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[release/8.0-staging] Fix a set of minor DAC bugs I encountered recently #104919

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Oct 15, 2024
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[release/8.0-staging] Fix a set of minor DAC bugs I encountered recently #104919

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17 changes: 14 additions & 3 deletions src/coreclr/debug/daccess/dacdbiimpl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5650,10 +5650,13 @@ void DacDbiInterfaceImpl::LookupEnCVersions(Module* pModule,
DebuggerJitInfo * pDJI = NULL;
EX_TRY_ALLOW_DATATARGET_MISSING_MEMORY
{
pDMI = g_pDebugger->GetOrCreateMethodInfo(pModule, mdMethod);
if (pDMI != NULL)
if (g_pDebugger != NULL)
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How do we get to this state? This gets allocated in EEStartup. Is the DBI getting called super early on? Feels like this is something that shouldn't happen. Data target missing memory like the catch gets should be the main reason to not have it (or init error)

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@leculver leculver Jul 17, 2024 •
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This is a good overall cleanup for defensive coding. To be clear for this PR, I did not encounter the dacdbiimpl.cpp change with a real world example. It would be fine with me to not backport this particular fix and just leave the fix shipping for v.next. It's only the collections.cpp issue that I'd like to backport since I ran into it.

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@hoyosjs I hit those particular issues when debugging CLR startup scenarios. ... I spend a lot of time debugging the runtime startup path, and I regularly was hitting DAC crashes when trying to diagnose the startup path. Typically, the DAC isn't super useful at that point, but its really annoying to be unable to step through the various process creation paths.

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Also, yes, the DBI is commonly called this early in the newer Windbg UI.

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I withdraw my comment. :) If this happens in CLR startup I do recommend backporting this part to .net 8 as well. We deal with that often in servicing, watson and elsewhere. Even if most CLR devs will be on .Net 9, it would be good to get ahead of this issue for our long term servicing release.

{
pDJI = pDMI->FindJitInfo(pMD, CORDB_ADDRESS_TO_TADDR(pNativeStartAddress));
pDMI = g_pDebugger->GetOrCreateMethodInfo(pModule, mdMethod);
if (pDMI != NULL)
{
pDJI = pDMI->FindJitInfo(pMD, CORDB_ADDRESS_TO_TADDR(pNativeStartAddress));
}
}
}
EX_END_CATCH_ALLOW_DATATARGET_MISSING_MEMORY;
Expand Down Expand Up @@ -7512,6 +7515,10 @@ HRESULT DacDbiInterfaceImpl::GetDefinesBitField(ULONG32 *pDefines)
DD_ENTER_MAY_THROW;
if (pDefines == NULL)
return E_INVALIDARG;

if (g_pDebugger == NULL)
return CORDBG_E_NOTREADY;

*pDefines = g_pDebugger->m_defines;
return S_OK;
}
Expand All @@ -7521,6 +7528,10 @@ HRESULT DacDbiInterfaceImpl::GetMDStructuresVersion(ULONG32* pMDStructuresVersio
DD_ENTER_MAY_THROW;
if (pMDStructuresVersion == NULL)
return E_INVALIDARG;

if (g_pDebugger == NULL)
return CORDBG_E_NOTREADY;

*pMDStructuresVersion = g_pDebugger->m_mdDataStructureVersion;
return S_OK;
}
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4 changes: 2 additions & 2 deletions src/coreclr/debug/di/module.cpp
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Expand Up @@ -4250,12 +4250,12 @@ HRESULT CordbNativeCode::GetILToNativeMapping(ULONG32 cMap,
LoadNativeInfo();

SequencePoints * pSeqPts = GetSequencePoints();
DebuggerILToNativeMap * rgMapInt = pSeqPts->GetMapAddr();
ULONG32 cMapIntCount = pSeqPts->GetEntryCount();

// If they gave us space to copy into...
if (map != NULL)
if (map != NULL && cMapIntCount != 0)
{
DebuggerILToNativeMap * rgMapInt = pSeqPts->GetMapAddr();
// Only copy as much as either they gave us or we have to copy.
ULONG32 cMapToCopy = min(cMap, cMapIntCount);

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6 changes: 6 additions & 0 deletions src/coreclr/utilcode/collections.cpp
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Expand Up @@ -268,6 +268,12 @@ BYTE *CHashTable::FindNextEntry( // The next entry, or0 for end of list.
if (psSrch->iNext != UINT32_MAX)
{
psEntry = EntryPtr(psSrch->iNext);
#if DACCESS_COMPILE
// If there is a simple infinite loop in the linked list
// If more complex forms of infinite loops are present, this code may need to be adjusted to handle an arbitrary cycle.
if (psEntry->iNext == psSrch->iNext)
return NULL;
#endif
psSrch->iNext = psEntry->iNext;
return ((BYTE *) psEntry);
}
Expand Down
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