Calculates stack address for current AP from LAPIC id and use it call…

… smp_finish_initialization C code. Introcuded spin lock to synchronize smp_bits and printing messages from initializing APs. Clears identity mapping when SMP initialization is finished.

README.md

@@ -21,12 +21,13 @@ 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 memory.c -o memory.o<br>
 gcc -m32 -std=gnu99 -nostdlib -nostdinc -fno-builtin -fno-stack-protector -nostartfiles -nodefaultlibs -ffreestanding -fno-pic -Wall -Wextra -Werror -c page32.c -o page32.o<br>
 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>
+gcc -m32 -std=gnu99 -nostdlib -nostdinc -fno-builtin -fno-stack-protector -nostartfiles -nodefaultlibs -ffreestanding -fno-pic -Wall -Wextra -Werror -c lock.c -o lock.o<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>
+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 lock.o start.o -o xiskernel.elf<br>
 objcopy -O binary xiskernel.elf xiskernel.bin<br>
 
 <b>Instructions for building boot loader -</b><br>
+cat krnlconst.hdr | awk '{print ".equ " $1 ", " $2};' > krnlconst.S<br>
 echo ".equ KERNEL_SIZE, &#96;ls -l xiskernel.bin | cut -f5 -d\ &#96;" > krnlsize.h<br>
 as --32 bootldr.S -o bootldr.o<br>
 ld -static -T bootldr.ld -m elf_i386 -nostdlib --nmagic -o bootldr.elf bootldr.o<br>

boot32.S

@@ -15,7 +15,7 @@
  .code32
  .text
 
- .equ KERNEL_VIRT_ADDR, 0x80000000
+ .include "krnlconst.S"
  .equ KERNEL_PGDIR_ENTRY, (KERNEL_VIRT_ADDR >> 20)
 
  .globl _start

kernel32.ld

@@ -17,7 +17,6 @@ SECTIONS
  _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_private_data = _kernel_stack_0_start + (0x2000 * 32);
  _kernel_heap_start = (_kernel_private_data + 0x1000) & ~(0xfff);
 }

krnlconst.hdr

@@ -6,4 +6,5 @@ AP_FIRST_STACK 0xfff0
 AP_LAPIC_BASE_REGISTER 0xfff4
 AP_COUNT_PHYS_ADDR 0xfff8
 AP_KERNEL_PG_DIR 0xfffc
+AP_FINISH_CODE 0x10000
 KERNEL_VIRT_ADDR 0x80000000

lock.c

@@ -0,0 +1,32 @@
+/*****************************************************************************/
+/* File: lock.c */
+/* */
+/* Description: Source file for synchonization primitives. */
+/* */
+/* Author: Shoily O Rahman <[email protected]> */
+/* */
+/* Date: Oct 16, 2020 */
+/* */
+/*****************************************************************************/
+
+#include "lock.h"
+
+void spinlock_lock(spin_lock *lock) {
+
+ __asm__ __volatile__("movl $1, %%eax;"
+ "1:;"
+ "lock xchgl %0, %%eax;"
+ "testl %%eax, %%eax;"
+ "jne 1b;"
+ : "=m" (lock->val)
+ : "m" (lock->val)
+ : "%eax", "%ebx", "cc", "memory" );
+}
+
+void spinlock_unlock(spin_lock *lock) {
+
+ __asm__ __volatile__("movl $0, %0;"
+ : "=m" (lock->val)
+ :
+ : "cc", "memory" );
+}

lock.h

@@ -0,0 +1,24 @@
+/*****************************************************************************/
+/* File: lock.h */
+/* */
+/* Description: Header file for synchonization primitives. */
+/* */
+/* Author: Shoily O Rahman <[email protected]> */
+/* */
+/* Date: Oct 16, 2020 */
+/* */
+/*****************************************************************************/
+
+#ifndef _LOCK_H
+#define _LOCK_H
+
+typedef struct _spin_lock {
+ int val;
+} spin_lock;
+
+#define INIT_SPIN_LOCK(spinlock) memset(spinlock, sizeof(spin_lock), 0)
+
+void spinlock_lock(spin_lock *lock);
+void spinlock_unlock(spin_lock *lock);
+
+#endif

mpinit.S

@@ -38,7 +38,7 @@ _start:
  cli
 
  // jump to protected mode
- ljmpl *codesegaddr
+ ljmpl *protectmodecodesegaddr
 
  // protected mode code
  .code32
@@ -52,29 +52,49 @@ protectedmodeaddress:
  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
+ ljmpl *highcodesegaddr
 
  .code32
  .section ".high", "ax"
 
 highaddress:
 
+ // get LAPIC id
+ movl AP_LAPIC_BASE_REGISTER, %ebx
+ addl $0x20, %ebx
+ movl (%ebx), %eax
+ shrl $24, %eax
+ movl %eax, %ecx
+
+ // calculate start of kernel mode stack for this processor
+ movl $0x2000, %ebx
+ mull %ebx
+ movl AP_FIRST_STACK, %ebx
+ addl %ebx, %eax
+
  // initialize protected mode stack
- movl $PROTECTED_MODE_STACK, %eax
  movl %eax, %esp
- movl %eax, %ebp
+ movl %esp, %ebp
+
+ pushl %ecx
 
- hlt
+ // increment AP count
+ lock incw AP_COUNT_PHYS_ADDR+KERNEL_VIRT_ADDR
+
+ movl AP_FINISH_CODE+KERNEL_VIRT_ADDR, %eax
+
+ // call finish_mp_initialization
+ call *%eax
+
+loop:
+ jmp loop
 
  .data
  // global descriptor table (GDT)
@@ -103,10 +123,14 @@ data_seg_addr:
 
 end_of_gdt: 
 
-codesegaddr:
+protectmodecodesegaddr:
  .long protectedmodeaddress
  .word code_seg
 
+highcodesegaddr:
+ .long highaddress
+ .word code_seg
+
 gdtdescriptor:
  .word end_of_gdt-gdt-1
  .long gdt

smp.c

@@ -13,6 +13,7 @@
 #include "system.h"
 #include "apic.h"
 #include "krnlconst.h"
+#include "lock.h"
 
 #define AP_INIT_PHYS_TEXT 0x7c00
 
@@ -21,10 +22,25 @@ 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;
 
+extern int _kernel_stack_0_start;
+
+int smp_bits = 0;
+
+spin_lock spinlock_smp;
+
+void finish_smp_initialization(int lapic_id) {
+
+ spinlock_lock(&spinlock_smp);
+
+ smp_bits |= 1 << lapic_id;
+ print_msg("Init SMP lapic id", lapic_id, 16, false);
+
+ spinlock_unlock(&spinlock_smp);
+}
+
 void copy_smp_init_to_low_mem() {
 
  char *s = (char*)&init_ap;
@@ -39,19 +55,22 @@ void copy_smp_init_to_low_mem() {
 
 void smp_start() {
 
+ INIT_SPIN_LOCK(&spinlock_smp);
+
  copy_smp_init_to_low_mem();
 
  // 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_FIRST_STACK+KERNEL_VIRT_ADDR) = (int)&_kernel_stack_0_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);
+ *(int*)(AP_FINISH_CODE+KERNEL_VIRT_ADDR) = (int)finish_smp_initialization;
 
  // 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;
+ ((int*)&_kernel_pg_dir)[0] = (((int)&_kernel_pg_table_0) - KERNEL_VIRT_ADDR) | 1;
 
  MFENCE;
 
@@ -65,5 +84,12 @@ void smp_start() {
  write_lapic_register(LAPIC_ICR_2, 0);
  pit_wait_ms(200);
 
+ // clear identity mapping
+ ((int*)&_kernel_pg_dir)[0] = 0;
+ __asm__ __volatile__("invlpg (0);"
+ : : :
+ );
+
  print_msg("Number of APs", *(int*)(AP_COUNT_PHYS_ADDR+KERNEL_VIRT_ADDR), 10, true);
+ print_msg("SMP bits", smp_bits, 16, true);
 }