[PATCH v2 1/2] tpm: implement TPM 2.0 capability to get active PCR banks

[Nayna Jain]

This patch implements the TPM 2.0 capability TPM_CAP_PCRS to
retrieve the active PCR banks from the TPM. This is needed
to enable extending all active banks as recommended by TPM 2.0
TCG Specification.

Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxxxxxxx>
---
 drivers/char/tpm/tpm.h      |  5 +++
 drivers/char/tpm/tpm2-cmd.c | 79 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 1ae9768..3d8121e 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -43,6 +43,7 @@ enum tpm_const {
 	TPM_NUM_DEVICES = 65536,
 	TPM_RETRY = 50,		/* 5 seconds */
 	TPM_NUM_EVENT_LOG_FILES = 3,
+	TPM2_MAX_PCR_BANKS = 7,
 };
 
 enum tpm_timeout {
@@ -127,6 +128,7 @@ enum tpm2_permanent_handles {
 };
 
 enum tpm2_capabilities {
+	TPM2_CAP_PCRS		= 5,
 	TPM2_CAP_TPM_PROPERTIES = 6,
 };
 
@@ -187,6 +189,8 @@ struct tpm_chip {
 
 	const struct attribute_group *groups[3];
 	unsigned int groups_cnt;
+
+	enum tpm2_algorithms active_banks[TPM2_MAX_PCR_BANKS];
 #ifdef CONFIG_ACPI
 	acpi_handle acpi_dev_handle;
 	char ppi_version[TPM_PPI_VERSION_LEN + 1];
@@ -545,4 +549,5 @@ int tpm2_auto_startup(struct tpm_chip *chip);
 void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type);
 unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal);
 int tpm2_probe(struct tpm_chip *chip);
+ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip);
 #endif
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 6eda239..dd03fd8 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -83,6 +83,25 @@ struct tpm2_get_tpm_pt_out {
 	__be32	value;
 } __packed;
 
+struct tpm2_tpms_pcr_selection {
+	__be16  hash_alg;
+	u8  size_of_select;
+	u8  pcr_select[3];
+} __packed;
+
+struct tpm2_getcap_in {
+	__be32	cap_id;
+	__be32	property_id;
+	__be32	property_cnt;
+} __packed;
+
+struct tpm2_getcap_out {
+	u8	more_data;
+	__be32  subcap_id;
+	__be32  count;
+	char	cap_data[0];
+} __packed;
+
 struct tpm2_get_random_in {
 	__be16	size;
 } __packed;
@@ -100,6 +119,8 @@ union tpm2_cmd_params {
 	struct	tpm2_pcr_extend_in	pcrextend_in;
 	struct	tpm2_get_tpm_pt_in	get_tpm_pt_in;
 	struct	tpm2_get_tpm_pt_out	get_tpm_pt_out;
+	struct	tpm2_getcap_in		getcap_in;
+	struct	tpm2_getcap_out		getcap_out;
 	struct	tpm2_get_random_in	getrandom_in;
 	struct	tpm2_get_random_out	getrandom_out;
 };
@@ -993,8 +1014,66 @@ int tpm2_auto_startup(struct tpm_chip *chip)
 		}
 	}
 
+	rc = tpm2_get_pcr_allocation(chip);
+
 out:
 	if (rc > 0)
 		rc = -ENODEV;
 	return rc;
 }
+
+#define TPM2_GETCAP_IN_SIZE \
+	(sizeof(struct tpm_input_header) + sizeof(struct tpm2_getcap_in))
+
+static const struct tpm_input_header tpm2_getcap_header = {
+	.tag = cpu_to_be16(TPM2_ST_NO_SESSIONS),
+	.length = cpu_to_be32(TPM2_GETCAP_IN_SIZE),
+	.ordinal = cpu_to_be32(TPM2_CC_GET_CAPABILITY)
+};
+
+/**
+ * tpm2_get_pcr_allocation() - get TPM active PCR banks.
+ *
+ * @chip: TPM chip to use.
+ *
+ * Return: Same as with tpm_transmit_cmd.
+ */
+ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
+{
+	struct tpm2_cmd cmd;
+	struct tpm2_tpms_pcr_selection pcr_selection;
+	void *marker;
+	unsigned int count = 0;
+	int rc;
+	int i;
+
+	cmd.header.in = tpm2_getcap_header;
+	cmd.params.getcap_in.cap_id = cpu_to_be32(TPM2_CAP_PCRS);
+	cmd.params.getcap_in.property_id = cpu_to_be32(0);
+	cmd.params.getcap_in.property_cnt = cpu_to_be32(1);
+
+	rc = tpm_transmit_cmd(chip, &cmd, sizeof(cmd), 0,
+			      "get tpm pcr allocation");
+	if (rc < 0)
+		goto out;
+
+	count = be32_to_cpu(cmd.params.getcap_out.count);
+	if (count > TPM2_MAX_PCR_BANKS) {
+		dev_err(&chip->dev,
+			"%s: Error: Invalid active PCR banks count\n",
+			__func__);
+		return -ENODEV;
+	}
+
+	marker = &cmd.params.getcap_out.cap_data;
+	for (i = 0; i < count; i++) {
+		memcpy(&pcr_selection, marker, sizeof(pcr_selection));
+		chip->active_banks[i] = be16_to_cpu(pcr_selection.hash_alg);
+		marker = marker + sizeof(struct tpm2_tpms_pcr_selection);
+	}
+
+out:
+	if (count < TPM2_MAX_PCR_BANKS)
+		chip->active_banks[count] = 0;
+	return rc;
+}
-- 
2.5.0