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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(u32 *stack){
// Note that this function is called by clock()
// and clock() is called by INT_CLOCK (cf core/int.S)
// which stores all the processes registers on
// the stack.
// No proc to schedule, just skip this function
if(nproc<2)
return;
PROC *p=&procs[current_id];
p->regs.gs=stack[0]; // cf function specification in scheduler.h
p->regs.fs=stack[1];
p->regs.es=stack[2];
p->regs.ds=stack[3];
p->regs.edi=stack[4];
p->regs.esi=stack[5];
p->regs.ebp=stack[6];
// 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[8];
p->regs.ecx=stack[9];
p->regs.ebx=stack[10];
p->regs.eax=stack[11];
p->regs.eip=stack[12];
p->regs.cs=stack[13];
p->regs.eflags=stack[14];
// If clock occurs during a syscall (another interrupt)
if(p->regs.cs==0x08){
// Since we where already in kernel mode
// the CPU did not push ss and esp
// thus esp point to
p->regs.esp=&stack[15]; // Since we came from another interrupt this value will be restore by the last interrupt
p->regs.ss=TSS.ss0;
}
else {
p->regs.esp=stack[15];
p->regs.ss=stack[16];
}
// Get the next task to run
current_id++;
if(current_id>=nproc)
current_id=0;
p=&procs[current_id];
// Use kernel stack of the next task
TSS.ss0=p->regs.ss0;
TSS.esp0=p->regs.esp0;
// Ensure interrupts are activated and NT flag is clear
p->regs.eflags|=0x200;
p->regs.eflags&=0xffffbfff;
// Perform task switch
asm(
"push %0 \n\t"
"jmp task_switch \n\t"
:: "a" (p)
);
}
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;
tic++;
if(tic>=20){
tic=0;
sec++;
if(show_tics)
putchar('.');
}
if(scheduler_on==1)
schedule(stack);
}
void task_create(void *task, int task_size){
if(nproc<=MAX_PROC){
// Allocate at least 1 page and 1 page for the user stack
int allocated=1+task_size/4096+1;
int* page_dir=paging_allocate(allocated);
// Compute various addresses
void *entry_point=PAGING_ENTRY_POINT_VIRT;
// User stack start at the end of last allocated page (since addresses are going down)
void *ustack=(void*)(PAGING_ENTRY_POINT_VIRT+allocated*4096);
// Kernel stack start at the end of last allocated page +1 (see paging_allocate() implementation)
void *kstack=(void*)(PAGING_ENTRY_POINT_VIRT+(allocated+1)*4096);
// Load the task into memory
memcpy(task,PAGING_ENTRY_POINT_PHY(page_dir), task_size);
// Setup process registers
PROC *p=&procs[nproc];
p->regs.cs=0x23; // Task cs which is 0x30 along with prlv which is 0x3
p->regs.eip=entry_point;
p->regs.ss=0x33; // Task ss which is 0x20 along with prlv which is 0x3
p->regs.esp=ustack; // Stack is here for now...
p->regs.ds=0x2B; // GDT entry 0x28 along with prlv which is 0x3
p->regs.eax=0;
p->regs.ebx=0;
p->regs.ecx=0;
p->regs.edx=0;
p->regs.ss0=0x18;
p->regs.esp0=kstack;
// Manage eflags
u32 eflags;
asm (
"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
"mov %%eax, %0 \n\t" // Get flags into eflag
: "=m" (eflags)
);
p->regs.eflags=eflags;
// Setup other attributes
p->id=nproc;
p->pid=nproc;
p->page_dir=page_dir;
nproc++;
}
else
print("Could not create more task!");
}
void scheduler_start(){
if(nproc>0){
// Disable interrupt to not be interrupted
asm("cli");
// Enable scheduling
scheduler_on=1;
// Get first stack
current_id=0;
PROC *p=&procs[current_id];
// Ensure interrupts are activated and NT flag is clear
p->regs.eflags|=0x200;
p->regs.eflags&=0xffffbfff;
// Use task kernel stack
TSS.ss0=p->regs.ss0;
TSS.esp0=p->regs.esp0;
// Switch to user task
asm(
"push %0 \n\t"
"jmp task_switch"
:: "a" (p)
);
}
}
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