1 files changed, 58 insertions, 2 deletions
diff --git a/src/core/scheduler.c b/src/core/scheduler.c
index 848b7b7..0a8c5c7 100644
--- a/src/core/scheduler.c
+++ b/src/core/scheduler.c
@@ -1,12 +1,67 @@
+#include "scheduler.h"
 #include "libc/stdio.h"
 #include "gdt.h"
-#include "mem.h"
 #include "paging.h"
 
 char show_tics=0;
+char scheduler_on=0;
+PROC procs[MAX_PROC];
+u16 current_id;
+u16 nproc;
 
 void schedule(){
+  // Note that this function is called by clock
+  // clock is called by INT_CLOCK (core/int.S)
+  // which store all the process information on
+  // the stack. Thus, knowing the C calling conventions
+  // and that schedule() is call by two functions with no parameters,
+  // the first process register can be accessed by ebp+2
+  u32 *stack;
+  asm("mov %%ebp, %0":"=r" (stack));
+  
+  // No proc to schedule
+  if(nproc<2)
+    return;
+  
+  PROC *p=&procs[current_id];
+  p->regs.gs=stack[2]; // ebp+2=gs cf note above
+  p->regs.fs=stack[3];
+  p->regs.es=stack[4];
+  p->regs.ds=stack[5];
+  p->regs.edi=stack[6];
+  p->regs.esi=stack[7];
+  p->regs.ebp=stack[8];
+  // We do not take p->regs.esp=stack[9]
+  // since it corresponds to the kernel stack 
+  // (it was push during the interruption)
+  p->regs.edx=stack[10];
+  p->regs.ecx=stack[11];
+  p->regs.ebx=stack[12];
+  p->regs.eax=stack[13];
+  p->regs.eip=stack[14];
+  p->regs.cs=stack[15];
+  p->regs.eflags=stack[16];
+  p->regs.esp=stack[17];
+  p->regs.ss=stack[18];
+
+  current_id++;
+  if(current_id>=nproc)
+    current_id=0;
 
+  // Have a clean stack on next interrupt
+  TSS.esp0=(u32)stack+19;
+  asm("mov %%ss, %0": "=m" (TSS.ss0));
+
+  // Ensure interrupts are activated and NT flag is clear
+  p->regs.eflags|=0x200;
+  p->regs.eflags&=0xffffbfff;
+
+  // Perform task switch
+  asm(
+    "mov %0, %%esi    \n\t"
+    "jmp task_switch  \n\t"
+    :: "a" (p)
+  );
 }
 
 void clock(){
@@ -19,7 +74,8 @@ void clock(){
     if(show_tics)
       putchar('.');
   }
-  schedule();
+  if(scheduler_on==1)
+    schedule();
 }
 
 void run_task(int *page_dir, void *task, int task_size){