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gh-116195: Implement win32_getppid_fast #116207

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gh-116195: Implement win32_getppid_fast #116207

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49474e1
Re-implement win32_getppid efficiently.
Mar 1, 2024
4bb90fb
Include fallback for win32_getppid, split new implementation into a s…
Mar 1, 2024
002524a
Merge branch 'python:main' into patch-1
Mar 1, 2024
6159002
Fix a header file that was left out
Mar 1, 2024
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93 changes: 91 additions & 2 deletions Modules/posixmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -9115,16 +9115,105 @@ os_setpgrp_impl(PyObject *module)
#ifdef HAVE_GETPPID

#ifdef MS_WINDOWS
#include <processsnapshot.h>
#include <winternl.h>
#include <ProcessSnapshot.h>

// The structure definition in winternl.h may be incomplete.
// This structure is the full version from the MSDN documentation.
typedef struct _PROCESS_BASIC_INFORMATION_FULL {
NTSTATUS ExitStatus;
PVOID PebBaseAddress;
ULONG_PTR AffinityMask;
LONG BasePriority;
ULONG_PTR UniqueProcessId;
ULONG_PTR InheritedFromUniqueProcessId;
} PROCESS_BASIC_INFORMATION_FULL;

typedef NTSTATUS (NTAPI *PNT_QUERY_INFORMATION_PROCESS) (
IN HANDLE ProcessHandle,
IN PROCESSINFOCLASS ProcessInformationClass,
OUT PVOID ProcessInformation,
IN ULONG ProcessInformationLength,
OUT PULONG ReturnLength OPTIONAL);

// This function returns the process ID of the parent process.
// Returns 0 on failure.
static ULONG
win32_getppid_fast(void)
{
NTSTATUS Status;
HMODULE Ntdll;
PNT_QUERY_INFORMATION_PROCESS pNtQueryInformationProcess;
PROCESS_BASIC_INFORMATION_FULL BasicInformation;
static ULONG CachedParentProcessId = 0;

if (CachedParentProcessId) {
// No need to query the kernel again.
return CachedParentProcessId;
}

Ntdll = GetModuleHandleW(L"ntdll.dll");
if (!Ntdll) {
return 0;
}

pNtQueryInformationProcess = (PNT_QUERY_INFORMATION_PROCESS) GetProcAddress(Ntdll, "NtQueryInformationProcess");
if (!pNtQueryInformationProcess) {
return 0;
}

Status = pNtQueryInformationProcess(
GetCurrentProcess(),
ProcessBasicInformation,
&BasicInformation,
sizeof(BasicInformation),
NULL);

if (!NT_SUCCESS(Status)) {
return 0;
}

//
// Perform sanity check on the parent process ID we received from NtQueryInformationProcess.
// The check covers values which exceed the 32-bit range (if running on x64) as well as
// zero and (ULONG) -1.
//

if (BasicInformation.InheritedFromUniqueProcessId == 0 ||
BasicInformation.InheritedFromUniqueProcessId >= ULONG_MAX) {

return 0;
}

//
// Now that we have reached this point, the BasicInformation.InheritedFromUniqueProcessId
// structure member contains a ULONG_PTR which represents the process ID of our parent
// process. This process ID will be correctly returned even if the parent process has
// exited or been terminated.
//

CachedParentProcessId = (ULONG) BasicInformation.InheritedFromUniqueProcessId;
return CachedParentProcessId;
}

static PyObject*
win32_getppid(void)
{
DWORD error;
PyObject* result = NULL;
HANDLE process = GetCurrentProcess();

HPSS snapshot = NULL;
ULONG pid;

pid = win32_getppid_fast();
if (pid != 0) {
return PyLong_FromUnsignedLong(pid);
}

//
// If failure occurs in win32_getppid_fast(), fall back to using the PSS API.
//

error = PssCaptureSnapshot(process, PSS_CAPTURE_NONE, 0, &snapshot);
if (error != ERROR_SUCCESS) {
return PyErr_SetFromWindowsErr(error);
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