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Fix race in real mode event handling. 

Merge real mode pending event checking routines.
Remove some obsolete code.
This commit is contained in:
Jukka Heinonen 2003-11-11 00:44:10 +00:00 committed by Alexandre Julliard
parent 63c1093f24
commit d7ee5f3f31
2 changed files with 79 additions and 53 deletions
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129
dlls/ntdll/signal_i386.c
View File

@ -532,6 +532,71 @@ static void restore_vm86_context( const CONTEXT *context, struct vm86plus_struct
vm86->regs.ss = context->SegSs;
vm86->regs.eflags = context->EFlags;
}
/**********************************************************************
* merge_vm86_pending_flags
*
* Merges TEB.vm86_ptr and TEB.vm86_pending VIP flags and
* raises exception if there are pending events and VIF flag
* has been turned on.
*
* Called from __wine_enter_vm86 because vm86_enter
* doesn't check for pending events.
*
* Called from raise_vm86_sti_exception to check for
* pending events in a signal safe way.
*/
static void merge_vm86_pending_flags( EXCEPTION_RECORD *rec )
{
BOOL check_pending = TRUE;
struct vm86plus_struct *vm86 =
(struct vm86plus_struct*)(NtCurrentTeb()->vm86_ptr);
/*
* In order to prevent a race when SIGUSR2 occurs while
* we are returning from exception handler, pending events
* will be rechecked after each raised exception.
*/
while (check_pending && NtCurrentTeb()->vm86_pending)
{
check_pending = FALSE;
NtCurrentTeb()->vm86_ptr = NULL;
/*
* If VIF is set, throw exception.
* Note that SIGUSR2 may turn VIF flag off so
* VIF check must occur only when TEB.vm86_ptr is NULL.
*/
if (vm86->regs.eflags & VIF_MASK)
{
CONTEXT vcontext;
save_vm86_context( &vcontext, vm86 );
rec->ExceptionCode = EXCEPTION_VM86_STI;
rec->ExceptionFlags = EXCEPTION_CONTINUABLE;
rec->ExceptionRecord = NULL;
rec->NumberParameters = 0;
rec->ExceptionAddress = (LPVOID)vcontext.Eip;
vcontext.EFlags &= ~VIP_MASK;
NtCurrentTeb()->vm86_pending = 0;
EXC_RtlRaiseException( rec, &vcontext );
restore_vm86_context( &vcontext, vm86 );
check_pending = TRUE;
}
NtCurrentTeb()->vm86_ptr = vm86;
}
/*
* Merge VIP flags in a signal safe way. This requires
* that the following operation compiles into atomic
* instruction.
*/
vm86->regs.eflags |= NtCurrentTeb()->vm86_pending;
}
#endif /* __HAVE_VM86 */
@ -845,38 +910,21 @@ static void WINAPI raise_fpu_exception( EXCEPTION_RECORD *rec, CONTEXT *context
#ifdef __HAVE_VM86
/**********************************************************************
* raise_vm86_sti_exception
*
* FIXME: this is most likely broken.
*/
static void WINAPI raise_vm86_sti_exception( EXCEPTION_RECORD *rec, CONTEXT *context )
{
struct vm86plus_struct *vm86;
/* __wine_enter_vm86() merges the vm86_pending flag in safely */
/* merge_vm86_pending_flags merges the vm86_pending flag in safely */
NtCurrentTeb()->vm86_pending |= VIP_MASK;
vm86 = (struct vm86plus_struct*)(NtCurrentTeb()->vm86_ptr);
if (vm86)
if (NtCurrentTeb()->vm86_ptr)
{
if (vm86->regs.eflags & VIP_MASK) return;
vm86->regs.eflags |= VIP_MASK;
if (((char*)context->Eip >= (char*)vm86_return) &&
((char*)context->Eip <= (char*)vm86_return_end) &&
(VM86_TYPE(context->Eax) != VM86_SIGNAL)) {
/* exiting from VM86, can't throw */
return;
}
if (vm86->regs.eflags & VIF_MASK) {
/* VIF is set, throw exception */
CONTEXT vcontext;
NtCurrentTeb()->vm86_pending = 0;
NtCurrentTeb()->vm86_ptr = NULL;
save_vm86_context( &vcontext, vm86 );
rec->ExceptionAddress = (LPVOID)vcontext.Eip;
EXC_RtlRaiseException( rec, &vcontext );
restore_vm86_context( &vcontext, vm86 );
NtCurrentTeb()->vm86_ptr = vm86;
}
merge_vm86_pending_flags( rec );
}
else if (NtCurrentTeb()->dpmi_vif &&
!IS_SELECTOR_SYSTEM(context->SegCs) &&
@ -1195,40 +1243,18 @@ void __wine_enter_vm86( CONTEXT *context )
for (;;)
{
restore_vm86_context( context, &vm86 );
/* Linux doesn't preserve pending flag (VIP_MASK) on return,
* so save it on entry, just in case */
teb->vm86_pending |= (context->EFlags & VIP_MASK);
/* Work around race conditions with signal handler
* (avoiding sigprocmask for performance reasons) */
teb->vm86_ptr = &vm86;
vm86.regs.eflags |= teb->vm86_pending;
/* Check for VIF|VIP here, since vm86_enter doesn't */
if ((vm86.regs.eflags & (VIF_MASK|VIP_MASK)) == (VIF_MASK|VIP_MASK)) {
teb->vm86_ptr = NULL;
teb->vm86_pending = 0;
context->EFlags |= VIP_MASK;
rec.ExceptionCode = EXCEPTION_VM86_STI;
rec.ExceptionFlags = EXCEPTION_CONTINUABLE;
rec.ExceptionRecord = NULL;
rec.ExceptionAddress = (LPVOID)context->Eip;
rec.NumberParameters = 0;
EXC_RtlRaiseException( &rec, context );
continue;
teb->vm86_ptr = &vm86;
merge_vm86_pending_flags( &rec );
res = vm86_enter( &teb->vm86_ptr ); /* uses and clears teb->vm86_ptr */
if (res < 0)
{
errno = -res;
return;
}
do
{
res = vm86_enter( &teb->vm86_ptr ); /* uses and clears teb->vm86_ptr */
if (res < 0)
{
errno = -res;
return;
}
} while (VM86_TYPE(res) == VM86_SIGNAL);
save_vm86_context( context, &vm86 );
context->EFlags |= teb->vm86_pending;
rec.ExceptionFlags = EXCEPTION_CONTINUABLE;
rec.ExceptionRecord = NULL;
@ -1263,12 +1289,15 @@ void __wine_enter_vm86( CONTEXT *context )
rec.ExceptionInformation[0] = VM86_ARG(res);
break;
case VM86_STI: /* sti/popf/iret instruction enabled virtual interrupts */
context->EFlags |= VIF_MASK;
context->EFlags &= ~VIP_MASK;
teb->vm86_pending = 0;
rec.ExceptionCode = EXCEPTION_VM86_STI;
break;
case VM86_PICRETURN: /* return due to pending PIC request */
rec.ExceptionCode = EXCEPTION_VM86_PICRETURN;
break;
case VM86_SIGNAL: /* cannot happen because vm86_enter handles this case */
default:
ERR( "unhandled result from vm86 mode %x\n", res );
continue;

3
dlls/winedos/dosvm.c
View File

@ -557,9 +557,6 @@ static WINE_EXCEPTION_FILTER(exception_handler)
/* case EXCEPTION_VM86_PICRETURN: */
if (!ISV86(context))
ERR( "Protected mode STI caught by real mode handler!\n" );
context->EFlags |= VIF_MASK;
context->EFlags &= ~VIP_MASK;
DOSVM_SendQueuedEvents(context);
return EXCEPTION_CONTINUE_EXECUTION;
}