Commit d49a0626 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

arch: Introduce CONFIG_FUNCTION_ALIGNMENT 



Generic function-alignment infrastructure.

Architectures can select FUNCTION_ALIGNMENT_xxB symbols; the
FUNCTION_ALIGNMENT symbol is then set to the largest such selected
size, 0 otherwise.

From this the -falign-functions compiler argument and __ALIGN macro
are set.

This incorporates the DEBUG_FORCE_FUNCTION_ALIGN_64B knob and future
alignment requirements for x86_64 (later in this series) into a single
place.

NOTE: also removes the 0x90 filler byte from the generic __ALIGN
      primitive, that value makes no sense outside of x86.

NOTE: .balign 0 reverts to a no-op.

Requested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111143.719248727@infradead.org
parent 24a9c543

Makefile

+2 −2
Original line number Diff line number Diff line
@@ -1004,8 +1004,8 @@ KBUILD_CFLAGS += $(CC_FLAGS_CFI) 
export CC_FLAGS_CFI

endif



ifdef CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_64B

KBUILD_CFLAGS += -falign-functions=64

ifneq ($(CONFIG_FUNCTION_ALIGNMENT),0)

KBUILD_CFLAGS += -falign-functions=$(CONFIG_FUNCTION_ALIGNMENT)

endif



# arch Makefile may override CC so keep this after arch Makefile is included

arch/Kconfig

+24 −0
Original line number Diff line number Diff line
@@ -1428,4 +1428,28 @@ source "kernel/gcov/Kconfig" 


source "scripts/gcc-plugins/Kconfig"



config FUNCTION_ALIGNMENT_4B

	bool



config FUNCTION_ALIGNMENT_8B

	bool



config FUNCTION_ALIGNMENT_16B

	bool



config FUNCTION_ALIGNMENT_32B

	bool



config FUNCTION_ALIGNMENT_64B

	bool



config FUNCTION_ALIGNMENT

	int

	default 64 if FUNCTION_ALIGNMENT_64B

	default 32 if FUNCTION_ALIGNMENT_32B

	default 16 if FUNCTION_ALIGNMENT_16B

	default 8 if FUNCTION_ALIGNMENT_8B

	default 4 if FUNCTION_ALIGNMENT_4B

	default 0



endmenu

arch/ia64/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -63,6 +63,7 @@ config IA64 
	select NUMA if !FLATMEM

	select PCI_MSI_ARCH_FALLBACKS if PCI_MSI

	select ZONE_DMA32

	select FUNCTION_ALIGNMENT_32B

	default y

	help

	  The Itanium Processor Family is Intel's 64-bit successor to

arch/ia64/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -23,7 +23,7 @@ KBUILD_AFLAGS_KERNEL := -mconstant-gp 
EXTRA		:=



cflags-y	:= -pipe $(EXTRA) -ffixed-r13 -mfixed-range=f12-f15,f32-f127 \

		   -falign-functions=32 -frename-registers -fno-optimize-sibling-calls

		   -frename-registers -fno-optimize-sibling-calls

KBUILD_CFLAGS_KERNEL := -mconstant-gp



GAS_STATUS	= $(shell $(srctree)/arch/ia64/scripts/check-gas "$(CC)" "$(OBJDUMP)")

arch/x86/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -290,6 +290,8 @@ config X86 
	select X86_FEATURE_NAMES		if PROC_FS

	select PROC_PID_ARCH_STATUS		if PROC_FS

	select HAVE_ARCH_NODE_DEV_GROUP		if X86_SGX

	select FUNCTION_ALIGNMENT_16B		if X86_64 || X86_ALIGNMENT_16

	select FUNCTION_ALIGNMENT_4B

	imply IMA_SECURE_AND_OR_TRUSTED_BOOT    if EFI

	select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE