Revert "Revert "Lose the hand-written futex assembler.""

The problem with the original patch was that using syscall(3) means that
errno can be set, but pthread_create(3) was abusing the TLS errno slot as
a pthread_mutex_t for the thread startup handshake.

There was also a mistake in the check for syscall failures --- it should
have checked against -1 instead of 0 (not just because that's the default
idiom, but also here because futex(2) can legitimately return values > 0).

This patch stops abusing the TLS errno slot and adds a pthread_mutex_t to
pthread_internal_t instead. (Note that for LP64 sizeof(pthread_mutex_t) >
sizeof(uintptr_t), so we could potentially clobber other TLS slots too.)

I've also rewritten the LP32 compatibility stubs to directly reuse the
code from the .h file.

This reverts commit 75c55ff84e.

Bug: 15195455
Change-Id: I6ffb13e5cf6a35d8f59f692d94192aae9ab4593d

libc/arch-mips/bionic/futex_mips.S

@@ -1,50 +0,0 @@
-/*
- * 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)

libc/arch-mips/mips.mk

@@ -58,7 +58,6 @@ libc_bionic_src_files_mips += \
     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 \

libc/arch-mips/syscalls/futex.S

@@ -1,19 +0,0 @@
-/* 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)