Re: [PATCH v3 06/10] of: overlay: add FIT overlay support

[Marco Felsch <m.felsch@pengutronix.de>]

Hi Sascha,

On 24-07-15, Sascha Hauer wrote:
> On Wed, Jul 03, 2024 at 06:58:34PM +0200, Marco Felsch wrote:
> > This adds the support to load devicetree overlays from an FIT image.
> > There are quite a few options to handle FIT overlays since the FIT
> > overlay spec is not very strict.
> > 
> > This patch implement the most configurable case where each overlay does
> > have it's own config node (including the optional signature).
> > 
> > - The "name" filter check is performed on the config-node name (the node
> >   under the configurations) and not the FIT overlay image name (the node
> >   name under the images node).
> > - The "content" filter check does not differ from the file based overlay
> >   handling.
> > 
> > Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
> > ---
> >  drivers/of/overlay.c | 131 ++++++++++++++++++++++++++++++++++++++++++++++++---
> >  1 file changed, 124 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> > index 5617f322ddca..a980e7aa5e02 100644
> > --- a/drivers/of/overlay.c
> > +++ b/drivers/of/overlay.c
> > @@ -8,10 +8,13 @@
> >   */
> >  #define pr_fmt(fmt) "of_overlay: " fmt
> >  
> > +#include <bootm.h>
> >  #include <common.h>
> >  #include <of.h>
> >  #include <errno.h>
> > +#include <filetype.h>
> >  #include <globalvar.h>
> > +#include <image-fit.h>
> >  #include <magicvar.h>
> >  #include <string.h>
> >  #include <libfile.h>
> > @@ -470,9 +473,123 @@ static int of_overlay_global_fixup_dir(struct device_node *root, const char *ovl
> >  	return ret;
> >  }
> >  
> > +static int of_overlay_apply_fit(struct device_node *root, struct fit_handle *fit,
> > +				struct device_node *config)
> > +{
> > +	const char *name = config->name;
> > +	struct device_node *overlay;
> > +	unsigned long ovl_sz;
> > +	const void *ovl;
> > +	int ret;
> > +
> > +	if (!of_overlay_matches_filter(name, NULL))
> > +		return 0;
> > +
> > +	ret = fit_open_image(fit, config, "fdt", &ovl, &ovl_sz);
> > +	if (ret)
> > +		return ret;
> > +
> > +	overlay = of_unflatten_dtb(ovl, ovl_sz);
> > +
> > +	if (!of_overlay_matches_filter(NULL, overlay)) {
> > +		ret = 0;
> > +		goto out;
> > +	}
> > +
> > +	ret = of_overlay_apply_tree(root, overlay);
> > +	if (ret == -ENODEV)
> > +		pr_debug("Not applied %s (not compatible)\n", name);
> > +	else if (ret)
> > +		pr_err("Cannot apply %s: %s\n", name, strerror(-ret));
> > +	else
> > +		pr_info("Applied %s\n", name);
> > +
> > +out:
> > +	of_delete_node(overlay);
> > +
> > +	return ret;
> > +}
> > +
> > +static bool of_overlay_valid_config(struct fit_handle *fit,
> > +				    struct device_node *config)
> > +{
> > +	/*
> > +	 * Either kernel or firmware is marked as mandatory by U-Boot
> > +	 * (doc/usage/fit/source_file_format.rst) except for overlays
> > +	 * (doc/usage/fit/overlay-fdt-boot.rst). Therefore we need to ensure
> > +	 * that only "fdt" config nodes are recognized as overlay config node.
> > +	 */
> > +	if (!fit_has_image(fit, config, "fdt") ||
> > +	    fit_has_image(fit, config, "kernel") ||
> > +	    fit_has_image(fit, config, "firmware"))
> > +		return false;
> > +
> > +	return true;
> > +}
> > +
> > +static int of_overlay_global_fixup_fit(struct device_node *root,
> > +				       const char *fit_path, loff_t fit_size)
> > +{
> > +	enum bootm_verify verify = bootm_get_verify_mode();
> > +	struct device_node *conf_node;
> > +	struct fit_handle *fit;
> > +	int ret;
> > +
> > +	if (!IS_ENABLED(CONFIG_FITIMAGE))
> > +		return 0;
> 
> The user has explicitly passed a FIT image, but we don't have FIT
> support compiled in. Shouldn't this be an error?

Yes you're right. I will return the error and an error-message.

> > +	fit = fit_open(fit_path, 0, verify, fit_size);
> > +	if (IS_ERR(fit)) {
> > +		pr_err("Loading FIT image %s failed with: %pe\n", fit_path, fit);
> > +		return PTR_ERR(fit);
> > +	}
> > +
> > +	for_each_child_of_node(fit->configurations, conf_node) {
> > +		if (!of_overlay_valid_config(fit, conf_node))
> > +			continue;
> > +
> > +		ret = fit_config_verify_signature(fit, conf_node);
> > +		if (ret)
> > +			goto out;
> > +
> > +		ret = of_overlay_apply_fit(root, fit, conf_node);
> > +		if (ret)
> > +			goto out;
> > +	}
> > +
> > +out:
> > +	fit_close(fit);
> > +	return ret;
> > +}
> > +
> >  static int of_overlay_global_fixup(struct device_node *root, void *data)
> >  {
> > -	return of_overlay_global_fixup_dir(root, of_overlay_path);
> > +	enum filetype type;
> > +	struct stat s;
> > +	int ret;
> > +
> > +	if (isempty(of_overlay_path))
> > +		return 0;
> > +
> > +	if (stat(of_overlay_path, &s)) {
> > +		pr_err("Failed to detect file status\n");
> 
> Maybe something like:
> 
> 	pr_err("Cannot stat global.of.overlay.path (%s): %pe\n", of_overlay_path, ERR_PTR(ret));
> 
> To give the user a better clue what to do about this error?

ACK

> > +		return -errno;
> > +	}
> > +
> > +	if (S_ISDIR(s.st_mode))
> > +		return of_overlay_global_fixup_dir(root, of_overlay_path);
> > +
> > +	ret = file_name_detect_type(of_overlay_path, &type);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (type == filetype_oftree)
> > +		return of_overlay_global_fixup_fit(root, of_overlay_path,
> > +						   s.st_size);
> > +
> > +	pr_err("No suitable overlay provider found!\n");
> 
> What other file types are you anticipating here? I would rather assume a
> "... is not a FIT image" message to give the user a clue what is
> expected here.

E.g. overlays supplied via an unified kernel image (UKI) which of course
is not supported by barebox yet. Also if we reach this error it means
that the of_overlay_path was neither a DIR nor a FIT therefore I went
the generic way.

> I think you could also just drop the filetype detection here and just
> call of_overlay_global_fixup_fit() unconditionally. The resulting
> "Loading FIT image %s failed with: %pe\n" message when a non FIT image
> is to be opened should be enough information for the user.

You're right. I took an very defensive approach. We can extend this
later as well if we're going to support UKIs in the future.

> Note that it's a bit unfortunate that both a FIT image and a dtbo file
> are detected as device tree files. With the prvious naming
> "global.of.overlay.dir" it was clear that a directory was expected here.
> The "global.of.overlay.path" naming might confuse the user into thinking
> that a path to a dtbo file could be passed here which would then be
> opened as a FIT image. Would be nice to give a meaningful error message
> when a user falls into this trap.

Sorry I don't get this. With "global.of.overlay.path" there are now two
possibilities:
 1) It's a directory: in that case the already existing
    of_overlay_global_fixup_dir() is triggered.
 2) It's a file: in that case we try to apply the new fit-overlay
    handling.

Regards,
  Marco