Add build system scaffolding and libc headers

1 files changed, 101 insertions, 0 deletions

diff --git a/lib/libc/stdlib/free.c b/lib/libc/stdlib/free.c
new file mode 100644
index 00000000..40320dc7
--- /dev/null
+++ b/lib/libc/stdlib/free.c
@@ -0,0 +1,101 @@
+#include <libc.h>
+#include <sys/mman.h>
+#include <atomic.h>
+#include <malloc.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+void free(void *ptr)
+{
+	if (ptr == NULL) {
+		return;
+	}
+
+	LIBC_LOCK(libc.lock.malloc);
+
+	struct page *p = __malloc_pvec;
+	int found_in_pages = 0;
+
+	while (p) {
+		if ((uintptr_t)ptr >= (uintptr_t)p->heap &&
+		    (uintptr_t)ptr < (uintptr_t)(p->heap + (p->block.size *
+							    p->block.count))) {
+			size_t offset = (uintptr_t)ptr - (uintptr_t)p->heap;
+			size_t index = offset / p->block.size;
+			size_t byte_index = index / 8;
+			size_t bit_index = index % 8;
+
+			LIBC_LOCK(p->lock);
+			if (p->bitmap[byte_index] & (1 << bit_index)) {
+				p->bitmap[byte_index] &= ~(1 << bit_index);
+				p->block.used--;
+				found_in_pages = 1;
+			}
+			LIBC_UNLOCK(p->lock);
+
+			if (found_in_pages && p->block.used == 0) {
+				if (p->prev)
+					p->prev->next = p->next;
+				if (p->next)
+					p->next->prev = p->prev;
+				if (p == __malloc_pvec)
+					__malloc_pvec = p->next;
+
+				munmap(p, (p->flags == PAGE_SMALL) ?
+						  SMALL_PAGE_SIZE :
+					  (p->flags == PAGE_MEDIUM) ?
+						  MEDIUM_PAGE_SIZE :
+						  LARGE_PAGE_SIZE);
+			}
+
+			LIBC_UNLOCK(libc.lock.malloc);
+			return;
+		}
+		p = p->next;
+	}
+
+	void **orig_ptr_slot = (void **)((uintptr_t)ptr - sizeof(void *));
+	void *potential_orig = *orig_ptr_slot;
+
+	p = __malloc_pvec;
+	while (p) {
+		if ((uintptr_t)potential_orig >= (uintptr_t)p->heap &&
+		    (uintptr_t)potential_orig <
+			    (uintptr_t)(p->heap +
+					(p->block.size * p->block.count))) {
+			size_t offset =
+				(uintptr_t)potential_orig - (uintptr_t)p->heap;
+			size_t index = offset / p->block.size;
+			size_t byte_index = index / 8;
+			size_t bit_index = index % 8;
+
+			LIBC_LOCK(p->lock);
+			if (p->bitmap[byte_index] & (1 << bit_index)) {
+				p->bitmap[byte_index] &= ~(1 << bit_index);
+				p->block.used--;
+			}
+			LIBC_UNLOCK(p->lock);
+
+			if (p->block.used == 0) {
+				if (p->prev)
+					p->prev->next = p->next;
+				if (p->next)
+					p->next->prev = p->prev;
+				if (p == __malloc_pvec)
+					__malloc_pvec = p->next;
+
+				munmap(p, (p->flags == PAGE_SMALL) ?
+						  SMALL_PAGE_SIZE :
+					  (p->flags == PAGE_MEDIUM) ?
+						  MEDIUM_PAGE_SIZE :
+						  LARGE_PAGE_SIZE);
+			}
+
+			LIBC_UNLOCK(libc.lock.malloc);
+			return;
+		}
+		p = p->next;
+	}
+
+	LIBC_UNLOCK(libc.lock.malloc);
+}