Built SMP initialization code in a separate binary which will be incl…

…uded in kernel and later copied at 0x7c00 address to execute. Turned on protected mode and paging for APs. Reserved stack space for APs. Using common file krnlconst.hdr to define constant for C and assembly that will be processed by command line scripts and will generate krnlconst.h and krnlconst.S - these two files will be included by source files.

README.md

@@ -3,12 +3,18 @@
 It supports boot loader, kernel with protected mode, paging, E820 enumeration, interrupt and exception handling, system calls, user mode, local APIC and multiprocessor.
 
 <b>Instructions for building kernel -</b><br>
+cat krnlconst.hdr | awk 'BEGIN{print "#ifndef _KERNEL_CONST_H"};{print "#define " $1 " " $2};END{print "#endif";}' > krnlconst.h<br>
+cat krnlconst.hdr | awk '{print ".equ " $1 ", " $2};' > krnlconst.S<br>
+
+as --32 mpinit.S -o mpinit.o<br>
+ld -static -T mpinit.ld -m elf_i386 -nostdlib --nmagic -o mpinit.elf mpinit.o<br>
+objcopy -O binary mpinit.elf mpinit.bin<br>
+
 as --32 boot32.S -o boot32.o<br>
 gcc -m32 -std=gnu99 -nostdlib -nostdinc -fno-builtin -fno-stack-protector -nostartfiles -nodefaultlibs -ffreestanding -fno-pic -Wall -Wextra -Werror -c util.c -o util.o<br>
 gcc -m32 -std=gnu99 -nostdlib -nostdinc -fno-builtin -fno-stack-protector -nostartfiles -nodefaultlibs -ffreestanding -fno-pic -Wall -Wextra -Werror -c system.c -o system.o<br>
 gcc -m32 -std=gnu99 -nostdlib -nostdinc -fno-builtin -fno-stack-protector -nostartfiles -nodefaultlibs -ffreestanding -fno-pic -Wall -Wextra -Werror -c apic.c -o apic.o<br>
 as --32 handlr32.S -o handlr32.o<br>
-as --32 mpinit.S -o mpinit.o<br>
 gcc -m32 -std=gnu99 -nostdlib -nostdinc -fno-builtin -fno-stack-protector -nostartfiles -nodefaultlibs -ffreestanding -fno-pic -Wall -Wextra -Werror -c smp.c -o smp.o<br>
 gcc -m32 -std=gnu99 -nostdlib -nostdinc -fno-builtin -fno-stack-protector -nostartfiles -nodefaultlibs -ffreestanding -fno-pic -Wall -Wextra -Werror -c setup32.c -o setup32.o<br>
 gcc -m32 -std=gnu99 -nostdlib -nostdinc -fno-builtin -fno-stack-protector -nostartfiles -nodefaultlibs -ffreestanding -fno-pic -Wall -Wextra -Werror -c start.c -o start.o<br>
@@ -17,7 +23,7 @@ gcc -m32 -std=gnu99 -nostdlib -nostdinc -fno-builtin -fno-stack-protector -nosta
 gcc -m32 -std=gnu99 -nostdlib -nostdinc -fno-builtin -fno-stack-protector -nostartfiles -nodefaultlibs -ffreestanding -fno-pic -Wall -Wextra -Werror -c usermode.c -o usermode.o<br>
 
 
-ld -static -T kernel32.ld -m elf_i386 -nostdlib --nmagic boot32.o util.o system.o apic.o mpinit.o smp.o setup32.o handlr32.o memory.o page32.o usermode.o start.o -o xiskernel.elf<br>
+ld -static -T kernel32.ld -m elf_i386 -nostdlib --nmagic boot32.o util.o system.o apic.o smp.o setup32.o handlr32.o memory.o page32.o usermode.o start.o -o xiskernel.elf<br>
 objcopy -O binary xiskernel.elf xiskernel.bin<br>
 
 <b>Instructions for building boot loader -</b><br>

boot32.S

@@ -70,3 +70,16 @@ highaddress:
 
 loop:
  jmp loop
+
+ .section mp_init, "ax"
+ .global init_ap
+ .align 8
+init_ap:
+ .incbin "mpinit.bin"
+
+ .global init_ap_size
+ .align 8
+ .global init_ap_size
+
+init_ap_size:
+ .int init_ap_size - init_ap

bootldr.S

@@ -14,9 +14,8 @@
 /* */
 /*****************************************************************************/
 
- .include "krnlsize.h"
- .equ E820_MAP_ADDR, 0x1008
- .equ PROTECTED_MODE_STACK, 0xf000
+ .include "krnlsize.S"
+ .include "krnlconst.S"
  .equ KERNEL_SECTORS, ((KERNEL_SIZE + 0x200 -1) / 0x200)
 
  // machine boots in 16bit real mode
@@ -45,7 +44,7 @@ _start:
  xorl %ebx, %ebx
  movl $24, %ecx
  movl $0x534d4150, %edx
- movl $E820_MAP_ADDR, %edi
+ movl $E820_MAP_ADDRESS, %edi
  movl $1, 20(%edi)
  int $0x15
 
@@ -90,7 +89,7 @@ e820_failed:
 e820_done:
 
  // store e820 count in memory
- movl %ebp, E820_MAP_ADDR-4
+ movl %ebp, E820_MAP_COUNT
 
  // write '8' in the screen to indicate e820 success
  movb $'8', %al
@@ -174,7 +173,7 @@ a20_line:
  cli
 
  // jump to protected mode
- ljmpl *segmentoffsetvalue
+ ljmpl *codesegaddr
 
 lba_read_error:
 
@@ -264,7 +263,7 @@ gdtdescriptor:
  .word end_of_gdt-gdt-1
  .long gdt
 
-segmentoffsetvalue:
+codesegaddr:
  .long protectedmodeaddress
  .word code_seg
 

kernel32.ld

@@ -6,21 +6,18 @@ ENTRY(_start)
 SECTIONS
 {
  . = 0x80100000;
- .text : AT(ADDR(.text) - 0x80000000) {*(.text); }
- .data : AT(ADDR(.data) - 0x80000000) {*(.data); }
- .bss : AT(ADDR(.bss) - 0x80000000) {*(.bss); }
- . = ALIGN(4096);
- .um : AT(ADDR(.um) - 0x80000000) {*(.um);}
+ .text : {*(.text); }
+ .data : {*(.data); }
+ .bss : {*(.bss); }
  um_size = SIZEOF(um);
- . = ALIGN(4096);
- .mp_init : AT(ADDR(.mp_init) - 0x80000000) {*(.mp_init);}
- mp_init_size = SIZEOF(mp_init);
- .kernel_data ALIGN(4096) : AT(ADDR(.kernel_data) - 0x80000000) {*(.kernel_data); }
+ . = ALIGN(8);
+ .mp_init : {*(.mp_init); }
  . = ALIGN(4096);
  _kernel_pg_dir = .;
  _kernel_pg_table_0 = _kernel_pg_dir + 0x1000;
  _kernel_stack_0 = _kernel_pg_table_0 + 0x1000;
  _kernel_stack_0_start = _kernel_stack_0 + 0x2000;
+ _kernel_stack_ap_start = _kernel_stack_0_start + (0x2000 * 32);
  _kernel_private_data = _kernel_stack_0_start + 8;
  _kernel_heap_start = (_kernel_private_data + 0x1000) & ~(0xfff);
 }

krnlconst.hdr

@@ -0,0 +1,9 @@
+VIDEO_BUFFER 0xb8000
+E820_MAP_ADDRESS 0x1008
+E820_MAP_COUNT 0x1004
+PROTECTED_MODE_STACK 0xf000
+AP_FIRST_STACK 0xfff0
+AP_LAPIC_BASE_REGISTER 0xfff4
+AP_COUNT_PHYS_ADDR 0xfff8
+AP_KERNEL_PG_DIR 0xfffc
+KERNEL_VIRT_ADDR 0x80000000

mpinit.S

@@ -9,14 +9,13 @@
 /* */
 /*****************************************************************************/
 
- .equ AP_COUNT_PHYS_ADDR, 0xfff8
- .code16
-
- .globl init_ap
+ .include "krnlconst.S"
 
- .section "mp_init", "ax"
+ .code16
+ .text
 
-init_ap:
+.globl _start
+_start:
 
  cli
  xorw %ax, %ax
@@ -26,6 +25,91 @@ init_ap:
  movw %ax, %fs
  movw %ax, %gs
 
- incw AP_COUNT_PHYS_ADDR
+ // loads gdt
+ xorw %ax, %ax
+ movw %ax, %ds
+ lgdt gdtdescriptor
+
+ // turn on protected mode
+ movl %cr0, %eax
+ orl $1, %eax
+ movl %eax, %cr0
+
+ cli
+
+ // jump to protected mode
+ ljmpl *codesegaddr
+
+ // protected mode code
+ .code32
+
+protectedmodeaddress:
+
+ movl $data_seg, %eax
+ movl %eax, %ds
+ movl %eax, %es
+ movl %eax, %ss
+ movl %eax, %fs
+ movl %eax, %gs
+
+
+ // turning on paging
+ movl AP_KERNEL_PG_DIR, %eax
+ movl %eax, %cr3
+ movl %cr0, %eax
+ orl $0x80000000, %eax
+ movl %eax, %cr0
+
+ lock incw AP_COUNT_PHYS_ADDR+KERNEL_VIRT_ADDR
 
  hlt
+
+ .code32
+ .section ".high", "ax"
+
+highaddress:
+
+ // initialize protected mode stack
+ movl $PROTECTED_MODE_STACK, %eax
+ movl %eax, %esp
+ movl %eax, %ebp
+
+ hlt
+
+ .data
+ // global descriptor table (GDT)
+ .p2align 5
+gdt:
+// offset 0x0 - NULL descriptor
+ .quad 0
+
+code_seg_addr:
+// offset 0x8 - cs should point to this descriptor
+ .word 0xFFFF
+ .word 0
+ .byte 0
+ .byte 0x9A
+ .byte 0xCF
+ .byte 0
+
+data_seg_addr:
+// offset 0x10 - ds, ss, es, fs, and gs should point to this descriptor
+ .word 0xFFFF
+ .word 0
+ .byte 0
+ .byte 0x92
+ .byte 0xCF
+ .byte 0
+
+end_of_gdt: 
+
+codesegaddr:
+ .long protectedmodeaddress
+ .word code_seg
+
+gdtdescriptor:
+ .word end_of_gdt-gdt-1
+ .long gdt
+
+ .equ code_seg, code_seg_addr-gdt
+ .equ data_seg, data_seg_addr-gdt

setup32.h

@@ -13,14 +13,15 @@
 #ifndef _SETUP_32_H
 #define _SETUP_32_H
 
+#define NUM_SMPS 32
+
 #define USER_CODE_SEG 0x10
 #define USER_DATA_SEG 0x18
 #define KERNEL_CODE_SEG 0x20
 #define KERNEL_DATA_SEG 0x28
 #define LDT_SELECTOR 0x30
 #define TASK_SEG 0x38
-#define DUMMY_SEG 0x40
-#define LAST_SEG (DUMMY_SEG+8)
+#define LAST_SEG (TASK_SEG+(NUM_SMPS*8))
 
 #define USER_CODE_SEG_IN_LDT 0x0
 #define USER_DATA_SEG_IN_LDT 0x8

smp.c

@@ -12,19 +12,27 @@
 #include "util.h"
 #include "system.h"
 #include "apic.h"
+#include "krnlconst.h"
 
-#define AP_INIT_PHYS_TEXT 0xf000
-#define AP_COUNT_PHYS_ADDR 0xfff8
+#define AP_INIT_PHYS_TEXT 0x7c00
 
-extern int mp_init_size;
 extern int init_ap;
+extern int init_ap_size;
+
+extern int lapic_base_register;
+
+extern int _kernel_stack_ap_start;
+extern int _kernel_pg_dir;
+extern int _kernel_pg_table_0;
 
 void copy_smp_init_to_low_mem() {
 
  char *s = (char*)&init_ap;
  char *d = (char*)(AP_INIT_PHYS_TEXT+KERNEL_VIRT_ADDR);
 
- for(int i=0;i<(int)&mp_init_size;i++) {
+ print_msg("init_ap_size", (int)init_ap_size, 10, true);
+
+ for(int i=0;i<(int)init_ap_size;i++) {
  *d++ = *s++;
  }
 }
@@ -36,6 +44,14 @@ void smp_start() {
  // initialize AP processor count with 0
  // it will be increased by AP startup code
  *(int*)(AP_COUNT_PHYS_ADDR+KERNEL_VIRT_ADDR) = 0;
+ *(int*)(AP_FIRST_STACK+KERNEL_VIRT_ADDR) = (int)&_kernel_stack_ap_start;
+ *(int*)(AP_LAPIC_BASE_REGISTER+KERNEL_VIRT_ADDR) = (int)&lapic_base_register;
+ *(int*)(AP_KERNEL_PG_DIR+KERNEL_VIRT_ADDR) = (((int)&_kernel_pg_dir)-KERNEL_VIRT_ADDR);
+
+ // identity mapping to enable APs to use paging.
+ // It needs to be cleared after APs are initialized or it usermode programs
+ // sharing this page directory cannot access first 4MB virtual memory.
+ ((int*)&_kernel_pg_dir)[0] = (((int)&_kernel_pg_table_0) - KERNEL_VIRT_ADDR) | 3;
 
  MFENCE;
 

system.c

@@ -28,7 +28,7 @@ int vga_buffer_line = 0;
 //
 void print_vga(char *c, bool newline) {
 
- unsigned short *p = (unsigned short *)((char*)VIDEO_BUFFER+vga_buffer_index+(vga_buffer_line*160));
+ unsigned short *p = (unsigned short *)((char*)VIDEO_VIRT_BUFFER+vga_buffer_index+(vga_buffer_line*160));
 
  while(*c) {
 
@@ -52,7 +52,7 @@ void print_vga(char *c, bool newline) {
 
 void print_vga_fixed(char *c, int col, int row) {
 
- unsigned short *p = (unsigned short *)((char*)VIDEO_BUFFER+col+(row*160));
+ unsigned short *p = (unsigned short *)((char*)VIDEO_VIRT_BUFFER+col+(row*160));
 
  while(*c) {
 
@@ -75,8 +75,8 @@ void print_vga_fixed(char *c, int col, int row) {
 void dump_e820() {
 
  int i;
- int e820_count= *((int *) E820_MAP_COUNT);
- struct e820_map *e820 = (struct e820_map *) E820_MAP_ADDRESS;
+ int e820_count= *((int *) E820_MAP_VIRT_COUNT);
+ struct e820_map *e820 = (struct e820_map *) E820_MAP_VIRT_ADDRESS;
  char str[17];
 
  print_vga("E820 map", true);

system.h

@@ -14,11 +14,11 @@
 #define _SYSTEM_H
 
 #include "type.h"
+#include "krnlconst.h"
 
-#define KERNEL_VIRT_ADDR 0x80000000
-#define VIDEO_BUFFER (KERNEL_VIRT_ADDR+0xb8000)
-#define E820_MAP_ADDRESS (KERNEL_VIRT_ADDR+0x1008)
-#define E820_MAP_COUNT (KERNEL_VIRT_ADDR+0x1004)
+#define VIDEO_VIRT_BUFFER (KERNEL_VIRT_ADDR+VIDEO_BUFFER)
+#define E820_MAP_VIRT_ADDRESS (KERNEL_VIRT_ADDR+E820_MAP_ADDRESS)
+#define E820_MAP_VIRT_COUNT (KERNEL_VIRT_ADDR+E820_MAP_COUNT)
 
 #define PIT_CRYSTAL_FREQUENCY 1193182
 #define PIT_HZ (PIT_CRYSTAL_FREQUENCY/1000)