From 8d53812b361919abe5b990ff2501a93b9c7b35b0 Mon Sep 17 00:00:00 2001
From: Edgar Su <sjs333@outlook.com>
Date: Mon, 11 Oct 2021 23:36:05 +0800
Subject: [PATCH] memory: implememt sbrk() clone for dlmalloc

---
 memory/heap_break.c | 26 ++++++++++++++++++++++++++
 memory/heap_break.h | 10 ++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 memory/heap_break.c
 create mode 100644 memory/heap_break.h

diff --git a/memory/heap_break.c b/memory/heap_break.c
new file mode 100644
index 0000000..ca8dcf9
--- /dev/null
+++ b/memory/heap_break.c
@@ -0,0 +1,26 @@
+
+#include "heap_break.h"
+#include "memory.h"
+#include "paging_internal.h"
+#include "../runtime/stdio.h"
+
+
+static uintptr_t heapBreak = KERNEL_HEAP_VIRTUAL, pageBreak = KERNEL_HEAP_VIRTUAL;
+
+void *memory_AddBreak(intptr_t inc) {
+	if (heapBreak + inc < KERNEL_HEAP_VIRTUAL)
+		return (void *)-1;
+
+	heapBreak += inc;
+
+	if (heapBreak > pageBreak) {
+		// we need more pages
+		int pageCount = roundUpToPageCount(heapBreak - pageBreak);
+		io_Printf("memory_AddBreak(): 0x%llx -> 0x%llx, add %d, allocating %d pages\n", heapBreak - inc, heapBreak, inc, pageCount);
+		paging_map_PageAllocated(pageBreak, pageCount, MAP_PROT_READ | MAP_PROT_WRITE);
+		pageBreak += SYSTEM_PAGE_SIZE * pageCount;
+	} else
+		io_Printf("memory_AddBreak(): 0x%llx -> 0x%llx, add %d\n", heapBreak - inc, heapBreak, inc);
+
+	return (void *)(heapBreak - inc);
+}
diff --git a/memory/heap_break.h b/memory/heap_break.h
new file mode 100644
index 0000000..4a61db4
--- /dev/null
+++ b/memory/heap_break.h
@@ -0,0 +1,10 @@
+#pragma once
+
+#include "../main.h"
+#include <stdint.h>
+
+
+// memory_AddBreak is a sbrk() clone, increasing the kernel heap size mapped at KERNEL_HEAP_VIRTUAL.
+// TODO It does not handle negative increments well (yet), as it does not unmap freed heap pages.
+//      I don't know if I should actually implement this, given it's a rather simple fix.
+void *memory_AddBreak(intptr_t increment);