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 "ksalpha.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 (a0) - 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)
GET_THREAD_ENVIRONMENT_BLOCK // (PALcode) get TEB address in v0
ldl a1, TeClientId+4(v0) // get current thread unique id
//
// Attempt to enter the critical section.
//
10: ldl_l t0, CsLockCount(a0) // get addend value - locked
addl t0, 1, t1 // increment addend value
bne t1, 20f // critical section owned
stl_c t1, CsLockCount(a0) // store conditionally
beq t1, 40f // if lock-flag eq zero, store failed
mb // synchronize all future fetches
// after obtaining the lock
//
// The critical section is now owned by this thread. Initialize the owner
// thread id and return a successful status.
//
stl a1, CsOwningThread(a0) // set critical section owner
ldil v0, TRUE // set success status
ret zero, (ra)
20:
//
// 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.
//
ldl t2, CsOwningThread(a0) // get current owner
cmpeq t2, a1, t3 // compare equality
bne t3, 30f // if ne, this thread is already the owner
bis zero,zero,v0 // set failure status
ret zero, (ra) // return
//
// 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.
//
30:
ldl_l t0, CsLockCount(a0) // get addend value - locked
addl t0, 1, t1 // increment addend value
stl_c t1, CsLockCount(a0) // store conditionally
beq t1, 50f // if eqz, store failed
//
// normally you need a MB here, but in this case we already own the lock
// so it is not necessary.
//
//
// Increment the recursion count
//
ldl t0, CsRecursionCount(a0)
addl t0, 1, t1
stl t1, CsRecursionCount(a1)
ldil v0, TRUE // set success status
ret zero, (ra) // return
//
// We expect the store conditional will usually succeed the first time so it
// is faster to branch forward (predicted not taken) to here and then branch
// backward (predicted taken) to where we wanted to go.
//
40: br zero, 10b // go try lock again
50: br zero, 30b // retry lock
.end MpHeapTryEnterCriticalSection
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 (a0) - Supplies a pointer to the destination value.
//
// Exchange (a1) - Supplies the exchange.
//
// Comperand (a2) - Supplies the comperand value.
//
// Return Value:
//
// The initial destination value is returned as the function value.
//
//--
LEAF_ENTRY(MpHeapInterlockedCompareExchange)
10:
mb
ldl_l v0, 0(a0) // get current addend value
bis a1, zero, t0 // copy exchange value for store
cmpeq v0, a2, t1 // if ne, operands mismatch
beq t1, 20f
stl_c t0, 0(a0) // store updated addend value
beq t0,25f // if eq, store conditional failed
mb
20: ret zero, (ra) // return
//
// We expect the store conditional will usually succeed the first time so it
// is faster to branch forward (predicted not taken) to here and then branch
// backward (predicted taken) to where we wanted to go.
//
25: br zero, 10b // go try spin lock again
.end MpHeapInterlockedCompareExchange