Re: [PATCH] MIPS: malta: Set load address for 32bit kernel correctly

[Fangrui Song]

On 2020-04-06, Jiaxun Yang wrote:
> ä 2020å4æ6æ GMT+08:00 äå6:57:18, YunQiang Su <wzssyqa@xxxxxxxxx> åå:
> > Maciej W. Rozycki <macro@xxxxxxxxxxxxxx> ä2020å4æ6æåä äå1:23åéï
> > > On Mon, 6 Apr 2020, Jiaxun Yang wrote:
> > >
> > > > > Given the description above I think it should be done uniformly
> > and
> > > > >automatically across all platforms by trimming the address
> > supplied
> > > > >with
> > > > >$(load-y) to low 8 digits in a single place, that is at the place
> > where
> > > > >
> > > > >the variable is consumed.  This will reduce clutter across
> > Makefile
> > > > >fragments, avoid inconsistencies and extra work to handle
> > individual
> > > > >platforms as the problem is triggered over and over again, and
> > limit
> > > > >the
> > > > >risk of mistakes.
> > > >
> > > > I was intended to do like this but failed to find a proper way.
> > > >
> > > > Makefile isn't designed for any kind of calculation.
> > > > And shell variables are 64-bit signed so it can't hold such a huge
> > variable.
> > > >
> > > > Just wish somebody can give me a way to do like:
> > > >
> > > > ifndef CONFIG_64BIT
> > > > load-y = $(load-y) & 0xffffffff
> > > > endif
> > >
> > >  Use the usual shell tools like `sed', `cut', `awk', or whatever we
> > use in
> >
> > perl may be the easiest to use tool here.
> >
> > ifndef CONFIG_64BIT
> >  load-y := $(shell $(PERL) -e 'print $(load-y) & 0xffffffff')
> > endif
> >
> > Note that it is `:=' instead of '='.
>
> It seems like perl is not one of kernel's build dependencies.[1]
> I'm comsidering a alternative solution,
> write a small hostprog in C to deal with that.
>
> Thanks.
>
> [1]: https://www.kernel.org/doc/html/v5.6/process/changes.html

load-y := 0xffffffff80100000
load-y := 0x$(shell echo "$(load-y)" | rev | head -c 8 | rev)

> > > the kernel build already for other purposes.  There's no need to do
> > any
> > > actual calculation here to extract the last 8 characters (and the
> > leading
> > > `0x' prefix).  At worst you can write a small C program, compile it
> > with
> > > the build system compiler and run, as we already do for some stuff.
> > >
> > >   Maciej
>
> --
> Jiaxun Yang