[PATCH v3 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      |  4 +++
 drivers/char/tpm/tpm2-cmd.c | 59 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 1ae9768..dddd573 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -127,6 +127,7 @@ enum tpm2_permanent_handles {
 };
 
 enum tpm2_capabilities {
+	TPM2_CAP_PCRS		= 5,
 	TPM2_CAP_TPM_PROPERTIES = 6,
 };
 
@@ -187,6 +188,8 @@ struct tpm_chip {
 
 	const struct attribute_group *groups[3];
 	unsigned int groups_cnt;
+
+	u16 active_banks[7];
 #ifdef CONFIG_ACPI
 	acpi_handle acpi_dev_handle;
 	char ppi_version[TPM_PPI_VERSION_LEN + 1];
@@ -545,4 +548,5 @@ 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..87388921 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -83,6 +83,12 @@ 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_get_random_in {
 	__be16	size;
 } __packed;
@@ -993,8 +999,61 @@ int tpm2_auto_startup(struct tpm_chip *chip)
 		}
 	}
 
+	rc = tpm2_get_pcr_allocation(chip);
+
 out:
 	if (rc > 0)
 		rc = -ENODEV;
 	return rc;
 }
+
+/**
+ * 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_tpms_pcr_selection pcr_selection;
+	struct tpm_buf buf;
+	void *marker;
+	unsigned int count = 0;
+	int rc;
+	int i;
+
+	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
+	if (rc)
+		return rc;
+
+	tpm_buf_append_u32(&buf, TPM2_CAP_PCRS);
+	tpm_buf_append_u32(&buf, 0);
+	tpm_buf_append_u32(&buf, 1);
+
+	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, 0,
+			      "get tpm pcr allocation");
+	if (rc < 0)
+		goto out;
+
+	count = be32_to_cpup(
+		(__be32 *) &buf.data[TPM_HEADER_SIZE + 5]);
+
+	if (count > ARRAY_SIZE(chip->active_banks))
+		return -ENODEV;
+
+	marker = &buf.data[TPM_HEADER_SIZE + 9];
+	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 < ARRAY_SIZE(chip->active_banks))
+		chip->active_banks[count] = 0;
+
+	tpm_buf_destroy(&buf);
+
+	return rc;
+}
-- 
2.5.0