cbfs: Stop checking master header

The CBFS master header is a legacy structure that just conveys the same
information we already have from the FMAP these days. We're still
including it to support older CBFS implementations in some payloads, but
there's no need for coreboot itself to follow this indirection anymore.
This patch simplifies the default CBFS locator to just return the CBFS
offset and size from the FMAP directly.

Change-Id: I6b00dd7f276364d62fa1f637efbaee0e80607c49
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36688
Reviewed-by: Wim Vervoorn <wvervoorn@eltan.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/cbfs.h

@@ -74,7 +74,7 @@ struct cbfs_props {
 };
 
 /* Default CBFS locator .locate() callback that locates "COREBOOT" region. */
-int cbfs_master_header_props(struct cbfs_props *props);
+int cbfs_default_props(struct cbfs_props *props);
 
 /* Return < 0 on error otherwise props are filled out accordingly. */
 int cbfs_boot_region_properties(struct cbfs_props *props);

src/lib/cbfs.c

@@ -296,44 +296,16 @@ out:
 	return 0;
 }
 
-/* This only supports the "COREBOOT" fmap region. */
-int cbfs_master_header_props(struct cbfs_props *props)
+/* The default locator to find the CBFS in the "COREBOOT" FMAP region. */
+int cbfs_default_props(struct cbfs_props *props)
 {
-	struct cbfs_header header;
-	const struct region_device *bdev;
-	int32_t rel_offset;
-	size_t offset;
+	struct region region;
 
-	bdev = boot_device_ro();
-
-	if (bdev == NULL)
+	if (fmap_locate_area("COREBOOT", &region))
 		return -1;
 
-	struct region fmap_region;
-	if (fmap_locate_area("COREBOOT", &fmap_region))
-		return -1;
-	size_t fmap_top = region_end(&fmap_region);
-
-	/* Find location of header using signed 32-bit offset from
-	 * end of CBFS region. */
-	offset = fmap_top - sizeof(int32_t);
-	if (rdev_readat(bdev, &rel_offset, offset, sizeof(int32_t)) < 0)
-		return -1;
-
-	offset = fmap_top + (int32_t)le32_to_cpu(rel_offset);
-	if (rdev_readat(bdev, &header, offset, sizeof(header)) < 0)
-		return -1;
-
-	header.magic = ntohl(header.magic);
-	header.romsize = ntohl(header.romsize);
-	header.offset = ntohl(header.offset);
-
-	if (header.magic != CBFS_HEADER_MAGIC)
-		return -1;
-
-	props->offset = header.offset;
-	props->size = header.romsize;
-	props->size -= props->offset;
+	props->offset = region_offset(&region);
+	props->size = region_sz(&region);
 
 	printk(BIOS_SPEW, "CBFS @ %zx size %zx\n", props->offset, props->size);
 
@@ -343,9 +315,9 @@ int cbfs_master_header_props(struct cbfs_props *props)
 /* This struct is marked as weak to allow a particular platform to
  * override the master header logic. This implementation should work for most
  * devices. */
-const struct cbfs_locator __weak cbfs_master_header_locator = {
-	.name = "Master Header Locator",
-	.locate = cbfs_master_header_props,
+const struct cbfs_locator __weak cbfs_default_locator = {
+	.name = "COREBOOT Locator",
+	.locate = cbfs_default_props,
 };
 
 extern const struct cbfs_locator vboot_locator;
@@ -359,7 +331,7 @@ static const struct cbfs_locator *locators[] = {
 	 */
 	&vboot_locator,
 #endif
-	&cbfs_master_header_locator,
+	&cbfs_default_locator,
 };
 
 int cbfs_boot_region_properties(struct cbfs_props *props)

src/soc/intel/apollolake/mmap_boot.c

@@ -128,10 +128,10 @@ static int iafw_boot_region_properties(struct cbfs_props *props)
 }
 
 /*
- * Named cbfs_master_header_locator so that it overrides the default, but
- * incompatible locator in cbfs.c
+ * Named cbfs_default_locator so that it overrides the default, but incompatible
+ * locator in cbfs.c
  */
-const struct cbfs_locator cbfs_master_header_locator = {
+const struct cbfs_locator cbfs_default_locator = {
 	.name = "IAFW Locator",
 	.locate = iafw_boot_region_properties,
 };

src/vendorcode/eltan/security/verified_boot/vboot_check.c

@@ -355,8 +355,8 @@ static void vendor_secure_prepare(void)
 	}
 }
 
-const struct cbfs_locator cbfs_master_header_locator = {
+const struct cbfs_locator cbfs_default_locator = {
 	.name = "Vendorcode Header Locator",
 	.prepare = vendor_secure_prepare,
-	.locate = cbfs_master_header_props
+	.locate = cbfs_default_props
 };