Optimize address translation and write tracking on the MMU (#571)

* Implement faster address translation and write tracking on the MMU

* Rename MemoryAlloc to MemoryManagement, and other nits

* Support multi-level page tables

* Fix typo

* Reword comment a bit

* Support scalar vector loads/stores on the memory fast path, and minor fixes

* Add missing cast

* Alignment

* Fix VirtualFree function signature

* Change MemoryProtection enum to uint aswell for consistency

1 files changed, 70 insertions, 0 deletions

diff --git a/ChocolArm64/Memory/MemoryManagementUnix.cs b/ChocolArm64/Memory/MemoryManagementUnix.cs
new file mode 100644
index 00000000..9fe1aef0
--- /dev/null
+++ b/ChocolArm64/Memory/MemoryManagementUnix.cs
@@ -0,0 +1,70 @@
+using Mono.Unix.Native;
+using System;
+
+namespace ChocolArm64.Memory
+{
+    static class MemoryManagementUnix
+    {
+        public static IntPtr Allocate(ulong size)
+        {
+            ulong pageSize = (ulong)Syscall.sysconf(SysconfName._SC_PAGESIZE);
+
+            const MmapProts prot = MmapProts.PROT_READ | MmapProts.PROT_WRITE;
+
+            const MmapFlags flags = MmapFlags.MAP_PRIVATE | MmapFlags.MAP_ANONYMOUS;
+
+            IntPtr ptr = Syscall.mmap(IntPtr.Zero, size + pageSize, prot, flags, -1, 0);
+
+            if (ptr == IntPtr.Zero)
+            {
+                throw new OutOfMemoryException();
+            }
+
+            unsafe
+            {
+                ptr = new IntPtr(ptr.ToInt64() + (long)pageSize);
+
+                *((ulong*)ptr - 1) = size;
+            }
+
+            return ptr;
+        }
+
+        public static bool Reprotect(IntPtr address, ulong size, Memory.MemoryProtection protection)
+        {
+            MmapProts prot = GetProtection(protection);
+
+            return Syscall.mprotect(address, size, prot) == 0;
+        }
+
+        private static MmapProts GetProtection(Memory.MemoryProtection protection)
+        {
+            switch (protection)
+            {
+                case Memory.MemoryProtection.None:           return MmapProts.PROT_NONE;
+                case Memory.MemoryProtection.Read:           return MmapProts.PROT_READ;
+                case Memory.MemoryProtection.ReadAndWrite:   return MmapProts.PROT_READ | MmapProts.PROT_WRITE;
+                case Memory.MemoryProtection.ReadAndExecute: return MmapProts.PROT_READ | MmapProts.PROT_EXEC;
+                case Memory.MemoryProtection.Execute:        return MmapProts.PROT_EXEC;
+
+                default: throw new ArgumentException($"Invalid permission \"{protection}\".");
+            }
+        }
+
+        public static bool Free(IntPtr address)
+        {
+            ulong pageSize = (ulong)Syscall.sysconf(SysconfName._SC_PAGESIZE);
+
+            ulong size;
+
+            unsafe
+            {
+                size = *((ulong*)address - 1);
+
+                address = new IntPtr(address.ToInt64() - (long)pageSize);
+            }
+
+            return Syscall.munmap(address, size + pageSize) == 0;
+        }
+    }
+}
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