[PATCH v5 6/8] tpm: TPM2B formatted buffers

Jarkko Sakkinen
2023-11-21T22:32:04Z

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@kernel.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 3f39893f3bb1..099b4a56c5d5 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/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);
@@ -72,8 +102,6 @@ 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;
@@ -86,7 +114,11 @@ 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