[v2,03/11] tpm: add cursor based buffer functions for response parsing

Commit Message

James Bottomley Jan. 24, 2023, 5:55 p.m. UTC

Once we have encryption and authentication, marshalling and
unmarshalling sessions becomes hugely complex.  Add cursor based
functions which update the current pointer to make response parsing
easier.

Signed-off-by: James Bottomley <[e-mail]>
---
 drivers/char/tpm/tpm-buf.c | 29 +++++++++++++++++++++++++++++
 include/linux/tpm.h        |  3 +++
 2 files changed, 32 insertions(+)

Patch

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index f1d48f22d4b4..046b00bf7a81 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -7,6 +7,8 @@ 
 #include <linux/module.h>
 #include <linux/tpm.h>
 
+#include <asm/unaligned.h>
+
 static int __tpm_buf_init(struct tpm_buf *buf)
 {
 	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
@@ -155,3 +157,30 @@  void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *tpm2b)
 	tpm_buf_reset_int(tpm2b);
 }
 EXPORT_SYMBOL_GPL(tpm_buf_append_2b);
+
+/* functions for unmarshalling data and moving the cursor */
+u8 tpm_get_inc_u8(const u8 **ptr)
+{
+	return *((*ptr)++);
+}
+EXPORT_SYMBOL_GPL(tpm_get_inc_u8);
+
+u16 tpm_get_inc_u16(const u8 **ptr)
+{
+	u16 val;
+
+	val = get_unaligned_be16(*ptr);
+	*ptr += sizeof(val);
+	return val;
+}
+EXPORT_SYMBOL_GPL(tpm_get_inc_u16);
+
+u32 tpm_get_inc_u32(const u8 **ptr)
+{
+	u32 val;
+
+	val = get_unaligned_be32(*ptr);
+	*ptr += sizeof(val);
+	return val;
+}
+EXPORT_SYMBOL_GPL(tpm_get_inc_u32);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index f2d4dab6d832..f7cff1d114b0 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -335,6 +335,9 @@  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);
+u8 tpm_get_inc_u8(const u8 **ptr);
+u16 tpm_get_inc_u16(const u8 **ptr);
+u32 tpm_get_inc_u32(const u8 **ptr);
 
 /*
  * Check if TPM device is in the firmware upgrade mode.