[U-Boot] [PATCH v4] socfpga: Add socfpga preloader signing to mkimage

[Charles Manning]

Hello Wolfgang
On Monday 24 February 2014 19:48:36 Wolfgang Denk wrote:
> Dear Charles,
>
> In message <1393194939-29786-1-git-send-email-cdhmanning at gmail.com> you 
wrote:
> > Like many platforms, the Altera socfpga platform requires that the
> > preloader be "signed" in a certain way or the built-in boot ROM will
> > not boot the code.
> >
> > This change automatically creates an appropriately signed preloader
> > from an SPL image.
> >
> > Signed-off-by: Charles Manning <cdhmanning at gmail.com>
> > ---
> >
> > Changes for v3:
> >  - Fix some coding style issues.
> >  - Move from a standalone tool to the mkimgae framework.
> >
> > Changes for v4:
> >  - Fix more coding style issues.
> >  - Fix typos in Makefile.
> >  - Rebase on master (previous version was not on master, but on a
> >    working socfpga branch).
>
> There may be perfectly valid reasons why you might decide to ingore a
> review comments - sch comments may be wrong, too, after all.  But in
> such a case it is always a good idea to provide feedback to the
> reviewer why you decided not to follow his advice.  Otherwise he might
> think you just missed or ignored the comment.

I am sorry, I must have missed some of the comments. I have intended to 
implement them all, except one by Gerhard.

>
> And this is what is happeneing (again) in your patch...
>
> > diff --git a/spl/Makefile b/spl/Makefile
> > index bf98024..90faaa6 100644
> > --- a/spl/Makefile
> > +++ b/spl/Makefile
> > @@ -181,6 +181,14 @@ $(objtree)/SPL : $(obj)/u-boot-spl.bin
> >
> >  ALL-y	+= $(obj)/$(SPL_BIN).bin
> >
> > +$(OBJTREE)/socfpga-signed-preloader.bin: $(obj)/u-boot-spl.bin
> > +	$(OBJTREE)/tools/mkimage -T socfpgaimage -d $< $@
> > +
> > +
>
> One blank line is sufficient.

Ok, a blank line. I can delete that.

>
> I asked before:  "socfpga-signed-preloader.bin" is a terribly long
> name.  Can we find a better one?
>
> > +ifdef CONFIG_SOCFPGA
> > +ALL-y += $(OBJTREE)/socfpga-signed-preloader.bin
> > +endif
>
> I asked before: Can we not use "ALL-$(CONFIG_SOCFPGA)" and avoid the
> ifdef ?

I am sorry, I had developed this code in a different (older) branch where 
socfpga actually works. It is broken in master.

This I shall fix.

>
> > + * Reference doc
> > http://www.altera.com.cn/literature/hb/cyclone-v/cv_5400A.pdf + * Note
> > this doc is not entirely accurate.
>
> I aseked before: Would you care to explain the errors in the document
> that might cause problems to the reader?
>
> Noting that something contains errors without mentioning what these
> are is really not helpful.

Ok, I shall mention the errors pertinent to the code. Other errors I shall 
ignore.

>
> > + * This uses the CRC32 calc out of the well known Apple
> > + * crc32.c code. CRC32 algorithms do not produce the same results.
> > + * We need this one. Sorry about the coade bloat.
>
> Both Gerhard and me asked before: Why exactly do we need another
> implementation of CRC32.  We already have some - why cannot we use
> these?

Well I would have thought that obvious from the comment I put in the code, but 
email is an imperfect communications medium, so I shall explain in further 
detail here.

As I am sure you are aware, there are many different crc32 calculations. 
Indeed Wikipedia lists 5 and there are most likely others.

Even when they use the same polynomial, they give differences when you stuff 
the bits through the shift register lsb-first or msb-first.

Now from what I see looking through the u-boot lib/ directory u-boot provides 
just one crc32 version - Adler (and a bit flipped version thereof for use by 
jffs2). If there are others I did not see them.

Now as I expect you are aware, the purpose of a signer is to massage the code 
so that it is in a form that the boot ROM accepts. One of those criteria is 
that the crc in the code matches the crc the boot ROM is expecting. If not, 
the boot ROM refuses to execute the code.

It would be nice to use the Adler code. Indeed this is my favourite crc. 
However, this is not what the boot ROM wants.

The boot ROM does not enter into rational discussions, so we must, 
unfortunately, bow to its whims. If it wants a different CRC calculation then 
we must supply it.

I did much experimentation to find the crc that worked. I tried the zlib crc - 
no luck.  I tried different many things until I found something that worked.

>
> > + * Copyright for the CRC code:
> > + *
> > + * COPYRIGHT (C) 1986 Gary S. Brown.  You may use this program, or
> > + *  code or tables extracted from it, as desired without restriction.
>
> I asked before:  Please provide _exact_ reference. See
> http://www.denx.de/wiki/view/U-Boot/Patches#Attributing_Code_Copyrights_Sig
>n for instructions how to do this.

As it was, I had attributed this incorrectly. This is a file I generated 
myself, though I had used this as a reference during my research. The values 
will look the same as some other code floating out there, but that is because 
that is the way things have to be.

I shall fix this wen I make another file.


>
> I also commented before: If you really need this copied code (i. e.
> you canot use one of the already existing implementations of CRC32 -
> which I seriously doubt), then better move this into a separate file,
> and assign a separate license ID tag for it.

You say "already exiting implementations". I see only one: lib/crc32.c. 
Perhaps I am not looking in the right place?

I shall split this code out and call it alt_crc32 and put it in lib with one 
of those proxy files in tools.

>
>
> I also asked this before: I cannot find a license ID tag in your new
> code. Please add.

Ok.


>
> > +/* To work in with the mkimage framework, we do some ugly stuff...
> > + *
> > + * First we prepend a fake header big enough to make the file 64k.
> > + * When set_header is called, we fix this up by moving the image
> > + * around in the buffer.
> > + */
>
> Also asked before: Incorrect multiline comment style. Please fix
> globally.

Ok.

I am sorry I missed some of your comments earlier.

Regards

Charles