lab1

.gdbinit.tmpl

@@ -0,0 +1,30 @@
+set $lastcs = -1
+
+define hook-stop
+  # There doesn't seem to be a good way to detect if we're in 16- or
+  # 32-bit mode, but we always run with CS == 8 in 32-bit mode.
+  if $cs == 8 || $cs == 27
+    if $lastcs != 8 && $lastcs != 27
+      set architecture i386
+    end
+    x/i $pc
+  else
+    if $lastcs == -1 || $lastcs == 8 || $lastcs == 27
+      set architecture i8086
+    end
+    # Translate the segment:offset into a physical address
+    printf "[%4x:%4x] ", $cs, $eip
+    x/i $cs*16+$eip
+  end
+  set $lastcs = $cs
+end
+
+echo + target remote localhost:1234\n
+target remote localhost:1234
+
+# If this fails, it's probably because your GDB doesn't support ELF.
+# Look at the tools page at
+#  http://pdos.csail.mit.edu/6.828/2009/tools.html
+# for instructions on building GDB with ELF support.
+echo + symbol-file obj/kern/kernel\n
+symbol-file obj/kern/kernel

CODING

@@ -0,0 +1,37 @@
+JOS CODING STANDARDS
+
+It's easier on everyone if all authors working on a shared
+code base are consistent in the way they write their programs.
+We have the following conventions in our code:
+
+* No space after the name of a function in a call
+  For example, printf("hello") not printf ("hello").
+
+* One space after keywords "if", "for", "while", "switch".
+  For example, if (x) not if(x).
+
+* Space before braces.
+  For example, if (x) { not if (x){.
+
+* Function names are all lower-case separated by underscores.
+
+* Beginning-of-line indentation via tabs, not spaces.
+
+* Preprocessor macros are always UPPERCASE.
+  There are a few grandfathered exceptions: assert, panic,
+  static_assert, offsetof.
+
+* Pointer types have spaces: (uint16_t *) not (uint16_t*).
+
+* Multi-word names are lower_case_with_underscores.
+
+* Comments in imported code are usually C /* ... */ comments.
+  Comments in new code are C++ style //.
+
+* In a function definition, the function name starts a new line.
+  Then you can grep -n '^foo' */*.c to find the definition of foo.
+
+* Functions that take no arguments are declared f(void) not f().
+
+The included .dir-locals.el file will automatically set up the basic
+indentation style in Emacs.

GNUmakefile

@@ -0,0 +1,199 @@
+#
+# This makefile system follows the structuring conventions
+# recommended by Peter Miller in his excellent paper:
+#
+#	Recursive Make Considered Harmful
+#	http://aegis.sourceforge.net/auug97.pdf
+#
+OBJDIR := obj
+
+-include conf/lab.mk
+
+-include conf/env.mk
+
+ifndef LABSETUP
+LABSETUP := ./
+endif
+
+TOP = .
+
+# Cross-compiler jos toolchain
+#
+# This Makefile will automatically use the cross-compiler toolchain
+# installed as 'i386-jos-elf-*', if one exists.  If the host tools ('gcc',
+# 'objdump', and so forth) compile for a 32-bit x86 ELF target, that will
+# be detected as well.  If you have the right compiler toolchain installed
+# using a different name, set GCCPREFIX explicitly in conf/env.mk
+
+# try to infer the correct GCCPREFIX
+ifndef GCCPREFIX
+GCCPREFIX := $(shell if i386-jos-elf-objdump -i 2>&1 | grep '^elf32-i386$$' >/dev/null 2>&1; \
+	then echo 'i386-jos-elf-'; \
+	elif objdump -i 2>&1 | grep 'elf32-i386' >/dev/null 2>&1; \
+	then echo ''; \
+	else echo "***" 1>&2; \
+	echo "*** Error: Couldn't find an i386-*-elf version of GCC/binutils." 1>&2; \
+	echo "*** Is the directory with i386-jos-elf-gcc in your PATH?" 1>&2; \
+	echo "*** If your i386-*-elf toolchain is installed with a command" 1>&2; \
+	echo "*** prefix other than 'i386-jos-elf-', set your GCCPREFIX" 1>&2; \
+	echo "*** environment variable to that prefix and run 'make' again." 1>&2; \
+	echo "*** To turn off this error, run 'gmake GCCPREFIX= ...'." 1>&2; \
+	echo "***" 1>&2; exit 1; fi)
+endif
+
+# try to infer the correct QEMU
+ifndef QEMU
+QEMU := $(shell if which qemu > /dev/null; \
+	then echo qemu; exit; \
+	else \
+	qemu=/Applications/Q.app/Contents/MacOS/i386-softmmu.app/Contents/MacOS/i386-softmmu; \
+	if test -x $$qemu; then echo $$qemu; exit; fi; fi; \
+	echo "***" 1>&2; \
+	echo "*** Error: Couldn't find a working QEMU executable." 1>&2; \
+	echo "*** Is the directory containing the qemu binary in your PATH" 1>&2; \
+	echo "*** or have you tried setting the QEMU variable in conf/env.mk?" 1>&2; \
+	echo "***" 1>&2; exit 1)
+endif
+
+# try to generate a unique GDB port
+GDBPORT	:= $(shell expr `id -u` % 5000 + 25000)
+# QEMU's gdb stub command line changed in 0.11
+QEMUGDB = $(shell if $(QEMU) -nographic -help | grep -q '^-gdb'; \
+	then echo "-gdb tcp::$(GDBPORT)"; \
+	else echo "-s -p $(GDBPORT)"; fi)
+
+CC	:= $(GCCPREFIX)gcc -pipe
+AS	:= $(GCCPREFIX)as
+AR	:= $(GCCPREFIX)ar
+LD	:= $(GCCPREFIX)ld
+OBJCOPY	:= $(GCCPREFIX)objcopy
+OBJDUMP	:= $(GCCPREFIX)objdump
+NM	:= $(GCCPREFIX)nm
+
+# Native commands
+NCC	:= gcc $(CC_VER) -pipe
+TAR	:= gtar
+PERL	:= perl
+
+# Compiler flags
+# -fno-builtin is required to avoid refs to undefined functions in the kernel.
+# Only optimize to -O1 to discourage inlining, which complicates backtraces.
+CFLAGS := $(CFLAGS) $(DEFS) $(LABDEFS) -O1 -fno-builtin -I$(TOP) -MD 
+CFLAGS += -fno-omit-frame-pointer
+CFLAGS += -Wall -Wno-format -Wno-unused -Werror -gstabs -m32
+
+# Add -fno-stack-protector if the option exists.
+CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
+
+# Common linker flags
+LDFLAGS := -m elf_i386
+
+# Linker flags for JOS user programs
+ULDFLAGS := -T user/user.ld
+
+GCC_LIB := $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)
+
+# Lists that the */Makefrag makefile fragments will add to
+OBJDIRS :=
+
+# Make sure that 'all' is the first target
+all:
+
+# Eliminate default suffix rules
+.SUFFIXES:
+
+# Delete target files if there is an error (or make is interrupted)
+.DELETE_ON_ERROR:
+
+# make it so that no intermediate .o files are ever deleted
+.PRECIOUS: %.o $(OBJDIR)/boot/%.o $(OBJDIR)/kern/%.o \
+	   $(OBJDIR)/lib/%.o $(OBJDIR)/fs/%.o $(OBJDIR)/net/%.o \
+	   $(OBJDIR)/user/%.o
+
+KERN_CFLAGS := $(CFLAGS) -DJOS_KERNEL -gstabs
+USER_CFLAGS := $(CFLAGS) -DJOS_USER -gstabs
+
+
+
+
+# Include Makefrags for subdirectories
+include boot/Makefrag
+include kern/Makefrag
+
+
+IMAGES = $(OBJDIR)/kern/kernel.img
+QEMUOPTS = -hda $(OBJDIR)/kern/kernel.img -serial mon:stdio $(QEMUEXTRA)
+
+.gdbinit: .gdbinit.tmpl
+	sed "s/localhost:1234/localhost:$(GDBPORT)/" < $^ > $@
+
+qemu: $(IMAGES)
+	$(QEMU) $(QEMUOPTS)
+
+qemu-nox: $(IMAGES)
+	@echo "***"
+	@echo "*** Use Ctrl-a x to exit qemu"
+	@echo "***"
+	$(QEMU) -nographic $(QEMUOPTS)
+
+qemu-gdb: $(IMAGES) .gdbinit
+	@echo "***"
+	@echo "*** Now run 'gdb'." 1>&2
+	@echo "***"
+	$(QEMU) $(QEMUOPTS) -S $(QEMUGDB)
+
+qemu-nox-gdb: $(IMAGES) .gdbinit
+	@echo "***"
+	@echo "*** Now run 'gdb'." 1>&2
+	@echo "***"
+	$(QEMU) -nographic $(QEMUOPTS) -S $(QEMUGDB)
+
+print-qemu:
+	@echo $(QEMU)
+
+print-gdbport:
+	@echo $(GDBPORT)
+
+print-qemugdb:
+	@echo $(QEMUGDB)
+
+# For deleting the build
+clean:
+	rm -rf $(OBJDIR) .gdbinit jos.in
+
+realclean: clean
+	rm -rf lab$(LAB).tar.gz jos.out
+
+distclean: realclean
+	rm -rf conf/gcc.mk
+
+grade: $(LABSETUP)grade-lab$(LAB).sh
+	@echo $(MAKE) clean
+	@$(MAKE) clean || \
+	  (echo "'make clean' failed.  HINT: Do you have another running instance of JOS?" && exit 1)
+	$(MAKE) all
+	sh $(LABSETUP)grade-lab$(LAB).sh
+
+handin: tarball
+	@echo Please visit http://pdos.csail.mit.edu/6.828/submit/
+	@echo and upload lab$(LAB)-handin.tar.gz.  Thanks!
+
+tarball: realclean
+	tar cf - `find . -type f | grep -v '^\.*$$' | grep -v '/CVS/' | grep -v '/\.svn/' | grep -v '/\.git/' | grep -v 'lab[0-9].*\.tar\.gz'` | gzip > lab$(LAB)-handin.tar.gz
+
+
+# This magic automatically generates makefile dependencies
+# for header files included from C source files we compile,
+# and keeps those dependencies up-to-date every time we recompile.
+# See 'mergedep.pl' for more information.
+$(OBJDIR)/.deps: $(foreach dir, $(OBJDIRS), $(wildcard $(OBJDIR)/$(dir)/*.d))
+	@mkdir -p $(@D)
+	@$(PERL) mergedep.pl $@ $^
+
+-include $(OBJDIR)/.deps
+
+always:
+	@:
+
+.PHONY: all always \
+	handin tarball clean realclean distclean grade

boot/Makefrag

@@ -0,0 +1,32 @@
+#
+# Makefile fragment for the JOS kernel.
+# This is NOT a complete makefile;
+# you must run GNU make in the top-level directory
+# where the GNUmakefile is located.
+#
+
+OBJDIRS += boot
+
+BOOT_OBJS := $(OBJDIR)/boot/boot.o $(OBJDIR)/boot/main.o
+
+$(OBJDIR)/boot/%.o: boot/%.c
+	@echo + cc -Os $<
+	@mkdir -p $(@D)
+	$(V)$(CC) -nostdinc $(KERN_CFLAGS) -Os -c -o $@ $<
+
+$(OBJDIR)/boot/%.o: boot/%.S
+	@echo + as $<
+	@mkdir -p $(@D)
+	$(V)$(CC) -nostdinc $(KERN_CFLAGS) -c -o $@ $<
+
+$(OBJDIR)/boot/main.o: boot/main.c
+	@echo + cc -Os $<
+	$(V)$(CC) -nostdinc $(KERN_CFLAGS) -Os -c -o $(OBJDIR)/boot/main.o boot/main.c
+
+$(OBJDIR)/boot/boot: $(BOOT_OBJS)
+	@echo + ld boot/boot
+	$(V)$(LD) $(LDFLAGS) -N -e start -Ttext 0x7C00 -o $@.out $^
+	$(V)$(OBJDUMP) -S $@.out >$@.asm
+	$(V)$(OBJCOPY) -S -O binary -j .text $@.out $@
+	$(V)perl boot/sign.pl $(OBJDIR)/boot/boot
+

boot/boot.S

@@ -0,0 +1,85 @@
+#include <inc/mmu.h>
+
+# Start the CPU: switch to 32-bit protected mode, jump into C.
+# The BIOS loads this code from the first sector of the hard disk into
+# memory at physical address 0x7c00 and starts executing in real mode
+# with %cs=0 %ip=7c00.
+
+.set PROT_MODE_CSEG, 0x8         # kernel code segment selector
+.set PROT_MODE_DSEG, 0x10        # kernel data segment selector
+.set CR0_PE_ON,      0x1         # protected mode enable flag
+
+.globl start
+start:
+  .code16                     # Assemble for 16-bit mode
+  cli                         # Disable interrupts
+  cld                         # String operations increment
+
+  # Set up the important data segment registers (DS, ES, SS).
+  xorw    %ax,%ax             # Segment number zero
+  movw    %ax,%ds             # -> Data Segment
+  movw    %ax,%es             # -> Extra Segment
+  movw    %ax,%ss             # -> Stack Segment
+
+  # Enable A20:
+  #   For backwards compatibility with the earliest PCs, physical
+  #   address line 20 is tied low, so that addresses higher than
+  #   1MB wrap around to zero by default.  This code undoes this.
+seta20.1:
+  inb     $0x64,%al               # Wait for not busy
+  testb   $0x2,%al
+  jnz     seta20.1
+
+  movb    $0xd1,%al               # 0xd1 -> port 0x64
+  outb    %al,$0x64
+
+seta20.2:
+  inb     $0x64,%al               # Wait for not busy
+  testb   $0x2,%al
+  jnz     seta20.2
+
+  movb    $0xdf,%al               # 0xdf -> port 0x60
+  outb    %al,$0x60
+
+  # Switch from real to protected mode, using a bootstrap GDT
+  # and segment translation that makes virtual addresses 
+  # identical to their physical addresses, so that the 
+  # effective memory map does not change during the switch.
+  lgdt    gdtdesc
+  movl    %cr0, %eax
+  orl     $CR0_PE_ON, %eax
+  movl    %eax, %cr0
+
+  # Jump to next instruction, but in 32-bit code segment.
+  # Switches processor into 32-bit mode.
+  ljmp    $PROT_MODE_CSEG, $protcseg
+
+  .code32                     # Assemble for 32-bit mode
+protcseg:
+  # Set up the protected-mode data segment registers
+  movw    $PROT_MODE_DSEG, %ax    # Our data segment selector
+  movw    %ax, %ds                # -> DS: Data Segment
+  movw    %ax, %es                # -> ES: Extra Segment
+  movw    %ax, %fs                # -> FS
+  movw    %ax, %gs                # -> GS
+  movw    %ax, %ss                # -> SS: Stack Segment
+
+  # Set up the stack pointer and call into C.
+  movl    $start, %esp
+  call bootmain
+
+  # If bootmain returns (it shouldn't), loop.
+spin:
+  jmp spin
+
+# Bootstrap GDT
+.p2align 2                                # force 4 byte alignment
+gdt:
+  SEG_NULL				# null seg
+  SEG(STA_X|STA_R, 0x0, 0xffffffff)	# code seg
+  SEG(STA_W, 0x0, 0xffffffff)	        # data seg
+
+gdtdesc:
+  .word   0x17                            # sizeof(gdt) - 1
+  .long   gdt                             # address gdt
+