Merge pull request #38 from E-Almqvist/memory

Memory

Makefile

@@ -22,7 +22,7 @@ eos_grub.iso : kernel.bin grub/grub.cfg
 eos.iso: bootloader/bootloader.bin kernel.bin
 	cat $^ > eos.iso
 
-kernel.bin: kernel/kernel_entry.o $(OBJ) 
+kernel.bin: kernel/kernel_entry.o kernel/sr_memory.o kernel/enable_paging.o $(OBJ) 
 	gcc -o $@ $^ -Wl,--oformat=binary -ffreestanding -nostdlib -shared -Ttext 0x1000 -m32
 
 

drivers/vga.c

@@ -1,31 +1,37 @@
 // VGA Graphics Library
 #include "vga.h"
+#include "../lib/types.h"
 #include "../kernel/io.h"
+#include "../kernel/memory.h"
 #include "../lib/str.h"
+#include "../lib/conv.h"
 
-static unsigned int cursor_row = 0;
-static unsigned int cursor_col = 0;
+static uint cursor_row = 0;
+static uint cursor_col = 0;
 
 void vga_init() {
+	// Allocate VGA memory range
+	pm_alloc_range(VGA_ADDRESS, VGA_ADDRESS_MAX, true); // force alloc the VGA range
+
 	// Disable cursor
 	port_outb(0x3d4, 0x0a);
 	port_outb(0x3d5, 0x20);
 
 	// Clear screen
 	// clear_row(0);
-	// clear_screen();
+	clear_screen();
 
-	set_cursor_pos(0, 11);
+	set_cursor_pos(0, 0);
 }
 
 /*
 	VGA & Memory Functions
 */
-char* get_memory_charpos(unsigned int col, unsigned int row) { 
+char* get_memory_charpos(uint col, uint row) { 
 	return (char*)(VGA_ADDRESS + 2*((row*80) + col)); 
 }
 
-void writechar(char c, unsigned int col, unsigned int row, int attribute_byte) {
+void writechar(char c, uint col, uint row, int attribute_byte) {
 
 	if( !attribute_byte ) 
 		attribute_byte = DEFAULT_COLOR;
@@ -36,7 +42,7 @@ void writechar(char c, unsigned int col, unsigned int row, int attribute_byte) {
 
 }
 
-void set_cursor_pos(unsigned int col, unsigned int row) {
+void set_cursor_pos(uint col, uint row) {
 	cursor_col = col;
 	cursor_row = row;
 }
@@ -45,7 +51,7 @@ void set_cursor_pos(unsigned int col, unsigned int row) {
 /*
 	Graphics Functions
 */
-void clear_row(unsigned int row) {
+void clear_row(uint row) {
 	for( int c = 0; c < MAX_COLS; c++ ) 
 		writechar(0x20, c, row, 0x0);
 }
@@ -61,7 +67,7 @@ void clear_screen() {
 */
 void print(char* str, int attribute_byte) {
 	for( char* c = str; *c != '\0'; c++ ) 
-		writechar(*c, (unsigned int)(c - str) + cursor_col, cursor_row, attribute_byte);
+		writechar(*c, (uint)(c - str) + cursor_col, cursor_row, attribute_byte);
 }
 
 void println(char* str, int attribute_byte) {
@@ -69,11 +75,20 @@ void println(char* str, int attribute_byte) {
 	cursor_row++; // Increment to next y-pos (newline)
 }
 
+void printint(int i, int attribute_byte) {
+	/*
+	char* strbuf;
+
+	strbuf = int_to_str(i, strbuf);
+	println(strbuf, attribute_byte);
+	*/
+}
+
 void printalign(char* str, int attribute_byte, enum align alignment) {
-	unsigned int strlenbuf = strlen(str);
+	uint strlenbuf = strlen(str);
 
 	if( !alignment || alignment == LEFT ) {
-		print(str, attribute_byte);
+		set_cursor_pos(0, cursor_row);
 	} else if ( alignment == RIGHT ) {
 		set_cursor_pos(MAX_COLS - strlenbuf, cursor_row);
 	} else if ( alignment == MIDDLE ) {
@@ -81,4 +96,5 @@ void printalign(char* str, int attribute_byte, enum align alignment) {
 	}
 
 	print(str, attribute_byte);
+	set_cursor_pos(0, cursor_row+1);
 }

drivers/vga.h

@@ -1,7 +1,10 @@
-#define VGA_ADDRESS 	(char*)0xb8000
-#define VGA_ADDRESS_MAX	(char*)0xb8fa0
+#define VGA_ADDRESS 	0xb8000
+#define VGA_ADDRESS_MAX	0xb8fa0
 
 #define DEFAULT_COLOR 0x07 
+#define URGET_COLOR 0x0c
+#define SUCCESS_COLOR 0x0a
+
 #define MAX_ROWS 25
 #define MAX_COLS 80
 
@@ -17,5 +20,6 @@ void clear_row(unsigned int row);
 void set_cursor_pos();
 void print();
 void println();
+void printint(int i, int attribute_byte);
 void printalign(char* str, int attribute_byte, enum align alignment);
 void vga_init();

kernel/enable_paging.asm

@@ -0,0 +1,23 @@
+[bits 32]  ; 32-bit mode
+
+PAGING_ENABLE_FLAG equ 0x80000001
+PAGE_DIRECTORY_ADDR equ 0xffffffff ; TODO: change me to something good
+
+global enable_paging_registers ; make the SR "global" so that we can access it in the kernel etc
+enable_paging_registers:
+	push eax
+	mov eax, PAGE_DIRECTORY_ADDR ; Move the address of the 
+	; page register (page directory) into eax
+	; (Using eax as a middle-man register)
+	mov cr3, eax ; Put the address into the cr3 register (required by the MMU)
+
+	mov eax, cr0 ; eax as a middle-man register (again)
+	or eax, PAGING_ENABLE_FLAG ; perform the OR operation on eax (ex: 0b01 or 0b10 = 0b11)
+	; This is needed to enable paging (set the flag as "enabled")
+	
+	mov cr0, eax ; Move it into cr0 to finally enable paging 
+
+	pop eax
+	ret ; return to last location
+
+

kernel/kernel.c

@@ -1,23 +1,20 @@
 #include "kernel.h"
 #include "memory.h"
+#include "paging.h"
 #include "../drivers/vga.h"
 #include "../lib/str.h"
-#include "../lib/strf.h"
-
-void display_status(char* status_text, unsigned int bg_color) {
-	clear_row(0);
-	set_cursor_pos(0, 0);
-
-	print(status_text, bg_color | STATUS_TEXT_COLOR);
-}
+#include "../lib/conv.h"
 
 void init() {
-	display_status("Kernel loaded", 0x70);
-
 	vga_init(); 	// Initialize the screen first
 			// i.e. clear the screen et cetera.
 
-	char* title = "eOS Version 0.2 2021";
+	println("Kernel loaded", SUCCESS_COLOR);
+
+	// enable_paging();
+
+	println("");
+	char* title = "eOS Version 0.3 2021";
 	println(title, DEFAULT_COLOR);
 
 	char* subtitle = "A x86 operating system, licenced under GPL-2.0";
@@ -28,8 +25,35 @@ void init() {
 	println("0x1000", DEFAULT_COLOR);
 	*/
 
+
+	char* intbuf = "xxxx";
+	int num = 1234;
+	intbuf = int_to_str(num, intbuf);
+	print("TEST NUM: ", DEFAULT_COLOR);
+	println(intbuf, DEFAULT_COLOR);
+
+	/*
+
+	// Memory allocation testing
+	printalign("-- PMM Tests --", DEFAULT_COLOR, MIDDLE);
+
+	println("THESE ALLOC SHOULD WORK:", 0xa0);
+	for(int i=0; i < 4; i++) {
+		block_alloc(i);
+	}
+
+	println("(2) THIS ALLOC SHOULD FAIL:", 0xc0);
+	block_alloc(2); // this should fail
+
+	println("(2) Freeing 2nd block, alloc after should succeed", DEFAULT_COLOR);
+	block_free(2); // after this, allocation of 2nd block should work
+	block_alloc(2);
+
+	printalign("-- End of PMM Tests --", DEFAULT_COLOR, MIDDLE);
+
 	char* strbuf = "Concat test: ";
 	char* str2 = "Works!";
 	strbuf = strcat(strbuf, str2); 
 	println(strbuf, DEFAULT_COLOR);
+	*/
 }

kernel/memory.c

@@ -1,2 +1,102 @@
 #include "memory.h"
+#include "../drivers/vga.h"
 
+// https://wiki.osdev.org/Page_Frame_Allocation
+// page = block
+
+// MAX_BLOCK_SIZE_IN_BITS/8 bytes
+// i.e. : bit i of byte n define status of block 8n+i
+// block = 8n+i
+
+// in 32-bit mode, we have access to 2^32 blocks
+// which is (2^32)*BLOCK_SIZE blocks
+// and with a blocksize of 1024, we git around 4.3 trillion blocks
+// which is more than enough
+
+#define CHECK_BITMAP(map, idx) ((map) & (1<<(idx)))
+
+#define BLOCK_TO_MEMP(idx) (pointer)(PM_MEM_START + (idx*BLOCK_SIZE))
+
+#define MEMP_TO_BLOCK(memp) (uint)((memp - PM_MEM_START)/BLOCK_SIZE)
+
+static int bitmap = 0; 
+static uint last_block;
+void mod_bitmap(uint bit, uint bflag) {
+	// create a bitmask that will be applied to the bitmap
+	int bitmask = 1 << bit;
+
+	// apply the bitmask, resulting in the bit:n bit will set 
+	// set to bflag
+	bitmap = (((bitmap & ~bitmask)) | (bflag << bit));
+}
+
+
+pointer block_alloc(uint blockidx) {
+	int block_bflag;
+	block_bflag = CHECK_BITMAP(bitmap, blockidx);
+
+	if( block_bflag == BM_FREE ) { // check if block is free
+		println("Allocating block...", DEFAULT_COLOR);
+
+		mod_bitmap(blockidx, 1);
+		last_block = blockidx;
+
+		return BLOCK_TO_MEMP(blockidx); 
+	} else {
+		println("[ERROR] Attemped to allocate non-free block.", 0x0c);
+
+		return 0;
+	}
+}
+
+void block_free(uint blockidx) {
+	println("Dealloc block...", DEFAULT_COLOR);	
+	mod_bitmap(blockidx, BM_FREE);
+	last_block = blockidx;
+}
+
+uint find_free(uint block_count) {
+	// TODO: find a free start block to allocate	
+	// loop through bitmap
+	// check if range is free
+}
+
+bool check_block_range(uint start, uint end) {
+	bool allowed = true;	
+
+	uint idx;
+	for(idx = start; idx <= end; idx++) {
+		if( CHECK_BITMAP(bitmap, idx) != BM_FREE )
+			allowed = false;
+			break;
+	}
+
+	return allowed;
+}
+
+void pm_alloc_range(ulong start, ulong end, bool force) {
+	uint idx_start;
+	uint idx_end;
+
+	ulong d_addr = end - start; // memory size
+	uint num_blocks = (d_addr/BLOCK_SIZE) + 1; // amount of blocks to be allocated
+
+	uint start_block = MEMP_TO_BLOCK(start); // start idx, end = start_block + num_blocks - 1
+	bool allowed = true && check_block_range(start_block, start_block + num_blocks - 1);
+
+	// allocate (if permitted)
+	if( allowed ) {
+		uint idx;
+		for(idx=start_block; idx <= start_block + num_blocks - 1; idx++) 
+			block_alloc(idx);
+
+		return;
+	} else {
+		println("[ERROR] Tried to allocate memory range without permission!", 0x0c);
+		return;
+	}
+}
+
+pointer pm_malloc(uint block_count) {
+	
+}

kernel/memory.h

@@ -1,2 +1,25 @@
-char* malloc(unsigned int size);
-void mfree(char* p);
+#include "../lib/types.h"
+
+#define BLOCK_SIZE 1024 // 1 KiB
+#define MAX_BLOCK_COUNT 32 // placeholder
+#define MEMSIZE_TO_BLOCKS(n) ((n*1024)/BLOCK_SIZE)
+
+#define BM_FREE 0
+
+#define PM_MEM_START 0x000000 // start of memory
+#define PM_MEM_END 0xb7000 // end of memory  TODO: fix me/change or something
+
+// void init_pmm(uint map_addr, uint bsize); // Initialize physical memory manager
+
+void mod_bitmap(uint bit, uint flag);
+
+pointer block_alloc(uint blockidx); // allocate a block
+void block_free(uint blockidx); // free a block
+
+uint find_free(uint block_count);
+
+bool check_block_range(uint start, uint end);
+void pm_alloc_range(ulong start, ulong end, bool force); // allocate a range of memory 
+
+pointer pm_malloc(uint block_count); // allocate some blocks
+void pm_free(int* p); // free a var (if allocated with pm_malloc)

kernel/paging.c

@@ -0,0 +1,24 @@
+#include "paging.h"
+#include "../drivers/vga.h"
+
+void enable_paging() {
+	println("Enabling paging...", DEFAULT_COLOR);
+
+	// extern int enable_paging_registers(); // Call the assembly SR
+	// enable_paging_registers(); // and enable paging
+
+	return;
+}
+
+// Page Entry struct
+//struct page_entry {
+//	unsigned int index;
+//	unsigned int start_addr;
+//} page_table[PAGE_TABLE_SIZE];
+//
+//int get_phys_addr(int virt_addr) {
+//	int index = virt_addr / PAGE_SIZE; // page index for the virtual address
+//	int offset = virt_addr % PAGE_SIZE; // actual physical offset for the address
+//
+//	return page_table[index].start_addr + offset;
+//}

kernel/paging.h

@@ -0,0 +1,9 @@
+#define PAGE_SIZE 100
+#define PAGE_TABLE_SIZE 128
+
+void enable_paging();
+
+// struct page_entry;
+
+// char** heap_alloc(unsigned int size); // Process heap allocation
+// int get_phys_addr(int virt_addr);

lib/conv.c

@@ -0,0 +1,17 @@
+#include "conv.h"
+#include "../drivers/vga.h"
+
+char* int_to_str(int i, char* buf) {
+	ulong num = (ulong)i; // convert to ulong
+	uint len = ulong_len(num); // number of digits
+
+	*(buf+len) = '\0'; // add a "end-of-string" at the end
+
+	int j;
+	for(j = 0; j < len; j++) // iterate over each digit and assign it to the buffer
+		// super dangerous memory write 
+		println("char!", DEFAULT_COLOR);
+		*(buf+j) = (char)(ndigit(num, len-1-j) + ASCII_OFFSET); // apply the ascii offset so that i becomes a char
+	
+	return buf;
+}

lib/conv.h

@@ -0,0 +1,6 @@
+#include "types.h"
+#include "util.h"
+
+#define ASCII_OFFSET 0x30
+
+char* int_to_str(int i, char* buf);

lib/math.c

@@ -0,0 +1,10 @@
+#include "math.h"
+
+long pow(int num, uint expon) {
+	long prod = 1;
+	while(expon > 0)	
+		prod *= num;
+		expon--;
+
+	return prod;
+}

lib/math.h

@@ -0,0 +1,3 @@
+#include "types.h"
+
+long pow(int, uint);

lib/strf.c

@@ -1,15 +0,0 @@
-#include "strf.h"
-
-#define int_offset 48
-// 0:48 - 9:57
-
-char* int_to_str(int i, char* strbuf) {
-	if( i == 0 ) {
-		return (char*)(int_offset);
-	} else {
-		char cbuf;
-		cbuf = (char)((i % 10) + int_offset);
-
-		return int_to_str(i / 10, strbuf + cbuf);
-	}
-}

lib/strf.h

@@ -1 +0,0 @@
-char* int_to_str(int i, char* strbuf);

lib/types.h

@@ -0,0 +1,6 @@
+typedef unsigned int uint;
+typedef unsigned long ulong;
+typedef unsigned long* pointer;
+typedef int bool;
+#define true 1
+#define false 0

lib/util.c

@@ -0,0 +1,16 @@
+#include "util.h"
+#include "math.h"
+
+uint ulong_len(ulong n) { // get the digit length of a number
+    int len = 0;
+    while (n != 0) {
+        n = n / 10;
+        ++len;
+    }
+    return len;
+}
+
+uint ndigit(ulong n, uint i) { // OBS: index order is reversed
+	long den = pow(10, i);
+	return (n/den) % 10;
+}

lib/util.h

@@ -0,0 +1,4 @@
+#include "types.h"
+
+uint ulong_len(ulong n);
+uint ndigit(ulong n, uint i);