From fc00c656c96528112d05cf0edf8631bd5eaea446 Mon Sep 17 00:00:00 2001
From: Kacper <kacper@mail.openlinux.dev>
Date: Sun, 7 Dec 2025 20:10:31 +0100
Subject: Add build system scaffolding and libc headers

---
 lib/libc/stdlib/malloc.c | 181 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 181 insertions(+)
 create mode 100644 lib/libc/stdlib/malloc.c

(limited to 'lib/libc/stdlib/malloc.c')

diff --git a/lib/libc/stdlib/malloc.c b/lib/libc/stdlib/malloc.c
new file mode 100644
index 00000000..3d29e6a8
--- /dev/null
+++ b/lib/libc/stdlib/malloc.c
@@ -0,0 +1,181 @@
+#include <atomic.h>
+#include <features.h>
+#include <libc.h>
+#include <malloc.h>
+#include <linux/errno.h>
+#include <stdatomic.h>
+#include <stdint.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+struct page *__malloc_pvec = NULL;
+
+static __inline uint32_t get_size_class(size_t size)
+{
+	uintptr_t minblock_count = (size + (16 - 1)) / 16;
+
+	if (size <= (16 * 64)) {
+		return (uint32_t)(minblock_count ? minblock_count : 1);
+	}
+
+	const uint32_t most_significant_bit =
+		(uint32_t)(63 - (int)__builtin_clzll(minblock_count));
+
+	const uint32_t subclass_bits =
+		(minblock_count >> (most_significant_bit - 2)) & 0x03;
+
+	return (uint32_t)((most_significant_bit << 2) + subclass_bits) + 41;
+}
+
+weak void *malloc(size_t size);
+
+void *malloc(size_t size)
+{
+	if (size == 0)
+		return NULL;
+
+	LIBC_LOCK(libc.lock.malloc);
+
+	uint32_t class_index = get_size_class(size);
+	if (class_index >=
+	    sizeof(global_size_class) / sizeof(global_size_class[0])) {
+		LIBC_UNLOCK(libc.lock.malloc);
+		return NULL;
+	}
+	const struct class *cls = &global_size_class[class_index];
+
+	struct page *p = __malloc_pvec;
+	while (p) {
+		if (p->flags == PAGE_SMALL && cls->size <= 16 * 64) {
+			LIBC_LOCK(p->lock);
+			if (p->block.used < p->block.count &&
+			    p->block.size == cls->size) {
+				for (uint32_t i = 0; i < p->block.count; i++) {
+					int byte_index = i / 8;
+					int bit_index = i % 8;
+					if (!(p->bitmap[byte_index] &
+					      (1 << bit_index))) {
+						p->bitmap[byte_index] |=
+							(1 << bit_index);
+						p->block.used++;
+						LIBC_UNLOCK(p->lock);
+						LIBC_UNLOCK(libc.lock.malloc);
+						if (p->heap == NULL)
+							return NULL;
+						return p->heap +
+						       (i * p->block.size);
+					}
+				}
+			}
+			LIBC_UNLOCK(p->lock);
+		} else if (p->flags == PAGE_MEDIUM && cls->size > 16 * 64 &&
+			   cls->size <= 16 * 8192) {
+			LIBC_LOCK(p->lock);
+			if (p->block.used < p->block.count &&
+			    p->block.size == cls->size) {
+				for (uint32_t i = 0; i < p->block.count; i++) {
+					int byte_index = i / 8;
+					int bit_index = i % 8;
+					if (!(p->bitmap[byte_index] &
+					      (1 << bit_index))) {
+						// Mark block as used
+						p->bitmap[byte_index] |=
+							(1 << bit_index);
+						p->block.used++;
+						LIBC_UNLOCK(p->lock);
+						LIBC_UNLOCK(libc.lock.malloc);
+						if (p->heap == NULL)
+							return NULL;
+						return p->heap +
+						       (i * p->block.size);
+					}
+				}
+			}
+			LIBC_UNLOCK(p->lock);
+		} else if (p->flags == PAGE_LARGE && cls->size > 16 * 8192) {
+			LIBC_LOCK(p->lock);
+			if (p->block.used < p->block.count &&
+			    p->block.size == cls->size) {
+				// Find free block
+				for (uint32_t i = 0; i < p->block.count; i++) {
+					int byte_index = i / 8;
+					int bit_index = i % 8;
+					if (!(p->bitmap[byte_index] &
+					      (1 << bit_index))) {
+						p->bitmap[byte_index] |=
+							(1 << bit_index);
+						p->block.used++;
+						LIBC_UNLOCK(p->lock);
+						LIBC_UNLOCK(libc.lock.malloc);
+
+						if (p->heap == NULL)
+							return NULL;
+						return p->heap +
+						       (i * p->block.size);
+					}
+				}
+			}
+			LIBC_UNLOCK(p->lock);
+		}
+		p = p->next;
+	}
+
+	size_t page_size;
+	enum { PAGE_TYPE_SMALL, PAGE_TYPE_MEDIUM, PAGE_TYPE_LARGE } page_type;
+
+	if (cls->size <= 16 * 64) {
+		page_size = SMALL_PAGE_SIZE;
+		page_type = PAGE_TYPE_SMALL;
+	} else if (cls->size <= 16 * 8192) {
+		page_size = MEDIUM_PAGE_SIZE;
+		page_type = PAGE_TYPE_MEDIUM;
+	} else {
+		page_size = LARGE_PAGE_SIZE;
+		page_type = PAGE_TYPE_LARGE;
+	}
+
+	size_t bitmap_size = (cls->count + 7) / 8;
+	void *mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE,
+			 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+	if (mem == MAP_FAILED) {
+		LIBC_UNLOCK(libc.lock.malloc);
+		return NULL;
+	}
+
+	struct page *new_page = (struct page *)mem;
+	new_page->flags = (page_type == PAGE_TYPE_SMALL)  ? PAGE_SMALL :
+			  (page_type == PAGE_TYPE_MEDIUM) ? PAGE_MEDIUM :
+							    PAGE_LARGE;
+
+	new_page->block.size = cls->size;
+	new_page->block.used = 0;
+	new_page->block.count = cls->count;
+	new_page->bitmap = (uint8_t *)mem + sizeof(struct page);
+	memset(new_page->bitmap, 0, bitmap_size);
+	new_page->heap = (uint8_t *)mem + sizeof(struct page) + bitmap_size;
+
+	if (new_page->heap == NULL || new_page->bitmap == NULL) {
+		munmap(mem, page_size);
+		LIBC_UNLOCK(libc.lock.malloc);
+		return NULL;
+	}
+	atomic_flag_clear(&new_page->lock);
+	new_page->next = __malloc_pvec;
+	new_page->prev = NULL;
+
+	if (__malloc_pvec) {
+		__malloc_pvec->prev = new_page;
+	}
+
+	__malloc_pvec = new_page;
+
+	// Mark the first block as used and return it
+	new_page->bitmap[0] |= 1;
+	new_page->block.used = 1;
+
+	LIBC_UNLOCK(libc.lock.malloc);
+
+	return new_page->heap;
+}
-- 
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