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Date: Tue, 26 Jun 2018 11:21:10 -0400
From: Steven Rostedt <>
To: Thomas Garnier <>
Cc:, Ingo Molnar <>,
 Thomas Gleixner <>, "H. Peter Anvin" <>,, James Hogan <>, "Peter Zijlstra (Intel)"
 <>, nixiaoming <>, Guenter Roeck
Subject: Re: [PATCH v5 21/27] x86/ftrace: Adapt function tracing for PIE

On Mon, 25 Jun 2018 15:39:09 -0700
Thomas Garnier <> wrote:

> When using PIE with function tracing, the compiler generates a
> call through the GOT (call *__fentry__@...PCREL). This instruction
> takes 6-bytes instead of 5-bytes with a 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.
> Signed-off-by: Thomas Garnier <>

Thanks for doing it this way.

Reviewed-by: Steven Rostedt (VMware) <>

-- Steve

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