From 893a8bcac64193a6d5fb6e86cb7d871884b78cd0 Mon Sep 17 00:00:00 2001
From: Alex Ionescu <aionescu@gmail.com>
Date: Sun, 20 Aug 2006 20:09:25 +0000
Subject: [PATCH] - Don't use EFLAGS to store the Wait IRQL, just push
 directly, it's cleaner. - Detect if kernel APCs are pending and request
 APC_LEVEL software interrupt from HAL if they are, returning with the right
 apc status. - Also update INT21 VDM Descriptor handler when updating LDT
 descriptor.

svn path=/trunk/; revision=23624
---
 reactos/ntoskrnl/ke/i386/ctxswitch.S | 43 ++++++++++++++++++++++------
 reactos/ntoskrnl/ke/i386/thread.c    |  4 +--
 2 files changed, 37 insertions(+), 10 deletions(-)

diff --git a/reactos/ntoskrnl/ke/i386/ctxswitch.S b/reactos/ntoskrnl/ke/i386/ctxswitch.S
index 2d23bef0906..67840f04007 100644
--- a/reactos/ntoskrnl/ke/i386/ctxswitch.S
+++ b/reactos/ntoskrnl/ke/i386/ctxswitch.S
@@ -115,14 +115,11 @@ BadThread:
 .globl @KiSwapContextInternal@0
 @KiSwapContextInternal@0:
 
-    /* Save WaitIrql APC-bypass in EFLAGS */
-    or cl, cl
-
     /* Set the Thread to running */
     mov byte ptr [esi+KTHREAD_STATE], Running
 
-    /* Save the flags */
-    pushf
+    /* Save the IRQL */
+    push ecx
 
     /* Save the Exception list */
     push [ebx+KPCR_EXCEPTION_LIST]
@@ -224,13 +221,36 @@ SameProcess:
     /* Restore exception list */
     pop [ebx+KPCR_EXCEPTION_LIST]
 
-    /* Retore EFLAGS */
-    popf
+    /* Restore IRQL */
+    pop ecx
 
-    /* Return no APC pending */
+    /* Check if kernel APCs are pending */
+    cmp byte ptr [esi+KTHREAD_PENDING_KERNEL_APC], 0
+    jnz CheckApc
+
+    /* No APCs, return */
     xor eax, eax
     ret
 
+CheckApc:
+
+    /* Check if they're disabled */
+    cmp word ptr [esi+KTHREAD_SPECIAL_APC_DISABLE], 0
+    jnz ApcReturn
+    test cl, cl
+    jz ApcReturn
+
+    /* Request APC Delivery */
+    mov cl, APC_LEVEL
+    call @HalRequestSoftwareInterrupt@4
+    or eax, esp
+
+ApcReturn:
+
+    /* Return with APC pending */
+    setz al
+    ret
+
 LdtStuff:
 
     /* Write the LDT Selector */
@@ -240,6 +260,13 @@ LdtStuff:
     mov eax, [edi+KPROCESS_LDT_DESCRIPTOR1]
     mov [ecx+KGDT_LDT+4], eax
 
+    /* Write the INT21 handler */
+    mov ecx, [ebx+KPCR_IDT]
+    mov eax, [ebp+KPROCESS_INT21_DESCRIPTOR0]
+    mov [ecx+0x108], eax
+    mov eax, [ebp+KPROCESS_INT21_DESCRIPTOR1]
+    mov [ecx+0x10C], eax
+
     /* Save LDT Selector */
     mov eax, KGDT_LDT
     jmp LoadLdt
diff --git a/reactos/ntoskrnl/ke/i386/thread.c b/reactos/ntoskrnl/ke/i386/thread.c
index 466db3c63ba..b7469485525 100644
--- a/reactos/ntoskrnl/ke/i386/thread.c
+++ b/reactos/ntoskrnl/ke/i386/thread.c
@@ -15,7 +15,7 @@
 typedef struct _KSHARED_CTXSWITCH_FRAME
 {
     PVOID ExceptionList;
-    ULONG Flags;
+    KIRQL WaitIrql;
     PVOID RetEip;
 } KSHARED_CTXSWITCH_FRAME, *PKSHARED_CTXSWITCH_FRAME;
 
@@ -231,7 +231,7 @@ Ke386InitThreadWithContext(PKTHREAD Thread,
 
     /* And set up the Context Switch Frame */
     CtxSwitchFrame->RetEip = KiThreadStartup;
-    CtxSwitchFrame->Flags = EFLAGS_INTERRUPT_MASK;
+    CtxSwitchFrame->WaitIrql = APC_LEVEL;
     CtxSwitchFrame->ExceptionList = (PVOID)0xFFFFFFFF;
 
     /* Save back the new value of the kernel stack. */