Import PintOS

.gitignore

+# C/C++
+# Prerequisites
+*.d
+
+# Compiled Object files
+*.slo
+*.lo
+*.o
+*.obj
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Compiled Dynamic libraries
+*.so
+*.dylib
+*.dll
+
+# Fortran module files
+*.mod
+*.smod
+
+# Compiled Static libraries
+*.lai
+*.la
+*.a
+*.lib
+
+# Executables
+*.exe
+*.out
+*.app
+
+# Other
+*~
+\#*\#

AUTHORS

+src							-*- text -*-
+---
+
+* Pintos core originally written by Ben Pfaff <blp@cs.stanford.edu>.
+
+* Additional features contributed by Anthony Romano <chz@vt.edu>.
+
+* The original structure and form of this operating system is inspired
+  by the Nachos system from the University of California, Berkeley.  A
+  few of the source files are more-or-less literal translations of the
+  Nachos C++ code into C.  These files bear the original UCB license
+  notice.
+
+projects
+--------
+
+* The projects are primarily the creation of Ben Pfaff
+  <blp@cs.stanford.edu>.
+
+* Godmar Back <godmar@gmail.com> made significant contributions to
+  project design.
+
+* Although little remains unchanged, the projects were originally
+  derived from those designed for Nachos by current and former CS140
+  teaching assistants at Stanford University, including at least the
+  following people:
+	
+	- Yu Ping <yph@cs.stanford.edu>
+
+	- Greg Hutchins
+
+	- Kelly Shaw <kashaw (at) cs.stanford.edu>, 
+
+	- Paul Twohey <twohey AT cs DOT stanford DOT edu>
+
+	- Sameer Qureshi <squreshi@cs.stanford.edu>
+
+	- John Rector
+
+  If you're not on this list but should be, please let me know.
+
+* Example code for condition variables is from classroom slides
+  originally by Dawson Engler and updated by Mendel Roseblum.

LICENSE

+Pintos, including its documentation, is subject to the following
+license:
+
+    Copyright (C) 2004, 2005, 2006 Board of Trustees, Leland Stanford
+    Jr. University.  All rights reserved.
+
+    Permission is hereby granted, free of charge, to any person obtaining
+    a copy of this software and associated documentation files (the
+    "Software"), to deal in the Software without restriction, including
+    without limitation the rights to use, copy, modify, merge, publish,
+    distribute, sublicense, and/or sell copies of the Software, and to
+    permit persons to whom the Software is furnished to do so, subject to
+    the following conditions:
+
+    The above copyright notice and this permission notice shall be
+    included in all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+    NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+    LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+    OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+    WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+A few individual files in Pintos were originally derived from other
+projects, but they have been extensively modified for use in Pintos.
+The original code falls under the original license, and modifications
+for Pintos are additionally covered by the Pintos license above. 
+
+In particular, code derived from Nachos is subject to the following
+license:
+
+/* Copyright (c) 1992-1996 The Regents of the University of California.
+   All rights reserved.
+
+   Permission to use, copy, modify, and distribute this software
+   and its documentation for any purpose, without fee, and
+   without written agreement is hereby granted, provided that the
+   above copyright notice and the following two paragraphs appear
+   in all copies of this software.
+
+   IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO
+   ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR
+   CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF THIS SOFTWARE
+   AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA
+   HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+   THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY
+   WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+   WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+   PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS"
+   BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
+   PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR
+   MODIFICATIONS.
+*/

doc/.gitignore

+*.aux
+*.cp
+*.dvi
+*.fn
+*.info*
+*.ky
+*.log
+*.pg
+*.toc
+*.tp
+*.vr
+/pintos.fns
+/pintos.tps
+/pintos.vrs
+mlfqs1.pdf
+mlfqs1.png
+mlfqs2.pdf
+mlfqs2.png
+pintos.html
+pintos.pdf
+pintos.ps
+pintos.text
+pintos_*.html
+projects.html
+sample.tmpl.texi

setup.sh

+#!/bin/sh
+
+export PINTOS_HOME=`pwd`
+export PATH=$PATH:`pwd`/src/utils

src/.gitignore

+cscope.files
+cscope.out
+TAGS
+tags

src/LICENSE

+Pintos, including its documentation, is subject to the following
+license:
+
+    Copyright (C) 2004, 2005, 2006 Board of Trustees, Leland Stanford
+    Jr. University.  All rights reserved.
+
+    Permission is hereby granted, free of charge, to any person obtaining
+    a copy of this software and associated documentation files (the
+    "Software"), to deal in the Software without restriction, including
+    without limitation the rights to use, copy, modify, merge, publish,
+    distribute, sublicense, and/or sell copies of the Software, and to
+    permit persons to whom the Software is furnished to do so, subject to
+    the following conditions:
+
+    The above copyright notice and this permission notice shall be
+    included in all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+    NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+    LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+    OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+    WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+A few individual files in Pintos were originally derived from other
+projects, but they have been extensively modified for use in Pintos.
+The original code falls under the original license, and modifications
+for Pintos are additionally covered by the Pintos license above. 
+
+In particular, code derived from Nachos is subject to the following
+license:
+
+/* Copyright (c) 1992-1996 The Regents of the University of California.
+   All rights reserved.
+
+   Permission to use, copy, modify, and distribute this software
+   and its documentation for any purpose, without fee, and
+   without written agreement is hereby granted, provided that the
+   above copyright notice and the following two paragraphs appear
+   in all copies of this software.
+
+   IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO
+   ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR
+   CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF THIS SOFTWARE
+   AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA
+   HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+   THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY
+   WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+   WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+   PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS"
+   BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
+   PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR
+   MODIFICATIONS.
+*/
+
+Also, code derived from MIT's 6.828 course code is subject to the
+following license:
+
+/*
+ * Copyright (C) 1997 Massachusetts Institute of Technology 
+ *
+ * This software is being provided by the copyright holders under the
+ * following license. By obtaining, using and/or copying this software,
+ * you agree that you have read, understood, and will comply with the
+ * following terms and conditions:
+ *
+ * Permission to use, copy, modify, distribute, and sell this software
+ * and its documentation for any purpose and without fee or royalty is
+ * hereby granted, provided that the full text of this NOTICE appears on
+ * ALL copies of the software and documentation or portions thereof,
+ * including modifications, that you make.
+ *
+ * THIS SOFTWARE IS PROVIDED "AS IS," AND COPYRIGHT HOLDERS MAKE NO
+ * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED. BY WAY OF EXAMPLE,
+ * BUT NOT LIMITATION, COPYRIGHT HOLDERS MAKE NO REPRESENTATIONS OR
+ * WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR
+ * THAT THE USE OF THE SOFTWARE OR DOCUMENTATION WILL NOT INFRINGE ANY
+ * THIRD PARTY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS. COPYRIGHT
+ * HOLDERS WILL BEAR NO LIABILITY FOR ANY USE OF THIS SOFTWARE OR
+ * DOCUMENTATION.
+ *
+ * The name and trademarks of copyright holders may NOT be used in
+ * advertising or publicity pertaining to the software without specific,
+ * written prior permission. Title to copyright in this software and any
+ * associated documentation will at all times remain with copyright
+ * holders. See the file AUTHORS which should have accompanied this software
+ * for a list of all copyright holders.
+ *
+ * This file may be derived from previously copyrighted software. This
+ * copyright applies only to those changes made by the copyright
+ * holders listed in the AUTHORS file. The rest of this file is covered by
+ * the copyright notices, if any, listed below.
+ */

src/Make.config

+# -*- makefile -*-
+
+SHELL = /bin/sh
+
+VPATH = $(SRCDIR)
+
+# Binary utilities.
+# If the host appears to be x86, use the normal tools.
+# If it's x86-64, use the compiler and linker in 32-bit mode.
+# Otherwise assume cross-tools are installed as i386-elf-*.
+X86 = i.86\|pentium.*\|[pk][56]\|nexgen\|viac3\|6x86\|athlon.*\|i86pc
+X86_64 = x86_64
+ifneq (0, $(shell expr `uname -m` : '$(X86)'))
+  CC = gcc
+  LD = ld
+  OBJCOPY = objcopy
+else
+  ifneq (0, $(shell expr `uname -m` : '$(X86_64)'))
+    CC = gcc -m32
+    LD = ld -melf_i386
+    OBJCOPY = objcopy
+  else
+    CC = i386-elf-gcc
+    LD = i386-elf-ld
+    OBJCOPY = i386-elf-objcopy
+  endif
+endif
+
+ifeq ($(strip $(shell command -v $(CC) 2> /dev/null)),)
+$(warning *** Compiler ($(CC)) not found.  Did you set $$PATH properly?  Please refer to the Getting Started section in the documentation for details. ***)
+endif
+
+# Compiler and assembler invocation.
+DEFINES =
+WARNINGS = -Wall -W -Wstrict-prototypes -Wmissing-prototypes -Wsystem-headers
+CFLAGS = -g -msoft-float -O -march=i686 -fPIE -mno-stackrealign
+CPPFLAGS = -nostdinc -I$(SRCDIR) -I$(SRCDIR)/lib
+ASFLAGS = -Wa,--gstabs
+LDFLAGS = 
+DEPS = -MMD -MF $(@:.o=.d)
+
+# Turn off -fstack-protector, which we don't support.
+ifeq ($(strip $(shell echo | $(CC) -fno-stack-protector -E - > /dev/null 2>&1; echo $$?)),0)
+CFLAGS += -fno-stack-protector
+endif
+
+# Turn off --build-id in the linker, which confuses the Pintos loader.
+ifeq ($(strip $(shell $(LD) --help | grep -q build-id; echo $$?)),0)
+LDFLAGS += -Wl,--build-id=none
+endif
+
+%.o: %.c
+	$(CC) -c $< -o $@ $(CFLAGS) $(CPPFLAGS) $(WARNINGS) $(DEFINES) $(DEPS)
+
+%.o: %.S
+	$(CC) -c $< -o $@ $(ASFLAGS) $(CPPFLAGS) $(DEFINES) $(DEPS)

src/Makefile

+BUILD_SUBDIRS = threads userprog vm filesys
+
+all::
+	@echo "Run 'make' in subdirectories: $(BUILD_SUBDIRS)."
+	@echo "This top-level make has only 'clean' targets."
+
+CLEAN_SUBDIRS = $(BUILD_SUBDIRS) examples utils
+
+clean::
+	for d in $(CLEAN_SUBDIRS); do $(MAKE) -C $$d $@; done
+	rm -f TAGS tags
+
+distclean:: clean
+	find . -name '*~' -exec rm '{}' \;
+
+TAGS_SUBDIRS = $(BUILD_SUBDIRS) devices lib
+TAGS_SOURCES = find $(TAGS_SUBDIRS) -name \*.[chS] -print
+
+TAGS::
+	etags --members `$(TAGS_SOURCES)`
+
+tags::
+	ctags -T --no-warn `$(TAGS_SOURCES)`
+
+cscope.files::
+	$(TAGS_SOURCES) > cscope.files
+
+cscope:: cscope.files
+	cscope -b -q -k

src/Makefile.build

+# -*- makefile -*-
+
+SRCDIR = ../..
+
+all: kernel.bin loader.bin
+
+include ../../Make.config
+include ../Make.vars
+include ../../tests/Make.tests
+
+# Compiler and assembler options.
+kernel.bin: CPPFLAGS += -I$(SRCDIR)/lib/kernel
+
+# Core kernel.
+threads_SRC  = threads/start.S		# Startup code.
+threads_SRC += threads/init.c		# Main program.
+threads_SRC += threads/thread.c		# Thread management core.
+threads_SRC += threads/switch.S		# Thread switch routine.
+threads_SRC += threads/interrupt.c	# Interrupt core.
+threads_SRC += threads/intr-stubs.S	# Interrupt stubs.
+threads_SRC += threads/synch.c		# Synchronization.
+threads_SRC += threads/palloc.c		# Page allocator.
+threads_SRC += threads/malloc.c		# Subpage allocator.
+
+# Device driver code.
+devices_SRC  = devices/pit.c		# Programmable interrupt timer chip.
+devices_SRC += devices/timer.c		# Periodic timer device.
+devices_SRC += devices/kbd.c		# Keyboard device.
+devices_SRC += devices/vga.c		# Video device.
+devices_SRC += devices/serial.c		# Serial port device.
+devices_SRC += devices/block.c		# Block device abstraction layer.
+devices_SRC += devices/partition.c	# Partition block device.
+devices_SRC += devices/ide.c		# IDE disk block device.
+devices_SRC += devices/input.c		# Serial and keyboard input.
+devices_SRC += devices/intq.c		# Interrupt queue.
+devices_SRC += devices/rtc.c		# Real-time clock.
+devices_SRC += devices/shutdown.c	# Reboot and power off.
+devices_SRC += devices/speaker.c	# PC speaker.
+
+# Library code shared between kernel and user programs.
+lib_SRC  = lib/debug.c			# Debug helpers.
+lib_SRC += lib/random.c			# Pseudo-random numbers.
+lib_SRC += lib/stdio.c			# I/O library.
+lib_SRC += lib/stdlib.c			# Utility functions.
+lib_SRC += lib/string.c			# String functions.
+lib_SRC += lib/arithmetic.c		# 64-bit arithmetic for GCC.
+lib_SRC += lib/ustar.c			# Unix standard tar format utilities.
+
+# Kernel-specific library code.
+lib/kernel_SRC  = lib/kernel/debug.c	# Debug helpers.
+lib/kernel_SRC += lib/kernel/list.c	# Doubly-linked lists.
+lib/kernel_SRC += lib/kernel/bitmap.c	# Bitmaps.
+lib/kernel_SRC += lib/kernel/hash.c	# Hash tables.
+lib/kernel_SRC += lib/kernel/console.c	# printf(), putchar().
+
+# User process code.
+userprog_SRC  = userprog/process.c	# Process loading.
+userprog_SRC += userprog/pagedir.c	# Page directories.
+userprog_SRC += userprog/exception.c	# User exception handler.
+userprog_SRC += userprog/syscall.c	# System call handler.
+userprog_SRC += userprog/gdt.c		# GDT initialization.
+userprog_SRC += userprog/tss.c		# TSS management.
+
+# No virtual memory code yet.
+#vm_SRC = vm/file.c			# Some file.
+vm_SRC = vm/frame.c			# Frame table
+vm_SRC += vm/sup_page.c			# Supplemental page table
+
+# Filesystem code.
+filesys_SRC  = filesys/filesys.c	# Filesystem core.
+filesys_SRC += filesys/free-map.c	# Free sector bitmap.
+filesys_SRC += filesys/file.c		# Files.
+filesys_SRC += filesys/directory.c	# Directories.
+filesys_SRC += filesys/inode.c		# File headers.
+filesys_SRC += filesys/fsutil.c		# Utilities.
+
+SOURCES = $(foreach dir,$(KERNEL_SUBDIRS),$($(dir)_SRC))
+OBJECTS = $(patsubst %.c,%.o,$(patsubst %.S,%.o,$(SOURCES)))
+DEPENDS = $(patsubst %.o,%.d,$(OBJECTS))
+
+threads/kernel.lds.s: CPPFLAGS += -P
+threads/kernel.lds.s: threads/kernel.lds.S threads/loader.h
+
+kernel.o: threads/kernel.lds.s $(OBJECTS) 
+	$(LD) -T $< -o $@ $(OBJECTS)
+
+kernel.bin: kernel.o
+	$(OBJCOPY) -R .note -R .comment -S $< $@
+
+threads/loader.o: threads/loader.S
+	$(CC) -c $< -o $@ $(ASFLAGS) $(CPPFLAGS) $(DEFINES)
+
+loader.bin: threads/loader.o
+	$(LD) -N -e 0 -Ttext 0x7c00 --oformat binary -o $@ $<
+
+os.dsk: kernel.bin
+	cat $^ > $@
+
+clean::
+	rm -f $(OBJECTS) $(DEPENDS) 
+	rm -f threads/loader.o threads/kernel.lds.s threads/loader.d
+	rm -f kernel.bin.tmp
+	rm -f kernel.o kernel.lds.s
+	rm -f kernel.bin loader.bin
+	rm -f bochsout.txt bochsrc.txt
+	rm -f results grade
+
+Makefile: $(SRCDIR)/Makefile.build
+	cp $< $@
+
+-include $(DEPENDS)

src/Makefile.kernel

+# -*- makefile -*-
+
+all:
+
+include Make.vars
+
+DIRS = $(sort $(addprefix build/,$(KERNEL_SUBDIRS) $(TEST_SUBDIRS) lib/user))
+
+all grade check: $(DIRS) build/Makefile
+	cd build && $(MAKE) $@
+$(DIRS):
+	mkdir -p $@
+build/Makefile: ../Makefile.build
+	cp $< $@
+
+build/%: $(DIRS) build/Makefile
+	cd build && $(MAKE) $*
+
+clean:
+	rm -rf build

src/Makefile.userprog

+# -*- makefile -*-
+
+$(PROGS): CPPFLAGS += -I$(SRCDIR)/lib/user -I.
+
+# Linker flags.
+$(PROGS): LDFLAGS += -nostdlib -static -Wl,-T,$(LDSCRIPT)
+$(PROGS): LDSCRIPT = $(SRCDIR)/lib/user/user.lds
+
+# Library code shared between kernel and user programs.
+lib_SRC  = lib/debug.c			# Debug code.
+lib_SRC += lib/random.c			# Pseudo-random numbers.
+lib_SRC += lib/stdio.c			# I/O library.
+lib_SRC += lib/stdlib.c			# Utility functions.
+lib_SRC += lib/string.c			# String functions.
+lib_SRC += lib/arithmetic.c		# 64-bit arithmetic for GCC.
+lib_SRC += lib/ustar.c			# Unix standard tar format utilities.
+
+# User level only library code.
+lib/user_SRC  = lib/user/debug.c	# Debug helpers.
+lib/user_SRC += lib/user/syscall.c	# System calls.
+lib/user_SRC += lib/user/console.c	# Console code.
+
+LIB_OBJ = $(patsubst %.c,%.o,$(patsubst %.S,%.o,$(lib_SRC) $(lib/user_SRC)))
+LIB_DEP = $(patsubst %.o,%.d,$(LIB_OBJ))
+LIB = lib/user/entry.o libc.a
+
+PROGS_SRC = $(foreach prog,$(PROGS),$($(prog)_SRC))
+PROGS_OBJ = $(patsubst %.c,%.o,$(patsubst %.S,%.o,$(PROGS_SRC)))
+PROGS_DEP = $(patsubst %.o,%.d,$(PROGS_OBJ))
+
+all: $(PROGS)
+
+define TEMPLATE
+$(1)_OBJ = $(patsubst %.c,%.o,$(patsubst %.S,%.o,$($(1)_SRC)))
+$(1): $$($(1)_OBJ) $$(LIB) $$(LDSCRIPT)
+	$$(CC) $$(LDFLAGS) $$($(1)_OBJ) $$(LIB) -o $$@
+endef
+
+$(foreach prog,$(PROGS),$(eval $(call TEMPLATE,$(prog))))
+
+libc.a: $(LIB_OBJ)
+	rm -f $@
+	ar r $@ $^
+	ranlib $@
+
+clean::
+	rm -f $(PROGS) $(PROGS_OBJ) $(PROGS_DEP)
+	rm -f $(LIB_DEP) $(LIB_OBJ) lib/user/entry.[do] libc.a 
+
+.PHONY: all clean
+
+-include $(LIB_DEP) $(PROGS_DEP)

src/devices/block.c

+#include "devices/block.h"
+#include <list.h>
+#include <string.h>
+#include <stdio.h>
+#include "devices/ide.h"
+#include "threads/malloc.h"
+
+/* A block device. */
+struct block
+  {
+    struct list_elem list_elem;         /* Element in all_blocks. */
+
+    char name[16];                      /* Block device name. */
+    enum block_type type;                /* Type of block device. */
+    block_sector_t size;                 /* Size in sectors. */
+
+    const struct block_operations *ops;  /* Driver operations. */
+    void *aux;                          /* Extra data owned by driver. */
+
+    unsigned long long read_cnt;        /* Number of sectors read. */
+    unsigned long long write_cnt;       /* Number of sectors written. */
+  };
+
+/* List of all block devices. */
+static struct list all_blocks = LIST_INITIALIZER (all_blocks);
+
+/* The block block assigned to each Pintos role. */
+static struct block *block_by_role[BLOCK_ROLE_CNT];
+
+static struct block *list_elem_to_block (struct list_elem *);
+
+/* Returns a human-readable name for the given block device
+   TYPE. */
+const char *
+block_type_name (enum block_type type)
+{
+  static const char *block_type_names[BLOCK_CNT] =
+    {
+      "kernel",
+      "filesys",
+      "scratch",
+      "swap",
+      "raw",
+      "foreign",
+    };
+
+  ASSERT (type < BLOCK_CNT);
+  return block_type_names[type];
+}
+
+/* Returns the block device fulfilling the given ROLE, or a null
+   pointer if no block device has been assigned that role. */
+struct block *
+block_get_role (enum block_type role)
+{
+  ASSERT (role < BLOCK_ROLE_CNT);
+  return block_by_role[role];
+}
+
+/* Assigns BLOCK the given ROLE. */
+void
+block_set_role (enum block_type role, struct block *block)
+{
+  ASSERT (role < BLOCK_ROLE_CNT);
+  block_by_role[role] = block;
+}
+
+/* Returns the first block device in kernel probe order, or a
+   null pointer if no block devices are registered. */
+struct block *
+block_first (void)
+{
+  return list_elem_to_block (list_begin (&all_blocks));
+}
+
+/* Returns the block device following BLOCK in kernel probe
+   order, or a null pointer if BLOCK is the last block device. */
+struct block *
+block_next (struct block *block)
+{
+  return list_elem_to_block (list_next (&block->list_elem));
+}
+
+/* Returns the block device with the given NAME, or a null
+   pointer if no block device has that name. */
+struct block *
+block_get_by_name (const char *name)
+{
+  struct list_elem *e;
+
+  for (e = list_begin (&all_blocks); e != list_end (&all_blocks);
+       e = list_next (e))
+    {
+      struct block *block = list_entry (e, struct block, list_elem);
+      if (!strcmp (name, block->name))