FIT: add first support for compressed images

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@pengutronix.de>
Link: https://lore.barebox.org/20220809091946.3906847-1-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 31 insertions, 1 deletions

diff --git a/common/image-fit.c b/common/image-fit.c
index 507a857cad..3e6e7fbd6d 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
@@ -581,7 +587,8 @@ 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 char *unit = name, *type = NULL, *compression = NULL,
+	      *desc= "(no description)";
 	const void *data;
 	int data_len;
 	int ret = 0;
@@ -613,6 +620,29 @@ 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) {
+		void *uc_data;
+
+		if (!IS_ENABLED(CONFIG_UNCOMPRESS)) {
+			pr_err("image has compression = \"%s\", but support not compiled in\n",
+			       compression);
+			return -ENOSYS;
+		}
+
+		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;
+		}
+
+		data = uc_data;
+
+		/* associate buffer with FIT, so it's not leaked */
+		__of_new_property(image, "uncompressed-data", uc_data, data_len);
+	}
+
 	*outdata = data;
 	*outsize = data_len;