From b141582f40c91cdd59af0e852ac12ed578c52d3a Mon Sep 17 00:00:00 2001
From: ngiddings <nathang567@gmail.com>
Date: Sat, 17 Apr 2021 01:18:14 -0500
Subject: [PATCH] Added very simple kernel memory allocator

---
 include/allocator.h |  9 +++++++++
 src/Makefile.am     |  2 +-
 src/allocator.c     | 34 ++++++++++++++++++++++++++++++++++
 3 files changed, 44 insertions(+), 1 deletion(-)
 create mode 100644 include/allocator.h
 create mode 100644 src/allocator.c

diff --git a/include/allocator.h b/include/allocator.h
new file mode 100644
index 0000000..a9c0699
--- /dev/null
+++ b/include/allocator.h
@@ -0,0 +1,9 @@
+#pragma once
+
+#include <stddef.h>
+
+void initialize_allocator(void *bottom, void *top);
+
+void *allocate_from_bottom(size_t size);
+
+void *allocate_from_top(size_t size);
\ No newline at end of file
diff --git a/src/Makefile.am b/src/Makefile.am
index ca01154..e55eca4 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,5 +1,5 @@
 noinst_PROGRAMS = quark-kernel
-quark_kernel_SOURCES = kernel.c memorymap.c pageallocator.c priorityqueue.c stdio.c string.c elf.c resource.c
+quark_kernel_SOURCES = kernel.c memorymap.c pageallocator.c priorityqueue.c stdio.c string.c elf.c resource.c allocator.c
 quark_kernel_LDADD = -lgcc
 quark_kernel_CFLAGS = -I$(top_srcdir)/include -ffreestanding -mgeneral-regs-only -O0 -Wall -ggdb
 quark_kernel_LDFLAGS = -nostdlib
diff --git a/src/allocator.c b/src/allocator.c
new file mode 100644
index 0000000..574b195
--- /dev/null
+++ b/src/allocator.c
@@ -0,0 +1,34 @@
+#include "allocator.h"
+
+struct linear_allocator_t
+{
+    void *bottom;
+    void *top;
+} allocator;
+
+void initialize_allocator(void *bottom, void *top)
+{
+    allocator.bottom = bottom;
+    allocator.top = top;
+}
+
+void *allocate_from_bottom(size_t size)
+{
+    if((size_t)allocator.bottom + size <= (size_t)allocator.top)
+    {
+        void *ptr = allocator.bottom;
+        allocator.bottom += size;
+        return ptr;
+    }
+    return (void*)NULL;
+}
+
+void *allocate_from_top(size_t size)
+{
+    if((size_t)allocator.top - size >= (size_t)allocator.bottom)
+    {
+        allocator.top -= size;
+        return allocator.top;
+    }
+    return (void*)NULL;
+}