Added kernel size assertion

LICENSE.md

@@ -0,0 +1,25 @@
+BSD 2-Clause License
+
+Copyright (c) 2020, Lucian
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

README.md

@@ -1,20 +1,60 @@
 # lucicOS
 
-![OS logo](logo.png)
+![OS logo](demo/logo.png)
 
 lucicOS is an educational, UNIX-like operating system built from scratch using
 the following resources:
   * [OSdev](https://wiki.osdev.org/Expanded_Main_Page)
   * [Little OS Book](https://littleosbook.github.io/)
   * [JamesM kernel development tutorial](http://www.jamesmolloy.co.uk/tutorial_html/)
-  * [OS from 0 to 1](https://github.com/tuhdo/os01)
+  * [Intel manuals](http://web.eecs.umich.edu/~farnam/482/Winter99/intarch.html)
+  * [BrokenThron](http://www.brokenthorn.com/Resources/OSDevIndex.html)
+
+At the moment it is not aimed to be portable or support multiple architectures.
+It is just my attempt to learn some important concepts about operating systems
+and develop my coding techniques.
+
+It only supports x86 architecture.
+
+## Building the project
 
 It can be built using the following command: `./build.sh`. To run the OS in
 bochs, just run `./bochs.sh`, the same applies to qemu, just run `./qemu.sh`.
 
+For building, running and testing, I use the following tools:
+  * i686-elf-gcc (GCC) 8.2.0
+  * GNU ld (GNU Binutils) 2.31.1
+  * GNU ar (GNU Binutils) 2.31.1
+  * QEMU emulator version 2.11.
+  * Bochs ??
+
+## Screenshots
+
+![Screenshot](demo/screenshot.png)
+
+## Features
+
 At this moment there is still a lot of work to do in order to call this a real
-Operating System. It has some modules for writing to VGA, for writing to
-a serial port and it has support for entering in protected mode.
+Operating System. 
+These are some features that I managed to understand and implement:
+  * VGA (writing on screen)
+  * Serial (writing on serial ports)
+  * Keyboard (reading characters/shortcuts from keyboard)
+  * Timer (Receiving data from Programmable Interval Timer)
+  * Physical and Virtual Memory Mangers
+  * Interrupt request and Interrupt Service Routines
+  * Global Descriptor Table and Protected Mode
+
+What I am currently working at:
+  * Moving the kernel in the Higher Half
+  * Writing a consistent Page Allocator
+  * Making a tutorial out of this project
+
+## License
+
+This project is licensed under BSD-2-Clause License.
+
+## Notes
 
 The only supported architecture is x86 because it has the richest documentation
 and all the tutorials on the internet are x86 oriented.

kernel/arch/i386/linker.ld

@@ -52,8 +52,12 @@ SECTIONS {
         *(.note.gnu.build-id)
     }
 
+    _kernel_size = _kernel_end - _kernel_start;
+
 }
 
+ASSERT(_kernel_size < 0x300000, "Kernel size exceeds 3MB");
+
 /*
  * Note:
  *  COMMON section keeps data objects that are not yet allocated,

kernel/pmm/include/pmm_internals.h

@@ -1,9 +1,9 @@
 #ifndef PMM_INTERNALS_H_
 #define PMM_INTERNALS_H_
 
-#define BLOCKS_PER_BYTE 8
-#define BLOCK_SIZE      4096
-#define BLOCK_ALIGN     BLOCK_SIZE
+#define BLOCKS_PER_DWORD 32
+#define BLOCK_SIZE       4096
+#define BLOCK_ALIGN      BLOCK_SIZE
 
 /* Macros for testing and aligning memory. */
 

kernel/pmm/src/pmm.c

@@ -24,8 +24,8 @@ void pmm_init(uint32_t pmmap_addr, size_t size) {
     used_blocks = max_blocks;
     pmmap       = (uint32_t *) pmmap_addr;
 
-    pmmap_size = mem_size / BLOCKS_PER_BYTE;
-    if (mem_size % BLOCKS_PER_BYTE)
+    pmmap_size = max_blocks / BLOCKS_PER_DWORD;
+    if (max_blocks % BLOCKS_PER_DWORD)
         pmmap_size++;
 
     memset(pmmap, 0xFF, pmmap_size);