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using ARMeilleure.CodeGen;
using ARMeilleure.Memory;
using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
namespace ARMeilleure.Translation
{
static class JitCache
{
private const int PageSize = 4 * 1024;
private const int PageMask = PageSize - 1;
private const int CodeAlignment = 4; // Bytes
private const int CacheSize = 512 * 1024 * 1024;
private static IntPtr _basePointer;
private static int _offset;
private static List<JitCacheEntry> _cacheEntries;
private static object _lock;
static JitCache()
{
_basePointer = MemoryManagement.Allocate(CacheSize);
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
{
JitUnwindWindows.InstallFunctionTableHandler(_basePointer, CacheSize);
// The first page is used for the table based SEH structs.
_offset = PageSize;
}
_cacheEntries = new List<JitCacheEntry>();
_lock = new object();
}
public static IntPtr Map(CompiledFunction func)
{
byte[] code = func.Code;
lock (_lock)
{
int funcOffset = Allocate(code.Length);
IntPtr funcPtr = _basePointer + funcOffset;
Marshal.Copy(code, 0, funcPtr, code.Length);
ReprotectRange(funcOffset, code.Length);
Add(new JitCacheEntry(funcOffset, code.Length, func.UnwindInfo));
return funcPtr;
}
}
private static void ReprotectRange(int offset, int size)
{
// Map pages that are already full as RX.
// Map pages that are not full yet as RWX.
// On unix, the address must be page aligned.
int endOffs = offset + size;
int pageStart = offset & ~PageMask;
int pageEnd = endOffs & ~PageMask;
int fullPagesSize = pageEnd - pageStart;
if (fullPagesSize != 0)
{
IntPtr funcPtr = _basePointer + pageStart;
MemoryManagement.Reprotect(funcPtr, (ulong)fullPagesSize, MemoryProtection.ReadAndExecute);
}
int remaining = endOffs - pageEnd;
if (remaining != 0)
{
IntPtr funcPtr = _basePointer + pageEnd;
MemoryManagement.Reprotect(funcPtr, (ulong)remaining, MemoryProtection.ReadWriteExecute);
}
}
private static int Allocate(int codeSize)
{
codeSize = checked(codeSize + (CodeAlignment - 1)) & ~(CodeAlignment - 1);
int allocOffset = _offset;
_offset += codeSize;
if ((ulong)(uint)_offset > CacheSize)
{
throw new OutOfMemoryException();
}
return allocOffset;
}
private static void Add(JitCacheEntry entry)
{
_cacheEntries.Add(entry);
}
public static bool TryFind(int offset, out JitCacheEntry entry)
{
lock (_lock)
{
foreach (JitCacheEntry cacheEntry in _cacheEntries)
{
int endOffset = cacheEntry.Offset + cacheEntry.Size;
if (offset >= cacheEntry.Offset && offset < endOffset)
{
entry = cacheEntry;
return true;
}
}
}
entry = default(JitCacheEntry);
return false;
}
}
}
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