Add listing to EXT2
diff --git a/src/kernel/Jmk b/src/kernel/Jmk
index cbce0a2..05e2b8e 100644
--- a/src/kernel/Jmk
+++ b/src/kernel/Jmk
@@ -1,7 +1,8 @@
 init(kernel, kernel.elf)
 
 preset(freestanding)
-preset(optimize)
+# This makes debugging hard :(
+# preset(optimize)
 preset(debug)
 preset(32)
 preset(warn)
@@ -60,7 +61,7 @@
 type(custom_link)
 
 debug-wait: kernel.elf
-	qemu-system-i386 -s -S -kernel kernel.elf
+	qemu-system-i386 -s -S $(QEMUFLAGS) -kernel kernel.elf
 
 debug: kernel.elf
 	qemu-system-i386 -s -S $(QEMUFLAGS) -kernel kernel.elf &
diff --git a/src/kernel/dri/fs/ext2/ext2.c b/src/kernel/dri/fs/ext2/ext2.c
index 31d3b26..3a1e183 100644
--- a/src/kernel/dri/fs/ext2/ext2.c
+++ b/src/kernel/dri/fs/ext2/ext2.c
@@ -2,6 +2,20 @@
 #include <dri/fs/ext2/ext2.h>
 #include <kint.h>
 #include <log.h>
+#include <io.h>
+
+inline uint ext2_block_size(struct ext2_superblock *sb)
+{
+	return 1024 << sb->block_size_shift;
+}
+
+void ext2_read_block(struct ext2_superblock *sb, void *buffer, uint block)
+{
+	uint block_size = ext2_block_size(sb) / 512;
+	uint block_start = block_size * block;
+
+	ata_pio_read_sectors(buffer, block_start, block_size);
+}
 
 struct ext2_superblock ext2_read_superblock()
 {
@@ -31,13 +45,8 @@
 	}
 }
 
-uint ext2_block_size(struct ext2_superblock *sb)
-{
-	return 1024 << sb->block_size_shift;
-}
-
-void ext2_load_block_group_descriptor_table(struct ext2_superblock *sb,
-											uint num_block_groups)
+struct ext2_block_group_descriptor ext2_load_block_group_descriptor(
+	struct ext2_superblock *sb, uint block_group)
 {
 	/**
 	 * The BGDT (not to be confused with the GDT) is located the block after the
@@ -51,7 +60,26 @@
 	if (block_size == 1024)
 		bgdt_block = 2;
 
-	kprintf(DEBUG "BGDT block = %d block size = %d\n", bgdt_block, block_size);
+	const uint bgd_size = sizeof(struct ext2_block_group_descriptor);
+
+	// Disk page that the BGD is on relative to the initial FILE SYSTEM block
+	uint hd_page = block_group / (512 / bgd_size);
+	// The offset from the beginning of that page the BGD is at
+	uint bgd_offset = block_group % (512 / bgd_size);
+
+	struct ext2_block_group_descriptor descriptors[512 / bgd_size];
+	kassert(sizeof(descriptors) == 512, "Wrong BGD size");
+
+	uint lba = (block_size / 512) * bgdt_block + hd_page;
+
+	ata_pio_read_sectors(&descriptors, lba, 1);
+
+	return descriptors[bgd_offset];
+}
+
+static void print_entry(uint inode, const char *name, void *data)
+{
+	kprintf("%d\t %s\n", inode, name);
 }
 
 void ext2_mount(struct fs_node *where)
@@ -59,9 +87,25 @@
 	struct ext2_superblock sb = ext2_read_superblock();
 
 	kprintf(DEBUG "EXT2 magic = 0x%x\n", sb.signature);
+	
+	// Read the root inode 2
+	struct ext2_inode root;
 
-	uint num_block_groups = ext2_num_block_groups(&sb);
-	ext2_load_block_group_descriptor_table(&sb, num_block_groups);
+	if (ext2_find_inode(&sb, 2, &root))
+	{
+		kprintf(OKAY "Found root inode 2 (size=0x%x, num_blocks=0x%x)\n", root.size, root.num_blocks);
+		// kprintf(DEBUG "Root.mode = 0x%x\n", root.mode & 0xf000);
+		kassert((root.mode & 0xf000) == EXT2_S_IFDIR, "Root (inode 2) is not a directory.");
+
+		kprintf("ls /\n");
+		kprintf("inode\t name\n");
+		kprintf("--------------------\n");
+		ext2_dir_ls(&sb, &root, print_entry, NULL);
+	}
+	else
+	{
+		kprintf(WARN "Failed to find root inode 2\n");
+	}
 }
 
 bool ext2_valid_filesystem()
@@ -72,3 +116,111 @@
 
 	return sb.signature == EXT2_SIGNATURE;
 }
+
+void ext2_write_superblock(struct ext2_superblock *sb)
+{
+	ushort *wp = (ushort *)sb;
+
+	ata_pio_write_sectors(2, 2, wp);
+}
+
+void ext2_corrupt_superblock_for_fun()
+{
+	struct ext2_superblock sb = ext2_read_superblock();
+	sb.signature = 0xDEAD;
+	ext2_write_superblock(&sb);
+}
+
+bool ext2_find_inode(struct ext2_superblock *sb, uint number, struct ext2_inode *inode)
+{
+	if (number == 0)
+		return false;
+
+	uint block_group = (number - 1) / sb->inodes_per_block_group;
+	uint local_index = (number - 1) % sb->inodes_per_block_group;
+
+	// Load this from the block group descriptor table
+	struct ext2_block_group_descriptor descriptor =
+		ext2_load_block_group_descriptor(sb, block_group);
+
+	kprintf(DEBUG "Descriptor inode_table = 0x%x\n", descriptor.inode_table_start_block);
+
+	// We need to figure out what FS block the inode is on, we know how many
+	// inodes there are total in this BGD and the number per page, so this is
+	// simple.
+
+	const uint block_size = ext2_block_size(sb);
+
+	const uint inodes_per_block = block_size / sizeof(struct ext2_inode);
+
+	uint inode_block = local_index / inodes_per_block;
+	uint inode_index = local_index % inodes_per_block;
+
+	struct ext2_inode inodes[block_size / sizeof(struct ext2_inode)];
+
+	ext2_read_block(sb, inodes, descriptor.inode_table_start_block +
+								inode_block);
+
+	*inode = inodes[inode_index];
+
+	return true;
+}
+
+bool ext2_dir_ls(struct ext2_superblock *sb,
+				 struct ext2_inode *dir,
+				 void (*cb)(uint inode,
+							const char *name,
+							void *data),
+				 void *data)
+{
+	if ((dir->mode & 0xf000) != EXT2_S_IFDIR)
+		return false;
+
+	for (int i = 0; i < dir->num_blocks; i++)
+	{
+		uchar buffer[ext2_block_size(sb)];
+		ext2_read_inode_block(sb, dir, buffer, i);
+
+		struct ext2_dirent *ent = (void *)buffer;
+
+		// While there are files in this block
+		while (ent < buffer + ext2_block_size(sb))
+		{
+			if (ent->inode == 0)
+				return true;
+
+			if (cb)
+			{
+				char name[257];
+
+				memcpy(name, ent->name, ent->name_len);
+				name[ent->name_len] = '\0';
+				
+				cb(ent->inode, name, data);
+			}
+
+			ent = (void *)(((uint)(void *)ent) + ent->rec_len);
+		}
+		// We ran out of files in this block, continue to the next one. This
+		// works because files cannot span blocks
+	}
+
+	return true;
+}
+
+bool ext2_read_inode_block(struct ext2_superblock *sb,
+						   struct ext2_inode *inode,
+						   void *buffer,
+						   uint block)
+{
+	if (block >= 12)
+	{
+		kprintf(ERROR "Sorry, EXT2 can only access the first 12 (direct) blocks "
+					  "of an inode for now. Indirect look-up will be added later\n");
+		kpanic("Invalid inode block");
+	}
+
+	uint block_address = inode->blocks[block];
+
+	ext2_read_block(sb, buffer, block_address);
+}
diff --git a/src/kernel/main.c b/src/kernel/main.c
index 53fb71e..59fc111 100644
--- a/src/kernel/main.c
+++ b/src/kernel/main.c
@@ -101,19 +101,15 @@
 	test_ata_pio();
 #endif
 
-#if 1 // ifdef TEST_EXT2
 	if (ext2_valid_filesystem())
 	{
-		kprintf(OKAY "EXT2 filesystem is valid, again = %b\n", ext2_valid_filesystem());
-
-		//kprintf(INFO "Mounting EXT2 to /\n");
-		//ext2_mount(&root);
+		kprintf(OKAY "EXT2 filesystem is valid\n");
+		ext2_mount(&root);
 	}
-
-	// Try reading the regions that the ext2 needs
-	// uchar buffer[1024];
-	// ata_pio_read_sectors(buffer, 2, 2);
-#endif
+	else
+	{
+		kprintf(WARN "Filesystem is not a valid EXT2 format, only EXT2 is supported\n");
+	}
 
 	while (true)
 		asm("hlt");