diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index 785d191..60cf980 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -305,6 +305,8 @@
 void _exit|_Exit:exit_group(int)  all
 void __exit:exit(int)  all
 
+int futex(void*, int, int, void*, void*, int)  all
+
 int inotify_init1(int)  all
 int inotify_add_watch(int, const char*, unsigned int)  all
 int inotify_rm_watch(int, unsigned int)  all
diff --git a/libc/arch-arm/arm.mk b/libc/arch-arm/arm.mk
index c509b83..3821854 100644
--- a/libc/arch-arm/arm.mk
+++ b/libc/arch-arm/arm.mk
@@ -53,6 +53,7 @@
     arch-arm/bionic/__bionic_clone.S \
     arch-arm/bionic/eabi.c \
     arch-arm/bionic/_exit_with_stack_teardown.S \
+    arch-arm/bionic/futex_arm.S \
     arch-arm/bionic/__get_sp.S \
     arch-arm/bionic/libgcc_compat.c \
     arch-arm/bionic/memcmp16.S \
diff --git a/libc/arch-arm/bionic/futex_arm.S b/libc/arch-arm/bionic/futex_arm.S
new file mode 100644
index 0000000..89a1e96
--- /dev/null
+++ b/libc/arch-arm/bionic/futex_arm.S
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <private/bionic_asm.h>
+
+// int __futex_syscall4(volatile void* ftx, int op, int val, const struct timespec* timeout)
+ENTRY_PRIVATE(__futex_syscall4)
+    mov     ip, r7
+    ldr     r7, =__NR_futex
+    swi     #0
+    mov     r7, ip
+    bx      lr
+END(__futex_syscall4)
diff --git a/libc/arch-arm/syscalls/futex.S b/libc/arch-arm/syscalls/futex.S
new file mode 100644
index 0000000..1646ca2
--- /dev/null
+++ b/libc/arch-arm/syscalls/futex.S
@@ -0,0 +1,22 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <private/bionic_asm.h>
+
+ENTRY(futex)
+    mov     ip, sp
+    stmfd   sp!, {r4, r5, r6, r7}
+    .cfi_def_cfa_offset 16
+    .cfi_rel_offset r4, 0
+    .cfi_rel_offset r5, 4
+    .cfi_rel_offset r6, 8
+    .cfi_rel_offset r7, 12
+    ldmfd   ip, {r4, r5, r6}
+    ldr     r7, =__NR_futex
+    swi     #0
+    ldmfd   sp!, {r4, r5, r6, r7}
+    .cfi_def_cfa_offset 0
+    cmn     r0, #(MAX_ERRNO + 1)
+    bxls    lr
+    neg     r0, r0
+    b       __set_errno
+END(futex)
diff --git a/libc/arch-arm64/arm64.mk b/libc/arch-arm64/arm64.mk
index 93b0b0b..7a9eb4e 100644
--- a/libc/arch-arm64/arm64.mk
+++ b/libc/arch-arm64/arm64.mk
@@ -37,6 +37,7 @@
     arch-arm64/bionic/__bionic_clone.S \
     arch-arm64/bionic/bzero_arm64.c \
     arch-arm64/bionic/_exit_with_stack_teardown.S \
+    arch-arm64/bionic/futex_arm64.S \
     arch-arm64/bionic/__get_sp.S \
     arch-arm64/bionic/__rt_sigreturn.S \
     arch-arm64/bionic/_setjmp.S \
diff --git a/libc/arch-arm64/bionic/futex_arm64.S b/libc/arch-arm64/bionic/futex_arm64.S
new file mode 100644
index 0000000..9d7465a
--- /dev/null
+++ b/libc/arch-arm64/bionic/futex_arm64.S
@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <private/bionic_asm.h>
+
+// int __futex_syscall4(volatile void* ftx, int op, int val, const struct timespec* timeout)
+ENTRY_PRIVATE(__futex_syscall4)
+  stp x29, x30, [sp, #-16]!
+  .cfi_def_cfa_offset 16
+  .cfi_rel_offset x29, 0
+  .cfi_rel_offset x30, 8
+  mov x29, sp
+
+  mov x8, __NR_futex
+  svc #0
+
+  ldp x29, x30, [sp], #16
+  .cfi_def_cfa_offset 0
+  .cfi_restore x29
+  .cfi_restore x30
+  ret
+END(__futex_syscall4)
diff --git a/libc/arch-arm64/syscalls/futex.S b/libc/arch-arm64/syscalls/futex.S
new file mode 100644
index 0000000..c14ebbf
--- /dev/null
+++ b/libc/arch-arm64/syscalls/futex.S
@@ -0,0 +1,25 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <private/bionic_asm.h>
+
+ENTRY(futex)
+    stp     x29, x30, [sp, #-16]!
+    .cfi_def_cfa_offset 16
+    .cfi_rel_offset x29, 0
+    .cfi_rel_offset x30, 8
+    mov     x29,  sp
+
+    mov     x8, __NR_futex
+    svc     #0
+
+    ldp     x29, x30, [sp], #16
+    .cfi_def_cfa_offset 0
+    .cfi_restore x29
+    .cfi_restore x30
+
+    cmn     x0, #(MAX_ERRNO + 1)
+    cneg    x0, x0, hi
+    b.hi    __set_errno
+
+    ret
+END(futex)
diff --git a/libc/arch-mips/bionic/futex_mips.S b/libc/arch-mips/bionic/futex_mips.S
new file mode 100644
index 0000000..5a09f32
--- /dev/null
+++ b/libc/arch-mips/bionic/futex_mips.S
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <private/bionic_asm.h>
+
+// int __futex_syscall4(volatile void* ftx, int op, int val, const struct timespec* timeout)
+ENTRY_PRIVATE(__futex_syscall4)
+	subu	sp,4*6
+	sw	$0,20(sp)	/* val3 */
+	sw	$0,16(sp)	/* addr2 */
+#	move	a3,a3		/* timespec */
+#	move	a2,a2		/* val */
+#	li	a1,a1		/* op */
+#	move	a0,a0		/* ftx */
+	li	v0,__NR_futex
+	syscall
+	.set noreorder
+	bnez	a3, 1f		/* Check for error */
+         neg	v0		/* Negate error number if it's valid */
+	move	v0,$0		/* Otherwise return 0 */
+1:
+	.set reorder
+	addu	sp,4*6
+	j	ra
+END(__futex_syscall4)
diff --git a/libc/arch-mips/mips.mk b/libc/arch-mips/mips.mk
index 2c87a9e..d7d1df4 100644
--- a/libc/arch-mips/mips.mk
+++ b/libc/arch-mips/mips.mk
@@ -58,6 +58,7 @@
     arch-mips/bionic/bzero.S \
     arch-mips/bionic/cacheflush.cpp \
     arch-mips/bionic/_exit_with_stack_teardown.S \
+    arch-mips/bionic/futex_mips.S \
     arch-mips/bionic/__get_sp.S \
     arch-mips/bionic/memcmp16.S \
     arch-mips/bionic/_setjmp.S \
diff --git a/libc/arch-mips/syscalls/futex.S b/libc/arch-mips/syscalls/futex.S
new file mode 100644
index 0000000..a865fea
--- /dev/null
+++ b/libc/arch-mips/syscalls/futex.S
@@ -0,0 +1,19 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <private/bionic_asm.h>
+
+ENTRY(futex)
+    .set noreorder
+    .cpload t9
+    li v0, __NR_futex
+    syscall
+    bnez a3, 1f
+    move a0, v0
+    j ra
+    nop
+1:
+    la t9,__set_errno
+    j t9
+    nop
+    .set reorder
+END(futex)
diff --git a/libc/arch-mips64/bionic/futex_mips.S b/libc/arch-mips64/bionic/futex_mips.S
new file mode 100644
index 0000000..60c218c
--- /dev/null
+++ b/libc/arch-mips64/bionic/futex_mips.S
@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <private/bionic_asm.h>
+
+#if (_MIPS_SIM == _ABIO32) || (_MIPS_SIM == _ABI32)
+FRAMESZ		=	MKFSIZ(NARGSAVE+2,0)
+FRAME_A4	=	4*REGSZ
+FRAME_A5	=	5*REGSZ
+#else
+FRAMESZ		=	0
+#endif
+
+// int __futex_syscall4(volatile void* ftx, int op, int val, const struct timespec* timeout)
+LEAF(__futex_syscall4,FRAMESZ)
+#if (_MIPS_SIM == _ABIO32) || (_MIPS_SIM == _ABI32)
+	PTR_SUBU sp, FRAMESZ
+	REG_S	$0,FRAME_A5(sp)	/* val3 */
+	REG_S	$0,FRAME_A4(sp)	/* addr2 */
+#else
+	move	a5,$0		/* val3 */
+	move	a4,$0		/* addr2 */
+#endif
+#	move	a3,a3		/* timespec */
+#	move	a2,a2		/* val */
+#	move	a1,a1		/* op */
+#	move	a0,a0		/* ftx */
+	LI	v0,__NR_futex
+	syscall
+	neg	v0		/* Negate errno */
+	bnez	a3,1f		/* Check for error */
+	move	v0,$0		/* Return 0 if no error */
+1:
+#if (_MIPS_SIM == _ABIO32) || (_MIPS_SIM == _ABI32)
+	PTR_ADDU sp,FRAMESZ
+#endif
+	j	ra
+	END(__futex_syscall4)
+.hidden __futex_syscall4
diff --git a/libc/arch-mips64/mips64.mk b/libc/arch-mips64/mips64.mk
index 26390a6..b6e0209 100644
--- a/libc/arch-mips64/mips64.mk
+++ b/libc/arch-mips64/mips64.mk
@@ -43,6 +43,7 @@
     arch-mips64/bionic/__bionic_clone.S \
     arch-mips64/bionic/bzero.S \
     arch-mips64/bionic/_exit_with_stack_teardown.S \
+    arch-mips64/bionic/futex_mips.S \
     arch-mips64/bionic/__get_sp.S \
     arch-mips64/bionic/getdents.cpp \
     arch-mips64/bionic/memcmp16.S \
diff --git a/libc/arch-mips64/syscalls/futex.S b/libc/arch-mips64/syscalls/futex.S
new file mode 100644
index 0000000..dc7dcc6
--- /dev/null
+++ b/libc/arch-mips64/syscalls/futex.S
@@ -0,0 +1,25 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <private/bionic_asm.h>
+
+ENTRY(futex)
+    .set push
+    .set noreorder
+    li v0, __NR_futex
+    syscall
+    bnez a3, 1f
+    move a0, v0
+    j ra
+    nop
+1:
+    move t0, ra
+    bal     2f
+    nop
+2:
+    .cpsetup ra, t1, 2b
+    LA t9,__set_errno
+    .cpreturn
+    j t9
+    move ra, t0
+    .set pop
+END(futex)
diff --git a/libc/arch-x86/bionic/futex_x86.S b/libc/arch-x86/bionic/futex_x86.S
new file mode 100644
index 0000000..94647ca
--- /dev/null
+++ b/libc/arch-x86/bionic/futex_x86.S
@@ -0,0 +1,16 @@
+#include <private/bionic_asm.h>
+
+// int __futex_syscall4(volatile void* ftx, int op, int val, const struct timespec* timeout)
+ENTRY_PRIVATE(__futex_syscall4)
+    pushl   %ebx
+    pushl   %esi
+    movl    12(%esp), %ebx      /* ftx */
+    movl    16(%esp), %ecx      /* op */
+    movl    20(%esp), %edx      /* val */
+    movl    24(%esp), %esi      /* timeout */
+    movl    $__NR_futex, %eax
+    int     $0x80
+    popl    %esi
+    popl    %ebx
+    ret
+END(__futex_syscall4)
diff --git a/libc/arch-x86/syscalls/futex.S b/libc/arch-x86/syscalls/futex.S
new file mode 100644
index 0000000..7a52913
--- /dev/null
+++ b/libc/arch-x86/syscalls/futex.S
@@ -0,0 +1,42 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <private/bionic_asm.h>
+
+ENTRY(futex)
+    pushl   %ebx
+    pushl   %ecx
+    pushl   %edx
+    pushl   %esi
+    pushl   %edi
+    pushl   %ebp
+    .cfi_def_cfa_offset 24
+    .cfi_rel_offset ebx, 0
+    .cfi_rel_offset ecx, 4
+    .cfi_rel_offset edx, 8
+    .cfi_rel_offset esi, 12
+    .cfi_rel_offset edi, 16
+    .cfi_rel_offset ebp, 20
+    mov     28(%esp), %ebx
+    mov     32(%esp), %ecx
+    mov     36(%esp), %edx
+    mov     40(%esp), %esi
+    mov     44(%esp), %edi
+    mov     48(%esp), %ebp
+    movl    $__NR_futex, %eax
+    int     $0x80
+    cmpl    $-MAX_ERRNO, %eax
+    jb      1f
+    negl    %eax
+    pushl   %eax
+    call    __set_errno
+    addl    $4, %esp
+    orl     $-1, %eax
+1:
+    popl    %ebp
+    popl    %edi
+    popl    %esi
+    popl    %edx
+    popl    %ecx
+    popl    %ebx
+    ret
+END(futex)
diff --git a/libc/arch-x86/x86.mk b/libc/arch-x86/x86.mk
index aa183cb..34da0ce 100644
--- a/libc/arch-x86/x86.mk
+++ b/libc/arch-x86/x86.mk
@@ -23,6 +23,7 @@
 libc_bionic_src_files_x86 += \
     arch-x86/bionic/__bionic_clone.S \
     arch-x86/bionic/_exit_with_stack_teardown.S \
+    arch-x86/bionic/futex_x86.S \
     arch-x86/bionic/__get_sp.S \
     arch-x86/bionic/_setjmp.S \
     arch-x86/bionic/setjmp.S \
diff --git a/libc/arch-x86_64/bionic/futex_x86_64.S b/libc/arch-x86_64/bionic/futex_x86_64.S
new file mode 100644
index 0000000..c248439
--- /dev/null
+++ b/libc/arch-x86_64/bionic/futex_x86_64.S
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <private/bionic_asm.h>
+
+// int __futex_syscall4(volatile void* ftx, int op, int val, const struct timespec* timeout)
+ENTRY_PRIVATE(__futex_syscall4)
+    mov     %rcx, %r10      /* timeout */
+    mov     $__NR_futex, %eax
+    syscall
+    ret
+END(__futex_syscall4)
diff --git a/libc/arch-x86_64/syscalls/futex.S b/libc/arch-x86_64/syscalls/futex.S
new file mode 100644
index 0000000..62f64bd
--- /dev/null
+++ b/libc/arch-x86_64/syscalls/futex.S
@@ -0,0 +1,17 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <private/bionic_asm.h>
+
+ENTRY(futex)
+    movq    %rcx, %r10
+    movl    $__NR_futex, %eax
+    syscall
+    cmpq    $-MAX_ERRNO, %rax
+    jb      1f
+    negl    %eax
+    movl    %eax, %edi
+    call    __set_errno
+    orq     $-1, %rax
+1:
+    ret
+END(futex)
diff --git a/libc/arch-x86_64/x86_64.mk b/libc/arch-x86_64/x86_64.mk
index e3c2562..2bcf432 100644
--- a/libc/arch-x86_64/x86_64.mk
+++ b/libc/arch-x86_64/x86_64.mk
@@ -30,6 +30,7 @@
 libc_bionic_src_files_x86_64 := \
     arch-x86_64/bionic/__bionic_clone.S \
     arch-x86_64/bionic/_exit_with_stack_teardown.S \
+    arch-x86_64/bionic/futex_x86_64.S \
     arch-x86_64/bionic/__get_sp.S \
     arch-x86_64/bionic/__rt_sigreturn.S \
     arch-x86_64/bionic/_setjmp.S \
diff --git a/libc/private/bionic_futex.h b/libc/private/bionic_futex.h
index dd277ed..11699ce 100644
--- a/libc/private/bionic_futex.h
+++ b/libc/private/bionic_futex.h
@@ -28,42 +28,31 @@
 #ifndef _BIONIC_FUTEX_H
 #define _BIONIC_FUTEX_H
 
-#include <errno.h>
 #include <linux/futex.h>
+#include <sys/cdefs.h>
 #include <stdbool.h>
 #include <stddef.h>
-#include <sys/cdefs.h>
-#include <sys/syscall.h>
 
 __BEGIN_DECLS
 
 struct timespec;
 
-static inline int __futex(volatile void* ftx, int op, int value, const struct timespec* timeout) {
-  // Our generated syscall assembler sets errno, but our callers (pthread functions) don't want to.
-  int saved_errno = errno;
-  if (syscall(__NR_futex, ftx, op, value, timeout) == 0) {
-    return 0;
-  }
-  int result = -errno;
-  errno = saved_errno;
-  return result;
-}
+extern int __futex_syscall4(volatile void* ftx, int op, int value, const struct timespec* timeout);
 
 static inline int __futex_wake(volatile void* ftx, int count) {
-  return __futex(ftx, FUTEX_WAKE, count, NULL);
+  return __futex_syscall4(ftx, FUTEX_WAKE, count, NULL);
 }
 
 static inline int __futex_wake_ex(volatile void* ftx, bool shared, int count) {
-  return __futex(ftx, shared ? FUTEX_WAKE : FUTEX_WAKE_PRIVATE, count, NULL);
+  return __futex_syscall4(ftx, shared ? FUTEX_WAKE : FUTEX_WAKE_PRIVATE, count, NULL);
 }
 
 static inline int __futex_wait(volatile void* ftx, int value, const struct timespec* timeout) {
-  return __futex(ftx, FUTEX_WAIT, value, timeout);
+  return __futex_syscall4(ftx, FUTEX_WAIT, value, timeout);
 }
 
 static inline int __futex_wait_ex(volatile void* ftx, bool shared, int value, const struct timespec* timeout) {
-  return __futex(ftx, shared ? FUTEX_WAIT : FUTEX_WAIT_PRIVATE, value, timeout);
+  return __futex_syscall4(ftx, shared ? FUTEX_WAIT : FUTEX_WAIT_PRIVATE, value, timeout);
 }
 
 __END_DECLS