[PATCH v3] tpm: Parse event log from TPM2 ACPI table

[Jordan Hand <jorhand@linux.microsoft.com>]

For systems with a TPM2 chip which use ACPI to expose event logs, retrieve the
crypto-agile event log from the TPM2 ACPI table. The TPM2 table is defined
in section 7.3 of the TCG ACPI Specification (see link).

The TPM2 table is used by SeaBIOS in place of the TCPA table when the system's
TPM is version 2.0 to denote (among other metadata) the location of the
crypto-agile log.

Link: https://trustedcomputinggroup.org/resource/tcg-acpi-specification/
Signed-off-by: Jordan Hand <jorhand@linux.microsoft.com>
---
 drivers/char/tpm/eventlog/acpi.c | 60 ++++++++++++++++++++++----------
 1 file changed, 41 insertions(+), 19 deletions(-)

diff --git a/drivers/char/tpm/eventlog/acpi.c b/drivers/char/tpm/eventlog/acpi.c
index 63ada5e53f13..38a8bcec1dd5 100644
--- a/drivers/char/tpm/eventlog/acpi.c
+++ b/drivers/char/tpm/eventlog/acpi.c
@@ -41,17 +41,23 @@ struct acpi_tcpa {
 	};
 };
 
+/* If an event log is present, the TPM2 ACPI table will contain the full
+ * trailer
+ */
+
 /* read binary bios log */
 int tpm_read_log_acpi(struct tpm_chip *chip)
 {
-	struct acpi_tcpa *buff;
+	struct acpi_table_header *buff;
+	struct acpi_tcpa *tcpa;
+	struct acpi_tpm2_trailer *tpm2_trailer;
 	acpi_status status;
 	void __iomem *virt;
 	u64 len, start;
+	int log_type;
 	struct tpm_bios_log *log;
-
-	if (chip->flags & TPM_CHIP_FLAG_TPM2)
-		return -ENODEV;
+	bool is_tpm2 = chip->flags & TPM_CHIP_FLAG_TPM2;
+	acpi_string table_sig;
 
 	log = &chip->log;
 
@@ -61,26 +67,42 @@ int tpm_read_log_acpi(struct tpm_chip *chip)
 	if (!chip->acpi_dev_handle)
 		return -ENODEV;
 
-	/* Find TCPA entry in RSDT (ACPI_LOGICAL_ADDRESSING) */
-	status = acpi_get_table(ACPI_SIG_TCPA, 1,
-				(struct acpi_table_header **)&buff);
+	/* Find TCPA or TPM2 entry in RSDT (ACPI_LOGICAL_ADDRESSING) */
+	table_sig = is_tpm2 ? ACPI_SIG_TPM2 : ACPI_SIG_TCPA;
+	status = acpi_get_table(table_sig, 1, &buff);
 
 	if (ACPI_FAILURE(status))
 		return -ENODEV;
 
-	switch(buff->platform_class) {
-	case BIOS_SERVER:
-		len = buff->server.log_max_len;
-		start = buff->server.log_start_addr;
-		break;
-	case BIOS_CLIENT:
-	default:
-		len = buff->client.log_max_len;
-		start = buff->client.log_start_addr;
-		break;
+	if (!is_tpm2) {
+		tcpa = (struct acpi_tcpa *)buff;
+		switch (tcpa->platform_class) {
+		case BIOS_SERVER:
+			len = tcpa->server.log_max_len;
+			start = tcpa->server.log_start_addr;
+			break;
+		case BIOS_CLIENT:
+		default:
+			len = tcpa->client.log_max_len;
+			start = tcpa->client.log_start_addr;
+			break;
+		}
+		log_type = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
+	} else if (buff->length ==
+		   sizeof(struct acpi_table_tpm2) +
+		   sizeof(struct acpi_tpm2_trailer)) {
+		tpm2_trailer = (struct acpi_tpm2_trailer *)buff;
+
+		len = tpm2_trailer.minimum_log_length;
+		start = tpm2_trailer.log_address;
+		log_type = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2;
+	} else {
+		return -ENODEV;
 	}
+
 	if (!len) {
-		dev_warn(&chip->dev, "%s: TCPA log area empty\n", __func__);
+		dev_warn(&chip->dev, "%s: %s log area empty\n",
+			 __func__, table_sig);
 		return -EIO;
 	}
 
@@ -98,7 +120,7 @@ int tpm_read_log_acpi(struct tpm_chip *chip)
 	memcpy_fromio(log->bios_event_log, virt, len);
 
 	acpi_os_unmap_iomem(virt, len);
-	return EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
+	return log_type;
 
 err:
 	kfree(log->bios_event_log);
-- 
2.20.1