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#include "scheduler.h"
#include "libc/stdio.h"
#include "gdt.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(){
static int tic=0;
static int sec=0;
tic++;
if(tic>=20){
tic=0;
sec++;
if(show_tics)
putchar('.');
}
if(scheduler_on==1)
schedule();
}
void run_task(int *page_dir, void *task, int task_size){
// Compute various addresses
int*pt_addr=(int*)PADDR(page_dir[1]);
void *entry_point=(void*)(PADDR(pt_addr[3]));
void *ustack=(void*)((int)entry_point+0xFF);
// Load the task into memory
memcpy(task,entry_point, task_size);
// Load page directory
asm(
"mov %0, %%eax \n\t"
"mov %%eax,%%cr3 \n\t"
:: "b"(page_dir)
);
// Setup users adresses
// Switch to user task
asm (
"cli \n\t" // Ensure we do not get interrupted
"movl %%ss, %%eax \n\t"
"movl %%eax, %0 \n\t" // Save kernel ss segment into the TSS
"movl %%esp, %1 \n\t" // Save kernel esp into the TSS BEFORE setting up the stack
"pushl $0x33 \n\t" // Push task ss which is 0x30 along with prlv which is 0x3
"pushl %2 \n\t" // Push task esp
"pushfl \n\t" // Retrieve flags
"popl %%eax \n\t"
"orl $0x200, %%eax \n\t" // Enable interrupt for the user task
"and $0xffffbfff, %%eax \n\t" // Clear the NT flags
"push %%eax \n\t" // Push task flags
"push $0x23 \n\t" // Push task cs which is 0x20 along with prlv which is 0x3
"push %3 \n\t" // Push task entry point
"mov $0x2B, %%eax \n\t" // GDT entry 0x28 along with prlv which is 0x3
"mov %%eax, %%ds \n\t" // Setting up user data segment
"iret \n\t" // Launch user task
: "=m" (TSS.ss0), "=m" (TSS.esp0)
: "b" (ustack), "c" (entry_point)
);
}
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