feature: kalloc_frame and demo in the main

boot/linker.ld

@@ -24,5 +24,6 @@ SECTIONS
 	{
 		*(COMMON)
 		*(.bss)
+		end_kernel = .;
 	}
 }

headers/memory.h

@@ -2,28 +2,12 @@
 
 #include <stdint.h>
 
-#define NOT_PRESENT (1 << 0)
+#define PRESENT    (1 << 0)
 #define RW         (1 << 1)
 #define SUPERVISOR (0 << 2)
-#define INIT_FLAGS  (NOT_PRESENT | RW | SUPERVISOR)
+#define ACCESSED   (1 << 4)
-
+#define INIT_FLAGS (PRESENT | RW | SUPERVISOR)
-struct page_directory_entry {
+#define PAGE_SIZE  4096
-	uint32_t present : 1;
-	uint32_t rw : 1;
-	uint32_t user : 1;
-	uint32_t page_size : 1;
-	uint32_t unused : 8;
-	uint32_t frame : 20;
-};
-
-struct page_table_entry {
-	uint32_t present : 1;
-	uint32_t rw : 1;
-	uint32_t user : 1;
-	uint32_t accessed : 1;
-	uint32_t dirty : 1;
-	uint32_t unused : 7;
-	uint32_t frame : 20;
-};
 
 void init_memory(void);
+uintptr_t kalloc_frame(uint32_t nb_frames);

src/kernel.c

@@ -1,6 +1,8 @@
 #include "gdt.h"
+#include "kprintf.h"
 #include "memory.h"
 #include "shell.h"
+#include "string.h"
 #include "terminal.h"
 
 #include <stdbool.h>
@@ -23,5 +25,8 @@ void kernel_main(void)
 	terminal_initialize();
 	init_gdt();
 	init_memory();
+	char *str = (char *)kalloc_frame(1);
+	memcpy(str, "Hello world!\n", 15);
+	kprintf(KERN_INFO, "%s", str);
 	shell_init();
 }

src/memory/frame.c

@@ -0,0 +1,44 @@
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "kprintf.h"
+#include "memory.h"
+
+#define MAX_FRAMES   1048319
+#define CEIL(x, y)   (((x) + (y) - 1) / (y))
+#define GET_FRAME(i) (frame_table[i / 8] & (1 << (i % 8)))
+#define SET_FRAME(i, used)                                                     \
+	do {                                                                   \
+		if (used)                                                      \
+			frame_table[i / 8] |= (1 << (i % 8));                  \
+		else                                                           \
+			frame_table[i / 8] &= ~(1 << (i % 8));                 \
+	} while (0)
+
+extern uint32_t end_kernel;
+
+static uint8_t frame_table[CEIL(MAX_FRAMES, 8)];
+
+uintptr_t kalloc_frame(uint32_t nb_frames)
+{
+	if (nb_frames > MAX_FRAMES)
+		kprintf(KERN_CRIT, "Not enough frames (max: %d)\n", MAX_FRAMES);
+	size_t i = 0;
+	while (i < MAX_FRAMES) {
+		size_t free_frames = 1;
+		while (!GET_FRAME(i + free_frames) && free_frames < nb_frames)
+			free_frames++;
+		if (free_frames == nb_frames)
+			goto end;
+		i += free_frames;
+	}
+end:
+	if (i != MAX_FRAMES) {
+		for (size_t j = 0; j < nb_frames; j++)
+			SET_FRAME(j + i, 1);
+		return (uintptr_t)&end_kernel + i * PAGE_SIZE;
+	}
+	kprintf(KERN_WARNING, "Not enough frames available\n", MAX_FRAMES);
+	return 0;
+}