[U-Boot] [PATCH] 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 {
	kernel at 1 {
		description = "2nd stage U-Boot image";
		data = /incbin/("u-boot-dtb.img.gz");
		type = "kernel";
		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>
---
 common/image-fit.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/common/image-fit.c b/common/image-fit.c
index 6f920da..0c7b400 100644
--- a/common/image-fit.c
+++ b/common/image-fit.c
@@ -1690,6 +1690,7 @@ int fit_image_load(bootm_headers_t *images, ulong addr,

 	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