From ffc3a8ef5cce78dd389d6984d037f83891b3b0ef Mon Sep 17 00:00:00 2001 From: Sedat Dilek Date: Sun, 19 Jun 2016 12:04:52 +0200 Subject: [PATCH] x86/hweight: Get rid of the special calling convention From: Borislav Petkov People complained about ARCH_HWEIGHT_CFLAGS and how it throws a wrench into kcov, lto, etc, experimentations. Add asm versions for __sw_hweight{32,64}() and do explicit saving and restoring of clobbered registers. This gets rid of the special calling convention. We get to call those functions on !X86_FEATURE_POPCNT CPUs. We still need to hardcode POPCNT and register operands as some old gas versions which we support, do not know about POPCNT. Btw, remove redundant REX prefix from 32-bit POPCNT because alternatives can do padding now. Suggested-by: H. Peter Anvin Signed-off-by: Borislav Petkov Acked-by: Peter Zijlstra (Intel) Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1464605787-20603-1-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar [ Backport to Linux v4.4.0 LTS ] Signed-off-by: Sedat Dilek --- arch/x86/Kconfig | 5 --- arch/x86/include/asm/arch_hweight.h | 24 +++++------- arch/x86/kernel/i386_ksyms_32.c | 2 + arch/x86/kernel/x8664_ksyms_64.c | 3 ++ arch/x86/lib/Makefile | 2 +- arch/x86/lib/hweight.S | 77 +++++++++++++++++++++++++++++++++++++ lib/Makefile | 4 -- lib/hweight.c | 4 ++ 8 files changed, 97 insertions(+), 24 deletions(-) create mode 100644 arch/x86/lib/hweight.S diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index db3622f22b61..16f1eac1af96 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -278,11 +278,6 @@ config X86_32_LAZY_GS def_bool y depends on X86_32 && !CC_STACKPROTECTOR -config ARCH_HWEIGHT_CFLAGS - string - default "-fcall-saved-ecx -fcall-saved-edx" if X86_32 - default "-fcall-saved-rdi -fcall-saved-rsi -fcall-saved-rdx -fcall-saved-rcx -fcall-saved-r8 -fcall-saved-r9 -fcall-saved-r10 -fcall-saved-r11" if X86_64 - config ARCH_SUPPORTS_UPROBES def_bool y diff --git a/arch/x86/include/asm/arch_hweight.h b/arch/x86/include/asm/arch_hweight.h index 259a7c1ef709..44f825c80ed5 100644 --- a/arch/x86/include/asm/arch_hweight.h +++ b/arch/x86/include/asm/arch_hweight.h @@ -2,8 +2,8 @@ #define _ASM_X86_HWEIGHT_H #ifdef CONFIG_64BIT -/* popcnt %edi, %eax -- redundant REX prefix for alignment */ -#define POPCNT32 ".byte 0xf3,0x40,0x0f,0xb8,0xc7" +/* popcnt %edi, %eax */ +#define POPCNT32 ".byte 0xf3,0x0f,0xb8,0xc7" /* popcnt %rdi, %rax */ #define POPCNT64 ".byte 0xf3,0x48,0x0f,0xb8,0xc7" #define REG_IN "D" @@ -15,19 +15,15 @@ #define REG_OUT "a" #endif -/* - * __sw_hweightXX are called from within the alternatives below - * and callee-clobbered registers need to be taken care of. See - * ARCH_HWEIGHT_CFLAGS in for the respective - * compiler switches. - */ +#define __HAVE_ARCH_SW_HWEIGHT + static __always_inline unsigned int __arch_hweight32(unsigned int w) { - unsigned int res = 0; + unsigned int res; asm (ALTERNATIVE("call __sw_hweight32", POPCNT32, X86_FEATURE_POPCNT) - : "="REG_OUT (res) - : REG_IN (w)); + : "="REG_OUT (res) + : REG_IN (w)); return res; } @@ -51,11 +47,11 @@ static inline unsigned long __arch_hweight64(__u64 w) #else static __always_inline unsigned long __arch_hweight64(__u64 w) { - unsigned long res = 0; + unsigned long res; asm (ALTERNATIVE("call __sw_hweight64", POPCNT64, X86_FEATURE_POPCNT) - : "="REG_OUT (res) - : REG_IN (w)); + : "="REG_OUT (res) + : REG_IN (w)); return res; } diff --git a/arch/x86/kernel/i386_ksyms_32.c b/arch/x86/kernel/i386_ksyms_32.c index 64341aa485ae..d40ee8a38fed 100644 --- a/arch/x86/kernel/i386_ksyms_32.c +++ b/arch/x86/kernel/i386_ksyms_32.c @@ -42,3 +42,5 @@ EXPORT_SYMBOL(empty_zero_page); EXPORT_SYMBOL(___preempt_schedule); EXPORT_SYMBOL(___preempt_schedule_notrace); #endif + +EXPORT_SYMBOL(__sw_hweight32); diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c index a0695be19864..c7efd394c42b 100644 --- a/arch/x86/kernel/x8664_ksyms_64.c +++ b/arch/x86/kernel/x8664_ksyms_64.c @@ -42,6 +42,9 @@ EXPORT_SYMBOL(clear_page); EXPORT_SYMBOL(csum_partial); +EXPORT_SYMBOL(__sw_hweight32); +EXPORT_SYMBOL(__sw_hweight64); + /* * Export string functions. We normally rely on gcc builtin for most of these, * but gcc sometimes decides not to inline them. diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile index f2587888d987..db4a1c6ea785 100644 --- a/arch/x86/lib/Makefile +++ b/arch/x86/lib/Makefile @@ -22,7 +22,7 @@ lib-y += memcpy_$(BITS).o lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o lib-$(CONFIG_INSTRUCTION_DECODER) += insn.o inat.o -obj-y += msr.o msr-reg.o msr-reg-export.o +obj-y += msr.o msr-reg.o msr-reg-export.o hweight.o ifeq ($(CONFIG_X86_32),y) obj-y += atomic64_32.o diff --git a/arch/x86/lib/hweight.S b/arch/x86/lib/hweight.S new file mode 100644 index 000000000000..02de3d74d2c5 --- /dev/null +++ b/arch/x86/lib/hweight.S @@ -0,0 +1,77 @@ +#include + +#include + +/* + * unsigned int __sw_hweight32(unsigned int w) + * %rdi: w + */ +ENTRY(__sw_hweight32) + +#ifdef CONFIG_X86_64 + movl %edi, %eax # w +#endif + __ASM_SIZE(push,) %__ASM_REG(dx) + movl %eax, %edx # w -> t + shrl %edx # t >>= 1 + andl $0x55555555, %edx # t &= 0x55555555 + subl %edx, %eax # w -= t + + movl %eax, %edx # w -> t + shrl $2, %eax # w_tmp >>= 2 + andl $0x33333333, %edx # t &= 0x33333333 + andl $0x33333333, %eax # w_tmp &= 0x33333333 + addl %edx, %eax # w = w_tmp + t + + movl %eax, %edx # w -> t + shrl $4, %edx # t >>= 4 + addl %edx, %eax # w_tmp += t + andl $0x0f0f0f0f, %eax # w_tmp &= 0x0f0f0f0f + imull $0x01010101, %eax, %eax # w_tmp *= 0x01010101 + shrl $24, %eax # w = w_tmp >> 24 + __ASM_SIZE(pop,) %__ASM_REG(dx) + ret +ENDPROC(__sw_hweight32) + +ENTRY(__sw_hweight64) +#ifdef CONFIG_X86_64 + pushq %rdx + + movq %rdi, %rdx # w -> t + movabsq $0x5555555555555555, %rax + shrq %rdx # t >>= 1 + andq %rdx, %rax # t &= 0x5555555555555555 + movabsq $0x3333333333333333, %rdx + subq %rax, %rdi # w -= t + + movq %rdi, %rax # w -> t + shrq $2, %rdi # w_tmp >>= 2 + andq %rdx, %rax # t &= 0x3333333333333333 + andq %rdi, %rdx # w_tmp &= 0x3333333333333333 + addq %rdx, %rax # w = w_tmp + t + + movq %rax, %rdx # w -> t + shrq $4, %rdx # t >>= 4 + addq %rdx, %rax # w_tmp += t + movabsq $0x0f0f0f0f0f0f0f0f, %rdx + andq %rdx, %rax # w_tmp &= 0x0f0f0f0f0f0f0f0f + movabsq $0x0101010101010101, %rdx + imulq %rdx, %rax # w_tmp *= 0x0101010101010101 + shrq $56, %rax # w = w_tmp >> 56 + + popq %rdx + ret +#else /* CONFIG_X86_32 */ + /* We're getting an u64 arg in (%eax,%edx): unsigned long hweight64(__u64 w) */ + pushl %ecx + + call __sw_hweight32 + movl %eax, %ecx # stash away result + movl %edx, %eax # second part of input + call __sw_hweight32 + addl %ecx, %eax # result + + popl %ecx + ret +#endif +ENDPROC(__sw_hweight64) diff --git a/lib/Makefile b/lib/Makefile index 7f1de26613d2..e61159ec4b03 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -58,10 +58,6 @@ obj-$(CONFIG_HAS_IOMEM) += iomap_copy.o devres.o obj-$(CONFIG_CHECK_SIGNATURE) += check_signature.o obj-$(CONFIG_DEBUG_LOCKING_API_SELFTESTS) += locking-selftest.o -GCOV_PROFILE_hweight.o := n -CFLAGS_hweight.o = $(subst $(quote),,$(CONFIG_ARCH_HWEIGHT_CFLAGS)) -obj-$(CONFIG_GENERIC_HWEIGHT) += hweight.o - obj-$(CONFIG_BTREE) += btree.o obj-$(CONFIG_INTERVAL_TREE) += interval_tree.o obj-$(CONFIG_ASSOCIATIVE_ARRAY) += assoc_array.o diff --git a/lib/hweight.c b/lib/hweight.c index 9a5c1f221558..43273a7d83cf 100644 --- a/lib/hweight.c +++ b/lib/hweight.c @@ -9,6 +9,7 @@ * The Hamming Weight of a number is the total number of bits set in it. */ +#ifndef __HAVE_ARCH_SW_HWEIGHT unsigned int __sw_hweight32(unsigned int w) { #ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER @@ -25,6 +26,7 @@ unsigned int __sw_hweight32(unsigned int w) #endif } EXPORT_SYMBOL(__sw_hweight32); +#endif unsigned int __sw_hweight16(unsigned int w) { @@ -43,6 +45,7 @@ unsigned int __sw_hweight8(unsigned int w) } EXPORT_SYMBOL(__sw_hweight8); +#ifndef __HAVE_ARCH_SW_HWEIGHT unsigned long __sw_hweight64(__u64 w) { #if BITS_PER_LONG == 32 @@ -65,3 +68,4 @@ unsigned long __sw_hweight64(__u64 w) #endif } EXPORT_SYMBOL(__sw_hweight64); +#endif -- 2.9.0