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/*++
Copyright (c) 1989 Microsoft Corporation
Module Name:
context.c
Abstract:
This module implements user-mode callable context manipulation routines.
The interfaces exported from this module are portable, but they must
be re-implemented for each architecture.
Author:
Mark Lucovsky (markl) 20-Jun-1989
Revision History:
Bryan Willman (bryanwi) 8-Mar-90
Ported to the 80386
--*/
#include "ntrtlp.h"
#if defined(ALLOC_PRAGMA) && defined(NTOS_KERNEL_RUNTIME)
#pragma alloc_text(PAGE,RtlInitializeContext)
#pragma alloc_text(PAGE,RtlRemoteCall)
#endif
VOID
RtlInitializeContext(
IN HANDLE Process,
OUT PCONTEXT Context,
IN PVOID Parameter OPTIONAL,
IN PVOID InitialPc OPTIONAL,
IN PVOID InitialSp OPTIONAL
)
/*++
Routine Description:
This function initializes a context structure so that it can
be used in a subsequent call to NtCreateThread.
Arguments:
Context - Supplies a context buffer to be initialized by this routine.
InitialPc - Supplies an initial program counter value.
InitialSp - Supplies an initial stack pointer value.
Return Value:
Raises STATUS_BAD_INITIAL_STACK if the value of InitialSp is not properly
aligned.
Raises STATUS_BAD_INITIAL_PC if the value of InitialPc is not properly
aligned.
--*/
{
RTL_PAGED_CODE();
Context->Eax = 0L;
Context->Ebx = 1L;
Context->Ecx = 2L;
Context->Edx = 3L;
Context->Esi = 4L;
Context->Edi = 5L;
Context->Ebp = 0L;
Context->SegGs = 0;
Context->SegFs = KGDT_R3_TEB;
Context->SegEs = KGDT_R3_DATA;
Context->SegDs = KGDT_R3_DATA;
Context->SegSs = KGDT_R3_DATA;
Context->SegCs = KGDT_R3_CODE;
Context->EFlags = 0x200L; // force interrupts on, clear all else.
//
// Even though these are optional, they are used as is, since NULL
// is what these would have been initialized to anyway
//
Context->Esp = (ULONG) InitialSp;
Context->Eip = (ULONG) InitialPc;
//
// add code to check alignment and raise exception...
//
Context->ContextFlags = CONTEXT_CONTROL|CONTEXT_INTEGER|CONTEXT_SEGMENTS;
//
// Set the initial context of the thread in a machine specific way.
// ie, pass the initial parameter to the start address
//
Context->Esp -= sizeof(Parameter);
ZwWriteVirtualMemory(Process,
(PVOID)Context->Esp,
(PVOID)&Parameter,
sizeof(Parameter),
NULL);
Context->Esp -= sizeof(Parameter); // Reserve room for ret address
}
NTSTATUS
RtlRemoteCall(
HANDLE Process,
HANDLE Thread,
PVOID CallSite,
ULONG ArgumentCount,
PULONG Arguments,
BOOLEAN PassContext,
BOOLEAN AlreadySuspended
)
/*++
Routine Description:
This function calls a procedure in another thread/process, using
NtGetContext and NtSetContext. Parameters are passed to the
target procedure via its stack.
Arguments:
Process - Handle of the target process
Thread - Handle of the target thread within that process
CallSite - Address of the procedure to call in the target process.
ArgumentCount - Number of 32 bit parameters to pass to the target
procedure.
Arguments - Pointer to the array of 32 bit parameters to pass.
PassContext - TRUE if an additional parameter is to be passed that
points to a context record.
AlreadySuspended - TRUE if the target thread is already in a suspended
or waiting state.
Return Value:
Status - Status value
--*/
{
NTSTATUS Status;
CONTEXT Context;
ULONG NewSp;
ULONG ArgumentsCopy[5];
RTL_PAGED_CODE();
if (ArgumentCount > 4)
return STATUS_INVALID_PARAMETER;
//
// If necessary, suspend the guy before with we mess with his stack.
//
if (!AlreadySuspended) {
Status = NtSuspendThread( Thread, NULL );
if (!NT_SUCCESS( Status )) {
return( Status );
}
}
//
// Get the context record for the target thread.
//
Context.ContextFlags = CONTEXT_FULL;
Status = NtGetContextThread( Thread, &Context );
if (!NT_SUCCESS( Status )) {
if (!AlreadySuspended) {
NtResumeThread( Thread, NULL );
}
return( Status );
}
//
// Pass all parameters on the stack, regardless of whether a
// a context record is passed.
//
//
// Put Context Record on stack first, so it is above other args.
//
NewSp = Context.Esp;
if (PassContext) {
NewSp -= sizeof( CONTEXT );
Status = NtWriteVirtualMemory( Process,
(PVOID)NewSp,
&Context,
sizeof( CONTEXT ),
NULL
);
if (!NT_SUCCESS( Status )) {
if (!AlreadySuspended) {
NtResumeThread( Thread, NULL );
}
return( Status );
}
ArgumentsCopy[0] = NewSp; // pass pointer to context
RtlMoveMemory(&(ArgumentsCopy[1]),Arguments,ArgumentCount*sizeof( ULONG ));
ArgumentCount++;
}
else {
RtlMoveMemory(ArgumentsCopy,Arguments,ArgumentCount*sizeof( ULONG ));
}
//
// Copy the arguments onto the target stack
//
if (ArgumentCount) {
NewSp -= ArgumentCount * sizeof( ULONG );
Status = NtWriteVirtualMemory( Process,
(PVOID)NewSp,
ArgumentsCopy,
ArgumentCount * sizeof( ULONG ),
NULL
);
if (!NT_SUCCESS( Status )) {
if (!AlreadySuspended) {
NtResumeThread( Thread, NULL );
}
return( Status );
}
}
//
// Set the address of the target code into Eip, the new target stack
// into Esp, and reload context to make it happen.
//
Context.Esp = NewSp;
Context.Eip = (ULONG)CallSite;
Status = NtSetContextThread( Thread, &Context );
if (!AlreadySuspended) {
NtResumeThread( Thread, NULL );
}
return( Status );
}
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