linux-kernel - [PATCH v4 6/8] tpm: TPM2B formatted buffers

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Message-ID: <20231121211717.31681-7-jarkko@kernel.org>
Date:   Tue, 21 Nov 2023 23:17:15 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     linux-integrity@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Jarkko Sakkinen <jarkko@...nel.org>,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        William Roberts <bill.c.roberts@...il.com>,
        Stefan Berger <stefanb@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Mario Limonciello <mario.limonciello@....com>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        Peter Huewe <peterhuewe@....de>,
        James Bottomley <jejb@...ux.ibm.com>,
        Paul Moore <paul@...l-moore.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Julien Gomes <julien@...sta.com>
Subject: [PATCH v4 6/8] 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: Jarkko Sakkinen <jarkko@...nel.org>
---
v2: [2021-11-21] Refine the API according to the comments for
    https://lore.kernel.org/linux-integrity/20231024011531.442587-5-jarkko@kernel.org/
---
 drivers/char/tpm/tpm-buf.c | 38 +++++++++++++++++++++++++++++++++++---
 include/linux/tpm.h        |  4 ++++
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index 545d9c74abf1..12bfade11372 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -48,6 +48,36 @@ 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);
 
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 1d7b39b5c383..715db4a91c1f 100644
--- a/include/linux/tpm.h
+++ b/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);
-- 
2.42.1