compiler-gcc.h: Introduce __nostackprotector function attribute

Create a new function attribute, __nostackprotector, that can used to turn off
stack protection on a per function basis.

Signed-off-by: Tom Lendacky <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brijesh Singh <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: Larry Woodman <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Matt Fleming <[email protected]>
Cc: Michael S. Tsirkin <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Toshimitsu Kani <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/0576fd5c74440ad0250f16ac6609ecf587812456.1500319216.git.thomas.lendacky@amd.com
Signed-off-by: Ingo Molnar <[email protected]>

include/linux/compiler-gcc.h

@@ -166,6 +166,8 @@
 
 #if GCC_VERSION >= 40100
 # define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
+
+#define __nostackprotector	__attribute__((__optimize__("no-stack-protector")))
 #endif
 
 #if GCC_VERSION >= 40300

include/linux/compiler.h

@@ -470,6 +470,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
 #define __visible
 #endif
 
+#ifndef __nostackprotector
+# define __nostackprotector
+#endif
+
 /*
  * Assume alignment of return value.
  */