[PATCH] FIT: add first support for compressed images

[Sascha Hauer]

On Mon, Aug 08, 2022 at 08:56:48AM +0200, Ahmad Fatoum wrote:
> FIT image contents are often compressed, but we got by so far, because
> a compressed initramfs is usually meant to be decompressed by the kernel
> (and so has compression = "none") and arm32 kernels had their own
> decompresser embedded. On ARM64, bootloader is responsible for
> uncompressing kernel, so we should properly process the compression
> property we so far ignored.
> 
> The decompression isn't as efficient as one would hope for, because
> the FIT format only describes length of the compressed data. We thus
> have two options:
> 
>   - define an output size up-front, e.g. by guessing the uncompressed
>      buffer size for decompression or hardcoding it (e.g. U-Boot's
>      CONFIG_SYS_BOOTM_LEN).
> 
>   -  Uncompress to a file descriptor
> 
> We choose the second one to play it safe, but it comes with worse
> performance because of extra memory copies. Intention is to go with
> first option for the kernel image: We know how much size we can spare
> for the kernel image and can have bootm_load_os uncompress there
> directly without intermittent memory copies. This would involve slight
> change to the barebox decompresser API to align it with the kernel's,
> which allows to have it accept and observe an output buffer size.
> So far, we had the kernel PREBOOT API, which lacks such a parameter,
> but that's an optimization for another day.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
> ---
>  common/image-fit.c   | 38 +++++++++++++++++++++++++++++++++++---
>  include/uncompress.h |  6 ++++++
>  lib/uncompress.c     | 40 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 81 insertions(+), 3 deletions(-)
> 
> diff --git a/common/image-fit.c b/common/image-fit.c
> index 507a857cadb4..e692fcdaa737 100644
> --- a/common/image-fit.c
> +++ b/common/image-fit.c
> @@ -21,6 +21,7 @@
>  #include <linux/err.h>
>  #include <stringlist.h>
>  #include <rsa.h>
> +#include <uncompress.h>
>  #include <image-fit.h>
>  
>  #define FDT_MAX_DEPTH 32
> @@ -559,6 +560,11 @@ int fit_get_image_address(struct fit_handle *handle, void *configuration,
>  	return ret;
>  }
>  
> +static void fit_uncompress_error_fn(char *x)
> +{
> +	pr_err("%s\n", x);
> +}
> +
>  /**
>   * fit_open_image - Open an image in a FIT image
>   * @handle: The FIT image handle
> @@ -581,8 +587,10 @@ int fit_open_image(struct fit_handle *handle, void *configuration,
>  		   unsigned long *outsize)
>  {
>  	struct device_node *image;
> -	const char *unit = name, *type = NULL, *desc= "(no description)";
> -	const void *data;
> +	const char *unit = name, *type = NULL, *compression = NULL,
> +	      *desc= "(no description)";
> +	struct property *dataprop;
> +	const void *data = NULL;
>  	int data_len;
>  	int ret = 0;
>  
> @@ -599,7 +607,9 @@ int fit_open_image(struct fit_handle *handle, void *configuration,
>  		return -EINVAL;
>  	}
>  
> -	data = of_get_property(image, "data", &data_len);
> +	dataprop = of_find_property(image, "data", &data_len);
> +	if (dataprop)
> +		data = of_property_get_value(dataprop);
>  	if (!data) {
>  		pr_err("data not found\n");
>  		return -EINVAL;
> @@ -613,6 +623,28 @@ int fit_open_image(struct fit_handle *handle, void *configuration,
>  	if (ret < 0)
>  		return ret;
>  
> +	of_property_read_string(image, "compression", &compression);
> +	if (compression && strcmp(compression, "none") != 0) {
> +		if (!IS_ENABLED(CONFIG_UNCOMPRESS)) {
> +			pr_err("image has compression = \"%s\", but support not compiled in\n");
> +			return -ENOSYS;
> +		}
> +		if (!dataprop->value) {
> +			void *uc_data;
> +
> +			data_len = uncompress_buf_to_buf(data, data_len, &uc_data,
> +						    fit_uncompress_error_fn);
> +			if (data_len < 0) {
> +				pr_err("data couldn't be decompressed\n");
> +				return data_len;
> +			}
> +
> +			/* associate buffer with FIT, so it's not leaked */
> +			data = dataprop->value = uc_data;
> +			dataprop->length = data_len;

Why are you fiddling with struct property fields directly?
of_get_property() and of_set_property() should do what you want.

Sascha

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