Windows NT 4.0 source code leak
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// TITLE("Interlocked Increment and Decrement Support")
//++
//
// Copyright (c) 1995 Microsoft Corporation
//
// Module Name:
//
// critsect.s
//
// Abstract:
//
// This module implements functions to support trying to acquire
// user mode critical sections.
//
// These are private copies of the new NT4.0 Win32 apis
// TryEnterCriticalSection and InterlockedCompareExchange. This
// allows the MP heap package to run on NT3.51 systems.
//
// Author:
//
// John Vert (jvert) 12-Jul-1995
//
// Revision History:
//
//--
#include "ksppc.h"
// SBTTL("Try to Enter Critical Section")
//++
//
// BOOL
// TryEnterCriticalSection(
// IN PRTL_CRITICAL_SECTION CriticalSection
// )
//
// Routine Description:
//
// This function attempts to enter a critical section without blocking.
//
// Arguments:
//
// CriticalSection (r3) - Supplies a pointer to a critical section.
//
// Return Value:
//
// If the critical section was successfully entered, then a value of TRUE
// is returned as the function value. Otherwise, a value of FALSE is returned.
//
//--
LEAF_ENTRY(MpHeapTryEnterCriticalSection)
lwz r4, KiPcr + PcTeb(r0) // get address of current TEB
li r6, CsLockCount // offset into critical section
lwz r5, TeClientId+4(r4) // get current thread unique id
//
// Attempt to enter the critical section.
//
tecs10:
lwarx r7, r6, r3 // get addend value - locked
cmpwi r7, 0 // critical section owned?
addi r8, r7, 1 // increment addend value
bne- tecs20 // jump if critical section owned
stwcx. r8, r6, r3 // store conditionally
bne- tecs10 // loop if store failed
//
// The critical section is now owned by this thread. Initialize the owner
// thread id and return a successful status.
//
stw r5, CsOwningThread(r3) // set critical section owner
li r3, TRUE // set success status
blr // return
tecs20:
//
// The critical section is already owned. If it is owned by another thread,
// return FALSE immediately. If it is owned by this thread, we must increment
// the lock count here.
//
lwz r7, CsOwningThread(r3) // get current owner
cmpw r7, r5 // same thread?
beq tecs30 // if eq, this thread is already the owner
li r3, FALSE // set failure status
blr // return
tecs30:
lwz r4, CsRecursionCount(r3)
//
// This thread is already the owner of the critical section. Perform an atomic
// increment of the LockCount and a normal increment of the RecursionCount and
// return success.
//
tecs40:
lwarx r7, r6, r3 // get addend value - locked
addi r8, r7, 1 // increment addend value
stwcx. r8, r6, r3 // store conditionally
bne- tecs40 // loop if store failed
//
// Increment the recursion count
//
addi r5, r4, 1
stw r5, CsRecursionCount(r3)
li r3, TRUE // set success status
LEAF_EXIT(MpHeapTryEnterCriticalSection) // return
SBTTL("Interlocked Compare Exchange")
//++
//
// PVOID
// InterlockedCompareExchange (
// IN OUT PVOID *Destination,
// IN PVOID Exchange,
// IN PVOID Comperand
// )
//
// Routine Description:
//
// This function performs an interlocked compare of the destination
// value with the comperand value. If the destination value is equal
// to the comperand value, then the exchange value is stored in the
// destination. Otherwise, no opeation is performed.
//
// Arguments:
//
// Destination (r3) - Supplies a pointer to the destination value.
//
// Exchange (r4) - Supplies the exchange.
//
// Comperand (r5) - Supplies the comperand value.
//
// Return Value:
//
// The initial destination value is returned as the function value.
//
//--
LEAF_ENTRY(MpHeapInterlockedCompareExchange)
ice10:
lwarx r6, 0, r3 // get current addend value
cmpw r6, r5 // compare
bne- ice20 // if ne, operands mismatch
stwcx. r4, 0, r3 // store updated addend value
bne- ice10 // loop if store failed
ice20:
mr r3, r6 // return original value
LEAF_EXIT(MpHeapInterlockedCompareExchange) // return