Commit d49a0626 authored by Peter Zijlstra's avatar Peter Zijlstra

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
......@@ -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
......
......@@ -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
......@@ -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
......
......@@ -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)")
......
......@@ -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
......
......@@ -37,6 +37,14 @@
#include <asm/trapnr.h>
#include "pgtable.h"
/*
* Fix alignment at 16 bytes. Following CONFIG_FUNCTION_ALIGNMENT will result
* in assembly errors due to trying to move .org backward due to the excessive
* alignment.
*/
#undef __ALIGN
#define __ALIGN .balign 16, 0x90
/*
* Locally defined symbols should be marked hidden:
*/
......
......@@ -14,10 +14,8 @@
#ifdef __ASSEMBLY__
#if defined(CONFIG_X86_64) || defined(CONFIG_X86_ALIGNMENT_16)
#define __ALIGN .p2align 4, 0x90
#define __ALIGN .balign CONFIG_FUNCTION_ALIGNMENT, 0x90;
#define __ALIGN_STR __stringify(__ALIGN)
#endif
#if defined(CONFIG_RETHUNK) && !defined(__DISABLE_EXPORTS) && !defined(BUILD_VDSO)
#define RET jmp __x86_return_thunk
......
......@@ -81,8 +81,8 @@
#define RO_EXCEPTION_TABLE
#endif
/* Align . to a 8 byte boundary equals to maximum function alignment. */
#define ALIGN_FUNCTION() . = ALIGN(8)
/* Align . function alignment. */
#define ALIGN_FUNCTION() . = ALIGN(CONFIG_FUNCTION_ALIGNMENT)
/*
* LD_DEAD_CODE_DATA_ELIMINATION option enables -fdata-sections, which
......
......@@ -69,8 +69,8 @@
#endif
#ifndef __ALIGN
#define __ALIGN .align 4,0x90
#define __ALIGN_STR ".align 4,0x90"
#define __ALIGN .balign CONFIG_FUNCTION_ALIGNMENT
#define __ALIGN_STR __stringify(__ALIGN)
#endif
#ifdef __ASSEMBLY__
......
......@@ -467,6 +467,7 @@ config SECTION_MISMATCH_WARN_ONLY
config DEBUG_FORCE_FUNCTION_ALIGN_64B
bool "Force all function address 64B aligned"
depends on EXPERT && (X86_64 || ARM64 || PPC32 || PPC64 || ARC)
select FUNCTION_ALIGNMENT_64B
help
There are cases that a commit from one domain changes the function
address alignment of other domains, and cause magic performance
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment