Re: [patch] set prefix on PPC

[Hollis Blanchard]

On Feb 14, 2005, at 1:01 PM, Marco Gerards wrote:

> Hollis Blanchard <address@hidden> writes:
>
> > 2) HFS has a concept called "blessed"; basically the firmware can
> > automatically find and boot blessed executables without needing to
> > specify a file name or even partition. Some versions of Mac OS
> > allegedly will unbless a non-Mac OS blessed file. For that reason,
> > ybin  prefers the HFS "bootstrap" partition be of a type that Mac OS
> > will not  mount (and so will not alter).
>
> How is the file blessed and why does that make it a problem to keep
> /boot on a HFS partition?

The file is blessed with hfsutils, spefically hattrib(1). I do not know 
if the in-kernel HFS(+) drivers allow for such changes (via ioctls for 
example). That will be worth investigating.

Actually it seems I was mistaken, and "blessed" refers to the directory 
rather than the file itself. I believe then the proper file to be 
booted is found from its 4-byte HFS file type, "tbxi" being the magic 
"Mac OS kernel" type.

> > > What I would prefer is this:
> > >
> > > 1)  Set prefix to whatever was set in the binary.
> >
> > This would involve more post-compilation ELF manipulation. To
> > accomplish that, if we do decide to go that route, I think it would be
> > worth converting the existing module segment into a more
> > general-purpose segment, containing all the added arguments.
>
> Ok.  If we use your patch, this is not that important, I guess.  If it
> works right that is.

Ok. I assume you want to test my patch and review it further, so I will 
wait for more comments before committing it.

> > > 3)  Read the arguments and if a prefix was passed to GRUB, use it to
> > >     override the prefix.
> > >
> > > For #3 I wrote a patch, but I forgot to send it to grub-devel... It's
> > > included with this email.  As far as I am concerned #1 is what is
> > > really important for us.
> > >
> > > 2005-02-13  Marco Gerards  <address@hidden>
> > >
> > >         * kern/powerpc/ieee1275/init.c (grub_machine_init): Initialize the
> > >         prefix env variable with the bootargs when it has a valid value.
> >
> > I don't like that this assumes bootargs only contains the prefix. For
> > example, if we ever get our fancy debugging support, it would be very
> > nice to boot grub with "debug=all" as an argument.
>
> I don't want to add a fancy parser yet.  At the moment we just use a
> single argument.  If more will be used, this code has to be changed.

And in that case, the format of "bootargs" will have to change too. 
It's never too early to think about backwards compatibility, especially 
if people are thinking of packaging and distributing a grub2.deb... :)

> > >         * loader/powerpc/ieee1275/linux.c (grub_rescue_cmd_linux): Don't
> > >         initialize `init_addr' yet, set it to 0 instead.
> >
> > Confused... how is this related to bootargs and prefix?
>
> It is required to make GNU/Linux boot here, just like the bootargs
> stuff. ;)
>
> It is separated with a blank line to make clear they do not serve the
> same purpose.

I thought each ChangeLog entry represented a distinct "changeset", with 
changesets being logically different changes to a group of files. The 
ChangeLog was explained to me as emulating a changeset in version 
control systems that lack the concept (such as CVS).

Since I believe the ChangeLog is an anachronism, I don't really care 
what it looks like or what format it's in. But since these changes are 
logically distinct, I believe they should at least be committed with 
separate "cvs commit" commands.

-Hollis