tpm: add tpm_cmd_get_size() to tpm_util

The function is generally useful and used in the following patches.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NStefan Berger <stefanb@linux.vnet.ibm.com>
Signed-off-by: NStefan Berger <stefanb@linux.vnet.ibm.com>

hw/tpm/tpm_tis.c

@@ -30,6 +30,7 @@
 #include "hw/pci/pci_ids.h"
 #include "sysemu/tpm_backend.h"
 #include "tpm_int.h"
+#include "tpm_util.h"
 
 #define TPM_TIS_NUM_LOCALITIES      5     /* per spec */
 #define TPM_TIS_LOCALITY_SHIFT      12
@@ -215,7 +216,7 @@ static uint8_t tpm_tis_locality_from_addr(hwaddr addr)
 
 static uint32_t tpm_tis_get_size_from_buffer(const TPMSizedBuffer *sb)
 {
-    return be32_to_cpu(*(uint32_t *)&sb->buffer[2]);
+    return tpm_cmd_get_size(sb->buffer);
 }
 
 static void tpm_tis_show_buffer(const TPMSizedBuffer *sb, const char *string)

hw/tpm/tpm_util.h

@@ -22,7 +22,8 @@
 #ifndef TPM_TPM_UTIL_H
 #define TPM_TPM_UTIL_H
 
-#include "sysemu/tpm_backend.h"
+#include "sysemu/tpm.h"
+#include "qemu/bswap.h"
 
 void tpm_util_write_fatal_error_response(uint8_t *out, uint32_t out_len);
 
@@ -30,4 +31,9 @@ bool tpm_util_is_selftest(const uint8_t *in, uint32_t in_len);
 
 int tpm_util_test_tpmdev(int tpm_fd, TPMVersion *tpm_version);
 
+static inline uint32_t tpm_cmd_get_size(const void *b)
+{
+    return be32_to_cpu(*(const uint32_t *)(b + 2));
+}
+
 #endif /* TPM_TPM_UTIL_H */