kernel: Experimental move stack to 640k EMA boundary

Author: fwsGonzo

src/boot/bootloader.asm

@@ -6,9 +6,9 @@
 ;; Licensed under the Apache License, Version 2.0 (the "License");
 ;; you may not use this file except in compliance with the License.
 ;; You may obtain a copy of the License at
-;; 
+;;
 ;;     http:;;www.apache.org/licenses/LICENSE-2.0
-;; 
+;;
 ;; Unless required by applicable law or agreed to in writing, software
 ;; distributed under the License is distributed on an "AS IS" BASIS,
 ;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -17,16 +17,16 @@
 
 USE16
 ;; Memory layout, 16-bit
-%define _boot_segment 0x07c0 
+%define _boot_segment 0x07c0
 %define _vga_segment  0xb800
 
 ;; Memory layout, 32-bit
 %define _mode32_code_segment 0x08
 %define _mode32_data_segment 0x10
-  
-%define _kernel_loc   0x200000
-%define _kernel_stack 0x200000
-  
+
+%define _kernel_loc   0x100000
+%define _kernel_stack 0xA0000
+
 ;; We don't really need a stack, except for calls
 %define _stack_segment 0x7000
 %define _stack_pointer 0xfffe ;Within the ss, for 16 bit
@@ -37,13 +37,13 @@ USE16
 
 ; ELF offset of _start in text section
 %define _elf_start 0x34
-	
+
 ;;; START
 ;;; We'll start at the beginning, but jump over some data
 _start:
 	jmp boot
 
-;;; The size of the service on disk, to be loaded at boot. (Convenient to 
+;;; The size of the service on disk, to be loaded at boot. (Convenient to
 ;;; have it at the beginning, so it remains at a fixed location. )
 srv_size:
 	dd 0
@@ -53,10 +53,10 @@ srv_offs:
 ;;; Actual start
 boot:
 	;; Need to set data segment, to access strings
-	mov ax, _boot_segment	
-	mov ds, ax		
-	
-	; fast a20 enable	
+	mov ax, _boot_segment
+	mov ds, ax
+
+	; fast a20 enable
 	in al, 0x92
 	or al, 2
 	out 0x92, al
@@ -71,19 +71,19 @@ boot:
 	mov [color], ax
 	mov esi, str_literally
 	call printstr
-	
-  
+
+
   ; check that it was enabled
 	test al,0
-	jz .a20_ok	
+	jz .a20_ok
 	;; NOT OK
 	mov esi,str_a20_fail
-	call printstr	
+	call printstr
 	cli
 	hlt
 .a20_ok:
-	call protected_mode	
-	
+	call protected_mode
+
 protected_mode:
 	;xchg bx,bx
 	cli
@@ -100,16 +100,16 @@ fill_screen:
 	mov es, bx
 	mov bx, 0
 	mov al, 0
-	mov ah, [color]	
-.fill:	
+	mov ah, [color]
+.fill:
 	mov [es:bx], ax
 	add bx,2
 	cmp bx, (25*80*2)
 	jge .done
 	jmp .fill
 .done:
 	ret
-	
+
 printstr:
 	mov bx, _vga_segment
 	mov es, bx
@@ -126,18 +126,18 @@ printstr:
 .done:
 	mov [cursor], bx
 	ret
-	
+
 str_includeos:
 	db `#include <os> `,0
-str_literally:	
+str_literally:
 	db `\/\/ Literally `,0
-str_a20_fail:	
+str_a20_fail:
 	db `A20 Err\n\r`,0
-cursor:				
+cursor:
 	dw (80 * 11 * 2) + 48
 color:
 	dw 0x0d
-	
+
 USE32
 ALIGN 32
 ;; Global descriptor table
@@ -146,7 +146,7 @@ gdtr:
 	dq gdt32+(_boot_segment<<4)
 gdt32:
 	;; Entry 0x0: Null desriptor
-	dq 0x0 
+	dq 0x0
 	;; Entry 0x8: Code segment
 	dw 0xffff		       ;Limit
   dw 0x0000		       ;Base 15:00
@@ -158,68 +158,68 @@ gdt32:
 	dw 0x0000		       ;Base 15:00
 	db 0x00			       ;Base 23:16
 	dw 0xcf92		       ;Flags
-	db 0x00			       ;Base 32:24	
+	db 0x00			       ;Base 32:24
 gdt32_end:
 	db `32`
 ;;; GDT done
-	
+
 ;;; 32-bit code
-USE32				
+USE32
 ALIGN 32
 mode32:
-	;; Set up 32-bit data segment	
+	;; Set up 32-bit data segment
 	mov eax,_mode32_data_segment
 	;; Set up stack
 	mov ss,eax
 	mov esp,_kernel_stack
 	;; mov esi,_kernel_stack 	;Was e00c3
 	mov ebp,_kernel_stack
-	
+
 	;; Set up data segment
 	mov ds, eax
 	mov es, eax
 	mov fs, eax
 	mov gs, eax
-	
-	;; By default QEMU handles only 1 sector pr. read	
-	%define LOAD_SIZE 1 
-	
+
+	;; By default QEMU handles only 1 sector pr. read
+	%define LOAD_SIZE 1
+
 	;; Number of sectors to read for the entire service
   mov edx, [srv_size+(_boot_segment<<4)]
 	mov eax, 1
-	
+
 	;; Location to load kernel
 	mov edi,_kernel_loc
-  
+
 .more:
 	mov cl, LOAD_SIZE
-  
+
 	;; Load 1 sector from disk
 	call ata_lba_read
-	
+
 	;; Increase LBA by 1 sector
 	add eax, LOAD_SIZE
-  
+
 	;; Increase destination (in bytes)
 	add edi, LOAD_SIZE * 512
-  
+
 	;; Decrement counter (srv_size) by 1 sector
 	sub edx, LOAD_SIZE
-  
+
 	;; If all sectors loaded, move on, else get .more
 	cmp edx, 0
 	jge .more  ;; jump when gequal
-	
+
 	;; Bochs breakpoint
 	;;xchg bx,bx
-  
+
 	;; GERONIMO!
 	;; Jump to service
 	call DWORD [srv_offs+(_boot_segment<<4)]
-	
-  
+
+
 	%include "boot/disk_read_lba.asm"
-	
+
 	;; BOOT SIGNATURE
 	times 510-($-$$) db 0	;
 	dw 0xAA55

src/kernel/os.cpp

@@ -71,6 +71,7 @@ extern "C" uintptr_t get_cpu_esp();
 
 void OS::start(uint32_t boot_magic, uint32_t boot_addr) {
 
+  atexit(default_exit);
   default_stdout_handlers();
 
   // Print a fancy header
@@ -80,7 +81,7 @@ void OS::start(uint32_t boot_magic, uint32_t boot_addr) {
 
   auto esp = get_cpu_esp();
   MYINFO ("Stack: 0x%x", esp);
-  Expects (esp < (uintptr_t)&_LOAD_START_ and esp >= 0x100000 and "Stack location OK");
+  Expects (esp < 0xA0000 and esp > 0x0 and "Stack location OK");
 
   MYINFO("Boot args: 0x%x (multiboot magic), 0x%x (bootinfo addr)",
          boot_magic, boot_addr);
@@ -107,9 +108,6 @@ void OS::start(uint32_t boot_magic, uint32_t boot_addr) {
     }
   }
 
-  // ?
-  atexit(default_exit);
-
   MYINFO("Assigning fixed memory ranges (Memory map)");
   auto& memmap = memory_map();
 
@@ -118,8 +116,8 @@ void OS::start(uint32_t boot_magic, uint32_t boot_addr) {
         "EBDA", "Extended BIOS data area"});
   memmap.assign_range({0x000A0000, 0x000FFFFF,
         "VGA/ROM", "Memory mapped video memory"});
-  memmap.assign_range({0x00100000, (uintptr_t)&_LOAD_START_ -1 ,
-        "Stack", "Kernel / service main stack"});
+  //memmap.assign_range({0x00100000, (uintptr_t)&_LOAD_START_ -1 ,
+  //      "Stack", "Kernel / service main stack"});
   memmap.assign_range({(uintptr_t)&_LOAD_START_, (uintptr_t)&_end,
         "ELF", "Your service binary including OS"});
 

src/kernel/start.asm

@@ -16,39 +16,17 @@
 ;; limitations under the License.
 
 USE32
-section .text
-
 extern kernel_start
-extern _LOAD_START_
-extern __stack_rand_ba
-
 global _start
 
+section .text
 ;; Multiboot places boot paramters on eax and ebx.
 _start:
-        ;; Stack base address
-        mov esp, _LOAD_START_
-        ;; Primitive stack base address randomization
-        mov ecx, __stack_rand_ba
-        and ecx, 0xff
-        shl ecx, 10 ;; up to 256kb per 256 seconds
-        sub esp, ecx
-        mov [boot_magic], eax
-        rdtsc
-        and eax, 0xff
-        shl eax, 6 ;; 64 byte per tick, up to 16kb
-
-        ;; NOTE: Stack changes here (pushes before this point won't pop right)
-        sub esp, eax
-
-        ;; make esp page-aligned
-        and esp, 0xfffff000
+        ;; Stack base address to EMA boundary
+        mov esp, 0xA0000
+        sub esp, 0x10
 
         ;;  Place multiboot parameters on stack
-        mov eax, [boot_magic]
         push ebx
         push eax
         call kernel_start
-
-boot_magic:
-        dw 0

src/linker.ld

@@ -24,7 +24,7 @@ PHDRS {
 
 SECTIONS
 {
-  PROVIDE ( _ELF_START_ = . + 0x200000);
+  PROVIDE ( _ELF_START_ = . + 0x100000);
   PROVIDE ( _LOAD_START_ = _ELF_START_); /* For convenience w. multiboot */
 
   .multiboot (_ELF_START_ + SIZEOF_HEADERS): {