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Date: Mon, 4 Jun 2018 16:16:12 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Thomas Garnier <thgarnie@...gle.com>
Cc: kernel-hardening@...ts.openwall.com, Ingo Molnar <mingo@...hat.com>,
 Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>,
 x86@...nel.org, Francis Deslauriers <francis.deslauriers@...icios.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Andrew Morton
 <akpm@...ux-foundation.org>, "Peter Zijlstra (Intel)"
 <peterz@...radead.org>, Guenter Roeck <linux@...ck-us.net>, nixiaoming
 <nixiaoming@...wei.com>, James Hogan <jhogan@...nel.org>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 21/27] x86/ftrace: Adapt function tracing for PIE
 support

On Tue, 29 May 2018 15:15:22 -0700
Thomas Garnier <thgarnie@...gle.com> wrote:

> When using -fPIE/PIC with function tracing, the compiler generates a
> call through the GOT (call *__fentry__@...PCREL). This instruction
> takes 6 bytes instead of 5 on the usual relative call.
> 
> If PIE is enabled, replace the 6th byte of the GOT call by a 1-byte nop
> so ftrace can handle the previous 5-bytes as before.
> 
> Position Independent Executable (PIE) support will allow to extend the
> KASLR randomization range 0xffffffff80000000.

I thought you were going to write a update to recordmcount.c to handle
this at compile time?

-- Steve

> 
> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
> ---
>

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