Cleaning scheduler code

src/bringelle.c

@@ -49,10 +49,10 @@ void bringelle(){
   print("Launch user tasks \n");
 
   int* page_dir=paging_allocate(2);
-  task_create(page_dir, utask,100);
+  task_create(page_dir, utask,100, 0xFF);
 
   int* page_dir2=paging_allocate(2);
-  task_create(page_dir2, utask2,100);
+  task_create(page_dir2, utask2,100,0xFF);
 
   scheduler_start();
 

src/core/scheduler.c

@@ -10,45 +10,44 @@ u16 current_id;
 u16 nproc;
 
 void schedule(u32 *stack){
-  // Note that this function is called by clock
+  // Note that this function is called by clock()
-  // clock is called by INT_CLOCK (core/int.S)
+  // and clock() is called by INT_CLOCK (cf core/int.S)
-  // which store all the process information on
+  // which stores all the processes registers on
-  // the stack. Thus, knowing the C calling conventions
+  // the stack.
-  // and that schedule() is call by two functions with no parameters,
-  // the first process register can be accessed by ebp+2
 
-  // No proc to schedule
+  // No proc to schedule, just skip this function
   if(nproc<2)
     return;
   
   PROC *p=&procs[current_id];
-  p->regs.gs=stack[2]; // ebp+2=gs cf note above
+  p->regs.gs=stack[0]; // cf function specification in scheduler.h
-  p->regs.fs=stack[3];
+  p->regs.fs=stack[1];
-  p->regs.es=stack[4];
+  p->regs.es=stack[2];
-  p->regs.ds=stack[5];
+  p->regs.ds=stack[3];
-  p->regs.edi=stack[6];
+  p->regs.edi=stack[4];
-  p->regs.esi=stack[7];
+  p->regs.esi=stack[5];
-  p->regs.ebp=stack[8];
+  p->regs.ebp=stack[6];
-  // We do not take p->regs.esp=stack[9]
+  // We do not take p->regs.esp=stack[7]
   // since it corresponds to the kernel stack 
   // (it was push during the interruption)
-  p->regs.edx=stack[10];
+  p->regs.edx=stack[8];
-  p->regs.ecx=stack[11];
+  p->regs.ecx=stack[9];
-  p->regs.ebx=stack[12];
+  p->regs.ebx=stack[10];
-  p->regs.eax=stack[13];
+  p->regs.eax=stack[11];
-  p->regs.eip=stack[14];
+  p->regs.eip=stack[12];
-  p->regs.cs=stack[15];
+  p->regs.cs=stack[13];
-  p->regs.eflags=stack[16];
+  p->regs.eflags=stack[14];
-  p->regs.esp=stack[17];
+  p->regs.esp=stack[15];
-  p->regs.ss=stack[18];
+  p->regs.ss=stack[16];
 
+  // Get the next task to run
   current_id++;
   if(current_id>=nproc)
     current_id=0;
   p=&procs[current_id];
  
   // Have a clean stack on next interrupt
-  TSS.esp0=(u32)stack+19;
+  TSS.esp0=(u32)stack+17;
   asm("mov %%ss, %0": "=m" (TSS.ss0));
 
   // Ensure interrupts are activated and NT flag is clear
@@ -66,6 +65,7 @@ void schedule(u32 *stack){
 void clock(){
   u32* stack;
   asm("mov %%ebp, %0":"=r" (stack));
+  stack=&stack[2]; // Make stack pointing to gs
 
   static int tic=0;
   static int sec=0;
@@ -80,11 +80,11 @@ void clock(){
     schedule(stack);
 }
 
-void task_create(int *page_dir, void *task, int task_size){
+void task_create(int *page_dir, void *task, int task_size, int stack_offset){
   if(nproc<=MAX_PROC){
     // Compute various addresses
     void *entry_point=PAGING_ENTRY_POINT_VIRT;
-    void *ustack=(void*)(PAGING_ENTRY_POINT_VIRT+0xFF);
+    void *ustack=(void*)(PAGING_ENTRY_POINT_VIRT+stack_offset);
 
     // Load the task into memory
     memcpy(task,PAGING_ENTRY_POINT_PHY(page_dir), task_size);

src/core/scheduler.h

@@ -3,7 +3,6 @@
 
 #include "mem.h"
 
-
 #define MAX_PROC 10
 
 // If you change the following struct
@@ -29,11 +28,27 @@ typedef struct PROC {
 extern char show_tics;
 extern char scheduler_on;
 extern PROC procs[MAX_PROC];
-extern u16 current_id;
+extern u16 current_id; // Current running task PID/id
-extern u16 nproc;
+extern u16 nproc; // Number of active tasks
 
+/**
+ * Must be called at each clock interrupt
+ */
 void clock();
-void schedule();
+/**
-void task_create(int *page_dir, void *task, int task_size);
+ * Called by clock() and schedule the next task
+ * Stack is a pointer pointing to the gs register on the stack.
+ * The stack must contains the interrupted process registers in the following
+ * order: gs,fs,es,ds,edi,esi,ebp,UNUSED,edx,ecx,ebx,eax,eip,cs,eflags,esp,ss
+ */
+void schedule(u32 *stack);
+/**
+ * Create a new task to be schedule
+ */
+void task_create(int *page_dir, void *task, int task_size, int stack_offset);
+/**
+ * Stack the scheduler starting by task with PID 0
+ */
 void scheduler_start();
+
 #endif