1 files changed, 118 insertions, 0 deletions
diff --git a/libc-top-half/musl/src/malloc/lite_malloc.c b/libc-top-half/musl/src/malloc/lite_malloc.c
new file mode 100644
index 0000000..43a988f
--- /dev/null
+++ b/libc-top-half/musl/src/malloc/lite_malloc.c
@@ -0,0 +1,118 @@
+#include <stdlib.h>
+#include <stdint.h>
+#include <limits.h>
+#include <errno.h>
+#include <sys/mman.h>
+#include "libc.h"
+#include "lock.h"
+#include "syscall.h"
+#include "fork_impl.h"
+
+#define ALIGN 16
+
+/* This function returns true if the interval [old,new]
+ * intersects the 'len'-sized interval below &libc.auxv
+ * (interpreted as the main-thread stack) or below &b
+ * (the current stack). It is used to defend against
+ * buggy brk implementations that can cross the stack. */
+
+static int traverses_stack_p(uintptr_t old, uintptr_t new)
+{
+	const uintptr_t len = 8<<20;
+	uintptr_t a, b;
+
+	b = (uintptr_t)libc.auxv;
+	a = b > len ? b-len : 0;
+	if (new>a && old<b) return 1;
+
+	b = (uintptr_t)&b;
+	a = b > len ? b-len : 0;
+	if (new>a && old<b) return 1;
+
+	return 0;
+}
+
+static volatile int lock[1];
+volatile int *const __bump_lockptr = lock;
+
+static void *__simple_malloc(size_t n)
+{
+	static uintptr_t brk, cur, end;
+	static unsigned mmap_step;
+	size_t align=1;
+	void *p;
+
+	if (n > SIZE_MAX/2) {
+		errno = ENOMEM;
+		return 0;
+	}
+
+	if (!n) n++;
+	while (align<n && align<ALIGN)
+		align += align;
+
+	LOCK(lock);
+
+	cur += -cur & align-1;
+
+	if (n > end-cur) {
+		size_t req = n - (end-cur) + PAGE_SIZE-1 & -PAGE_SIZE;
+
+		if (!cur) {
+			brk = __syscall(SYS_brk, 0);
+			brk += -brk & PAGE_SIZE-1;
+			cur = end = brk;
+		}
+
+		if (brk == end && req < SIZE_MAX-brk
+		    && !traverses_stack_p(brk, brk+req)
+		    && __syscall(SYS_brk, brk+req)==brk+req) {
+			brk = end += req;
+		} else {
+			int new_area = 0;
+			req = n + PAGE_SIZE-1 & -PAGE_SIZE;
+			/* Only make a new area rather than individual mmap
+			 * if wasted space would be over 1/8 of the map. */
+			if (req-n > req/8) {
+				/* Geometric area size growth up to 64 pages,
+				 * bounding waste by 1/8 of the area. */
+				size_t min = PAGE_SIZE<<(mmap_step/2);
+				if (min-n > end-cur) {
+					if (req < min) {
+						req = min;
+						if (mmap_step < 12)
+							mmap_step++;
+					}
+					new_area = 1;
+				}
+			}
+			void *mem = __mmap(0, req, PROT_READ|PROT_WRITE,
+				MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+			if (mem == MAP_FAILED || !new_area) {
+				UNLOCK(lock);
+				return mem==MAP_FAILED ? 0 : mem;
+			}
+			cur = (uintptr_t)mem;
+			end = cur + req;
+		}
+	}
+
+	p = (void *)cur;
+	cur += n;
+	UNLOCK(lock);
+	return p;
+}
+
+weak_alias(__simple_malloc, __libc_malloc_impl);
+
+void *__libc_malloc(size_t n)
+{
+	return __libc_malloc_impl(n);
+}
+
+static void *default_malloc(size_t n)
+{
+	return __libc_malloc_impl(n);
+}
+
+weak_alias(default_malloc, malloc);