vbnv: Do not initialize vbnv_copy in vbnv layer

If read_vbnv finds that the vbnv_copy is not valid, it initializes it
with the correct HEADER_SIGNATURE and other attributes. However, the
vbnv copy is checked for validity and initialized at the vboot layer as
well. Since, vboot is the owner of this data, it should be the one
initializing it. Thus, if read_vbnv sees that the data is not valid,
simply reset it to all 0s and let vboot layer take care of it. This also
removes the need for additional checks to ensure that the dirty vbnv
copy is properly updated on storage.

Change-Id: I6101ac41f31f720a6e357c9c56e571d62e0f2f47
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/15498
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/vendorcode/google/chromeos/vbnv.c

@@ -59,14 +59,9 @@ static uint8_t crc8_vbnv(const uint8_t *data, int len)
 	return (uint8_t) (crc >> 8);
 }
 
-/* Reset header and CRC to defaults. */
 static void reset_vbnv(uint8_t *vbnv_copy)
 {
 	memset(vbnv_copy, 0, VBNV_BLOCK_SIZE);
-	vbnv_copy[HEADER_OFFSET] = HEADER_SIGNATURE |
-				   HEADER_FIRMWARE_SETTINGS_RESET |
-				   HEADER_KERNEL_SETTINGS_RESET;
-	vbnv_copy[CRC_OFFSET] = crc8_vbnv(vbnv_copy, CRC_OFFSET);
 }
 
 /* Read VBNV data into cache. */
@@ -88,9 +83,8 @@ int verify_vbnv(uint8_t *vbnv_copy)
 /*
  * Read VBNV data from configured storage backend.
  * If VBNV verification fails, reset the vbnv copy.
- * Returns 1 if write-back of vbnv copy is required. Else, returns 0.
  */
-int read_vbnv(uint8_t *vbnv_copy)
+void read_vbnv(uint8_t *vbnv_copy)
 {
 	if (IS_ENABLED(CONFIG_CHROMEOS_VBNV_CMOS))
 		read_vbnv_cmos(vbnv_copy);
@@ -100,11 +94,8 @@ int read_vbnv(uint8_t *vbnv_copy)
 		read_vbnv_flash(vbnv_copy);
 
 	/* Check data for consistency */
-	if (verify_vbnv(vbnv_copy))
-		return 0;
-
-	reset_vbnv(vbnv_copy);
-	return 1;
+	if (!verify_vbnv(vbnv_copy))
+		reset_vbnv(vbnv_copy);
 }
 
 /*

src/vendorcode/google/chromeos/vbnv.h

@@ -19,12 +19,7 @@
 #include <types.h>
 
 /* Generic functions */
-/*
- * Return value for read_vbnv:
- * 1 = write-back of vbnv copy is required.
- * 0 = otherwise
- */
-int read_vbnv(uint8_t *vbnv_copy);
+void read_vbnv(uint8_t *vbnv_copy);
 void save_vbnv(const uint8_t *vbnv_copy);
 int verify_vbnv(uint8_t *vbnv_copy);
 int get_recovery_mode_from_vbnv(void);

src/vendorcode/google/chromeos/vboot2/vboot_logic.c

@@ -301,12 +301,8 @@ void verstage_main(void)
 	/* Set up context and work buffer */
 	vb2_init_work_context(&ctx);
 
-	/*
-	 * Read nvdata from a non-volatile storage and mark data as changed
-	 * if instructed.
-	 */
-	if (read_vbnv(ctx.nvdata))
-		ctx.flags |= VB2_CONTEXT_NVDATA_CHANGED;
+	/* Read nvdata from a non-volatile storage. */
+	read_vbnv(ctx.nvdata);
 
 	/* Set S3 resume flag if vboot should behave differently when selecting
 	 * which slot to boot.  This is only relevant to vboot if the platform