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
146
147
148
149
150
151
|
#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];
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];
// Have a clean stack on next interrupt
TSS.esp0=(u32)stack+17;
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));
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(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+stack_offset);
// 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){
// Disable interrupt to not be interrupted
asm("cli");
// Enable scheduling
scheduler_on=1;
// Save kernel stack state
u32 *stack;
asm("mov %%ebp, %0":"=r" (stack));
// Remove ebp from the (c call convention) and return address (call)
TSS.esp0=(u32)stack+2;
asm("mov %%ss, %0": "=m" (TSS.ss0));
// 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;
// Switch to user task
asm(
"push %0 \n\t"
"jmp task_switch"
:: "a" (p)
);
}
}
|
