Re: Using conditionals in embedded config?

[Shea Levy]

On 2016-02-06 13:13, Andrei Borzenkov wrote:
> 06.02.2016 17:07, Shea Levy пишет:
> > I'm setting up an unassisted android boot process, where I first 
> > check
> > to see if the system has requested boot into recovery and boot from 
> > the
> > recovery bootimg if so (booting from the normal bootimg otherwise). 
> > None
> > of the traditional android partitions are appropriate for a grub 
> > config.
>
> You can build standalone image with GRUB on internal memory disk that 
> is
> embedded into core.img. That memory disk may then contain grub.cfg 
> with
> full scripting capabilities.

Ah, I didn't know about the memory disk option, that solves this.

> OTOH it just another argument in favor of dedicated android loader 
> that
> handles all this logic internally. From what you said so far it does 
> not
> look like there is much flexibility in boot process anyway.

I still stand by leaving this up to the grub config. Suppose I want to 
add an option to my grub menu to do a factory reset. With my patches 
as-is, this is easy. With a dedicated loader, someone would have to 
modify grub itself to make the loader accept an option to set up the BCB 
and boot into recovery appropriately.

> > I can just add an extra partition (which I'm doing for now), but a) 
> > this
> > is not supported by official flashing/update mechanisms and b) this
> > increases the window during an update to the bootloader where loss 
> > of
> > power would result in a corrupt system (with embedded config doing 
> > all
> > of the work, I only need to update boot.img and core.img, with a 
> > config
> > on a separate partition I also need to update that partition.
>
> This is rather orthogonal, but yes, having better support for 
> alternate
> install location would indeed reduce risk of unbootable system.
>
> > ~Shea
> >
> > On 2016-02-06 08:59, Andrei Borzenkov wrote:
> > > 06.02.2016 15:28, Shea Levy пишет:
> > > > I see. This seems to severely limit the possible use cases of 
> > > > embedded
> > > > configs; it also contradicts the example in the manual [1]. Is 
> > > > there
> > >
> > > Yes, someone already complained about manual. Patches are welcome.
> > >
> > > > really no way to branch in embedded configs? Would it be possible 
> > > > to
> > > > enable branching by including some optional module in the core 
> > > > img?
> > >
> > > Why do you need to do it in the first place? What is your use case?
> > >
> > > > ~Shea
> > > >
> > > > [1]
> > > >
> > > >
> > > > https://www.gnu.org/software/grub/manual/html_node/Embedded-configuration.html#Embedded-configuration
> > > >
> > > >
> > > > On 2016-02-06 00:42, Andrei Borzenkov wrote:
> > > > > 06.02.2016 06:24, Shea Levy пишет:
> > > > > > Hi all,
> > > > > >
> > > > > > How can I use if statements in an embedded config? When I try, I 
> > > > > > get
> > > > >
> > > > > You can't. embedded config is processed early using rescue mode 
> > > > > parser
> > > > > which is very simple. Embedded config exists to locate device 
> > > > > where
> > > > > grub
> > > > > is installed in case this information is not available from 
> > > > > firmware.
> > > > > Everything else cam be done using grub.cfg in this location.
> > > > >
> > > > > > "unknown command "if"", "unknown command "fi"", etc. I'm 
> > > > > > including
> > > > > > normal, part_gpt, android_bootimg, android_bcb, linux, test, and
> > > > > > biosdisk in the core.img (the android_* modules are local
> > > > > > modifications,
> > > > > > see the grub-devel list for their details but they shouldn't 
> > > > > > matter).
> > > > > >
> > > > > > Thanks,
> > > > > > Shea
> > > > > >
> > > > > > _______________________________________________
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> > > > >
> > > > >
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