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

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Date:   Mon, 06 Apr 2020 19:10:58 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     YunQiang Su <wzssyqa@...il.com>,
        "Maciej W. Rozycki" <macro@...ux-mips.org>
CC:     linux-mips <linux-mips@...r.kernel.org>,
        Fangrui Song <maskray@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] MIPS: malta: Set load address for 32bit kernel correctly



于 2020年4月6日 GMT+08:00 下午6:57:18, YunQiang Su <wzssyqa@...il.com> 写到:
>Maciej W. Rozycki <macro@...ux-mips.org> 于2020年4月6日周一 上午1:23写道：
>>
>> 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


>
>> 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