2 files changed, 23 insertions, 33 deletions

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 6895f183396b..51d147675b1f 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -382,13 +382,10 @@ typedef union {
 	struct	tpm_output_header out;
 } tpm_cmd_header;
 
-struct tpm_pcrread_out {
-	u8	pcr_result[TPM_DIGEST_SIZE];
+struct tpm_cmd_t {
+	tpm_cmd_header	header;
 } __packed;
 
-struct tpm_pcrread_in {
-	__be32	pcr_idx;
-} __packed;
 
 /* 128 bytes is an arbitrary cap. This could be as large as TPM_BUFSIZE - 18
  * bytes, but 128 is still a relatively large number of random bytes and
@@ -396,17 +393,6 @@ struct tpm_pcrread_in {
  * compiler warnings about stack frame size. */
 #define TPM_MAX_RNG_DATA	128
 
-typedef union {
-	struct	tpm_pcrread_in	pcrread_in;
-	struct	tpm_pcrread_out	pcrread_out;
-} tpm_cmd_params;
-
-struct tpm_cmd_t {
-	tpm_cmd_header	header;
-	tpm_cmd_params	params;
-} __packed;
-
-
 /* A string buffer type for constructing TPM commands. This is based on the
  * ideas of string buffer code in security/keys/trusted.h but is heap based
  * in order to keep the stack usage minimal.
diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
index b5c4fa158c30..d30f336518f6 100644
--- a/drivers/char/tpm/tpm1-cmd.c
+++ b/drivers/char/tpm/tpm1-cmd.c
@@ -571,29 +571,33 @@ out:
 	return rc;
 }
 
-#define TPM_ORDINAL_PCRREAD 21
-#define READ_PCR_RESULT_SIZE 30
-#define READ_PCR_RESULT_BODY_SIZE 20
-static const struct tpm_input_header pcrread_header = {
-	.tag = cpu_to_be16(TPM_TAG_RQU_COMMAND),
-	.length = cpu_to_be32(14),
-	.ordinal = cpu_to_be32(TPM_ORDINAL_PCRREAD)
-};
-
+#define TPM_ORD_PCRREAD 21
 int tpm1_pcr_read_dev(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
 {
+	struct tpm_buf buf;
 	int rc;
-	struct tpm_cmd_t cmd;
 
-	cmd.header.in = pcrread_header;
-	cmd.params.pcrread_in.pcr_idx = cpu_to_be32(pcr_idx);
-	rc = tpm_transmit_cmd(chip, NULL, &cmd, READ_PCR_RESULT_SIZE,
-			      READ_PCR_RESULT_BODY_SIZE, 0,
+	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCRREAD);
+	if (rc)
+		return rc;
+
+	tpm_buf_append_u32(&buf, pcr_idx);
+
+	rc = tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE,
+			      TPM_DIGEST_SIZE, 0,
 			      "attempting to read a pcr value");
+	if (rc)
+		goto out;
 
-	if (rc == 0)
-		memcpy(res_buf, cmd.params.pcrread_out.pcr_result,
-		       TPM_DIGEST_SIZE);
+	if (tpm_buf_length(&buf) < TPM_DIGEST_SIZE) {
+		rc = -EFAULT;
+		goto out;
+	}
+
+	memcpy(res_buf, &buf.data[TPM_HEADER_SIZE], TPM_DIGEST_SIZE);
+
+out:
+	tpm_buf_destroy(&buf);
 	return rc;
 }