linux-kernel - arch/x86/kernel/vsyscall_64.c: overeager NOP of syscalls

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Message-ID: <kjm4pc3d92p.fsf@pelargir.dolphinics.no>
Date:	Wed, 20 Feb 2008 14:57:34 +0100
From:	Arne Georg Gleditsch <arne.gleditsch@...phinics.no>
To:	linux-kernel@...r.kernel.org
Cc:	Roman Zippel <zippel@...ux-m68k.org>
Subject: arch/x86/kernel/vsyscall_64.c: overeager NOP of syscalls

Hi,

I'm looking at 2.6.25-rc2.  vsyscall_sysctl_change contains code to NOP
out the actual system call instructions of the vsyscall page when
vsyscall64 is enabled.  This seems to interact badly with the fallback
code in do_vgettimeofday which tries to call gettimeofday if the
configured clock source does not support vread.  (In effect,
gettimeofday() becomes a nop and time() always returns 0.  Not very
useful.)

Is there a good reason to keep this?  Aren't the instructions in
question avoided (or invoked) according to the vsyscall64 flag by the
surrounding logic anyway?

-- 
								Arne.
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