userspace and kernelspace taskswitching

2 files changed, 59 insertions, 28 deletions

diff --git a/asm/pit.s b/asm/pit.s
index ab8dcdb..c25e9a1 100644
--- a/asm/pit.s
+++ b/asm/pit.s
@@ -12,32 +12,38 @@ pit_get_ticks:
 
 pit_interrupt_handler:
 
-    // increase tick counter
-    push %eax
-    mov $ticks, %eax
-    incl (%eax)
-    pop %eax
-
-    ////
-
-    pusha          //Push all standard registers
-
-    mov %esp, %eax	//save current stack pointer (pointing to registers!)
-
-    movl $stack_top, %esp	//use stack from multiboot.s(16Kb)
+    push %eax // persist
 
-    // call our scheduler passing it the old stack addres (pointing to pushed registers (pusha))
-    push %eax   
-    call task_switch_next 
-
-    // the scheduler returned the new stack pointer (after taskswitch)
-    mov %eax, %esp   //Replace the stack with what the C code gave us
+    // INC TICK COUNTER
+    mov $ticks, %eax    
+    incl (%eax)
 
-    // acknowlege irq
-    mov $0x20,%al   
+    // ACK IRQ
+    mov $0x20,%al
     out %al,$0x20   
+
+    pop %eax // load original
     
-    popa           //Put the standard registers back
+    ///////
+
+    pusha          //Push all standard registers
+    push %ds       //Push data segment
+    push %es       //etc...
+    push %fs
+    push %gs
+
+    mov %esp, %eax          // remember current %esp
+    movl $stack_top, %esp   // switch to our small scheduler stack
+
+    push %eax               // set original %esp as param and... 
+    call task_switch_next   // call scheduler
+    mov  %eax, %esp         // use %esp we got from scheduler
+
+    pop %gs
+    pop %fs
+    pop %es
+    pop %ds
+    popa           
 
     iret
 
diff --git a/asm/task.s b/asm/task.s
index 7611d4a..c29bdae 100644
--- a/asm/task.s
+++ b/asm/task.s
@@ -2,15 +2,21 @@
 task_pusha:
 
     pushf
-
-    push $0x8
+    push $0x8	   // code segment
     push $userfunc
 
     pusha
+
+    push %ds
+    push %es
+    push %fs
+    push %gs
+
 	/*
+
 	now stack looks like:
 
-	param			 // esp+48
+	param			 // esp+64
 	returnaddy		
 
 	eflags			
@@ -26,9 +32,14 @@ task_pusha:
 	esi			
 	edi			
 
+	ds
+	es
+	fs
+	gs
+
 	*/
 
-    mov 48(%esp),%eax // get address of alternative stack where we want to simulate the pusha
+    mov 64(%esp),%eax // get address of alternative stack where we want to simulate the pusha
 
     mov (%esp),%ecx
     mov %ecx,(%eax)
@@ -66,10 +77,24 @@ task_pusha:
     mov 44(%esp),%ecx
     mov %ecx,44(%eax)
 
+    mov 48(%esp),%ecx
+    mov %ecx,48(%eax)
+
+    mov 52(%esp),%ecx
+    mov %ecx,52(%eax)
+
+    mov 56(%esp),%ecx
+    mov %ecx,56(%eax)
+
+    pop %gs
+    pop %fs
+    pop %es
+    pop %ds
+
+    popa
+
     pop %eax
     pop %eax
     pop %eax
 
-    popa
-
     ret