1 files changed, 392 insertions, 0 deletions
diff --git a/boot/load.c b/boot/load.c
new file mode 100644
index 0000000..19ddce9
--- /dev/null
+++ b/boot/load.c
@@ -0,0 +1,392 @@
+// MIT License, Copyright (c) 2020 Marvin Borner
+// Independent ext2 loader
+
+typedef signed char s8;
+typedef unsigned char u8;
+
+typedef signed short s16;
+typedef unsigned short u16;
+
+typedef signed long s32;
+typedef unsigned long u32;
+
+typedef signed long long s64;
+typedef unsigned long long u64;
+
+#define BLOCK_SIZE 1024
+#define BLOCK_COUNT 256 // BLOCK_SIZE / sizeof(u32)
+#define SECTOR_SIZE 512
+#define IDE_BUSY (1 << 7)
+#define IDE_READY (1 << 6)
+#define IDE_DRIVE_FAULT (1 << 5)
+#define IDE_ERROR (1 << 0)
+#define IDE_IO 0x1F0
+#define IDE_DATA 0x0
+#define IDE_FEATURES 0x1
+#define IDE_SECTOR_COUNT 0x2
+#define IDE_LOW 0x3
+#define IDE_MID 0x4
+#define IDE_HIGH 0x5
+#define IDE_HEAD 0x6
+#define IDE_CMD 0x7
+#define IDE_ALTERNATE 0x3F6
+#define LBA_LOW(c) ((u8)(c & 0xFF))
+#define LBA_MID(c) ((u8)(c >> 8) & 0xFF)
+#define LBA_HIGH(c) ((u8)(c >> 16) & 0xFF)
+#define LBA_LAST(c) ((u8)(c >> 24) & 0xF)
+#define IDE_CMD_READ (BLOCK_SIZE / SECTOR_SIZE == 1) ? 0x20 : 0xC4
+#define IDE_CMD_WRITE (BLOCK_SIZE / SECTOR_SIZE == 1) ? 0x30 : 0xC5
+#define IDE_CMD_READ_MUL 0xC4
+#define IDE_CMD_WRITE_MUL 0xC5
+
+#define EXT2_BOOT 0
+#define EXT2_SUPER 1
+#define EXT2_ROOT 2
+#define EXT2_MAGIC 0x0000EF53
+
+struct superblock {
+	u32 total_inodes;
+	u32 total_blocks;
+	u32 su_res_blocks; // Superuser reserved
+	u32 free_blocks;
+	u32 free_inodes;
+	u32 superblock_block_num;
+	u32 log2_block_size;
+	u32 log2_frag_size;
+	u32 blocks_per_group;
+	u32 frags_per_group;
+	u32 inodes_per_group;
+	u32 last_mount_time;
+	u32 last_write_time;
+	u16 mounts_since_fsck;
+	u16 max_mounts_since_fsck;
+	u16 magic;
+	u16 state; // 1 clean; 2 errors
+	u16 error_action;
+	u16 minor_version;
+	u32 last_fsck_time;
+	u32 max_time_since_fsck;
+	u32 creator_os_id;
+	u32 major_version;
+	u16 res_block_uid;
+	u16 res_block_gid;
+};
+
+struct bgd {
+	u32 block_bitmap;
+	u32 inode_bitmap;
+	u32 inode_table;
+	u16 free_blocks;
+	u16 free_inodes;
+	u16 used_dirs;
+	u16 pad;
+	u8 bg_reserved[12];
+};
+
+struct inode {
+	u16 mode;
+	u16 uid;
+	u32 size;
+
+	u32 last_access_time;
+	u32 creation_time;
+	u32 last_modification_time;
+	u32 deletion_time;
+
+	u16 gid;
+	u16 link_count;
+	u32 blocks;
+	u32 flags;
+	u32 os_specific_val1;
+	u32 block[15];
+	u32 generation;
+
+	u32 reserved1;
+	u32 reserved2;
+
+	u32 fragment_addr;
+	u8 os_specific_val2[12];
+};
+
+#define INODE_SIZE (sizeof(struct inode))
+
+struct dirent {
+	u32 inode_num;
+	u16 total_len;
+	u8 name_len;
+	u8 type_indicator;
+	u8 name[];
+};
+
+struct file {
+	struct inode inode;
+	u32 pos;
+	u8 block_index;
+	u8 *buf;
+	u32 curr_block_pos;
+};
+
+static u32 heap;
+void *read_inode(struct inode *in);
+struct inode *get_inode(int i);
+int find_inode(const char *name, int dir_inode);
+void serial_install();
+void serial_print(const char *data);
+int main()
+{
+	serial_install();
+	heap = 0xf000;
+	void (*entry)();
+	*(void **)(&entry) = read_inode(get_inode(find_inode("kernel.bin", 2)));
+	if (entry) {
+		serial_print("Loaded kernel!\n");
+		entry();
+	}
+	return 0;
+}
+
+u8 inb(u16 port)
+{
+	u8 value;
+	__asm__ volatile("inb %1, %0" : "=a"(value) : "Nd"(port));
+	return value;
+}
+
+void insl(u16 port, void *addr, int n)
+{
+	__asm__ volatile("cld; rep insl"
+			 : "=D"(addr), "=c"(n)
+			 : "d"(port), "0"(addr), "1"(n)
+			 : "memory", "cc");
+}
+
+void outb(u16 port, u8 data)
+{
+	__asm__ volatile("outb %0, %1" ::"a"(data), "Nd"(port));
+}
+
+void *memcpy(void *dst, const void *src, u32 n)
+{
+	const char *sp = (const char *)src;
+	char *dp = (char *)dst;
+	for (; n != 0; n--)
+		*dp++ = *sp++;
+	return dst;
+}
+
+void *memset(void *dst, char val, u32 n)
+{
+	char *temp = (char *)dst;
+	for (; n != 0; n--)
+		*temp++ = val;
+	return dst;
+}
+
+int strncmp(const char *s1, const char *s2, u32 n)
+{
+	const u8 *c1 = (const u8 *)s1;
+	const u8 *c2 = (const u8 *)s2;
+	u8 ch;
+	int d = 0;
+
+	while (n--) {
+		d = (int)(ch = *c1++) - (int)*c2++;
+		if (d || !ch)
+			break;
+	}
+
+	return d;
+}
+
+u32 strlen(const char *s)
+{
+	const char *ss = s;
+	while (*ss)
+		ss++;
+	return ss - s;
+}
+
+void serial_install()
+{
+	outb(0x3f8 + 1, 0x00);
+	outb(0x3f8 + 3, 0x80);
+	outb(0x3f8 + 0, 0x03);
+	outb(0x3f8 + 1, 0x00);
+	outb(0x3f8 + 3, 0x03);
+	outb(0x3f8 + 2, 0xC7);
+	outb(0x3f8 + 4, 0x0B);
+}
+
+int is_transmit_empty()
+{
+	return inb(0x3f8 + 5) & 0x20;
+}
+
+void serial_put(char ch)
+{
+	while (is_transmit_empty() == 0)
+		;
+	outb(0x3f8, (u8)ch);
+}
+
+void serial_print(const char *data)
+{
+	for (u32 i = 0; i < strlen(data); i++)
+		serial_put(data[i]);
+}
+
+void *malloc(u32 size)
+{
+	return (u32 *)(heap += size);
+}
+
+int ide_wait(int check)
+{
+	char r;
+
+	// Wait while drive is busy. Once just ready is set, exit the loop
+	while (((r = (char)inb(IDE_IO | IDE_CMD)) & (IDE_BUSY | IDE_READY)) != IDE_READY)
+		;
+
+	// Check for errors
+	if (check && (r & (IDE_DRIVE_FAULT | IDE_ERROR)) != 0)
+		return 0xF;
+	return 0;
+}
+
+void *ide_read(void *b, u32 block)
+{
+	int sector_per_block = BLOCK_SIZE / SECTOR_SIZE; // 2
+	int sector = block * sector_per_block;
+
+	ide_wait(0);
+	outb(IDE_IO | IDE_SECTOR_COUNT, sector_per_block); // Number of sectors
+	outb(IDE_IO | IDE_LOW, LBA_LOW(sector));
+	outb(IDE_IO | IDE_MID, LBA_MID(sector));
+	outb(IDE_IO | IDE_HIGH, LBA_HIGH(sector));
+
+	// Slave/Master << 4 and last 4 bits
+	outb(IDE_IO | IDE_HEAD, 0xE0 | (1 << 4) | LBA_LAST(sector));
+	outb(IDE_IO | IDE_CMD, IDE_CMD_READ);
+	ide_wait(0);
+
+	// Read-only
+	insl(IDE_IO, b, BLOCK_SIZE / 4);
+
+	return b;
+}
+
+void *buffer_read(int block)
+{
+	return ide_read(malloc(BLOCK_SIZE), block);
+}
+
+struct superblock *get_superblock()
+{
+	struct superblock *sb = buffer_read(EXT2_SUPER);
+	if (sb->magic != EXT2_MAGIC)
+		return 0;
+	return sb;
+}
+
+struct bgd *get_bgd()
+{
+	return buffer_read(EXT2_SUPER + 1);
+}
+
+struct inode *get_inode(int i)
+{
+	struct superblock *s = get_superblock();
+	//assert(s);
+	struct bgd *b = get_bgd();
+	//assert(b);
+
+	int block_group = (i - 1) / s->inodes_per_group;
+	int index = (i - 1) % s->inodes_per_group;
+	int block = (index * INODE_SIZE) / BLOCK_SIZE;
+	b += block_group;
+
+	u32 *data = buffer_read(b->inode_table + block);
+	struct inode *in =
+		(struct inode *)((u32)data + (index % (BLOCK_SIZE / INODE_SIZE)) * INODE_SIZE);
+	return in;
+}
+
+u32 read_indirect(u32 indirect, u32 block_num)
+{
+	char *data = buffer_read(indirect);
+	return *(u32 *)((u32)data + block_num * sizeof(u32));
+}
+
+void *read_inode(struct inode *in)
+{
+	//assert(in);
+	if (!in)
+		return 0;
+
+	int num_blocks = in->blocks / (BLOCK_SIZE / SECTOR_SIZE);
+
+	//assert(num_blocks != 0);
+	if (!num_blocks)
+		return 0;
+
+	/* u32 sz = BLOCK_SIZE * num_blocks; */
+	/* void *buf = malloc(sz); */
+	void *buf = (void *)0x50000;
+	//assert(buf != 0);
+
+	int indirect;
+
+	int blocknum;
+	char *data;
+	for (int i = 0; i < num_blocks; i++) {
+		if (i < 12) {
+			blocknum = in->block[i];
+			data = buffer_read(blocknum);
+			memcpy((u32 *)((u32)buf + i * BLOCK_SIZE), data, BLOCK_SIZE);
+		} else if (i < BLOCK_COUNT + 12) {
+			indirect = in->block[12];
+			blocknum = read_indirect(indirect, i - 12);
+			data = buffer_read(blocknum);
+			memcpy((u32 *)((u32)buf + (i - 1) * BLOCK_SIZE), data, BLOCK_SIZE);
+		} else {
+			indirect = in->block[13];
+			blocknum = read_indirect(indirect, (i - (BLOCK_COUNT + 12)) / BLOCK_COUNT);
+			blocknum = read_indirect(blocknum, (i - (BLOCK_COUNT + 12)) % BLOCK_COUNT);
+			data = buffer_read(blocknum);
+			memcpy((u32 *)((u32)buf + (i - 1) * BLOCK_SIZE), data, BLOCK_SIZE);
+		}
+	}
+
+	return buf;
+}
+
+int find_inode(const char *name, int dir_inode)
+{
+	if (!dir_inode)
+		return -1;
+
+	struct inode *i = get_inode(dir_inode);
+
+	char *buf = malloc(BLOCK_SIZE * i->blocks / 2);
+	memset(buf, 0, BLOCK_SIZE * i->blocks / 2);
+
+	for (u32 q = 0; q < i->blocks / 2; q++) {
+		char *data = buffer_read(i->block[q]);
+		memcpy((u32 *)((u32)buf + q * BLOCK_SIZE), data, BLOCK_SIZE);
+	}
+
+	struct dirent *d = (struct dirent *)buf;
+
+	u32 sum = 0;
+	do {
+		// Calculate the 4byte aligned size of each entry
+		sum += d->total_len;
+		if (strncmp((void *)d->name, name, d->name_len) == 0) {
+			return d->inode_num;
+		}
+		d = (struct dirent *)((u32)d + d->total_len);
+
+	} while (sum < (1024 * i->blocks / 2));
+	return -1;
+}