[PATCH RFC] image: apply FDTOs on FDT image node without a load property

[Quentin Schulz]

From: Quentin Schulz <quentin.schulz at cherry.de>

A FIT image which is NOT using -E when created by mkimage - that is with
image data within the FIT - will fail to apply FDTO if the base FDT
image node does not specify a load property (which points to an address
in DRAM). This is because we check that the FDT address we want to apply
overlay to (i.e. modify and likely increase in size) is not inside the
FIT and give up otherwise. This is assumed necessary because we may then
overwrite other data when applying in-place.

However, we can do better than giving up: relocating the FDT in another
place in DRAM where it's safe to increase its size and apply FDTOs.

Suggested-by: Marek Vasut <marex at denx.de>
Signed-off-by: Quentin Schulz <quentin.schulz at cherry.de>
---
Tested with extlinux with:
- conf node with multiple fdt entries
- conf node with base fdt + conf node with fdto (stored in fdt property)
- FDT image node with load property (behavior unchanged)
- FDT image node without load property

I'll be frank, I don't really know what I'm doing here and I'm on
holidays for a month in a few hours, so take this with a bigger grain of
salt than usual (hence the RFC). It works (tm) for now.

Cc: Heiko Stuebner <heiko at sntech.de>
---
 boot/image-fit.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/boot/image-fit.c b/boot/image-fit.c
index 7d56f0b5e6ed39a75e029b09dc95d605835c0f91..088482c4d5d2e194cce66f10b0acd9e586f826b2 100644
--- a/boot/image-fit.c
+++ b/boot/image-fit.c
@@ -2392,13 +2392,18 @@ int boot_get_fdt_fit(struct bootm_headers *images, ulong addr,
 	image_end = addr + fit_get_size(fit);
 	/* verify that relocation took place by load address not being in fit */
 	if (load >= image_start && load < image_end) {
-		/* check is simplified; fit load checks for overlaps */
-		printf("Overlayed FDT requires relocation\n");
-		fdt_noffset = -EBADF;
-		goto out;
-	}
+		/* Cannot overlay an FDT stored inside the fitImage, so let's relocate */
+		char *of_flat_tree = map_sysmem(load, len);
 
-	base = map_sysmem(load, len);
+		len = ALIGN(fdt_totalsize(load), SZ_4K);
+		if (boot_relocate_fdt(&of_flat_tree, &len)) {
+			printf("Required FDT relocation for applying overlays failed...");
+			fdt_noffset = -EBADF;
+			goto out;
+		}
+
+		load = (ulong)of_flat_tree;
+	}
 
 	/* apply extra configs in FIT first, followed by args */
 	for (i = 1; ; i++) {

---
base-commit: 69bd83568c57813cd23bc2d100c066a17e7e349d
change-id: 20241219-extlinux-relocate-dtb-when-dtbo-4c7536f880b2

Best regards,
-- 
Quentin Schulz <quentin.schulz at cherry.de>