x86/ftrace: Exclude functions in head64.c from function-tracing

A recent commit moved most logic of early boot up from startup_64() written
in assembly to __startup_64() written in C.

Fengguang reported breakage due to the change. It was tracked down to
CONFIG_FUNCTION_TRACER being enabled.

Tracing this function is not possible because it's invoked from the
earliest boot stage before the relocation fixups have been done. It is the
function doing the relocation.

Exclude it from being built with tracer stubs.

Fixes: c88d71508e36 ("x86/boot/64: Rewrite startup_64() in C")
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: lkp@01.org
Link: http://lkml.kernel.org/r/20170627115948.17938-1-kirill.shutemov@linux.intel.com

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 4b994232cb5739f15eef17c69be00aa3b3bc5243..0db512092f37001cd5263119cac85b4c591817f4 100644 (file)
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -18,6 +18,7 @@ CFLAGS_REMOVE_pvclock.o = -pg
 CFLAGS_REMOVE_kvmclock.o = -pg
 CFLAGS_REMOVE_ftrace.o = -pg
 CFLAGS_REMOVE_early_printk.o = -pg
+CFLAGS_REMOVE_head64.o = -pg
 endif
 
 KASAN_SANITIZE_head$(BITS).o                           := n