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

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From: Arne Georg Gleditsch
Subject: arch/x86/kernel/vsyscall_64.c: overeager NOP of syscalls
Date: Wednesday, February 20, 2008 - 6:57 am

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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Messages in current thread:
arch/x86/kernel/vsyscall_64.c: overeager NOP of syscalls, Arne Georg Gleditsch, (Wed Feb 20, 6:57 am)
Re: arch/x86/kernel/vsyscall_64.c: overeager NOP of syscalls, Thomas Gleixner, (Wed Feb 20, 11:08 am)
Re: arch/x86/kernel/vsyscall_64.c: overeager NOP of syscalls, Andi Kleen, (Thu Feb 21, 8:58 am)
Re: arch/x86/kernel/vsyscall_64.c: overeager NOP of syscalls, Thomas Gleixner, (Thu Feb 21, 12:45 pm)
Re: arch/x86/kernel/vsyscall_64.c: overeager NOP of syscalls, john stultz, (Thu Feb 21, 1:02 pm)
Re: arch/x86/kernel/vsyscall_64.c: overeager NOP of syscalls, Thomas Gleixner, (Thu Feb 21, 1:47 pm)
Re: arch/x86/kernel/vsyscall_64.c: overeager NOP of syscalls, Thomas Gleixner, (Thu Feb 21, 1:59 pm)
Re: arch/x86/kernel/vsyscall_64.c: overeager NOP of syscalls, Arne Georg Gleditsch, (Fri Feb 22, 3:38 am)
Re: arch/x86/kernel/vsyscall_64.c: overeager NOP of syscalls, Andi Kleen, (Fri Feb 22, 5:49 am)
Re: arch/x86/kernel/vsyscall_64.c: overeager NOP of syscalls, Andi Kleen, (Fri Feb 22, 5:55 am)