From 364bde73520f5ffc15c40c772fd5fe431a398507 Mon Sep 17 00:00:00 2001
From: Erin <erin@erindesu.cz>
Date: Fri, 24 Nov 2023 12:30:20 +0100
Subject: [PATCH] Added fuzzer back

---
 hbvm/fuzz/.gitignore         |  5 +++
 hbvm/fuzz/Cargo.toml         | 30 +++++++++++++
 hbvm/fuzz/fuzz_targets/vm.rs | 82 ++++++++++++++++++++++++++++++++++++
 3 files changed, 117 insertions(+)
 create mode 100644 hbvm/fuzz/.gitignore
 create mode 100644 hbvm/fuzz/Cargo.toml
 create mode 100644 hbvm/fuzz/fuzz_targets/vm.rs

diff --git a/hbvm/fuzz/.gitignore b/hbvm/fuzz/.gitignore
new file mode 100644
index 0000000..23a1dd8
--- /dev/null
+++ b/hbvm/fuzz/.gitignore
@@ -0,0 +1,5 @@
+target
+artifacts
+corpus
+coverage
+Cargo.lock
diff --git a/hbvm/fuzz/Cargo.toml b/hbvm/fuzz/Cargo.toml
new file mode 100644
index 0000000..42566bd
--- /dev/null
+++ b/hbvm/fuzz/Cargo.toml
@@ -0,0 +1,30 @@
+[package]
+name = "hbvm-fuzz"
+version = "0.0.0"
+publish = false
+edition = "2021"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+libfuzzer-sys = "0.4"
+
+[dependencies.hbvm]
+path = ".."
+
+[dependencies.hbbytecode]
+path = "../../hbbytecode"
+
+# Prevent this from interfering with workspaces
+[workspace]
+members = ["."]
+
+[profile.release]
+debug = 1
+
+[[bin]]
+name = "vm"
+path = "fuzz_targets/vm.rs"
+test = false
+doc = false
diff --git a/hbvm/fuzz/fuzz_targets/vm.rs b/hbvm/fuzz/fuzz_targets/vm.rs
new file mode 100644
index 0000000..aa6d7cc
--- /dev/null
+++ b/hbvm/fuzz/fuzz_targets/vm.rs
@@ -0,0 +1,82 @@
+#![no_main]
+
+use {
+    hbvm::{
+        mem::{
+            softpaging::{
+                paging::{PageTable, Permission},
+                HandlePageFault, PageSize, SoftPagedMem,
+            },
+            Address, MemoryAccessReason,
+        },
+        Vm,
+    },
+    libfuzzer_sys::fuzz_target,
+};
+
+fuzz_target!(|data: &[u8]| {
+    let mut vm = unsafe {
+        Vm::<_, 16384>::new(
+            SoftPagedMem::<_, true> {
+                pf_handler: TestTrapHandler,
+                program:    data,
+                root_pt:    Box::into_raw(Default::default()),
+                icache:     Default::default(),
+            },
+            Address::new(4),
+        )
+    };
+
+    // Alloc and map some memory
+    let pages = [
+        alloc_and_map(&mut vm.memory, 0),
+        alloc_and_map(&mut vm.memory, 4096),
+    ];
+
+    // Run VM
+    let _ = vm.run();
+
+    // Unmap and dealloc the memory
+    for (i, page) in pages.into_iter().enumerate() {
+        unmap_and_dealloc(&mut vm.memory, page, i as u64 * 4096);
+    }
+
+    let _ = unsafe { Box::from_raw(vm.memory.root_pt) };
+});
+
+fn alloc_and_map(memory: &mut SoftPagedMem<TestTrapHandler>, at: u64) -> *mut u8 {
+    let ptr = Box::into_raw(Box::<Page>::default()).cast();
+    unsafe {
+        memory
+            .map(ptr, Address::new(at), Permission::Write, PageSize::Size4K)
+            .unwrap()
+    };
+    ptr
+}
+
+fn unmap_and_dealloc(memory: &mut SoftPagedMem<TestTrapHandler>, ptr: *mut u8, from: u64) {
+    memory.unmap(Address::new(from)).unwrap();
+    let _ = unsafe { Box::from_raw(ptr.cast::<Page>()) };
+}
+
+#[repr(align(4096))]
+struct Page([u8; 4096]);
+impl Default for Page {
+    fn default() -> Self {
+        unsafe { std::mem::MaybeUninit::zeroed().assume_init() }
+    }
+}
+
+struct TestTrapHandler;
+impl HandlePageFault for TestTrapHandler {
+    fn page_fault(
+        &mut self,
+        _: MemoryAccessReason,
+        _: &mut PageTable,
+        _: Address,
+        _: PageSize,
+        _: *mut u8,
+    ) -> bool {
+        false
+    }
+}