attach.c

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/*++
 
Module Name:
 
    attach.c
 
Purpose:
 
    This module contains the implementation of process attaching.
 
Author:
 
    slep (Matanel) 2025.
 
Revision History:
 
--*/
 
#include "../../includes/me.h"
#include "../../includes/ps.h"
#include "../../assert.h"
 
void
MeAttachProcess(
    IN PIPROCESS Process,
    OUT PAPC_STATE ApcState
)
 
/*++
 
    Routine description:
 
        Attach to a process address space, this routine should be managed carefully, and have simple code between the attaching and detaching.
        
 
    Arguments:
 
        [IN]    PIPROCESS Process - Pointer to process to attach to (IPROCESS)
        [OUT]   PAPC_STATE - Pointer to store the state in resident memory.
 
    Return Values:
 
        None.
 
    Notes:
 
        DPCs CANNOT attach to a different process.
 
--*/
 
{
    if (MeIsExecutingDpc()) {
        // CANNOT Attach to a process while executing a DPC.
        MeBugCheckEx(
            INVALID_PROCESS_ATTACH_ATTEMPT,
            (void*)Process,
            (void*)(uintptr_t)RETADDR(0),
            (void*)MeIsExecutingDpc(),
            NULL
        );
    }
 
    PITHREAD CurrentThread = MeGetCurrentThread();
    if (unlikely(!CurrentThread)) return;
 
    // Save the process we were running on.
    ApcState->SavedApcProcess = CurrentThread->ApcState.SavedApcProcess;
    ApcState->SavedCr3 = __read_cr3();
    ApcState->AttachedToProcess = true;
    ApcState->SavedThreadAttached = CurrentThread->ApcState.AttachedToProcess;
 
    // Raise to SYNCH and lock scheduler.
    // TODO SYNCH
    MeAcquireSchedulerLock();
 
    // Switch identity to new process.
    CurrentThread->ApcState.SavedApcProcess = PsGetEProcessFromIProcess(Process);
    CurrentThread->ApcState.AttachedToProcess = true;
 
    // Switch CR3s.
    uint64_t TargetCr3 = Process->PageDirectoryPhysical;
    assert(TargetCr3 != 0);
 
    if (ApcState->SavedCr3 != TargetCr3) {
        __write_cr3(TargetCr3);
    }
}
 
void
MeDetachProcess(
    IN PAPC_STATE ApcState
)
 
/*++
 
    Routine description:
 
        Detach from a process address space.
 
    Arguments:
 
        [IN]    PAPC_STATE ApcState - The APC_STATE stored by MeAttachProcess.
 
    Return Values:
 
        None.
 
--*/
 
{
    PITHREAD CurrentThread = MeGetCurrentThread();
    if (unlikely(!CurrentThread)) return;
    if (!ApcState->AttachedToProcess) return;
 
    // Restore original CR3.
    uint64_t CurrentCr3 = __read_cr3();
    if (CurrentCr3 != ApcState->SavedCr3) {
        __write_cr3(ApcState->SavedCr3);
    }
 
    // Restore thread's identity to original process.
    CurrentThread->ApcState.SavedApcProcess = ApcState->SavedApcProcess;
    CurrentThread->ApcState.AttachedToProcess = ApcState->SavedThreadAttached;
 
    // Restore scheduler lock / IRQL.
    // TODO SYNCH LEVEL
    MeReleaseSchedulerLock();
 
    // Clear attached state.
    ApcState->AttachedToProcess = false;
}