1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
|
#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
// 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
// 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;
p=&procs[current_id];
// 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(
"push %0 \n\t"
"jmp task_switch \n\t"
:: "a" (p)
);
}
void clock(){
u32* stack;
asm("mov %%ebp, %0":"=r" (stack));
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(int *page_dir, void *task, int task_size){
if(nproc<=MAX_PROC){
// Compute various addresses
void *entry_point=PAGING_ENTRY_POINT_VIRT;
void *ustack=(void*)(PAGING_ENTRY_POINT_VIRT+0xFF);
// 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;
// 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++;
}
}
void scheduler_start(){
if(nproc>0){
asm("cli");
scheduler_on=1; // Enable scheduling
u32 *stack;
asm("mov %%ebp, %0":"=r" (stack));
TSS.esp0=(u32)stack+1; // Remove ebp (c call convention)
asm("mov %%ss, %0": "=m" (TSS.ss0));
current_id=1;
PROC *p=&procs[current_id];
// Ensure interrupts are activated and NT flag is clear
p->regs.eflags|=0x200;
p->regs.eflags&=0xffffbfff;
asm(
"push %0 \n\t"
"jmp task_switch"
:: "a" (p)
);
}
}
|
