tpm: TPM2B formatted buffers

Declare tpm_buf_init_sized() and tpm_buf_reset_sized() for creating TPM2B
formatted buffers. These buffers are also known as sized buffers in the
specifications and literature.
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Tested-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

drivers/char/tpm/tpm-buf.c

@@ -47,6 +47,36 @@ void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
 }
 EXPORT_SYMBOL_GPL(tpm_buf_reset);
 
+/**
+ * tpm_buf_init_sized() - Allocate and initialize a sized (TPM2B) buffer
+ * @buf:	A @tpm_buf
+ *
+ * Return: 0 or -ENOMEM
+ */
+int tpm_buf_init_sized(struct tpm_buf *buf)
+{
+	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
+	if (!buf->data)
+		return -ENOMEM;
+
+	tpm_buf_reset_sized(buf);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_init_sized);
+
+/**
+ * tpm_buf_reset_sized() - Initialize a sized buffer
+ * @buf:	A &tpm_buf
+ */
+void tpm_buf_reset_sized(struct tpm_buf *buf)
+{
+	buf->flags = TPM_BUF_TPM2B;
+	buf->length = 2;
+	buf->data[0] = 0;
+	buf->data[1] = 0;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_reset_sized);
+
 void tpm_buf_destroy(struct tpm_buf *buf)
 {
 	free_page((unsigned long)buf->data);
@@ -73,8 +103,6 @@ EXPORT_SYMBOL_GPL(tpm_buf_length);
  */
 void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
 {
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-
 	/* Return silently if overflow has already happened. */
 	if (buf->flags & TPM_BUF_OVERFLOW)
 		return;
@@ -87,7 +115,11 @@ void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
 
 	memcpy(&buf->data[buf->length], new_data, new_length);
 	buf->length += new_length;
-	head->length = cpu_to_be32(buf->length);
+
+	if (buf->flags & TPM_BUF_TPM2B)
+		((__be16 *)buf->data)[0] = cpu_to_be16(buf->length - 2);
+	else
+		((struct tpm_header *)buf->data)->length = cpu_to_be32(buf->length);
 }
 EXPORT_SYMBOL_GPL(tpm_buf_append);
 

include/linux/tpm.h

@@ -300,6 +300,8 @@ struct tpm_header {
 enum tpm_buf_flags {
 	/* the capacity exceeded: */
 	TPM_BUF_OVERFLOW	= BIT(0),
+	/* TPM2B format: */
+	TPM_BUF_TPM2B		= BIT(1),
 };
 
 /*
@@ -328,6 +330,8 @@ struct tpm2_hash {
 
 int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
 void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal);
+int tpm_buf_init_sized(struct tpm_buf *buf);
+void tpm_buf_reset_sized(struct tpm_buf *buf);
 void tpm_buf_destroy(struct tpm_buf *buf);
 u32 tpm_buf_length(struct tpm_buf *buf);
 void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length);