Scanning for RSD PTR. Updated bootloader code so that loads kernel at…

… a different address and don't clobber ACPI tables.

README.md

@@ -1,6 +1,6 @@
 <b>XIS</b> operating system needs only 2MB of memory to run.<br>
 
-It supports boot loader, kernel with protected mode, paging, E820 enumeration, interrupt and exception handling, system calls, user mode, local APIC and multiprocessor.
+It supports boot loader, kernel with protected mode, paging, E820 enumeration, interrupt and exception handling, system calls, user mode, local APIC, ACPI 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>
@@ -23,8 +23,9 @@ 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>
 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>
 gcc -m32 -std=gnu99 -nostdlib -nostdinc -fno-builtin -fno-stack-protector -nostartfiles -nodefaultlibs -ffreestanding -fno-pic -Wall -Wextra -Werror -c debug.c -o debug.o<br>
+gcc -m32 -std=gnu99 -nostdlib -nostdinc -fno-builtin -fno-stack-protector -nostartfiles -nodefaultlibs -ffreestanding -fno-pic -Wall -Wextra -Werror -c acpi.c -o acpi.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 lock.o debug.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 acpi.o debug.o start.o -o xiskernel.elf<br>
 objcopy -O binary xiskernel.elf xiskernel.bin<br>
 
 <b>Instructions for building boot loader -</b><br>

acpi.c

@@ -0,0 +1,62 @@
+/*****************************************************************************/
+/* File: acpi.c */
+/* */
+/* Description: Source file for ACPI. */
+/* */
+/* Author: Shoily O Rahman <[email protected]> */
+/* */
+/* Date: Nov 3, 2020 */
+/* */
+/*****************************************************************************/
+
+#include "acpi.h"
+#include "debug.h"
+#include "krnlconst.h"
+#include "debug.h"
+
+extern int ebda;
+
+void *rsd_ptr;
+
+#define CHECK_RSD_PTR(p) (((char*)p)[0]=='R' && \
+ ((char*)p)[1]=='S' && \
+ ((char*)p)[2]=='D' && \
+ ((char*)p)[3]==' ' && \
+ ((char*)p)[4]=='P' && \
+ ((char*)p)[5]=='T' && \
+ ((char*)p)[6]=='R' && \
+ ((char*)p)[7]==' ')
+
+void acpi_find_rsdp() {
+
+ int phase = 0;
+ int cur, end;
+
+ rsd_ptr = 0;
+
+ cur = ebda + KERNEL_VIRT_ADDR;
+ end = ebda + 1024;
+
+ while(phase < 2) {
+
+ if (cur == end) {
+
+ phase++;
+
+ if (phase == 1) {
+
+ cur = 0xE0000 + KERNEL_VIRT_ADDR;
+ end = cur + 0x20000;
+ }
+ }
+
+ if (CHECK_RSD_PTR(cur)) {
+
+ rsd_ptr = (void*)cur;
+ printf(KERNEL_INFO, "RSD PTR: %p\n", rsd_ptr-KERNEL_VIRT_ADDR);
+ break;
+ }
+
+ cur += 16;
+ }
+}

acpi.h

@@ -0,0 +1,17 @@
+/*****************************************************************************/
+/* File: acpi.h */
+/* */
+/* Description: Header file for ACPI. */
+/* */
+/* Author: Shoily O Rahman <[email protected]> */
+/* */
+/* Date: Nov 3, 2020 */
+/* */
+/*****************************************************************************/
+
+#ifndef _ACPI_H
+#define _ACPI_H
+
+void acpi_find_rsdp();
+
+#endif

bootldr.S

@@ -24,7 +24,9 @@
  .text
  .globl _start
 _start:
- movb %dl, boot_drive
+
+ movb %dl, boot_drive
+
 
  // clear screen
  movb $0, %ah
@@ -114,14 +116,16 @@ a20_line:
  movw %ax, %ss
 
  // memory buffer location of disk address packet
- movw dap, %si
+ movw $dap, %si
  xorw %ax, %ax
- movw %ax, 4(%si)
+ movw %ax, 4(%si)
+
+
 
  movw $KERNEL_SECTORS, %ax
 
  // check kernel can fit into existing memory
- cmpw $160, %ax
+ cmpw $255, %ax
  ja kernel_too_big
 
  // read enough sectors to load kernel
@@ -137,7 +141,7 @@ a20_line:
  movl %ebx, 12(%si)
 
  // segment of buffer address
- movw $0x5000, 6(%si)
+ movw $0x7e0, 6(%si)
 
  // set stack location at 4K offset
  movl $0x1000, %ebp
@@ -147,7 +151,10 @@ a20_line:
  movb $0x42, %ah
  int $0x13
 
- jc lba_read_error
+ jc lba_read_error
+
+
+
 
  // initialize protected mode
  cli
@@ -170,7 +177,7 @@ a20_line:
  orl $1, %eax
  movl %eax, %cr0
 
- cli
+ cli
 
  // jump to protected mode
  ljmpl *codesegaddr
@@ -210,7 +217,7 @@ protectedmodeaddress:
  // copy kernel to 1 MB offset
  cld
  movl $(KERNEL_SECTORS * 0x200 / 4), %ecx
- movl $0x50000, %esi
+ movl $0x7e00, %esi
  movl $0x100000, %edi
  rep movsl
 

krnlconst.hdr

@@ -1,7 +1,7 @@
 VIDEO_BUFFER 0xb8000
-E820_MAP_ADDRESS 0x1008
-E820_MAP_COUNT 0x1004
-PROTECTED_MODE_STACK 0xf000
+E820_MAP_ADDRESS 0x2008
+E820_MAP_COUNT 0x2004
+PROTECTED_MODE_STACK 0x1000
 AP_FIRST_STACK 0xfff0
 AP_LAPIC_BASE_REGISTER 0xfff4
 AP_COUNT_PHYS_ADDR 0xfff8

start.c

@@ -33,7 +33,7 @@ int start_kernel(void) {
  setup32();
  init_memory();
  bda_read_table();
- //acpi_find_rsdp();
+ acpi_find_rsdp();
  usermode_load_first_program();
  smp_start();
  initialize_usermode();