ecall.cpp

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
// ECALL.CPP -
//
// Handles our private native calling interface.
//



#include "common.h"

#include "ecall.h"

#include "comdelegate.h"

#ifndef DACCESS_COMPILE

#ifdef CROSSGEN_COMPILE
namespace CrossGenMscorlib
{
    extern const ECClass c_rgECClasses[];
    extern const int c_nECClasses;
};
using namespace CrossGenMscorlib;
#else // CROSSGEN_COMPILE
extern const ECClass c_rgECClasses[];
extern const int c_nECClasses;
#endif // CROSSGEN_COMPILE


// METHOD__STRING__CTORF_XXX has to be in same order as ECall::CtorCharXxx
#define METHOD__STRING__CTORF_FIRST METHOD__STRING__CTORF_CHARARRAY
static_assert_no_msg(METHOD__STRING__CTORF_FIRST + 0 == METHOD__STRING__CTORF_CHARARRAY);
static_assert_no_msg(METHOD__STRING__CTORF_FIRST + 1 == METHOD__STRING__CTORF_CHARARRAY_START_LEN);
static_assert_no_msg(METHOD__STRING__CTORF_FIRST + 2 == METHOD__STRING__CTORF_CHAR_COUNT);
static_assert_no_msg(METHOD__STRING__CTORF_FIRST + 3 == METHOD__STRING__CTORF_CHARPTR);
static_assert_no_msg(METHOD__STRING__CTORF_FIRST + 4 == METHOD__STRING__CTORF_CHARPTR_START_LEN);
static_assert_no_msg(METHOD__STRING__CTORF_FIRST + 5 == METHOD__STRING__CTORF_READONLYSPANOFCHAR);

// ECall::CtorCharXxx has to be in same order as METHOD__STRING__CTORF_XXX
#define ECallCtor_First ECall::CtorCharArrayManaged
static_assert_no_msg(ECallCtor_First + 0 == ECall::CtorCharArrayManaged);
static_assert_no_msg(ECallCtor_First + 1 == ECall::CtorCharArrayStartLengthManaged);
static_assert_no_msg(ECallCtor_First + 2 == ECall::CtorCharCountManaged);
static_assert_no_msg(ECallCtor_First + 3 == ECall::CtorCharPtrManaged);
static_assert_no_msg(ECallCtor_First + 4 == ECall::CtorCharPtrStartLengthManaged);
static_assert_no_msg(ECallCtor_First + 5 == ECall::CtorReadOnlySpanOfCharManaged);

#define NumberOfStringConstructors 6

void ECall::PopulateManagedStringConstructors()
{
    STANDARD_VM_CONTRACT;

    INDEBUG(static bool fInitialized = false);
    _ASSERTE(!fInitialized);    // assume this method is only called once
    _ASSERTE(g_pStringClass != NULL);

    for (int i = 0; i < NumberOfStringConstructors; i++)
    {
        MethodDesc* pMD = MscorlibBinder::GetMethod((BinderMethodID)(METHOD__STRING__CTORF_FIRST + i));
        _ASSERTE(pMD != NULL);
    
        PCODE pDest = pMD->GetMultiCallableAddrOfCode();

        ECall::DynamicallyAssignFCallImpl(pDest, ECallCtor_First + i);
    }
    INDEBUG(fInitialized = true);
}

static CrstStatic gFCallLock;

// This variable is used to force the compiler not to tailcall a function.
int FC_NO_TAILCALL;

#endif // !DACCESS_COMPILE

// To provide a quick check, this is the lowest and highest
// addresses of any FCALL starting address
GVAL_IMPL_INIT(TADDR, gLowestFCall, (TADDR)-1);
GVAL_IMPL(TADDR, gHighestFCall);

GARY_IMPL(PTR_ECHash, gFCallMethods, FCALL_HASH_SIZE);

inline unsigned FCallHash(PCODE pTarg) {
    LIMITED_METHOD_DAC_CONTRACT;
    return pTarg % FCALL_HASH_SIZE;
}

#ifdef DACCESS_COMPILE

GARY_IMPL(PCODE, g_FCDynamicallyAssignedImplementations,
          ECall::NUM_DYNAMICALLY_ASSIGNED_FCALL_IMPLEMENTATIONS);

#else // !DACCESS_COMPILE

PCODE g_FCDynamicallyAssignedImplementations[ECall::NUM_DYNAMICALLY_ASSIGNED_FCALL_IMPLEMENTATIONS] = {
    #undef DYNAMICALLY_ASSIGNED_FCALL_IMPL
    #define DYNAMICALLY_ASSIGNED_FCALL_IMPL(id,defaultimpl) GetEEFuncEntryPoint(defaultimpl),
    DYNAMICALLY_ASSIGNED_FCALLS()
};

void ECall::DynamicallyAssignFCallImpl(PCODE impl, DWORD index)
{
    CONTRACTL
    {
        NOTHROW;
        GC_NOTRIGGER;
        MODE_ANY;
    }
    CONTRACTL_END;

    _ASSERTE(index < NUM_DYNAMICALLY_ASSIGNED_FCALL_IMPLEMENTATIONS);
    g_FCDynamicallyAssignedImplementations[index] = impl;
}

/*******************************************************************************/
static INT FindImplsIndexForClass(MethodTable* pMT)
{
    CONTRACTL
    {
        NOTHROW;
        GC_NOTRIGGER;
        MODE_ANY;
    }
    CONTRACTL_END;

    LPCUTF8 pszNamespace = 0;
    LPCUTF8 pszName = pMT->GetFullyQualifiedNameInfo(&pszNamespace);

    // Array classes get null from the above routine, but they have no ecalls.
    if (pszName == NULL)
        return (-1);

    unsigned low  = 0;
    unsigned high = c_nECClasses;

#ifdef _DEBUG
    static bool checkedSort = false;
    if (!checkedSort) {
        checkedSort = true;
        for (unsigned i = 1; i < high; i++)  {
                // Make certain list is sorted!
            int cmp = strcmp(c_rgECClasses[i].m_szClassName, c_rgECClasses[i-1].m_szClassName);
            if (cmp == 0)
                cmp = strcmp(c_rgECClasses[i].m_szNameSpace, c_rgECClasses[i-1].m_szNameSpace);
            _ASSERTE(cmp > 0 && W("You forgot to keep ECall class names sorted"));      // Hey, you forgot to sort the new class
        }
    }
#endif // _DEBUG
    while (high > low) {
        unsigned mid  = (high + low) / 2;
        int cmp = strcmp(pszName, c_rgECClasses[mid].m_szClassName);
        if (cmp == 0)
            cmp = strcmp(pszNamespace, c_rgECClasses[mid].m_szNameSpace);

        if (cmp == 0) {
            return(mid);
        }
        if (cmp > 0)
            low = mid+1;
        else
            high = mid;
    }

    return (-1);
}

/*******************************************************************************/
/*  Finds the implementation for the given method desc.  */

static INT FindECIndexForMethod(MethodDesc *pMD, const LPVOID* impls)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_ANY;
    }
    CONTRACTL_END;

    LPCUTF8 szMethodName = pMD->GetName();
    PCCOR_SIGNATURE pMethodSig;
    ULONG       cbMethodSigLen;

    pMD->GetSig(&pMethodSig, &cbMethodSigLen);
    Module* pModule = pMD->GetModule();

    for (ECFunc* cur = (ECFunc*)impls; !cur->IsEndOfArray(); cur = cur->NextInArray())
    {
        if (strcmp(cur->m_szMethodName, szMethodName) != 0)
            continue;

        if (cur->HasSignature())
        {
            Signature sig = MscorlibBinder::GetTargetSignature(cur->m_pMethodSig);

            //@GENERICS: none of these methods belong to generic classes so there is no instantiation info to pass in
            if (!MetaSig::CompareMethodSigs(pMethodSig, cbMethodSigLen, pModule, NULL,
                                            sig.GetRawSig(), sig.GetRawSigLen(), MscorlibBinder::GetModule(), NULL))
            {
                continue;
            }
        }

        // We have found a match!
        return static_cast<INT>((LPVOID*)cur - impls);
    }

    return -1;
}

/*******************************************************************************/
/* ID is formed of 2 USHORTs - class index  in high word, method index in low word.  */
/* class index starts at 1. id == 0 means no implementation.                    */

DWORD ECall::GetIDForMethod(MethodDesc *pMD)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_ANY;
    }
    CONTRACTL_END;

    // We should not go here for NGened methods
    _ASSERTE(!pMD->IsZapped());

    INT ImplsIndex = FindImplsIndexForClass(pMD->GetMethodTable());
    if (ImplsIndex < 0)
        return 0;
    INT ECIndex = FindECIndexForMethod(pMD, c_rgECClasses[ImplsIndex].m_pECFunc);
    if (ECIndex < 0)
        return 0;

    return (ImplsIndex<<16) | (ECIndex + 1);
}

static ECFunc *FindECFuncForID(DWORD id)
{
    LIMITED_METHOD_CONTRACT;

    if (id == 0)
        return NULL;

    INT ImplsIndex  = (id >> 16);
    INT ECIndex     = (id & 0xffff) - 1;

    return (ECFunc*)(c_rgECClasses[ImplsIndex].m_pECFunc + ECIndex);
}

static ECFunc* FindECFuncForMethod(MethodDesc* pMD)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_ANY;
        PRECONDITION(pMD->IsFCall());
    }
    CONTRACTL_END;

    DWORD id = ((FCallMethodDesc *)pMD)->GetECallID();
    if (id == 0)
    {
        id = ECall::GetIDForMethod(pMD);
        
        CONSISTENCY_CHECK_MSGF(0 != id,
                    ("No method entry found for %s::%s.\n",
                    pMD->m_pszDebugClassName, pMD->m_pszDebugMethodName));
            
        // Cache the id
        ((FCallMethodDesc *)pMD)->SetECallID(id);
    }

    return FindECFuncForID(id);
}

/*******************************************************************************
* Returns 0 if it is an ECALL,
* Otherwise returns the native entry point (FCALL)
*/
PCODE ECall::GetFCallImpl(MethodDesc * pMD, BOOL * pfSharedOrDynamicFCallImpl /*=NULL*/)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_ANY;
        PRECONDITION(pMD->IsFCall());
    }
    CONTRACTL_END;

    MethodTable * pMT = pMD->GetMethodTable();

    //
    // Delegate constructors are FCalls for which the entrypoint points to the target of the delegate
    // We have to intercept these and set the call target to the helper COMDelegate::DelegateConstruct
    //
    if (pMT->IsDelegate())
    {
        if (pfSharedOrDynamicFCallImpl)
            *pfSharedOrDynamicFCallImpl = TRUE;

        // COMDelegate::DelegateConstruct is the only fcall used by user delegates.
        // All the other gDelegateFuncs are only used by System.Delegate
        _ASSERTE(pMD->IsCtor());

        // We need to set up the ECFunc properly.  We don't want to use the pMD passed in,
        // since it may disappear.  Instead, use the stable one on Delegate.  Remember
        // that this is 1:M between the FCall and the pMDs.
        return GetFCallImpl(MscorlibBinder::GetMethod(METHOD__DELEGATE__CONSTRUCT_DELEGATE));
    }

#ifdef FEATURE_COMINTEROP
    // COM imported classes have special constructors
    if (pMT->IsComObjectType() && pMT != g_pBaseCOMObject && pMT != g_pBaseRuntimeClass)
    {
        if (pfSharedOrDynamicFCallImpl)
            *pfSharedOrDynamicFCallImpl = TRUE;

        // This has to be tlbimp constructor
        _ASSERTE(pMD->IsCtor());
        _ASSERTE(!pMT->IsProjectedFromWinRT());

        // FCComCtor does not need to be in the fcall hashtable since it does not erect frame.
        return GetEEFuncEntryPoint(FCComCtor);
    }
#endif // FEATURE_COMINTEROP

    if (!pMD->GetModule()->IsSystem())
        COMPlusThrow(kSecurityException, BFA_ECALLS_MUST_BE_IN_SYS_MOD);

    ECFunc* ret = FindECFuncForMethod(pMD);

    // ECall is a set of tables to call functions within the EE from the classlibs.
    // First we use the class name & namespace to find an array of function pointers for
    // a class, then use the function name (& sometimes signature) to find the correct
    // function pointer for your method.  Methods in the BCL will be marked as
    // [MethodImplAttribute(MethodImplOptions.InternalCall)] and extern.
    //
    // You'll see this assert in several situations, almost all being the fault of whomever
    // last touched a particular ecall or fcall method, either here or in the classlibs.
    // However, you must also ensure you don't have stray copies of mscorlib.dll on your machine.
    // 1) You forgot to add your class to c_rgECClasses, the list of classes w/ ecall & fcall methods.
    // 2) You forgot to add your particular method to the ECFunc array for your class.
    // 3) You misspelled the name of your function and/or classname.
    // 4) The signature of the managed function doesn't match the hardcoded metadata signature
    //    listed in your ECFunc array.  The hardcoded metadata sig is only necessary to disambiguate
    //    overloaded ecall functions - usually you can leave it set to NULL.
    // 5) Your copy of mscorlib.dll & mscoree.dll are out of sync - rebuild both.
    // 6) You've loaded the wrong copy of mscorlib.dll.  In msdev's debug menu,
    //    select the "Modules..." dialog.  Verify the path for mscorlib is right.
    // 7) Someone mucked around with how the signatures in metasig.h are parsed, changing the
    //    interpretation of a part of the signature (this is very rare & extremely unlikely,
    //    but has happened at least once).

    CONSISTENCY_CHECK_MSGF(ret != NULL,
        ("Could not find an ECALL entry for %s::%s.\n"
        "Read comment above this assert in vm/ecall.cpp\n",
        pMD->m_pszDebugClassName, pMD->m_pszDebugMethodName));

    CONSISTENCY_CHECK_MSGF(!ret->IsQCall(),
        ("%s::%s is not registered using FCFuncElement macro in ecall.cpp",
        pMD->m_pszDebugClassName, pMD->m_pszDebugMethodName));

#ifdef CROSSGEN_COMPILE

    // Use the ECFunc address as a unique fake entrypoint to make the entrypoint<->MethodDesc mapping work
    PCODE pImplementation = (PCODE)ret;
#ifdef _TARGET_ARM_
    pImplementation |= THUMB_CODE;
#endif

#else // CROSSGEN_COMPILE

    PCODE pImplementation = (PCODE)ret->m_pImplementation;

    int iDynamicID = ret->DynamicID();
    if (iDynamicID != InvalidDynamicFCallId)
    {
        if (pfSharedOrDynamicFCallImpl)
            *pfSharedOrDynamicFCallImpl = TRUE;

        pImplementation = g_FCDynamicallyAssignedImplementations[iDynamicID];
        _ASSERTE(pImplementation != NULL);
        return pImplementation;
    }

#endif // CROSSGEN_COMPILE

    // Insert the implementation into hash table if it is not there already.

    CrstHolder holder(&gFCallLock);

    MethodDesc * pMDinTable = ECall::MapTargetBackToMethod(pImplementation, &pImplementation);

    if (pMDinTable != NULL)
    {
        if (pMDinTable != pMD)
        {
            // The fcall entrypoints has to be at unique addresses. If you get failure here, use the following steps
            // to fix it:
            // 1. Consider merging the offending fcalls into one fcall. Do they really do different things?
            // 2. If it does not make sense to merge the offending fcalls into one,
            // add FCUnique(<a random unique number here>); to one of the offending fcalls.

            _ASSERTE(!"Duplicate pImplementation entries found in reverse fcall table");
            ThrowHR(E_FAIL);
        }
    }
    else
    {
        ECHash * pEntry = (ECHash *)(PVOID)SystemDomain::GetGlobalLoaderAllocator()->GetHighFrequencyHeap()->AllocMem(S_SIZE_T(sizeof(ECHash)));

        pEntry->m_pImplementation = pImplementation;
        pEntry->m_pMD = pMD;

        if(gLowestFCall > pImplementation)
            gLowestFCall = pImplementation;
        if(gHighestFCall < pImplementation)
            gHighestFCall = pImplementation;

        // add to hash table
        ECHash** spot = &gFCallMethods[FCallHash(pImplementation)];
        for(;;) {
            if (*spot == 0) {                   // found end of list
                *spot = pEntry;
                break;
            }
            spot = &(*spot)->m_pNext;
        }
    }

    if (pfSharedOrDynamicFCallImpl)
        *pfSharedOrDynamicFCallImpl = FALSE;

    _ASSERTE(pImplementation != NULL);
    return pImplementation;
}

BOOL ECall::IsSharedFCallImpl(PCODE pImpl)
{
    LIMITED_METHOD_CONTRACT;

    PCODE pNativeCode = pImpl;

    return
#ifdef FEATURE_COMINTEROP
        (pNativeCode == GetEEFuncEntryPoint(FCComCtor)) ||
#endif
        (pNativeCode == GetEEFuncEntryPoint(COMDelegate::DelegateConstruct));
}

BOOL ECall::CheckUnusedECalls(SetSHash<DWORD>& usedIDs)
{
    STANDARD_VM_CONTRACT;

    BOOL fUnusedFCallsFound = FALSE;

    INT num = c_nECClasses;
    for (INT ImplsIndex=0; ImplsIndex < num; ImplsIndex++)
    {
        const ECClass * pECClass = c_rgECClasses + ImplsIndex;

        BOOL fUnreferencedType = TRUE;
        for (ECFunc* ptr = (ECFunc*)pECClass->m_pECFunc; !ptr->IsEndOfArray(); ptr = ptr->NextInArray())
        {
            if (ptr->DynamicID() == InvalidDynamicFCallId && !ptr->IsUnreferenced())
            {
                INT ECIndex = static_cast<INT>((LPVOID*)ptr - pECClass->m_pECFunc);

                DWORD id = (ImplsIndex<<16) | (ECIndex + 1);

                if (!usedIDs.Contains(id))
                {
                    printf("CheckMscorlibExtended: Unused ecall found: %s.%s::%s\n", pECClass->m_szNameSpace, c_rgECClasses[ImplsIndex].m_szClassName, ptr->m_szMethodName);
                    fUnusedFCallsFound = TRUE;
                    continue;
                }
            }
            fUnreferencedType = FALSE;
        }

        if (fUnreferencedType)
        {
            printf("CheckMscorlibExtended: Unused type found: %s.%s\n", c_rgECClasses[ImplsIndex].m_szNameSpace, c_rgECClasses[ImplsIndex].m_szClassName);
            fUnusedFCallsFound = TRUE;
            continue;
        }
    }

    return !fUnusedFCallsFound;
}


#if defined(FEATURE_COMINTEROP) && !defined(CROSSGEN_COMPILE)
FCIMPL1(VOID, FCComCtor, LPVOID pV)
{
    FCALL_CONTRACT;

    FCUnique(0x34);
}
FCIMPLEND
#endif // FEATURE_COMINTEROP && !CROSSGEN_COMPILE



/* static */
void ECall::Init()
{
    CONTRACTL
    {
        THROWS;
        GC_NOTRIGGER;
        MODE_ANY;
    }
    CONTRACTL_END;

    gFCallLock.Init(CrstFCall);

    // It is important to do an explicit increment here instead of just in-place initialization
    // so that the global optimizer cannot figure out the value and remove the side-effect that
    // we depend on in FC_INNER_RETURN macros and other places
    FC_NO_TAILCALL++;
}

LPVOID ECall::GetQCallImpl(MethodDesc * pMD)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_ANY;
        PRECONDITION(pMD->IsNDirect());
    }
    CONTRACTL_END;

    DWORD id = ((NDirectMethodDesc *)pMD)->GetECallID();
    if (id == 0)
    {
        id = ECall::GetIDForMethod(pMD);
        _ASSERTE(id != 0);

        // Cache the id
        ((NDirectMethodDesc *)pMD)->SetECallID(id);
    }

    ECFunc * cur = FindECFuncForID(id);

#ifdef _DEBUG
    CONSISTENCY_CHECK_MSGF(cur != NULL, 
        ("%s::%s is not registered in ecall.cpp",
        pMD->m_pszDebugClassName, pMD->m_pszDebugMethodName));

    CONSISTENCY_CHECK_MSGF(cur->IsQCall(), 
        ("%s::%s is not registered using QCFuncElement macro in ecall.cpp",
        pMD->m_pszDebugClassName, pMD->m_pszDebugMethodName));

    CONSISTENCY_CHECK_MSGF(pMD->HasSuppressUnmanagedCodeAccessAttr(),       
        ("%s::%s is not marked with SuppressUnmanagedCodeSecurityAttribute()", 
        pMD->m_pszDebugClassName, pMD->m_pszDebugMethodName));

    DWORD dwAttrs = pMD->GetAttrs();
    BOOL fPublicOrProtected = IsMdPublic(dwAttrs) || IsMdFamily(dwAttrs) || IsMdFamORAssem(dwAttrs);

    // SuppressUnmanagedCodeSecurityAttribute on QCalls suppresses a full demand, but there's still a link demand 
    // for unmanaged code permission. All QCalls should be private or internal and wrapped in a managed method 
    // to suppress this link demand.
    CONSISTENCY_CHECK_MSGF(!fPublicOrProtected,
        ("%s::%s has to be private or internal.",
        pMD->m_pszDebugClassName, pMD->m_pszDebugMethodName));
#endif
 
    return cur->m_pImplementation;
}

#endif // !DACCESS_COMPILE

MethodDesc* ECall::MapTargetBackToMethod(PCODE pTarg, PCODE * ppAdjustedEntryPoint /*=NULL*/)
{
    CONTRACTL
    {
        NOTHROW;
        GC_NOTRIGGER;
        MODE_ANY;
        HOST_NOCALLS;
        SO_TOLERANT;
        SUPPORTS_DAC;
    }
    CONTRACTL_END;

    // Searching all of the entries is expensive
    // and we are often called with pTarg == NULL so
    // check for this value and early exit.

    if (!pTarg)
        return NULL;

    // Could this possibily be an FCall?
    if ((pTarg < gLowestFCall) || (pTarg > gHighestFCall))
        return NULL;

    ECHash * pECHash = gFCallMethods[FCallHash(pTarg)];
    while (pECHash != NULL)
    {
        if (pECHash->m_pImplementation == pTarg)
        {
            return pECHash->m_pMD;
        }
        pECHash = pECHash->m_pNext;
    }
    return NULL;
}

#ifndef DACCESS_COMPILE

/* static */
CorInfoIntrinsics ECall::GetIntrinsicID(MethodDesc* pMD)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_ANY;
        SO_TOLERANT;
        PRECONDITION(pMD->IsFCall());
    }
    CONTRACTL_END;

    MethodTable * pMT = pMD->GetMethodTable();

#ifdef FEATURE_COMINTEROP
    // COM imported classes have special constructors
    if (pMT->IsComObjectType())
    {
        // This has to be tlbimp constructor
        return(CORINFO_INTRINSIC_Illegal);
    }
#endif // FEATURE_COMINTEROP

    //
    // Delegate constructors are FCalls for which the entrypoint points to the target of the delegate
    // We have to intercept these and set the call target to the helper COMDelegate::DelegateConstruct
    //
    if (pMT->IsDelegate())
    {
        // COMDelegate::DelegateConstruct is the only fcall used by user delegates.
        // All the other gDelegateFuncs are only used by System.Delegate
        _ASSERTE(pMD->IsCtor());

        return(CORINFO_INTRINSIC_Illegal);
    }

    // All intrinsic live in mscorlib.dll (FindECFuncForMethod does not work for non-mscorlib intrinsics)
    if (!pMD->GetModule()->IsSystem())
    {
        return(CORINFO_INTRINSIC_Illegal);
    }

    ECFunc* info = FindECFuncForMethod(pMD);

    if (info == NULL)
        return(CORINFO_INTRINSIC_Illegal);

    return info->IntrinsicID();
}

#ifdef _DEBUG

void FCallAssert(void*& cache, void* target)
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_DEBUG_ONLY;

    if (cache != 0)
    {
        return;
    }

    //
    // Special case fcalls with 1:N mapping between implementation and methoddesc
    //
    if (ECall::IsSharedFCallImpl((PCODE)target))
    {
        cache = (void*)1;
        return;
    }

    MethodDesc* pMD = ECall::MapTargetBackToMethod((PCODE)target);
    if (pMD != 0)
    {
        return;
    }

    // Slow but only for debugging.  This is needed because in some places
    // we call FCALLs directly from EE code.

    unsigned num = c_nECClasses;
    for (unsigned i=0; i < num; i++)
    {
        for (ECFunc* ptr = (ECFunc*)c_rgECClasses[i].m_pECFunc; !ptr->IsEndOfArray(); ptr = ptr->NextInArray())
        {
            if (ptr->m_pImplementation  == target)
            {                
                cache = target;
                return;
            }
        }
    }

    // Now check the dynamically assigned table too.
    for (unsigned i=0; i<ECall::NUM_DYNAMICALLY_ASSIGNED_FCALL_IMPLEMENTATIONS; i++)
    {
        if (g_FCDynamicallyAssignedImplementations[i] == (PCODE)target)
        {
            cache = target;
            return;
        }
    }

    _ASSERTE(!"Could not find FCall implemenation in ECall.cpp");
}

void HCallAssert(void*& cache, void* target)
{
    CONTRACTL
    {
        SO_TOLERANT;     // STATIC_CONTRACT_DEBUG_ONLY
        NOTHROW;
        GC_NOTRIGGER;
        MODE_ANY;
        DEBUG_ONLY;
    }
    CONTRACTL_END;

    if (cache != 0)
        cache = ECall::MapTargetBackToMethod((PCODE)target);
    _ASSERTE(cache == 0 || "Use FCIMPL for fcalls");
}

#endif // _DEBUG

#endif // !DACCESS_COMPILE

#ifdef DACCESS_COMPILE

void ECall::EnumFCallMethods()
{
    SUPPORTS_DAC;
    gLowestFCall.EnumMem();
    gHighestFCall.EnumMem();
    gFCallMethods.EnumMem();
    
    // save all ECFunc for stackwalks.
    // TODO: we could be smarter and only save buckets referenced during stackwalks. But we 
    // need that entire bucket so that traversals such as MethodDesc* ECall::MapTargetBackToMethod will work.
    for (UINT i=0;i<FCALL_HASH_SIZE;i++)
    {
        ECHash *ecHash = gFCallMethods[i];
        while (ecHash)
        {
            // If we can't read the target memory, stop immediately so we don't work
            // with broken data.
            if (!DacEnumMemoryRegion(dac_cast<TADDR>(ecHash), sizeof(ECHash)))
                break;
            ecHash = ecHash->m_pNext;

#if defined (_DEBUG)
            // Test hook: when testing on debug builds, we want an easy way to test that the while
            // correctly terminates in the face of ridiculous stuff from the target.
            if (CLRConfig::GetConfigValue(CLRConfig::INTERNAL_DumpGeneration_IntentionallyCorruptDataFromTarget) == 1)
            {
                // Force us to struggle on with something bad.
                if (!ecHash)
                {
                    ecHash = (ECHash *)(((unsigned char *)&gFCallMethods[i])+1);
                }
            }
#endif // defined (_DEBUG)

        }
    }
}

#endif // DACCESS_COMPILE