diff --git a/src/sljit/sljitExecAllocator.c b/src/sljit/sljitExecAllocator.c
index 2e1c138..6e5bf78 100644
--- a/src/sljit/sljitExecAllocator.c
+++ b/src/sljit/sljitExecAllocator.c
@@ -166,23 +166,28 @@ static SLJIT_INLINE void apple_update_wx_flags(sljit_s32 enable_exec)
 static SLJIT_INLINE void* alloc_chunk(sljit_uw size)
 {
 	void *retval;
-	const int prot = PROT_READ | PROT_WRITE | PROT_EXEC;
+	int prot = PROT_READ | PROT_WRITE | PROT_EXEC;
+	int flags = MAP_PRIVATE;
+	int fd = -1;
+
+#ifdef PROT_MAX
+	prot |= PROT_MAX(prot);
+#endif
 
 #ifdef MAP_ANON
-	int flags = MAP_PRIVATE | MAP_ANON | SLJIT_MAP_JIT;
-
-	retval = mmap(NULL, size, prot, flags, -1, 0);
+	flags |= MAP_ANON | SLJIT_MAP_JIT;
 #else /* !MAP_ANON */
 	if (SLJIT_UNLIKELY((dev_zero < 0) && open_dev_zero()))
 		return NULL;
 
-	retval = mmap(NULL, size, prot, MAP_PRIVATE, dev_zero, 0);
+	fd = dev_zero;
 #endif /* MAP_ANON */
 
+	retval = mmap(NULL, size, prot, flags, fd, 0);
 	if (retval == MAP_FAILED)
 		return NULL;
 
-	if (mprotect(retval, size, prot) < 0) {
+	if (mprotect(retval, size, PROT_READ | PROT_WRITE | PROT_EXEC) < 0) {
 		munmap(retval, size);
 		return NULL;
 	}
diff --git a/src/sljit/sljitUtils.c b/src/sljit/sljitUtils.c
index 08ca35c..9bce714 100644
--- a/src/sljit/sljitUtils.c
+++ b/src/sljit/sljitUtils.c
@@ -48,7 +48,7 @@ static HANDLE allocator_lock;
 static SLJIT_INLINE void allocator_grab_lock(void)
 {
 	HANDLE lock;
-	if (SLJIT_UNLIKELY(!allocator_lock)) {
+	if (SLJIT_UNLIKELY(!InterlockedCompareExchangePointer(&allocator_lock, NULL, NULL))) {
 		lock = CreateMutex(NULL, FALSE, NULL);
 		if (InterlockedCompareExchangePointer(&allocator_lock, lock, NULL))
 			CloseHandle(lock);
@@ -146,9 +146,13 @@ static SLJIT_INLINE sljit_sw get_page_alignment(void) {
 #include <unistd.h>
 
 static SLJIT_INLINE sljit_sw get_page_alignment(void) {
-	static sljit_sw sljit_page_align;
-	if (!sljit_page_align) {
+	static sljit_sw sljit_page_align = -1;
+	if (sljit_page_align < 0) {
+#ifdef _SC_PAGESIZE
 		sljit_page_align = sysconf(_SC_PAGESIZE);
+#else
+		sljit_page_align = getpagesize();
+#endif
 		/* Should never happen. */
 		if (sljit_page_align < 0)
 			sljit_page_align = 4096;
diff --git a/src/sljit/sljitWXExecAllocator.c b/src/sljit/sljitWXExecAllocator.c
index 6ef71f7..72d5b8d 100644
--- a/src/sljit/sljitWXExecAllocator.c
+++ b/src/sljit/sljitWXExecAllocator.c
@@ -121,14 +121,18 @@ SLJIT_API_FUNC_ATTRIBUTE void* sljit_malloc_exec(sljit_uw size)
 	static pthread_mutex_t se_lock = PTHREAD_MUTEX_INITIALIZER;
 #endif
 	static int se_protected = !SLJIT_PROT_WX;
+	int prot = PROT_READ | PROT_WRITE | SLJIT_PROT_WX;
 	sljit_uw* ptr;
 
 	if (SLJIT_UNLIKELY(se_protected < 0))
 		return NULL;
 
+#ifdef PROT_MAX
+	prot |= PROT_MAX(PROT_READ | PROT_WRITE | PROT_EXEC);
+#endif
+
 	size += sizeof(sljit_uw);
-	ptr = (sljit_uw*)mmap(NULL, size, PROT_READ | PROT_WRITE | SLJIT_PROT_WX,
-				MAP_PRIVATE | MAP_ANON, -1, 0);
+	ptr = (sljit_uw*)mmap(NULL, size, prot, MAP_PRIVATE | MAP_ANON, -1, 0);
 
 	if (ptr == MAP_FAILED)
 		return NULL;