Re: [PATCH v4 21/27] x86/ftrace: Adapt function tracing for PIE support

[Steven Rostedt]

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

> When using -fPIE/PIC with function tracing, the compiler generates a
> call through the GOT (call *__fentry__@GOTPCREL). 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@xxxxxxxxxx>
> ---
>