From 4600a8c7742b4c01f71490de25cc50282dd65ff7 Mon Sep 17 00:00:00 2001
From: Yash Karandikar <nerdstep710@gmail.com>
Date: Sun, 19 Sep 2021 13:59:28 -0500
Subject: [PATCH] Create dummy allocator

---
 .cargo/config.toml |  2 +-
 src/allocator.rs   | 17 +++++++++++++++++
 src/main.rs        |  9 +++++++++
 src/memory.rs      |  2 +-
 4 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 src/allocator.rs

diff --git a/.cargo/config.toml b/.cargo/config.toml
index ebcc395..add8ee1 100644
--- a/.cargo/config.toml
+++ b/.cargo/config.toml
@@ -1,6 +1,6 @@
 [unstable]
 build-std-features = ["compiler-builtins-mem"]
-build-std = ["core", "compiler_builtins"]
+build-std = ["core", "compiler_builtins", "alloc"]
 
 [build]
 target = "x86_64-karxos.json"
diff --git a/src/allocator.rs b/src/allocator.rs
new file mode 100644
index 0000000..c2146b9
--- /dev/null
+++ b/src/allocator.rs
@@ -0,0 +1,17 @@
+use alloc::alloc::{GlobalAlloc, Layout};
+use core::ptr::null_mut;
+
+pub struct Dummy;
+
+unsafe impl GlobalAlloc for Dummy {
+    unsafe fn alloc(&self, _layout: Layout) -> *mut u8 {
+        null_mut()
+    }
+
+    unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
+        panic!("dealloc should never be called");
+    }
+}
+
+#[global_allocator]
+static ALLOCATOR: Dummy = Dummy;
diff --git a/src/main.rs b/src/main.rs
index 34148cf..b35cfe5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,22 +5,31 @@
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 #![feature(abi_x86_interrupt)]
+#![feature(alloc_error_handler)]
 
 mod gdt;
 mod interrupts;
 mod shell;
 mod vga_buffer;
 mod memory;
+mod allocator;
 
 use core::panic::PanicInfo;
 use bootloader::BootInfo;
 
+extern crate alloc;
+
 #[panic_handler]
 fn panic(info: &PanicInfo) -> ! {
     println!("{}", info);
     loop {}
 }
 
+#[alloc_error_handler]
+fn alloc_error_handler(layout: alloc::alloc::Layout) -> ! {
+    panic!("allocation error: {:?}", layout)
+}
+
 fn init() {
     gdt::init_gdt();
     interrupts::init();
diff --git a/src/memory.rs b/src/memory.rs
index d173d37..b725b24 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -1,4 +1,4 @@
-use x86_64::{PhysAddr, VirtAddr, structures::paging::{FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB}};
+use x86_64::{PhysAddr, VirtAddr, structures::paging::{FrameAllocator, OffsetPageTable, PageTable, PhysFrame, Size4KiB}};
 use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
 
 pub unsafe fn init(physical_memory_offset: VirtAddr) -> OffsetPageTable<'static> {