4.4-stable review patch. If anyone has any objections, please let me know.
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From: Borislav Petkov bp@suse.de
commit f5967101e9de12addcda4510dfbac66d7c5779c3 upstream.
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 hpa@zytor.com Signed-off-by: Borislav Petkov bp@suse.de Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: Andy Lutomirski luto@amacapital.net Cc: Borislav Petkov bp@alien8.de Cc: Brian Gerst brgerst@gmail.com Cc: Denys Vlasenko dvlasenk@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Link: http://lkml.kernel.org/r/1464605787-20603-1-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Matthias Kaehlcke mka@chromium.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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 | 2 lib/hweight.c | 4 + 8 files changed, 97 insertions(+), 22 deletions(-)
--- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -280,11 +280,6 @@ 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
--- 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 <arch/x86/Kconfig> 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_hweig #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; } --- 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); --- 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. --- a/arch/x86/lib/Makefile +++ b/arch/x86/lib/Makefile @@ -23,7 +23,7 @@ lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += lib-$(CONFIG_INSTRUCTION_DECODER) += insn.o inat.o lib-$(CONFIG_RETPOLINE) += retpoline.o
-obj-y += msr.o msr-reg.o msr-reg-export.o +obj-y += msr.o msr-reg.o msr-reg-export.o hweight.o
ifeq ($(CONFIG_X86_32),y) obj-y += atomic64_32.o --- /dev/null +++ b/arch/x86/lib/hweight.S @@ -0,0 +1,77 @@ +#include <linux/linkage.h> + +#include <asm/asm.h> + +/* + * 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 $56, %rax # w = w_tmp >> 56 + + popq %rdx + ret +#else /* CONFIG_X86_32 */ + /* We're getting an u64 arg in (%eax,%edx): unsigned long hweight64(__u64 w) */ + pushl %ecx + + call __sw_hweight32 + movl %eax, %ecx # stash away result + movl %edx, %eax # second part of input + call __sw_hweight32 + addl %ecx, %eax # result + + popl %ecx + ret +#endif +ENDPROC(__sw_hweight64) --- a/lib/Makefile +++ b/lib/Makefile @@ -58,8 +58,6 @@ obj-$(CONFIG_HAS_IOMEM) += iomap_copy.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 --- 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 #endif } EXPORT_SYMBOL(__sw_hweight32); +#endif
unsigned int __sw_hweight16(unsigned int w) { @@ -43,6 +45,7 @@ unsigned int __sw_hweight8(unsigned int } 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