Extracting values from returned TPM buffers can be hard. Add cursor
based (moving poiner) functions that make it easier to extract TPM
returned values from a buffer.
Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
---
v4: add kernel doc and reword commit
---
drivers/char/tpm/tpm-buf.c | 48 ++++++++++++++++++++++++++++++++++++++
include/linux/tpm.h | 3 +++
2 files changed, 51 insertions(+)
diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index b7e42fb6266c..da0f6e725c3f 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -6,6 +6,8 @@
#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);
@@ -229,3 +231,49 @@ 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 */
+
+/**
+ * tpm_get_inc_u8 - read a u8 and move pointer beyond it
+ * @ptr: pointer to pointer
+ *
+ * @return: value read
+ */
+u8 tpm_get_inc_u8(const u8 **ptr)
+{
+ return *((*ptr)++);
+}
+EXPORT_SYMBOL_GPL(tpm_get_inc_u8);
+
+/**
+ * tpm_get_inc_u16 - read a u16 and move pointer beyond it
+ * @ptr: pointer to pointer
+ *
+ * @return: value read (converted from big endian)
+ */
+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);
+
+/**
+ * tpm_get_inc_u32 - read a u32 and move pointer beyond it
+ * @ptr: pointer to pointer
+ *
+ * @return: value read (converted from big endian)
+ */
+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 76d495cb5b08..845eadfed715 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -336,6 +336,9 @@ 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.
--
2.35.3
