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Message-ID: <20171020152028.syq6woeet6it3z3h@gmail.com>
Date: Fri, 20 Oct 2017 17:20:28 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Thomas Garnier <thgarnie@...gle.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>,
"David S . Miller" <davem@...emloft.net>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>,
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Subject: Re: [PATCH v1 06/27] x86/entry/64: Adapt assembly for PIE support
* Thomas Garnier <thgarnie@...gle.com> wrote:
> >> */
> >> - cmpq $.Lentry_SYSCALL_64_after_fastpath_call, (%rsp)
> >> + leaq .Lentry_SYSCALL_64_after_fastpath_call(%rip), %r11
> >> + cmpq %r11, (%rsp)
> >> jne 1f
> > This patch seems to add extra overhead to the syscall fast-path even when PIE is
> > disabled, right?
>
> It does add extra instructions when one is not possible, I preferred
> that over ifdefing but I can change it.
So my problem is, this pattern repeats in many other places as well, but sprinking
various pieces of assembly code with #ifdefs would be very bad as well.
I have no good idea how to solve this.
Thanks,
Ingo
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