From: Namhyung Kim <namhyung@gmail.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: remove __phys_reloc_hide
Date: Mon, 09 Aug 2010 16:47:39 +0900 [thread overview]
Message-ID: <1281340059.976.27.camel@leonhard> (raw)
In-Reply-To: <20100809072226.GD29524@basil.fritz.box>
2010-08-09 (월), 09:22 +0200, Andi Kleen:
> The original reason was that the C standard allows the compiler
> to make some assumptions on the pointer arithmetic that is done
> on symbol addresses (e.g. no wrapping). This is exploited
> by the optimizer in the compiler to generate better code.
>
> This lead to a miscompilation on PowerPC a couple of years back at
> least with the va->pa conversion.
>
> After that RELOC_HIDE was introduced after funelling the
> symbol address through an empty asm statement was recommended
> as the official way to do this by the gcc developers.
>
> I think x86-64 does not normally wrap here, but it's
> still safer to do it this way.
>
> -Andi
OK, then. Thanks for the comment.
p.s. The funny thing I found is there's no use of RELOC_HIDE on
arch/powerpc. Hmm...
--
Regards,
Namhyung Kim
next prev parent reply other threads:[~2010-08-09 7:47 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-08 21:38 [PATCH] x86: remove __phys_reloc_hide Namhyung Kim
2010-08-09 6:22 ` Andi Kleen
2010-08-09 6:40 ` Namhyung Kim
2010-08-09 6:44 ` Andi Kleen
2010-08-09 7:04 ` Namhyung Kim
2010-08-09 7:22 ` Andi Kleen
2010-08-09 7:47 ` Namhyung Kim [this message]
2010-08-09 18:56 ` H. Peter Anvin
2010-08-10 7:05 ` Ingo Molnar
2010-08-10 10:46 ` Namhyung Kim
2010-08-11 5:44 ` Namhyung Kim
2010-08-11 19:09 ` H. Peter Anvin
2010-08-11 6:37 ` [PATCH] x86: add a comment to __pa_symbol Namhyung Kim
2010-08-11 7:44 ` [tip:x86/urgent] x86: Document __phys_reloc_hide() usage in __pa_symbol() tip-bot for Namhyung Kim
2018-06-19 23:00 ` [PATCH] x86: remove __phys_reloc_hide Thomas Gleixner
2010-08-09 8:07 ` Ingo Molnar
2010-08-09 18:56 ` H. Peter Anvin
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