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Date: Thu, 5 Oct 2017 09:06:33 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Thomas Garnier <thgarnie@...gle.com>
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Subject: Re: [RFC v3 20/27] x86/ftrace: Adapt function tracing for PIE
 support

On Wed,  4 Oct 2017 14:19:56 -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.
> 
> With this change, function tracing supports 6 bytes on traceable
> function and can still replace relative calls on the ftrace assembly
> functions.
> 
> Position Independent Executable (PIE) support will allow to extended the
> KASLR randomization range below the -2G memory limit.

Question: This 6 bytes is only the initial call that gcc creates. When
function tracing is enabled, the calls are back to the normal call to
the ftrace trampoline?

-- Steve

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