Calculate the hash only of the actual RW code

No need to hash a bunch of 0xff's at the end.  We explicitly set a
0xea byte after the end of the code in firmware_image.lds.S.

BUG=chrome-os-partner:11087
TEST=look for the hash start line in the EC debug output:

   [0.011543 hash start 0x00014000 0x00011590]

The second number is the code size.  It should be the same size as
ec.RW.bin, instead of 0x14000.

Change-Id: Ibc94851dc1a09eb46cad46bb97dc5762f9c521f0
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/28300

3 files changed, 44 insertions, 7 deletions

diff --git a/common/system_common.c b/common/system_common.c
index 22e42272c2..2fd978d6cd 100644
--- a/common/system_common.c
+++ b/common/system_common.c
@@ -31,7 +31,6 @@ struct jump_tag {
 	uint8_t data_version;
 };
 
-
 /*
  * Data passed between the current image and the next one when jumping between
  * images.
@@ -230,6 +229,32 @@ enum system_image_copy_t system_get_image_copy(void)
 	return SYSTEM_IMAGE_UNKNOWN;
 }
 
+int system_get_image_used(enum system_image_copy_t copy)
+{
+	const uint8_t *image;
+	int size = 0;
+
+	if (copy == SYSTEM_IMAGE_RO) {
+		image = (const uint8_t *)CONFIG_SECTION_RO_OFF;
+		size = CONFIG_SECTION_RO_SIZE;
+	} else if (copy == SYSTEM_IMAGE_RW) {
+		image = (const uint8_t *)CONFIG_SECTION_RW_OFF;
+		size = CONFIG_SECTION_RW_SIZE;
+	}
+
+	if (size <= 0)
+		return 0;
+
+	/* If the last byte isn't 0xff, the image is completely full */
+	if (image[size - 1] != 0xff)
+		return size;
+
+	/* Scan backwards looking for 0xea byte */
+	for (size--; size > 0 && image[size] != 0xea; size--)
+		;
+
+	return size;
+}
 
 /* Returns true if the given range is overlapped with the active image.
  *
@@ -606,11 +631,11 @@ DECLARE_CONSOLE_COMMAND(hibernate, command_hibernate,
 
 static int command_version(int argc, char **argv)
 {
-	ccprintf("Chip:  %s %s %s\n", system_get_chip_vendor(),
+	ccprintf("Chip:    %s %s %s\n", system_get_chip_vendor(),
 		 system_get_chip_name(), system_get_chip_revision());
-	ccprintf("Board: %d\n", system_get_board_version());
-	ccprintf("RO:    %s\n", system_get_version(SYSTEM_IMAGE_RO));
-	ccprintf("RW:    %s\n", system_get_version(SYSTEM_IMAGE_RW));
+	ccprintf("Board:   %d\n", system_get_board_version());
+	ccprintf("RO:      %s\n", system_get_version(SYSTEM_IMAGE_RO));
+	ccprintf("RW:      %s\n", system_get_version(SYSTEM_IMAGE_RW));
 	ccprintf("Build: %s\n", system_get_build_info());
 	return EC_SUCCESS;
 }
diff --git a/common/vboot_hash.c b/common/vboot_hash.c
index c8afce6efe..49e3e4797b 100644
--- a/common/vboot_hash.c
+++ b/common/vboot_hash.c
@@ -114,7 +114,8 @@ static void vboot_hash_init(void)
 	} else {
 		/* Start computing the hash of firmware A */
 		vboot_hash_start(CONFIG_FW_RW_OFF - CONFIG_FLASH_BASE,
-				 CONFIG_FW_RW_SIZE, NULL, 0);
+				 system_get_image_used(SYSTEM_IMAGE_RW),
+				 NULL, 0);
 	}
 }
 
diff --git a/include/system.h b/include/system.h
index 4bcde16aae..d1975c9fed 100644
--- a/include/system.h
+++ b/include/system.h
@@ -104,12 +104,23 @@ const uint8_t *system_get_jump_tag(uint16_t tag, int *version, int *size);
 /* Return the address just past the last usable byte in RAM. */
 int system_usable_ram_end(void);
 
-/* Returns true if the given range is overlapped with the active image. */
+/* Return true if the given range is overlapped with the active image. */
 int system_unsafe_to_overwrite(uint32_t offset, uint32_t size);
 
 /* Return a text description of the image copy which is currently running. */
 const char *system_get_image_copy_string(void);
 
+/**
+ * Return the number of bytes used in the specified image.
+ *
+ * This is the actual size of code+data in the image, as opposed to the
+ * amount of space reserved in flash for that image.
+ *
+ * @return actual image size in bytes, 0 if the image contains no content or
+ * error.
+ */
+int system_get_image_used(enum system_image_copy_t copy);
+
 /* Jump to the specified image copy. */
 int system_run_image_copy(enum system_image_copy_t copy);