[U-Boot] [PATCH] tools: default image: use ih_size for checking data size

[Wolfgang Denk]

Dear Jonas Gorski,

In message <20130503174205.00000070 at unknown> you wrote:
>
> > Sorry, I don't know how you create your image files, but you must be
> > doing something fundamentally wrong.  If mkimage reports a bug here,
> > it is probably right.  If the actual payload size is different from
> > the content of the  ih_size  field, then your image _is_ broken.
> 
> That what else for is the ih_size field then except to say what the
> actual datasize is? mkuimage also sets this fields to the
> correct size.

It's exactly for this very purpose, and allows for consistency
checking.  You run into errors, becuase your images are not correct.
For plain legacy image format (i. e. we are not talking about
multi-file image format here), header size (= 64 bytes) plus the
content of the ih_size  field will give the total file size of the
image.  If this condition is not met, then your image is broken.

> And this isn't from me, but this is how most firmware images are

Define "most".

> created for devices using U-Boot, i.e. uImage packed kernel + appended
> rootfs. Also U-Boot itself only cares for the first ih_size bytes of the
> image and not for any "garbage" that might be behind it:

Yes, because in U-Boot we have no notion of "files" and thus no
indication where an image ends.  Otherwise such a check would be
there.

> It checks the crc of the first ih_size bytes after the image_header -
> and my change changes mkimage to mirror that behaviour.

But this is wrong.

> It still reports data errors if the checksum is wrong for the data
> actually specified by the image header, but now it actually respects
> the length of the data field.

Let me repeat: a valid image will have sizeof(struct image_header)
plus ih_size == file size.  If this condition is not true, then your
image is broken.


Best regards,

Wolfgang Denk

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