arm64: Silence gcc warnings about arch ABI drift

Since GCC 9, the compiler warns about evolution of the
platform-specific ABI, in particular relating for the marshaling of
certain structures involving bitfields.

The kernel is a standalone binary, and of course nobody would be
so stupid as to expose structs containing bitfields as function
arguments in ABI.  (Passing a pointer to such a struct, however
inadvisable, should be unaffected by this change.  perf and various
drivers rely on that.)

So these warnings do more harm than good: turn them off.

We may miss warnings about future ABI drift, but that's too bad.
Future ABI breaks of this class will have to be debugged and fixed
the traditional way unless the compiler evolves finer-grained
diagnostics.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
[sw0312.kim: backport mainline commit ebcc5928c5d9 for gcc 9 build]
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Change-Id: I87cc8594839fc04e1f91dcdfdc92283902230855

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 4bdd244e89d9c8acd365b603c74327b2cc4c5eb4..921d3245d9969a4b775034ab832e76f251062eb0 100644 (file)
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -21,6 +21,7 @@ KBUILD_DEFCONFIG := defconfig
 
 KBUILD_CFLAGS  += -mgeneral-regs-only
 KBUILD_CFLAGS  += -fno-pic
+KBUILD_CFLAGS  += -Wno-psabi
 ifeq ($(CONFIG_CPU_BIG_ENDIAN), y)
 KBUILD_CPPFLAGS        += -mbig-endian
 AS             += -EB