[PATCH v3] spl: return header size to spl_load in os boot

[Anshul Dalal]

During linux build process the header size is computed including the BSS
whereas it's removed when creating the uncompressed image. Therefore the
size of the uncompressed image on filesystem will be smaller than the
size specified in the header.

This causes issues when loading the kernel image from the SPL (as in
falcon boot) with spl_load since it compares the read file size from the
FS to the header size form the image. Which leads to the following check
in `include/spl_load.h` failing to -EIO when loading kernel image:

  return read < spl_image->size ? -EIO : 0;

Therefore we should return the header size back to spl_load instead of
the file size in falcon boot when not loading a FIT image.

Bug report:
https://lore.kernel.org/u-boot/20250214111656.2358748-1-anshuld@ti.com/

Fixes: 775074165d97 ("spl: Add generic spl_load function")
Reported-by: Anshul Dalal <anshuld at ti.com>
Reviewed-by: Sean Anderson <seanga2 at gmail.com>
Signed-off-by: Anshul Dalal <anshuld at ti.com>
---
Changes in v3:
 * Added header check for FIT image instead of using CMD_BOOTI
v2: https://lore.kernel.org/u-boot/20250225142522.9069-1-anshuld@ti.com/
Changes in v2:
 * Add R-by and fixes tags
 * Expanded commit description with more information
v1: https://lore.kernel.org/u-boot/20250221151752.2618666-1-anshuld@ti.com/
---
 common/spl/spl_ext.c | 8 ++++++++
 common/spl/spl_fat.c | 7 +++++++
 2 files changed, 15 insertions(+)

diff --git a/common/spl/spl_ext.c b/common/spl/spl_ext.c
index c5478820a9b..7e0274a3058 100644
--- a/common/spl/spl_ext.c
+++ b/common/spl/spl_ext.c
@@ -11,12 +11,20 @@
 static ulong spl_fit_read(struct spl_load_info *load, ulong file_offset,
 			  ulong size, void *buf)
 {
+	struct legacy_img_hdr *header;
 	int ret;
 	loff_t actlen;
 
 	ret = ext4fs_read(buf, file_offset, size, &actlen);
 	if (ret)
 		return ret;
+
+	if (CONFIG_IS_ENABLED(OS_BOOT)) {
+		header = (struct legacy_img_hdr *)buf;
+		if (image_get_magic(header) != FDT_MAGIC)
+			return size;
+	}
+
 	return actlen;
 }
 
diff --git a/common/spl/spl_fat.c b/common/spl/spl_fat.c
index fce451b7664..f426a068ff9 100644
--- a/common/spl/spl_fat.c
+++ b/common/spl/spl_fat.c
@@ -47,6 +47,7 @@ static int spl_register_fat_device(struct blk_desc *block_dev, int partition)
 static ulong spl_fit_read(struct spl_load_info *load, ulong file_offset,
 			  ulong size, void *buf)
 {
+	struct legacy_img_hdr *header;
 	loff_t actread;
 	int ret;
 	char *filename = load->priv;
@@ -55,6 +56,12 @@ static ulong spl_fit_read(struct spl_load_info *load, ulong file_offset,
 	if (ret)
 		return ret;
 
+	if (CONFIG_IS_ENABLED(OS_BOOT)) {
+		header = (struct legacy_img_hdr *)buf;
+		if (image_get_magic(header) != FDT_MAGIC)
+			return size;
+	}
+
 	return actread;
 }
 
-- 
2.43.0