On Thu, Feb 16, 2023 at 03:14:01PM -0500, James Bottomley wrote:
> Most complex TPM commands require appending TPM2B buffers to the
> command body. Since TPM2B types are essentially variable size arrays,
> it makes it impossible to represent these complex command arguments as
> structures and we simply have to build them up using append primitives
> like these.
>
> Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> ---
> drivers/char/tpm/tpm-buf.c | 71 +++++++++++++++++++++++++++++++++++---
> include/linux/tpm.h | 3 ++
> 2 files changed, 69 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index ca59b92e0f95..292c6f14f72c 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -7,17 +7,16 @@
> #include <linux/module.h>
> #include <linux/tpm.h>
>
> -int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
> +static int __tpm_buf_init(struct tpm_buf *buf)
> {
> buf->data = (u8 *)__get_free_page(GFP_KERNEL);
> if (!buf->data)
> return -ENOMEM;
>
> buf->flags = 0;
> - tpm_buf_reset(buf, tag, ordinal);
> +
> return 0;
> }
> -EXPORT_SYMBOL_GPL(tpm_buf_init);
>
> void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
> {
> @@ -29,17 +28,60 @@ void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
> }
> EXPORT_SYMBOL_GPL(tpm_buf_reset);
>
> +int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
> +{
> + int rc;
> +
> + rc = __tpm_buf_init(buf);
> + if (rc)
> + return rc;
> +
> + tpm_buf_reset(buf, tag, ordinal);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_init);
> +
> +int tpm_buf_init_2b(struct tpm_buf *buf)
kdoc
> +{
> + struct tpm_header *head;
> + int rc;
> +
> + rc = __tpm_buf_init(buf);
> + if (rc)
> + return rc;
> +
> + head = (struct tpm_header *) buf->data;
> +
> + head->length = cpu_to_be32(sizeof(*head));
> +
> + buf->flags = TPM_BUF_2B;
Please make tpm_buf_init() and tpm_buf_reset() to work for both cases.
This explodes the whole thing into an unmaintainable mess. It is better
to have a type as a parameter for tpm_buf_init() and have only single
flow instead of open coded and patched variation.
I'd simply just put it as:
struct tpm_buf *tpm_buf_init(u16 tag, u32 ordinal, bool tpm2b)
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_init_2b);
> +
> void tpm_buf_destroy(struct tpm_buf *buf)
> {
> free_page((unsigned long)buf->data);
> }
> EXPORT_SYMBOL_GPL(tpm_buf_destroy);
>
> +static void *tpm_buf_data(struct tpm_buf *buf)
> +{
> + if (buf->flags & TPM_BUF_2B)
> + return buf->data + TPM_HEADER_SIZE;
> + return buf->data;
> +}
> +
> u32 tpm_buf_length(struct tpm_buf *buf)
> {
> struct tpm_header *head = (struct tpm_header *)buf->data;
> + u32 len;
>
> - return be32_to_cpu(head->length);
> + len = be32_to_cpu(head->length);
> + if (buf->flags & TPM_BUF_2B)
> + len -= sizeof(*head);
> + return len;
> }
> EXPORT_SYMBOL_GPL(tpm_buf_length);
>
> @@ -55,7 +97,7 @@ void tpm_buf_append(struct tpm_buf *buf,
> unsigned int new_len)
> {
> struct tpm_header *head = (struct tpm_header *) buf->data;
> - u32 len = tpm_buf_length(buf);
> + u32 len = be32_to_cpu(head->length);
>
> /* Return silently if overflow has already happened. */
> if (buf->flags & TPM_BUF_OVERFLOW)
> @@ -93,3 +135,22 @@ void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
> tpm_buf_append(buf, (u8 *) &value2, 4);
> }
> EXPORT_SYMBOL_GPL(tpm_buf_append_u32);
> +
> +static void tpm_buf_reset_int(struct tpm_buf *buf)
> +{
> + struct tpm_header *head;
> +
> + head = (struct tpm_header *)buf->data;
> + head->length = cpu_to_be32(sizeof(*head));
> +}
> +
> +void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *tpm2b)
> +{
> + u16 len = tpm_buf_length(tpm2b);
> +
> + tpm_buf_append_u16(buf, len);
> + tpm_buf_append(buf, tpm_buf_data(tpm2b), len);
> + /* clear the buf for reuse */
> + tpm_buf_reset_int(tpm2b);
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_append_2b);
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 150b39b6190e..f2d4dab6d832 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -300,6 +300,7 @@ struct tpm_header {
>
> enum tpm_buf_flags {
> TPM_BUF_OVERFLOW = BIT(0),
> + TPM_BUF_2B = BIT(1),
> };
This is IMHO unnecessary complex.
I think we could just have two bools:
bool overflow;
bool tpm2b;
>
> struct tpm_buf {
> @@ -324,6 +325,7 @@ struct tpm2_hash {
>
>
> int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
> +int tpm_buf_init_2b(struct tpm_buf *buf);
> void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal);
> void tpm_buf_destroy(struct tpm_buf *buf);
> u32 tpm_buf_length(struct tpm_buf *buf);
> @@ -332,6 +334,7 @@ void tpm_buf_append(struct tpm_buf *buf, const unsigned char *new_data,
> void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value);
> void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value);
> void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value);
> +void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *tpm2b);
>
> /*
> * Check if TPM device is in the firmware upgrade mode.
> --
> 2.35.3
>
BR, Jarkko
