From: Peter Zijlstra peterz@infradead.org
commit d49a0626216b95cd4bf696f6acf55f39a16ab0bb upstream.
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: Linus Torvalds torvalds@linux-foundation.org Change-Id: I053b3c408d56988381feb8c8bdb5e27ea221755f Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lore.kernel.org/r/20220915111143.719248727@infradead.org [cascardo: adjust context at arch/x86/Kconfig] Signed-off-by: Thadeu Lima de Souza Cascardo cascardo@igalia.com --- Makefile | 4 ++-- arch/Kconfig | 24 ++++++++++++++++++++++++ arch/ia64/Kconfig | 1 + arch/ia64/Makefile | 2 +- arch/x86/Kconfig | 2 ++ arch/x86/boot/compressed/head_64.S | 8 ++++++++ arch/x86/include/asm/linkage.h | 4 +--- include/asm-generic/vmlinux.lds.h | 4 ++-- include/linux/linkage.h | 4 ++-- lib/Kconfig.debug | 1 + 10 files changed, 44 insertions(+), 10 deletions(-)
diff --git a/Makefile b/Makefile index bb73dba0e505..16f3838838d0 100644 --- a/Makefile +++ b/Makefile @@ -1000,8 +1000,8 @@ 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 diff --git a/arch/Kconfig b/arch/Kconfig index 2e2dc0975ab4..a541ce263865 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -1303,4 +1303,28 @@ 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 diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig index 89869aff8ca2..8902d1517894 100644 --- a/arch/ia64/Kconfig +++ b/arch/ia64/Kconfig @@ -63,6 +63,7 @@ config IA64 select PCI_MSI_ARCH_FALLBACKS if PCI_MSI select SET_FS select ZONE_DMA32 + select FUNCTION_ALIGNMENT_32B default y help The Itanium Processor Family is Intel's 64-bit successor to diff --git a/arch/ia64/Makefile b/arch/ia64/Makefile index 7e548c654a29..43cde968da88 100644 --- a/arch/ia64/Makefile +++ b/arch/ia64/Makefile @@ -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)") diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index cfb1edd25437..65b2cff3c93b 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -267,6 +267,8 @@ config X86 select HAVE_ARCH_KCSAN if X86_64 select X86_FEATURE_NAMES if PROC_FS select PROC_PID_ARCH_STATUS if PROC_FS + select FUNCTION_ALIGNMENT_16B if X86_64 || X86_ALIGNMENT_16 + select FUNCTION_ALIGNMENT_4B imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
config INSTRUCTION_DECODER diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index c3d427c817c7..e189a16ae40a 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -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: */ diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h index 5000cf59bdf5..3d7293d52950 100644 --- a/arch/x86/include/asm/linkage.h +++ b/arch/x86/include/asm/linkage.h @@ -13,10 +13,8 @@
#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 diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 8471717c5085..dd9ea351bc02 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -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 diff --git a/include/linux/linkage.h b/include/linux/linkage.h index dbf8506decca..fc81e51330b2 100644 --- a/include/linux/linkage.h +++ b/include/linux/linkage.h @@ -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__ diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 64d6292cf686..28faea9b5da6 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -424,6 +424,7 @@ 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