1 files changed, 42 insertions, 0 deletions
diff --git a/lib/tpm-v2.c b/lib/tpm-v2.c
index 476b4ee0d0..7d3834c0e4 100644
--- a/lib/tpm-v2.c
+++ b/lib/tpm-v2.c
@@ -115,3 +115,45 @@ u32 tpm2_pcr_extend(u32 index, const uint8_t *digest)
 
 	return tpm_sendrecv_command(command_v2,	NULL, NULL);
 }
+
+u32 tpm2_pcr_read(u32 idx, unsigned int idx_min_sz, void *data,
+		  unsigned int *updates)
+{
+	u8 idx_array_sz = max(idx_min_sz, DIV_ROUND_UP(idx, 8));
+	u8 command_v2[COMMAND_BUFFER_SIZE] = {
+		tpm_u16(TPM2_ST_NO_SESSIONS),	/* TAG */
+		tpm_u32(17 + idx_array_sz),	/* Length */
+		tpm_u32(TPM2_CC_PCR_READ),	/* Command code */
+
+		/* TPML_PCR_SELECTION */
+		tpm_u32(1),			/* Number of selections */
+		tpm_u16(TPM2_ALG_SHA256),	/* Algorithm of the hash */
+		idx_array_sz,			/* Array size for selection */
+		/* bitmap(idx)			   Selected PCR bitmap */
+	};
+	size_t response_len = COMMAND_BUFFER_SIZE;
+	u8 response[COMMAND_BUFFER_SIZE];
+	unsigned int pcr_sel_idx = idx / 8;
+	u8 pcr_sel_bit = BIT(idx % 8);
+	unsigned int counter = 0;
+	int ret;
+
+	if (pack_byte_string(command_v2, COMMAND_BUFFER_SIZE, "b",
+			     17 + pcr_sel_idx, pcr_sel_bit))
+		return TPM_LIB_ERROR;
+
+	ret = tpm_sendrecv_command(command_v2, response, &response_len);
+	if (ret)
+		return ret;
+
+	if (unpack_byte_string(response, response_len, "ds",
+			       10, &counter,
+			       response_len - TPM2_DIGEST_LEN, data,
+			       TPM2_DIGEST_LEN))
+		return TPM_LIB_ERROR;
+
+	if (updates)
+		*updates = counter;
+
+	return 0;
+}