Date: Sat, 9 Feb 2019 13:09:12 +0100 From: Greg KH <gregkh@...uxfoundation.org> To: "Reshetova, Elena" <elena.reshetova@...el.com> Cc: Peter Zijlstra <peterz@...radead.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, "luto@...nel.org" <luto@...nel.org>, "tglx@...utronix.de" <tglx@...utronix.de>, "mingo@...hat.com" <mingo@...hat.com>, "bp@...en8.de" <bp@...en8.de>, "keescook@...omium.org" <keescook@...omium.org>, "tytso@....edu" <tytso@....edu> Subject: Re: [RFC PATCH] x86/entry/64: randomize kernel stack offset upon system call On Sat, Feb 09, 2019 at 11:38:00AM +0000, Reshetova, Elena wrote: > > On Fri, Feb 08, 2019 at 01:20:09PM +0000, Reshetova, Elena wrote: > > > > On Fri, Feb 08, 2019 at 02:15:49PM +0200, Elena Reshetova wrote: > > > > > I can measure the impact with rdtsc(), I think it is *very* small. > > > Btw, what should be the good measurement test? > > > I am not that happy with just looping on fopen-fclose, too > > > much noise. > > > > IIRC amluto had a nice micro-bench for 'pure' syscall overhead > > somewhere. > > > > Something like getpid/gettid in a loop should work fairly well, that's a > > really light syscall to make. > > Thanks! Let me try this for measurements next. I was surprise that > there nothing ready-made in perf or rt-tools. You would think > this must be regularly in a need to measure. lmbench has traditionally been used for something like this in the past, you might want to look at that too. greg k-h
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