linux-kernel - Re: [PATCH 4/5] x86-64: Replace vsyscall gettimeofday fallback with int 0xcc

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Date:	Sun, 29 May 2011 16:05:00 -0400
From:	Andrew Lutomirski <luto@....edu>
To:	Jesper Juhl <jj@...osbits.net>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] x86-64: Replace vsyscall gettimeofday fallback with
 int 0xcc

On Sun, May 29, 2011 at 3:54 PM, Jesper Juhl <jj@...osbits.net> wrote:
> On Sun, 29 May 2011, Jesper Juhl wrote:
>
>> On Fri, 27 May 2011, Andy Lutomirski wrote:
>>
>> > Now the only way to issue a syscall with side effects through the
>> > vsyscall page is to call a misaligned instruction.  I haven't
>> > checked for that.
>> >
>> > Signed-off-by: Andy Lutomirski <luto@....edu>
>> > ---
>> >  arch/x86/include/asm/traps.h    |    4 +++
>> >  arch/x86/include/asm/vsyscall.h |    6 +++++
>> >  arch/x86/kernel/entry_64.S      |    2 +
>> >  arch/x86/kernel/traps.c         |    4 +++
>> >  arch/x86/kernel/vsyscall_64.c   |   47 ++++++++++++++++++++++++++++++++++-----
>> >  5 files changed, 57 insertions(+), 6 deletions(-)
>> >
>>
>> one very tiny nit below.
>>
>> [...]
>> > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
>> > index b9b6716..d34894e 100644
>> > --- a/arch/x86/kernel/traps.c
>> > +++ b/arch/x86/kernel/traps.c
>> > @@ -872,6 +872,10 @@ void __init trap_init(void)
>> >     set_bit(SYSCALL_VECTOR, used_vectors);
>> >  #endif
>> >
>> > +   set_system_intr_gate(0xCC, &intcc);
>> > +   set_bit(0xCC, used_vectors);
>> > +   printk(KERN_ERR "intcc gate isntalled\n");
>>
>> Let's spell the error message correctly:
>>
>>       printk(KERN_ERR "intcc gate installed\n");
>>
> Hmm, why is this KERN_ERR btw? Shouldn't it just be KERN_NOTICE or
> KERN_INFO ?

IMO it shouldn't be there at all.  It was a debugging leftover that I
forgot to delete.

--Andy
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