Fix access violation when loading script files

[crimsonskylark]

This PR addresses the "Access violation" reported in ivellioscolin/pykd#6.

The exception was caused by an unconditional usage of the _Py_fopen API which is no longer exported as of Python 3.10-3.13. According to python/cpython#127350 (comment) the API will return for Python 3.14 (and presumably future versions). My solution instead relies on the standard C++ file I/O APIs to read the file into memory and execute via PyRun_String in lieu of the previous PyRun_FileExFlags.

Finally, during the course of my investigation I found other APIs no longer exported by CPython (as of 3.13.5) also in-use by PyKD. As I cannot commit time to a bigger PR at this time I've left their usage intact, but the below list provides their names for future reference.

PyString_Type
_PyThreadState_Current
PyString_FromString
PyString_AsString
PyImport_Cleanup
PyClass_New
PyInstance_New
PyFile_FromString
PyFile_AsFile

[crimsonskylark]

I've also found other issues, e.g., when setting breakpoints via the API. I will leave this PR as-is since it resolves the original issue and open new PRs for the others.

[gerhart01]

Hello.
There are errors, when executing python scripts, which are working with Windows kernel.
Do that errors can be fixed in pykd-ext.dll only, or pykd.pyd had to be fixed too?

For example script for listing afd.sys driver endpoints: https://github.com/gerhart01/Hyper-V-scripts/blob/master/ParseAfdEndpointListHead.py

************* Path validation summary **************
Response                         Time (ms)     Location
Deferred                                       SRV*C:\Symbols*https://msdl.microsoft.com/download/symbols
Symbol search path is: SRV*C:\Symbols*https://msdl.microsoft.com/download/symbols
Executable search path is: 
Loading symbols for fffff806`7d800000     ntkrnlmp.exe ->   ntkrnlmp.exe
ModLoad: fffff806`7d800000 fffff806`7ec59000   ntkrnlmp.exe
Windows 10 Kernel Version 27975 MP (1 procs) Free x64
Product: WinNt, suite: TerminalServer SingleUserTS
Edition build lab: 27975.984.amd64fre.br_release_svc_prod3.251020-1700
Kernel base = 0xfffff806`7d800000 PsLoadedModuleList = 0xfffff806`7e6f9600
Debug session time: Tue Nov 11 10:24:20.253 2025 (UTC - 8:00)
System Uptime: 0 days 0:05:16.894
Loaded dbghelp extension DLL
Loaded exts extension DLL
Loaded kext extension DLL
Loaded kdexts extension DLL
nt!PpmIdleGuestExecute+0x1d:
fffff806`7dc9960d 48c1e220        shl     rdx,20h
kd> .load @"C:\scripts\pykd.dll"
Loaded C:\scripts\pykd.dll extension DLL
kd> !info

pykd bootstrapper version: 2.0.0.25

Installed python:

Version:        Status:     Image:
------------------------------------------------------------------------------
* 3.13 x86-64   Unloaded    C:\Python313\python313.dll


kd> !py @"C:\scripts\hello.py"
Hello
kd> !info

pykd bootstrapper version: 2.0.0.25

Installed python:

Version:        Status:     Image:
------------------------------------------------------------------------------
* 3.13 x86-64   Loaded      C:\Python313\python313.dll


kd> !py @"C:\scripts\ParseAfdEndpointListHead.py"
Script for AfdEndpointList parsing
Executing .reload command ...
c0000005 Exception in C:\scripts\pykd.dll.py debugger extension.
      PC: 00007ffa`e7808a19  VA: 00000000`00000010  R/W: 0  Parameter: 00000000`00000000

[crimsonskylark]

@gerhart01 Did you compile my branch or is this the official pykd release? If the former, my guess is you ran into one of the other problems I mentioned in my comment above.

I'm still planning on coming back to this and fix everything once and for all but haven't had the time.

[gerhart01]

Yes, i downloaded your compiled version from ivellioscolin/pykd#6 (comment).
Ok, understood - thanks for explanation.

[gerhart01]

It's working, if you replace getAttrByName in pykd\pymodule.h on that variant :

static python::object getAttrByName(kdlib::Module& module, const std::wstring& symbolName)
    {
        unsigned __int64 symbolVa = 0;
        kdlib::TypeInfoPtr typeInfo;
        bool symbolFound = false;
        bool typeFound = false;

        // Scope for AutoRestorePyState
        {
#if PY_VERSION_HEX < 0x030D0000  // Python < 3.13
            AutoRestorePyState  pystate;  
#endif

            try {
                symbolVa = module.getSymbolVa(symbolName);
                symbolFound = true;
            }
            catch (kdlib::DbgException&)
            {
            }

            if (!symbolFound)
            {
                try {
                    typeInfo = module.getTypeByName(symbolName);
                    typeFound = true;
                }
                catch (kdlib::DbgException&)
                {
                }
            }
        }

        if (symbolFound)
        {
            return python::object(symbolVa);
        }

        if (typeFound)
        {
            return python::object(typeInfo);
        }

        std::wstringstream sstr;
        sstr << L'\'' << module.getName() << L'\''
            << L" module has not a symbol "
            << L'\'' << symbolName << L'\'';
        throw AttributeException(std::string(_bstr_t(sstr.str().c_str())).c_str());
    }

[crimsonskylark]

@gerhart01 I'll include it in my PR with proper attribution, of course. Thanks.

[ivellioscolin]

Thank you all for your feedback.

If the access violation is due to unstable API _Py_fopen, it should been already fixed by commit
7c0c237

However the binary on release page https://github.com/ivellioscolin/pykd-ext/releases points to the original HEAD 857b62e, which doesn't include all fixes I made after. I should have put a HEAD build just as did for pykd.

I'm trying to make sometime to finish some other pending issues, and will put a pykd-ext nightly build on release page as well.

[gerhart01]

Fixes for pykd Python 3.14 supporting (partitially or full). Tested on WinDBG scripts for Kernel Mode:
https://github.com/gerhart01/pykd
https://github.com/gerhart01/pykd-ext
Probably, you can use them for patches.