Re: [PATCH v7 4/6] kho: fix kho_in_debugfs_init() to handle non-FDT blobs

[Mike Rapoport <rppt@kernel.org>]

On Fri, Mar 06, 2026 at 04:39:23AM -0800, Breno Leitao wrote:
> kho_in_debugfs_init() has two problems when displaying incoming
> sub-blobs in debugfs:
> 
> 1. It uses the hardcoded property name "fdt" instead of
>    KHO_FDT_SUB_TREE_PROP_NAME ("preserved-data"), so it never finds
>    subtrees stored by the current kho_add_subtree().
> 
> 2. It calls fdt_totalsize() to determine blob sizes, which assumes
>    all blobs are FDTs. This breaks for non-FDT blobs like struct
>    kho_kexec_metadata.
> 
> Fix both issues by using KHO_FDT_SUB_TREE_PROP_NAME to find subtrees
> and reading the "blob-size" property from the FDT (persisted by
> kho_add_subtree()) instead of calling fdt_totalsize().
> 
> Signed-off-by: Breno Leitao <leitao@debian.org>
> ---
>  kernel/liveupdate/kexec_handover_debugfs.c | 38 ++++++++++++++++++++----------
>  1 file changed, 26 insertions(+), 12 deletions(-)
> 
> diff --git a/kernel/liveupdate/kexec_handover_debugfs.c b/kernel/liveupdate/kexec_handover_debugfs.c
> index 7a100f2bf3947..fc2baa8b104fd 100644
> --- a/kernel/liveupdate/kexec_handover_debugfs.c
> +++ b/kernel/liveupdate/kexec_handover_debugfs.c
> @@ -13,6 +13,7 @@
>  #include <linux/io.h>
>  #include <linux/libfdt.h>
>  #include <linux/mm.h>
> +#include <linux/kho/abi/kexec_handover.h>
>  #include "kexec_handover_internal.h"
>  
>  static struct dentry *debugfs_root;
> @@ -121,23 +122,36 @@ __init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt)
>  	fdt_for_each_subnode(child, fdt, 0) {
>  		int len = 0;
>  		const char *name = fdt_get_name(fdt, child, NULL);
> -		const u64 *fdt_phys;
> -		void *sub_fdt;
> -
> -		fdt_phys = fdt_getprop(fdt, child, "fdt", &len);
> -		if (!fdt_phys)
> +		const u64 *blob_phys;
> +		const u64 *blob_size;
> +		void *blob;
> +		size_t size;

Do we really need two size variables? Can't we just have u64 *size and pass
*size to __kho_debugfs_blob_add()?

> +
> +		blob_phys = fdt_getprop(fdt, child,
> +					KHO_FDT_SUB_TREE_PROP_NAME, &len);
> +		if (!blob_phys)
>  			continue;
> -		if (len != sizeof(*fdt_phys)) {
> -			pr_warn("node %s prop fdt has invalid length: %d\n",
> -				name, len);
> +		if (len != sizeof(*blob_phys)) {
> +			pr_warn("node %s prop %s has invalid length: %d\n",
> +				name, KHO_FDT_SUB_TREE_PROP_NAME, len);
>  			continue;
>  		}
> -		sub_fdt = phys_to_virt(*fdt_phys);
> +
> +		blob_size = fdt_getprop(fdt, child,
> +					KHO_FDT_SUB_TREE_SIZE_PROP_NAME, &len);
> +		if (!blob_size || len != sizeof(*blob_size)) {
> +			pr_warn("node %s missing or invalid %s property\n",
> +				name, KHO_FDT_SUB_TREE_SIZE_PROP_NAME);
> +			continue;
> +		}
> +		size = (size_t)*blob_size;
> +
> +		blob = phys_to_virt(*blob_phys);
>  		err = __kho_debugfs_blob_add(&dbg->fdt_list, sub_fdt_dir, name,
> -					     sub_fdt, fdt_totalsize(sub_fdt));
> +					     blob, size);
>  		if (err) {
> -			pr_warn("failed to add fdt %s to debugfs: %pe\n", name,
> -				ERR_PTR(err));
> +			pr_warn("failed to add blob %s to debugfs: %pe\n",
> +				name, ERR_PTR(err));
>  			continue;
>  		}
>  	}
> 
> -- 
> 2.47.3
> 
> 

-- 
Sincerely yours,
Mike.