From: "Maciej W. Rozycki" <macro@linux-mips.org>
To: Jiaxun Yang <jiaxun.yang@flygoat.com>
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
Subject: Re: [PATCH] MIPS: malta: Set load address for 32bit kernel correctly
Date: Sun, 5 Apr 2020 17:47:29 +0100 (BST) [thread overview]
Message-ID: <alpine.LFD.2.21.2004051738000.4156324@eddie.linux-mips.org> (raw)
In-Reply-To: <20200405082451.694910-1-jiaxun.yang@flygoat.com>
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.
> To fix LLD build, we should supply a 32bit load address for 32bit
> kernel.
[...]
> diff --git a/arch/mips/mti-malta/Platform b/arch/mips/mti-malta/Platform
> index 2cc72c9b38e3..f9b49cba1764 100644
> --- a/arch/mips/mti-malta/Platform
> +++ b/arch/mips/mti-malta/Platform
> @@ -6,6 +6,10 @@ cflags-$(CONFIG_MIPS_MALTA) += -I$(srctree)/arch/mips/include/asm/mach-malta
> ifdef CONFIG_KVM_GUEST
> load-$(CONFIG_MIPS_MALTA) += 0x0000000040100000
> else
> +ifdef CONFIG_64BIT
> load-$(CONFIG_MIPS_MALTA) += 0xffffffff80100000
> +else
> + load-$(CONFIG_MIPS_MALTA) += 0x80100000
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.
Some error checking might be doable for verifying that the 64-bit address
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
outside the sign-extended 32-bit address range does not support a !64BIT
configuration anyway.
Maciej
next prev parent reply other threads:[~2020-04-05 16:47 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-05 8:24 [PATCH] MIPS: malta: Set load address for 32bit kernel correctly Jiaxun Yang
2020-04-05 16:47 ` Maciej W. Rozycki [this message]
2020-04-05 16:53 ` Jiaxun Yang
2020-04-05 17:23 ` Maciej W. Rozycki
2020-04-06 10:57 ` YunQiang Su
2020-04-06 11:10 ` Jiaxun Yang
2020-04-06 16:43 ` Fangrui Song
2020-04-07 8:06 ` [PATCH v2] MIPS: Truncate load-y into 32bit for 32bit kernel Jiaxun Yang
2020-04-07 17:21 ` Nick Desaulniers
2020-04-07 18:00 ` Fangrui Song
2020-04-07 18:10 ` Maciej W. Rozycki
2020-04-10 9:06 ` [PATCH v3] MIPS: Truncate link address " Jiaxun Yang
2020-04-10 20:45 ` Kees Cook
2020-04-10 23:40 ` Maciej W. Rozycki
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