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Date:   Mon, 06 Apr 2020 00:53:26 +0800
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Subject: Re: [PATCH] MIPS: malta: Set load address for 32bit kernel correctly
To:     "Maciej W. Rozycki" <macro@linux-mips.org>
CC:     linux-mips@vger.kernel.org, Fangrui Song <maskray@google.com>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        linux-kernel@vger.kernel.org
From:   Jiaxun Yang <jiaxun.yang@flygoat.com>
Message-ID: <96C9B1A0-2F89-4650-B0A4-6A6242A2AA0A@flygoat.com>
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=E4=BA=8E 2020=E5=B9=B44=E6=9C=886=E6=97=A5 GMT+08:00 =E4=B8=8A=E5=8D=8812=
:47:29, "Maciej W=2E Rozycki" <macro@linux-mips=2Eorg> =E5=86=99=E5=88=B0:
>On Sun, 5 Apr 2020, Jiaxun Yang wrote:
>
>> LLD failed to link vmlinux with 64bit load address for 32bit ELF
>> while bfd will strip 64bit address into 32bit silently=2E
>> To fix LLD build, we should supply a 32bit load address for 32bit
>> kernel=2E
>[=2E=2E=2E]
>> diff --git a/arch/mips/mti-malta/Platform
>b/arch/mips/mti-malta/Platform
>> index 2cc72c9b38e3=2E=2Ef9b49cba1764 100644
>> --- a/arch/mips/mti-malta/Platform
>> +++ b/arch/mips/mti-malta/Platform
>> @@ -6,6 +6,10 @@ cflags-$(CONFIG_MIPS_MALTA)	+=3D
>-I$(srctree)/arch/mips/include/asm/mach-malta
>>  ifdef CONFIG_KVM_GUEST
>>      load-$(CONFIG_MIPS_MALTA)	+=3D 0x0000000040100000
>>  else
>> +ifdef CONFIG_64BIT
>>      load-$(CONFIG_MIPS_MALTA)	+=3D 0xffffffff80100000
>> +else
>> +    load-$(CONFIG_MIPS_MALTA)	+=3D 0x80100000
>
> Given the description above I think it should be done uniformly and=20
>automatically across all platforms by trimming the address supplied
>with=20
>$(load-y) to low 8 digits in a single place, that is at the place where
>
>the variable is consumed=2E  This will reduce clutter across Makefile=20
>fragments, avoid inconsistencies and extra work to handle individual=20
>platforms as the problem is triggered over and over again, and limit
>the=20
>risk of mistakes=2E

I was intended to do like this but failed to find a proper way=2E

Makefile isn't designed for any kind of calculation=2E
And shell variables are 64-bit signed so it can't hold such a huge variabl=
e=2E

Just wish somebody can give me a way to do like:

ifndef CONFIG_64BIT
load-y =3D $(load-y) & 0xffffffff
endif

In makefiles=2E

Thanks=2E
>
>Some error checking might be doable for verifying that the 64-bit
>address=20
>truncated is a sign-extended 32-bit value, but that perhaps would be an
>
>overkill as certainly any 64-bit system that sets the load address to
>be=20
>outside the sign-extended 32-bit address range does not support a
>!64BIT=20
>configuration anyway=2E
>
>  Maciej

--=20
Jiaxun Yang