linux-kernel - Re: [PATCH v6 09/20] arm64:ilp32: share HWCAP between LP64 and ILP32

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Date:	Thu, 17 Dec 2015 14:56:24 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	bamvor.zhangjian@...wei.com, pinskia@...il.com,
	Prasun.Kapoor@...iumnetworks.com, schwab@...e.de,
	joseph@...esourcery.com, Nathan_Lynch@...tor.com, agraf@...e.de,
	linux-kernel@...r.kernel.org, klimov.linux@...il.com,
	Andrew Pinski <Andrew.Pinski@...iumnetworks.com>,
	broonie@...nel.org, Yury Norov <ynorov@...iumnetworks.com>,
	Andrew Pinski <apinski@...ium.com>, ddaney.cavm@...il.com,
	jan.dakinevich@...il.com, philipp.tomsich@...obroma-systems.com,
	linux-arm-kernel@...ts.infradead.org,
	christoph.muellner@...obroma-systems.com
Subject: Re: [PATCH v6 09/20] arm64:ilp32: share HWCAP between LP64 and ILP32

On Thursday 17 December 2015 10:54:47 Catalin Marinas wrote:
> > > IIUC, we may have a problem with this. elf_hwcap is 64-bit long while
> > > elf_info[n] is 32-bit (Elf32_Addr), so we truncate AT_HWCAP if we ever
> > > go beyond bit 31. The above may need to look something like:
> > > 
> > > #define COMPAT_ELF_HWCAP        \
> > >         (is_a32_compat_task()   \
> > >          ? compat_elf_hwcap     \
> > >          : (u32)elf_hwcap)
> > > 
> > > #define COMPAT_ELF_HWCAP2       \
> > >         (is_a32_compat_task()   \
> > >          ? compat_elf_hwcap2    \
> > >          : (u32)(elf_hwcap >> 32))
> > 
> > Yes, interesting find.
> 
> BTW, we need to make sure this series (primarily the ABI) is big-endian
> safe. I know it is not targeted at this initially but given that the
> reason for doing it is legacy networking code, I wouldn't be surprised
> if someone asks for BE at some point in the future.

Yes, I'm sure that will be needed.

	Arnd
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