Re: [RFC v3 20/27] x86/ftrace: Adapt function tracing for PIE support

On Wed,  4 Oct 2017 14:19:56 -0700
Thomas Garnier [off-list ref] 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.

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