init: dead simple malloc

1 files changed, 69 insertions, 0 deletions

diff --git a/src/init/malloc.c b/src/init/malloc.c
new file mode 100644
index 0000000..35b1741
--- /dev/null
+++ b/src/init/malloc.c
@@ -0,0 +1,69 @@
+#include <init/malloc.h>
+#include <shared/flags.h>
+#include <shared/syscalls.h>
+#include <stdbool.h>
+
+#include <init/stdlib.h>
+
+#define MBLOCK_MAGIC 0x1337BABE
+
+struct mblock {
+	uint32_t magic;
+	size_t length; // including this struct
+	bool used;
+	struct mblock *next;
+};
+
+static struct mblock *first = NULL, *last = NULL;
+static struct mblock *expand(size_t size);
+
+void *malloc(size_t size) {
+	struct mblock *iter = first;
+	size += sizeof(struct mblock);
+	while (iter) {
+		if (!iter->used && iter->length >= size)
+			break;
+		iter = iter->next;
+	}
+
+	if (!iter) iter = expand(size);
+	if (!iter) return NULL;
+
+	iter->used = true;
+	// TODO truncate and split
+
+	return &iter[1];
+}
+
+void free(void *ptr) {
+	struct mblock *block = ptr - sizeof(struct mblock);
+	if (block->magic != MBLOCK_MAGIC) {
+		// TODO debug log switch
+		printf("didn't find MBLOCK_MAGIC @ 0x%x\n", block);
+		return;
+	}
+
+	block->used = false;
+}
+
+static struct mblock *expand(size_t size) {
+	size = (size + 4095) & ~4095; // round up to nearest page
+
+	static void *start = (void*)0x80000000; // TODO workaround for unimplemented feature
+	_syscall_memflag(start, size, MEMFLAG_PRESENT);
+	struct mblock *block = start;
+	start += size;
+
+	block->magic = MBLOCK_MAGIC;
+	block->length = size;
+	block->used = false;
+	block->next = NULL;
+
+	if (!first) first = block;
+	if (last) last->next = block;
+	last = block;
+
+	// TODO collapse
+
+	return block;
+}