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Re: [PATCH] MIPS: use 32-bit wrapper for compat_sys_futex

To: David Daney <david.daney@cavium.com>
Subject: Re: [PATCH] MIPS: use 32-bit wrapper for compat_sys_futex
From: Yong Zhang <yong.zhang@windriver.com>
Date: Thu, 18 Aug 2011 10:32:47 +0800
Cc: <linux-mips@linux-mips.org>, <linux-kernel@vger.kernel.org>, Ralf Baechle <ralf@linux-mips.org>
In-reply-to: <4E4BF7C0.80703@cavium.com>
References: <1313546094-11882-1-git-send-email-yong.zhang@windriver.com> <4E4BF7C0.80703@cavium.com>
Reply-to: Yong Zhang <yong.zhang@windriver.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed, Aug 17, 2011 at 10:17:52AM -0700, David Daney wrote:
> >diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
> >index 46c4763..f48b18e 100644
> >--- a/arch/mips/kernel/scall64-o32.S
> >+++ b/arch/mips/kernel/scall64-o32.S
> >@@ -441,7 +441,7 @@ sys_call_table:
> >     PTR     sys_fremovexattr                /* 4235 */
> >     PTR     sys_tkill
> >     PTR     sys_sendfile64
> >-    PTR     compat_sys_futex
> >+    PTR     sys_32_futex
> 
> This change is redundant, scall64-o32.S already does the right thing

My first virsion(not sent out) doesn't include scall64-o32.S either.

> so additional zero extending is not needed and is just extra
> instructions to execute for no reason.

Why I'm adding it here is for:
1)code consistent, otherwise we must move SYSCALL_DEFINE6(32_futex,...)
  under CONFIG_MIPS32_N32;
2)I'm afraid there may be some other way to touch the high 32-bit of a
  register, so touching scall64-o32.S is also for safety(due to unknown
  reason, fix me if I'm wrong).

Thanks,
Yong

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