[PATCH 18/23] security: optee: add optee_extract_fdto helper

[Ahmad Fatoum]

Hello Marco,

On 11/10/25 9:34 PM, Marco Felsch wrote:
> Add a helper to extract the added OP-TEE FDT overlay fragments from the
> FDT provided via arg2 during the boot phase into a dedicated buffer.
> 
> The dedicated overlay buffer can be used later on by the PBL code to
> apply the overlay to the barebox runtime DTB and to the kernel DTB.
> 
> Signed-off-by: Marco Felsch <m.felsch at pengutronix.de>
> ---
>  include/tee/optee.h |  6 ++++++
>  security/optee.c    | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 50 insertions(+)
> 
> diff --git a/include/tee/optee.h b/include/tee/optee.h
> index 10e829c04f8832c4c04771800f1963e25f425482..679662a6e6944da59d24d6268ebcf5dff19d0980 100644
> --- a/include/tee/optee.h
> +++ b/include/tee/optee.h
> @@ -37,6 +37,7 @@ int optee_verify_header (const struct optee_header *hdr);
>  
>  void optee_set_membase(const struct optee_header *hdr);
>  int optee_get_membase(u64 *membase);
> +int optee_extract_fdto(const void *fdt, void *fdto, unsigned int fdto_sz);
>  
>  #else
>  
> @@ -49,6 +50,11 @@ static inline int optee_get_membase(u64 *membase)
>  	return -ENOSYS;
>  }
>  
> +static inline int optee_extract_fdto(const void *fdt, void *fdto, unsigned int fdto_sz)
> +{
> +	return 0;
> +}
> +
>  #endif /* CONFIG_HAVE_OPTEE */
>  
>  #ifdef __PBL__
> diff --git a/security/optee.c b/security/optee.c
> index 422bc1c90924ba8ab266b1aa8d06e52c819d2010..3750bb6f496af990d77f3629b470b174dd7a7c7a 100644
> --- a/security/optee.c
> +++ b/security/optee.c
> @@ -5,7 +5,9 @@
>  #include <tee/optee.h>
>  #include <linux/printk.h>
>  #include <linux/errno.h>
> +#include <linux/libfdt.h>
>  #include <linux/limits.h>
> +#include <pbl.h>
>  
>  static u64 optee_membase = U64_MAX;
>  
> @@ -60,3 +62,45 @@ void optee_set_membase(const struct optee_header *hdr)
>  	optee_membase = (u64)hdr->init_load_addr_hi << 32;
>  	optee_membase |= hdr->init_load_addr_lo;
>  }
> +
> +int optee_extract_fdto(const void *fdt, void *fdto, unsigned int fdto_sz)
> +{
> +	int err;
> +	int subnode;
> +
> +	err = fdt_check_header(fdt);
> +	if (err) {
> +		pr_err("Invalid device tree blob: %s\n", fdt_strerror(err));
> +		return err;
> +	}
> +
> +	err = fdt_create_empty_tree(fdto, fdto_sz);
> +	if (err) {
> +		pr_err("Failed to initialize OP-TEE FDTO space: %s\n", fdt_strerror(err));
> +		return err;
> +	}
> +
> +	fdt_for_each_subnode(subnode, fdt, 0) {
> +		const char *name;
> +		int len;
> +
> +		name = fdt_get_name(fdt, subnode, &len);
> +		if (!name) {
> +			pr_warn("Failed to query FDT node name: %s\n", fdt_strerror(len));
> +			continue;
> +		}
> +
> +		if (strncmp(name, "fragment@", 9) != 0) {
> +			pr_debug("Skip node %s\n", name);
> +			continue;
> +		}
> +
> +		err |= fdt_copy_node(fdt, fdto, "/", name);

Aren't these sequential error codes? OR'ing them will produce a
non-sensical error code if there are different error codes returned.

Better change to:

	ret = fdt_copy_node(fdt, fdto, "/", name);
	if (ret)
		err = ret;

with err being initialized as zero.

> +	}
> +
> +	/* Clear the FDTO memory to not supply incomplete overlays */
> +	if (err)
> +		memset(fdto, 0, fdto_sz);
> +
> +	return err;
> +}
> 

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