t common_tables[] = {
 	{EFI_PROPERTIES_TABLE_GUID, "PROP", &efi.properties_table},
 	{EFI_MEMORY_ATTRIBUTES_TABLE_GUID, "MEMATTR", &efi.mem_attr_table},
 	{LINUX_EFI_RANDOM_SEED_TABLE_GUID, "RNG", &efi.rng_seed},
+	{LINUX_EFI_TPM_EVENT_LOG_GUID, "TPMEventLog", &efi.tpm_log},
 	{NULL_GUID, NULL, NULL},
 };
 
@@ -552,6 +554,8 @@ int __init efi_config_parse_tables(void *config_tables, int count, int sz,
 	if (efi_enabled(EFI_MEMMAP))
 		efi_memattr_init();
 
+	efi_tpm_eventlog_init();
+
 	/* Parse the EFI Properties table if it exists */
 	if (efi.properties_table != EFI_INVALID_TABLE_ADDR) {
 		efi_properties_table_t *tbl;
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index adaa4a964f0c..7b3ba40f0745 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -30,8 +30,7 @@ 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
-lib-$(CONFIG_RESET_ATTACK_MITIGATION) += tpm.o
+lib-y				:= efi-stub-helper.o gop.o secureboot.o tpm.o
 
 # include the stub's generic dependencies from lib/ when building for ARM/arm64
 arm-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c
diff --git a/drivers/firmware/efi/libstub/tpm.c b/drivers/firmware/efi/libstub/tpm.c
index 6224cdbc9669..da661bf8cb96 100644
--- a/drivers/firmware/efi/libstub/tpm.c
+++ b/drivers/firmware/efi/libstub/tpm.c
@@ -4,15 +4,18 @@
  * Copyright (C) 2016 CoreOS, Inc
  * Copyright (C) 2017 Google, Inc.
  *     Matthew Garrett <mjg59@google.com>
+ *     Thiebaud Weksteen <tweek@google.com>
  *
  * This file is part of the Linux kernel, and is made available under the
  * terms of the GNU General Public License version 2.
  */
 #include <linux/efi.h>
+#include <linux/tpm_eventlog.h>
 #include <asm/efi.h>
 
 #include "efistub.h"
 
+#ifdef CONFIG_RESET_ATTACK_MITIGATION
 static const efi_char16_t efi_MemoryOverWriteRequest_name[] = {
 	'M', 'e', 'm', 'o', 'r', 'y', 'O', 'v', 'e', 'r', 'w', 'r', 'i', 't',
 	'e', 'R', 'e', 'q', 'u', 'e', 's', 't', 'C', 'o', 'n', 't', 'r', 'o',
@@ -56,3 +59,81 @@ void efi_enable_reset_attack_mitigation(efi_system_table_t *sys_table_arg)
 		    EFI_VARIABLE_BOOTSERVICE_ACCESS |
 		    EFI_VARIABLE_RUNTIME_ACCESS, sizeof(val), &val);
 }
+
+#endif
+
+void efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg)
+{
+	efi_guid_t tcg2_guid = EFI_TCG2_PROTOCOL_GUID;
+	efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID;
+	efi_status_t status;
+	efi_physical_addr_t log_location, log_last_entry;
+	struct linux_efi_tpm_eventlog *log_tbl;
+	unsigned long first_entry_addr, last_entry_addr;
+	size_t log_size, last_entry_size;
+	efi_bool_t truncated;
+	void *tcg2_protocol;
+
+	status = efi_call_early(locate_protocol, &tcg2_guid, NULL,
+				&tcg2_protocol);
+	if (status != EFI_SUCCESS)
+		return;
+
+	status = efi_call_proto(efi_tcg2_protocol, get_event_log, tcg2_protocol,
+				EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2,
+				&log_location, &log_last_entry, &truncated);
+	if (status != EFI_SUCCESS)
+		return;
+
+	if (!log_location)
+		return;
+	first_entry_addr = (unsigned long) log_location;
+
+	/*
+	 * We populate the EFI table even if the logs are empty.
+	 */
+	if (!log_last_entry) {
+		log_size = 0;
+	} else {
+		last_entry_addr = (unsigned long) log_last_entry;
+		/*
+		 * get_event_log only returns the address of the last entry.
+		 * We need to calculate its size to deduce the full size of
+		 * the logs.
+		 */
+		last_entry_size = sizeof(struct tcpa_event) +
+			((struct tcpa_event *) last_entry_addr)->event_size;
+		log_size = log_last_entry - log_location + last_entry_size;
+	}
+
+	/* Allocate space for the logs and copy them. */
+	status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
+				sizeof(*log_tbl) + log_size,
+				(void **) &log_tbl);
+
+	if (status != EFI_SUCCESS) {
+		efi_printk(sys_table_arg,
+			   "Unable to allocate memory for event log\n");
+		return;
+	}
+
+	memset(log_tbl, 0, sizeof(*log_tbl) + log_size);
+	log_tbl->size = log_size;
+	log_tbl->version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
+	memcpy(log_tbl->log, (void *) first_entry_addr, log_size);
+
+	status = efi_call_early(install_configuration_table,
+				&linux_eventlog_guid, log_tbl);
+	if (status != EFI_SUCCESS)
+		goto err_free;
+	return;
+
+err_free:
+	efi_call_early(free_pool, log_tbl);
+}
+
+void efi_retrieve_tpm2_eventlog(efi_system_table_t *sys_table_arg)
+{
+	/* Only try to retrieve the logs in 1.2 format. */
+	efi_retrieve_tpm2_eventlog_1_2(sys_table_arg);
+}
diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c
new file mode 100644
index 000000000000..0cbeb3d46b18
--- /dev/null
+++ b/drivers/firmware/efi/tpm.c
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2017 Google, Inc.
+ *     Thiebaud Weksteen <tweek@google.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/efi.h>
+#include <linux/init.h>
+#include <linux/memblock.h>
+
+#include <asm/early_ioremap.h>
+
+/*
+ * Reserve the memory associated with the TPM Event Log configuration table.
+ */
+int __init efi_tpm_eventlog_init(void)
+{
+	struct linux_efi_tpm_eventlog *log_tbl;
+	unsigned int tbl_size;
+
+	if (efi.tpm_log == EFI_INVALID_TABLE_ADDR)
+		return 0;
+
+	log_tbl = early_memremap(efi.tpm_log, sizeof(*log_tbl));
+	if (!log_tbl) {
+		pr_err("Failed to map TPM Event Log table @ 0x%lx\n",
+			efi.tpm_log);
+		efi.tpm_log = EFI_INVALID_TABLE_ADDR;
+		return -ENOMEM;
+	}
+
+	tbl_size = sizeof(*log_tbl) + log_tbl->size;
+	memblock_reserve(efi.tpm_log, tbl_size);
+	early_memunmap(log_tbl, sizeof(*log_tbl));
+	return 0;
+}
+