'Better' task management, needs more testing

Makefile

@@ -1,4 +1,4 @@
-objects = entry.o kernel.o handler.o interrupt.o v86.o print.o
+objects = entry.o kernel.o task.o handler.o interrupt.o v86.o print.o tss.o
 CFLAGS = -target "i686-elf" -m32 -mgeneral-regs-only -ffreestanding -march=pentium-m -fno-stack-protector -nostdlib -c
 
 %.o: %.nasm

bochsrc

@@ -1,6 +1,5 @@
 # configuration file generated by Bochs
 display_library: x, options="gui_debug"
-#magic_break: enabled=1
 plugin_ctrl: unmapped=true, biosdev=true, speaker=true, extfpuirq=true, parallel=true, serial=true, iodebug=true, pcidev=false, usb_uhci=false
 config_interface: textconfig
 display_library: x
@@ -32,7 +31,7 @@ vga: extension=vbe, update_freq=5, realtime=1, ddc=builtin
 cpu: count=1:1:1, ips=4000000, quantum=16, model=core_duo_t2400_yonah, reset_on_triple_fault=1, cpuid_limit_winnt=0, ignore_bad_msrs=1, mwait_is_nop=0
 print_timestamps: enabled=0
 debugger_log: -
-magic_break: enabled=0
+magic_break: enabled=1
 port_e9_hack: enabled=0
 private_colormap: enabled=0
 clock: sync=none, time0=local, rtc_sync=0

entry.nasm

@@ -76,17 +76,9 @@ global jmp_usermode_test
 jmp_usermode_test:
 pop eax ; return address
 mov ebp, esp ; return stack
-push ss
+call save_current_task
-push ebp
+mov esp, 0x500000 ; usermode stack
-pushfd
+mov eax, 0x20 | 3
-push cs
-push eax ; return address
-push ds ; other segs, pop
-push es ; before iret
-push fs ; in exit handler
-push gs
-mov dword [0x20004], esp   ; tss ESP0
-mov ax, 0x20 | 3
 mov ds, ax
 mov es, ax
 mov fs, ax
@@ -99,6 +91,8 @@ push 0x18 | 3
 push user_test
 iret
 
+extern save_current_task
+
 global flushTSS
 flushTSS:
 mov ax, 0x28

handler.nasm

@@ -35,12 +35,9 @@ movzx eax, word [eax]
 cmp eax, 0x30CD ; int 0x30
 jne gpf_unhandled
 pop eax ; return value
-mov esp, dword [0x20004] ; return info
+jmp return_prev_task
-pop gs
+
-pop fs
+extern return_prev_task
-pop es
-pop ds
-iret ; return to original caller
 
 scancodesToAscii: db 0, 0 ; 0x00 - 0x01
 db "1234567890" ; 0x02 - 0x0B

interrupt.c

@@ -87,6 +87,8 @@ extern void real_test();
 __attribute((__no_caller_saved_registers__))
 extern void kbd_wait();
 extern void jmp_usermode_test();
+__attribute((__no_caller_saved_registers__))
+extern void return_prev_task();
 #define VALID_FLAGS 0xDFF
 __attribute__ ((interrupt))
 void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
@@ -100,17 +102,17 @@ void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
     stack32 = (uint32_t*)stack;
 
     char *vga = (char*)0xb8000 + (160 * 10);
-    vga[0] = 'I'; vga[2] = 'P'; int_printWord(frame->eip, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'I'; vga[2] = 'P'; int_printWord(frame->eip, (uint16_t*)&vga[4]); vga += 14;
-    vga[0] = 'C'; vga[2] = 'S'; int_printWord(frame->cs, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'C'; vga[2] = 'S'; int_printWord(frame->cs, (uint16_t*)&vga[4]); vga += 14;
-    vga[0] = 'F'; vga[2] = 'L'; int_printDword(frame->eflags, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'F'; vga[2] = 'L'; int_printDword(frame->eflags, (uint16_t*)&vga[4]); vga += 14;
-    vga = (char*)0xb8000 + (160 * 11);
+    //vga = (char*)0xb8000 + (160 * 11);
-    vga[0] = 'S'; vga[2] = 'P'; int_printWord(frame->esp, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'S'; vga[2] = 'P'; int_printWord(frame->esp, (uint16_t*)&vga[4]); vga += 14;
-    vga[0] = 'S'; vga[2] = 'S'; int_printWord(frame->ss, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'S'; vga[2] = 'S'; int_printWord(frame->ss, (uint16_t*)&vga[4]); vga += 14;
-    vga = (char*)0xb8000 + (160 * 12);
+    //vga = (char*)0xb8000 + (160 * 12);
-    vga[0] = 'E'; vga[2] = 'S'; int_printWord(frame->es, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'E'; vga[2] = 'S'; int_printWord(frame->es, (uint16_t*)&vga[4]); vga += 14;
-    vga[0] = 'D'; vga[2] = 'S'; int_printWord(frame->ds, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'D'; vga[2] = 'S'; int_printWord(frame->ds, (uint16_t*)&vga[4]); vga += 14;
-    vga[0] = 'F'; vga[2] = 'S'; int_printWord(frame->fs, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'F'; vga[2] = 'S'; int_printWord(frame->fs, (uint16_t*)&vga[4]); vga += 14;
-    vga[0] = 'G'; vga[2] = 'S'; int_printWord(frame->gs, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'G'; vga[2] = 'S'; int_printWord(frame->gs, (uint16_t*)&vga[4]); vga += 14;
 
     //vga[2]++;
     //printDword(frame, &vga[20]);
@@ -128,7 +130,6 @@ void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
     //    vga += (sizeof(uint8_t)*2)*2;
     //}
     vga = (char*)0xb8000 + (160*3);
-    uint32_t *tss_esp0 = (uint32_t*)0x20004;
     for(;;) {
         switch (ip[0]) {
             case 0x66: // O32
@@ -177,7 +178,7 @@ void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
                 vga[0] = 'I'; vga[2]++; if (vga[2] < '0') vga[2] = '0';
                 switch (ip[1]) {
                     case 0x30:
-                        asm ("mov %%eax, %%esp\nret"::"a"(*tss_esp0));
+                        return_prev_task();
                         for(;;);
                     case 0x3:
                         kbd_wait();
@@ -219,18 +220,18 @@ void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
         }
     }
     done:;
-    vga = (char*)0xb8000 + (160 * 13);
+    //vga = (char*)0xb8000 + (160 * 13);
-    vga[0] = 'I'; vga[2] = 'P'; int_printWord(frame->eip, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'I'; vga[2] = 'P'; int_printWord(frame->eip, (uint16_t*)&vga[4]); vga += 14;
-    vga[0] = 'C'; vga[2] = 'S'; int_printWord(frame->cs, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'C'; vga[2] = 'S'; int_printWord(frame->cs, (uint16_t*)&vga[4]); vga += 14;
-    vga[0] = 'F'; vga[2] = 'L'; int_printDword(frame->eflags, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'F'; vga[2] = 'L'; int_printDword(frame->eflags, (uint16_t*)&vga[4]); vga += 14;
-    vga = (char*)0xb8000 + (160 * 14);
+    //vga = (char*)0xb8000 + (160 * 14);
-    vga[0] = 'S'; vga[2] = 'P'; int_printWord(frame->esp, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'S'; vga[2] = 'P'; int_printWord(frame->esp, (uint16_t*)&vga[4]); vga += 14;
-    vga[0] = 'S'; vga[2] = 'S'; int_printWord(frame->ss, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'S'; vga[2] = 'S'; int_printWord(frame->ss, (uint16_t*)&vga[4]); vga += 14;
-    vga = (char*)0xb8000 + (160 * 15);
+    //vga = (char*)0xb8000 + (160 * 15);
-    vga[0] = 'E'; vga[2] = 'S'; int_printWord(frame->es, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'E'; vga[2] = 'S'; int_printWord(frame->es, (uint16_t*)&vga[4]); vga += 14;
-    vga[0] = 'D'; vga[2] = 'S'; int_printWord(frame->ds, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'D'; vga[2] = 'S'; int_printWord(frame->ds, (uint16_t*)&vga[4]); vga += 14;
-    vga[0] = 'F'; vga[2] = 'S'; int_printWord(frame->fs, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'F'; vga[2] = 'S'; int_printWord(frame->fs, (uint16_t*)&vga[4]); vga += 14;
-    vga[0] = 'G'; vga[2] = 'S'; int_printWord(frame->gs, (uint16_t*)&vga[4]); vga += 14;
+    //vga[0] = 'G'; vga[2] = 'S'; int_printWord(frame->gs, (uint16_t*)&vga[4]); vga += 14;
 }
 
 extern void timerHandler();

kernel.c

@@ -3,7 +3,7 @@
 #include "print.h"
 #include "interrupt.h"
 
-#include "tss.c"
+#include "tss.h"
 
 typedef unsigned short word;
 
@@ -54,23 +54,33 @@ void print_cr4() {
 
 __attribute((__no_caller_saved_registers__))
 extern void enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip);
-extern void v86Code();
+extern void v86Test();
+extern void v86GfxMode();
 __attribute((__no_caller_saved_registers__))
 extern char *jmp_usermode_test();
 
 /*
 Real Mode Accessible (First MB)
- 00000 -  02000 IVT
+ 00000 -  00400 IVT (1kB)
- 01000 -  04000 Paging
+ 00400 -  01000 Unused (3kB)
- 04000 -  07C00 Free
+ 01000 -  04000 Paging (12kB)
- 07C00 -  08000 Boot
+ 04000 -  07C00 Free (15kB)
- 08000 -  20000 Kernel Code
+ 07C00 -  08000 Boot (512B)
- 20000 -  22080 TSS
+ 08000 -  20000 Kernel Code (96kB)
- 80000 -  90000 Real Mode Stack
+ 20000 -  20080 TSS (128B)
- 90000 -  A0000 Free
+ 20080 -  22080 TSS IOMAP (8kB)
- A0000 -  FFFFF BIOS Area
+ 22080 -  22400 Unused (896B)
+ 22400 -  23000 Free (3kB)
+ 23000 -  80000 Free (372kB)
+ 80000 -  90000 Real Mode Stack (64kB)
+ 90000 -  A0000 Free (64kB)
+ A0000 -  FFFFF BIOS Area (384kB)
 Protected Only (1MB+)
-100000 -        Free
+100000 - 300000 Free (2mB)
+300000 - 310000 Task Stack (64kB)
+310000 - 320000 Interrupt Stack (64kB)
+320000 - 400000 Kernel Stack (896kB)
+400000 - 500000 Usermode Stack (1mB)
 */
 
 void start() {
@@ -107,9 +117,12 @@ void start() {
     print_cr0();
     print_cr3();
     print_cr4();
-    FARPTR v86_entry = i386LinearToFp(v86Code);
+    FARPTR v86_entry = i386LinearToFp(v86Test);
+    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
+    v86_entry = i386LinearToFp(v86GfxMode);
     enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
     char *vga = jmp_usermode_test();
+    //asm ("xchgw %bx, %bx");
 
     for (int i = 0; i < 320; i++) {
         vga[i] = i;

task.nasm

@@ -0,0 +1,46 @@
+task_ptr: equ (0x310000-4)
+
+global save_current_task
+save_current_task:
+push ebx
+mov ebx, esp
+mov esp, dword [task_ptr] ; load current task pointer
+push ss
+push ebp ; return stack
+pushfd
+push cs
+push eax ; return address
+push ds ; other segs, pop
+push es ; before iret
+push fs ; in exit handler
+push gs
+mov dword [task_ptr], esp ; save new task pointer
+mov esp, ebx
+pop ebx
+ret
+
+global return_prev_task
+return_prev_task:
+mov edi, eax ; save for later
+mov esi, dword [task_ptr] ; load current task pointer
+add dword [task_ptr], 36 ; adjust to last task pointer
+mov eax, [esi+0] ; gs
+mov gs, ax
+mov eax, [esi+4] ; fs
+mov fs, ax
+mov eax, [esi+8] ; es
+mov es, ax
+mov ebx, [esi+16] ; eip
+mov ecx, [esi+20] ; cs
+mov edx, [esi+24] ; eflags
+; SS:ESP <- return stack
+mov esp, [esi+28] ; esp
+mov eax, [esi+32] ; ss
+mov ss, ax
+mov eax, [esi+12] ; ds
+mov ds, ax
+push edx ; eflags
+push ecx ; cs
+push ebx ; eip
+mov eax, edi ; restore return value
+iret

tss.c

@@ -1,5 +1,7 @@
 #include <stdint.h>
 
+#include "tss.h"
+
 struct __attribute__((__packed__)) tss_entry_struct {
     uint32_t prev_tss;
     uint32_t esp0;
@@ -35,8 +37,13 @@ void write_tss() {
     for (int i = 0; i < 0x2080; i++)
         ((uint8_t*)tss_data)[i] = 0;
     tss_data->ss0 = 0x10;
-    tss_data->esp0 = 0x400000;
+    tss_data->esp0 = 0x320000;
     tss_data->iomap_base = 0x80;
+
+    // not technically TSS but set up task pointer
+    uint32_t *current_task_ptr = (uint32_t*)(0x310000-4);
+    *current_task_ptr = 0x310000-40; // each task is 9 dwords, plus 1 for pointer
+    /* TODO setup null recovery task at start */
 }
 extern void flushTSS();
 

tss.h

@@ -0,0 +1,2 @@
+#pragma once
+void setup_tss();

v86.nasm

@@ -26,8 +26,8 @@ call real_hexprint
 mov ax, dx
 call real_hexprint
 ret
-extern v86Code
+global v86Test
-v86Code:
+v86Test:
 mov ax, 0xb814
 mov es, ax
 mov di, 20
@@ -41,43 +41,31 @@ mov ax, cs
 call real_printword
 .loop:
 inc byte [0]
-;mov ax, 0x1111
-;mov ds, ax
-;mov ax, 0x2222
-;mov es, ax
-;mov ax, 0x3333
-;mov fs, ax
-;mov ax, 0x4444
-;mov gs, ax
-;mov ax, 0x5555
-;mov ss, ax
-;mov ax, 0x6666
-;mov sp, ax
 int 3
 int 3
-;jmp .loop
-mov ax, 0x13
-int 0x10
 int 0x30 ; exit
 jmp $
-extern real_test
+global v86GfxMode
-real_test:
+v86GfxMode:
-nop
+mov ax, 0x13
-nop
+int 0x10
-nop
+int 0x30
 jmp $
 [BITS 32]
 ; extern void enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip);
 global enter_v86
 enter_v86:
+pop eax
 mov ebp, esp               ; save stack pointer
-mov dword [0x20004], ebp   ; tss ESP0
+call save_current_task
-push dword  [ebp+4]        ; ss
+push dword  [ebp+0]        ; ss
-push dword  [ebp+8]        ; esp
+push dword  [ebp+4]        ; esp
 pushfd                     ; eflags
 or dword [esp], (1 << 17)  ; set VM flags
 ;or dword [esp], (3 << 12) ; IOPL 3
-push dword [ebp+12]        ; cs
+push dword [ebp+8]        ; cs
-push dword  [ebp+16]       ; eip
+push dword  [ebp+12]       ; eip
 iret
 
+; return address in eax, return stack in ebp
+extern save_current_task