[U-Boot] [PATCH v2] common: fit: Allow U-Boot images to be booted

[Mario Six]

In certain circumstances it comes in handy to be able to boot into a second
U-Boot. But as of now it is not possible to boot a U-Boot binary that is inside
a FIT image, which is problematic for projects that e.g. need to guarantee a
unbroken chain of trust from SOC all the way into the OS, since the FIT signing
mechanism cannot be used.

This patch adds the capability to load such FIT images.

An example .its snippet (utilizing signature verification) might look
like the following:

images {
	firmware at 1 {
		description = "2nd stage U-Boot image";
		data = /incbin/("u-boot-dtb.img.gz");
		type = "firmware";
		arch = "arm";
		os = "u-boot";
		compression = "gzip";
		load = <0x8FFFC0>;
		entry = <0x900000>;
		signature at 1 {
			algo = "sha256,rsa4096";
			key-name-hint = "key";
		};
	};
};

Signed-off-by: Mario Six <mario.six at gdsys.cc>
---

Changes in v2:
 - Use images of type 'firmware' for U-Boot images (as per Wolfgang Denk's
   hint), and make them bootable

---
 common/image-fit.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/common/image-fit.c b/common/image-fit.c
index 6f920da..73ad34e 100644
--- a/common/image-fit.c
+++ b/common/image-fit.c
@@ -1684,12 +1684,13 @@ int fit_image_load(bootm_headers_t *images, ulong addr,

 	bootstage_mark(bootstage_id + BOOTSTAGE_SUB_CHECK_ALL);
 	type_ok = fit_image_check_type(fit, noffset, image_type) ||
-		(image_type == IH_TYPE_KERNEL &&
-			fit_image_check_type(fit, noffset,
-					     IH_TYPE_KERNEL_NOLOAD));
+		  fit_image_check_type(fit, noffset, IH_TYPE_FIRMWARE) ||
+		  (image_type == IH_TYPE_KERNEL &&
+		   fit_image_check_type(fit, noffset, IH_TYPE_KERNEL_NOLOAD));

 	os_ok = image_type == IH_TYPE_FLATDT || IH_TYPE_FPGA ||
 		fit_image_check_os(fit, noffset, IH_OS_LINUX) ||
+		fit_image_check_os(fit, noffset, IH_OS_U_BOOT) ||
 		fit_image_check_os(fit, noffset, IH_OS_OPENRTOS);

 	/*
--
2.9.0