MIT OS lab Makefile 分析

  1 #
  2 # This makefile system follows the structuring conventions
  3 # recommended by Peter Miller in his excellent paper:
  4 #
  5 #    Recursive Make Considered Harmful
  6 #    http://aegis.sourceforge.net/auug97.pdf
  7 #
  8 OBJDIR := obj
  9 
# 10-16行, 如果编译时使用make V=1，则会输出详细编译信息，否则输出类似 “CC MAIN”的简单信息
# 很多Makefile都采用这种方式, 包括Linux kernel.
 10 # Run ‘make V=1‘ to turn on verbose commands, or ‘make V=0‘ to turn them off.
 11 ifeq ($(V),1)
 12 override V =
 13 endif
 14 ifeq ($(V),0)
 15 override V = @
 16 endif
 17 
 18 -include conf/lab.mk
 19 
 20 -include conf/env.mk
 21 
 22 LABSETUP ?= ./
 23 
 24 TOP = .
 25 
 26 # Cross-compiler jos toolchain
 27 #
 28 # This Makefile will automatically use the cross-compiler toolchain
 29 # installed as ‘i386-jos-elf-*‘, if one exists.  If the host tools (‘gcc‘,
 30 # ‘objdump‘, and so forth) compile for a 32-bit x86 ELF target, that will
 31 # be detected as well.  If you have the right compiler toolchain installed
 32 # using a different name, set GCCPREFIX explicitly in conf/env.mk
 33 
# 34-48, 通过执行shell objdump 命令得到GCCPREFIX, 即如果 i386-jos-elf-objdump存在
# GCCPREFIX=i386-jos-elf-objdump, 否则GCCPREFIX=""
 34 # try to infer the correct GCCPREFIX
 35 ifndef GCCPREFIX
 36 GCCPREFIX := $(shell if i386-jos-elf-objdump -i 2>&1 | grep ‘^elf32-i386$$‘ >/dev/null 2>&1;  37     then echo ‘i386-jos-elf-‘;  38     elif objdump -i 2>&1 | grep ‘elf32-i386‘ >/dev/null 2>&1;  39     then echo ‘‘;  40     else echo "***" 1>&2;  41     echo "*** Error: Couldn‘t find an i386-*-elf version of GCC/binutils." 1>&2;  42     echo "*** Is the directory with i386-jos-elf-gcc in your PATH?" 1>&2;  43     echo "*** If your i386-*-elf toolchain is installed with a command" 1>&2;  44     echo "*** prefix other than ‘i386-jos-elf-‘, set your GCCPREFIX" 1>&2;  45     echo "*** environment variable to that prefix and run ‘make‘ again." 1>&2;  46     echo "*** To turn off this error, run ‘gmake GCCPREFIX= ...‘." 1>&2;  47     echo "***" 1>&2; exit 1; fi)
 48 endif
 49 
# 50-64, 和上面类似， 得到QEMU=qemu,或者QEMU=qemu-system-i386
 50 # try to infer the correct QEMU
 51 ifndef QEMU
 52 QEMU := $(shell if which qemu > /dev/null;  53     then echo qemu; exit;  54         elif which qemu-system-i386 > /dev/null;  55         then echo qemu-system-i386; exit;  56     else  57     qemu=/Applications/Q.app/Contents/MacOS/i386-softmmu.app/Contents/MacOS/i386-softmmu;  58     if test -x $$qemu; then echo $$qemu; exit; fi; fi;  59     echo "***" 1>&2;  60     echo "*** Error: Couldn‘t find a working QEMU executable." 1>&2;  61     echo "*** Is the directory containing the qemu binary in your PATH" 1>&2;  62     echo "*** or have you tried setting the QEMU variable in conf/env.mk?" 1>&2;  63     echo "***" 1>&2; exit 1)
 64 endif
 65 
 66 # try to generate a unique GDB port
 67 GDBPORT    := $(shell expr `id -u` % 5000 + 25000)
 68 
 69 CC    := $(GCCPREFIX)gcc -pipe
 70 AS    := $(GCCPREFIX)as
 71 AR    := $(GCCPREFIX)ar
 72 LD    := $(GCCPREFIX)ld
 73 OBJCOPY    := $(GCCPREFIX)objcopy
 74 OBJDUMP    := $(GCCPREFIX)objdump
 75 NM    := $(GCCPREFIX)nm
 76 
 77 # Native commands
 78 NCC    := gcc $(CC_VER) -pipe
# 79行, -I表示 include 包含路径, -M表示生成以来关系，比如：

#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[])
{
printf("Hello world\n");
return 0;
}
那么调用gcc -M hello.c, 则会得到类似如下输出：
hello.o: hello.c /usr/include/stdio.h /usr/include/features.h \
/usr/include/bits/predefs.h /usr/include/sys/cdefs.h \
/usr/include/bits/wordsize.h /usr/include/gnu/stubs.h \
/usr/include/gnu/stubs-32.h \
/usr/lib/gcc/i486-linux-gnu/4.3.5/include/stddef.h \
/usr/include/bits/types.h /usr/include/bits/typesizes.h \
/usr/include/libio.h /usr/include/_G_config.h /usr/include/wchar.h \
/usr/lib/gcc/i486-linux-gnu/4.3.5/include/stdarg.h \
/usr/include/bits/stdio_lim.h /usr/include/bits/sys_errlist.h \
/usr/include/stdlib.h /usr/include/sys/types.h /usr/include/time.h \
/usr/include/endian.h /usr/include/bits/endian.h \
/usr/include/bits/byteswap.h /usr/include/sys/select.h \
/usr/include/bits/select.h /usr/include/bits/sigset.h \
/usr/include/bits/time.h /usr/include/sys/sysmacros.h \
/usr/include/bits/pthreadtypes.h /usr/include/alloca.h

-MD的意思是将依赖关系保存在相应的.d文件. -Wall表示显示所有warning信息.
 79 NATIVE_CFLAGS := $(CFLAGS) $(DEFS) $(LABDEFS) -I$(TOP) -MD -Wall
 80 TAR    := gtar
 81 PERL    := perl
 82 
# 83-91, -O1表示编译器优化级别, 一般有-O0(没有优化)/O1/O2/O3,
# -fno-buildin: 不接受没有 __builtin_ 前缀的函数作为内建函数。
# -W前缀表示Warning, -Werror：把warning当做error. 
# -gstabs：生成汇编代码中包含stab格式的调试信息
 83 # Compiler flags
 84 # -fno-builtin is required to avoid refs to undefined functions in the kernel.
 85 # Only optimize to -O1 to discourage inlining, which complicates backtraces.
 86 CFLAGS := $(CFLAGS) $(DEFS) $(LABDEFS) -O1 -fno-builtin -I$(TOP) -MD
 87 CFLAGS += -fno-omit-frame-pointer
 88 CFLAGS += -Wall -Wno-format -Wno-unused -Werror -gstabs -m32
 89 # -fno-tree-ch prevented gcc from sometimes reordering read_ebp() before
 90 # mon_backtrace()‘s function prologue on gcc version: (Debian 4.7.2-5) 4.7.2
 91 CFLAGS += -fno-tree-ch
 92 
 93 # Add -fno-stack-protector if the option exists.
 94 CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
 95 
# 模拟器类型为i386
 96 # Common linker flags
 97 LDFLAGS := -m elf_i386
 98 
 99 # Linker flags for JOS user programs
100 ULDFLAGS := -T user/user.ld
101 
102 GCC_LIB := $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)
103 
104 # Lists that the */Makefrag makefile fragments will add to
105 OBJDIRS :=
106 
107 # Make sure that ‘all‘ is the first target
# 默认目标
108 all:
109 
110 # Eliminate default suffix rules
111 .SUFFIXES:
112 
113 # Delete target files if there is an error (or make is interrupted)
114 .DELETE_ON_ERROR:
115 
116 # make it so that no intermediate .o files are ever deleted
117 .PRECIOUS: %.o $(OBJDIR)/boot/%.o $(OBJDIR)/kern/%.o 118        $(OBJDIR)/lib/%.o $(OBJDIR)/fs/%.o $(OBJDIR)/net/%.o 119        $(OBJDIR)/user/%.o
120 
121 KERN_CFLAGS := $(CFLAGS) -DJOS_KERNEL -gstabs
122 USER_CFLAGS := $(CFLAGS) -DJOS_USER -gstabs
123 
124 # Update .vars.X if variable X has changed since the last make run.
125 #
126 # Rules that use variable X should depend on $(OBJDIR)/.vars.X.  If
127 # the variable‘s value has changed, this will update the vars file and
128 # force a rebuild of the rule that depends on it.
129 $(OBJDIR)/.vars.%: FORCE
130     $(V)echo "$($*)" | cmp -s $@ || echo "$($*)" > $@
131 .PRECIOUS: $(OBJDIR)/.vars.%
132 .PHONY: FORCE
133 
134 
# 包含的两个makefile, 后续分析
135 # Include Makefrags for subdirectories
136 include boot/Makefrag
137 include kern/Makefrag
138 
139 
# QEMU执行参数
140 QEMUOPTS = -hda $(OBJDIR)/kern/kernel.img -serial mon:stdio -gdb tcp::$(GDBPORT)
141 QEMUOPTS += $(shell if $(QEMU) -nographic -help | grep -q ‘^-D ‘; then echo ‘-D qemu.log‘; fi)
142 IMAGES = $(OBJDIR)/kern/kernel.img
143 QEMUOPTS += $(QEMUEXTRA)
144 
# sed 将 .gdbinit.teml中1234端口替换为GDBPORT导入.gdbinit中.
145 .gdbinit: .gdbinit.tmpl
146     sed "s/localhost:1234/localhost:$(GDBPORT)/" < $^ > $@
147 
148 gdb:
149     gdb -x .gdbinit
150 
# 以下为qemu启动命令.
151 pre-qemu: .gdbinit
152 
153 qemu: $(IMAGES) pre-qemu
154     $(QEMU) $(QEMUOPTS)
155 
156 qemu-nox: $(IMAGES) pre-qemu
157     @echo "***"
158     @echo "*** Use Ctrl-a x to exit qemu"
159     @echo "***"
160     $(QEMU) -nographic $(QEMUOPTS)
161 
162 qemu-gdb: $(IMAGES) pre-qemu
163     @echo "***"
164     @echo "*** Now run ‘make gdb‘." 1>&2
165     @echo "***"
166     $(QEMU) $(QEMUOPTS) -S
167 
168 qemu-nox-gdb: $(IMAGES) pre-qemu
169     @echo "***"
170     @echo "*** Now run ‘make gdb‘." 1>&2
171     @echo "***"
172     $(QEMU) -nographic $(QEMUOPTS) -S
173 
174 print-qemu:
175     @echo $(QEMU)
176 
177 print-gdbport:
178     @echo $(GDBPORT)
179 
# clean, realclean, distclean依次向上依赖, 删除逐渐彻底,distclean回复成直接git下来时的状态.
180 # For deleting the build
181 clean:
182     rm -rf $(OBJDIR) .gdbinit jos.in qemu.log
183 
184 realclean: clean
185     rm -rf lab$(LAB).tar.gz 186         jos.out $(wildcard jos.out.*) 187         qemu.pcap $(wildcard qemu.pcap.*) 188         myapi.key
189 
190 distclean: realclean
191     rm -rf conf/gcc.mk
192 
193 ifneq ($(V),@)
194 GRADEFLAGS += -v
195 endif
196 
197 grade:
198     @echo $(MAKE) clean
199     @$(MAKE) clean || 200       (echo "‘make clean‘ failed.  HINT: Do you have another running instance of JOS?" && exit 1)
201     ./grade-lab$(LAB) $(GRADEFLAGS)
202 
203 git-handin: handin-check
204     @if test -n "`git config remote.handin.url`"; then 205         echo "Hand in to remote repository using ‘git push handin HEAD‘ ..."; 206         if ! git push -f handin HEAD; then 207             echo ; 208             echo "Hand in failed."; 209             echo "As an alternative, please run ‘make tarball‘"; 210             echo "and visit http://pdos.csail.mit.edu/6.828/submit/"; 211             echo "to upload lab$(LAB)-handin.tar.gz.  Thanks!"; 212             false; 213         fi; 214     else 215         echo "Hand-in repository is not configured."; 216         echo "Please run ‘make handin-prep‘ first.  Thanks!"; 217         false; 218     fi
219 
220 WEBSUB = https://ccutler.scripts.mit.edu/6.828/handin.py
221 
222 handin: tarball-pref myapi.key
223     @curl -f -F file=@lab$(LAB)-handin.tar.gz -F key=\<myapi.key $(WEBSUB)/upload 224         > /dev/null || { 225         echo ; 226         echo Submit seems to have failed.; 227         echo Please go to $(WEBSUB)/ and upload the tarball manually.; }
228 
229 handin-check:
230     @if ! test -d .git; then 231         echo No .git directory, is this a git repository?; 232         false; 233     fi
234     @if test "$$(git symbolic-ref HEAD)" != refs/heads/lab$(LAB); then 235         git branch; 236         read -p "You are not on the lab$(LAB) branch.  Hand-in the current branch? [y/N] " r; 237         test "$$r" = y; 238     fi
239     @if ! git diff-files --quiet || ! git diff-index --quiet --cached HEAD; then 240         git status; 241         echo; 242         echo "You have uncomitted changes.  Please commit or stash them."; 243         false; 244     fi
245     @if test -n "`git ls-files -o --exclude-standard`"; then 246         git status; 247         read -p "Untracked files will not be handed in.  Continue? [y/N] " r; 248         test "$$r" = y; 249     fi
250 
251 tarball: handin-check
252     git archive --format=tar HEAD | gzip > lab$(LAB)-handin.tar.gz
253 
254 tarball-pref: handin-check
255     git archive --prefix=lab$(LAB)/ --format=tar HEAD | gzip > lab$(LAB)-handin.tar.gz
256 
257 myapi.key:
258     @echo Get an API key for yourself by visiting $(WEBSUB)
259     @read -p "Please enter your API key: " k; 260     if test `echo -n "$$k" |wc -c` = 32 ; then 261         TF=`mktemp -t tmp.XXXXXX`; 262         if test "x$$TF" != "x" ; then 263             echo -n "$$k" > $$TF; 264             mv -f $$TF $@; 265         else 266             echo mktemp failed; 267             false; 268         fi; 269     else 270         echo Bad API key: $$k; 271         echo An API key should be 32 characters long.; 272         false; 273     fi;
274 
275 handin-prep:
276     @./handin-prep
277 
278 
279 # This magic automatically generates makefile dependencies
280 # for header files included from C source files we compile,
281 # and keeps those dependencies up-to-date every time we recompile.
282 # See ‘mergedep.pl‘ for more information.
283 $(OBJDIR)/.deps: $(foreach dir, $(OBJDIRS), $(wildcard $(OBJDIR)/$(dir)/*.d))
284     @mkdir -p $(@D)
285     @$(PERL) mergedep.pl $@ $^
286 
287 -include $(OBJDIR)/.deps
288 
289 always:
290     @:
291 
292 .PHONY: all always 293     handin git-handin tarball tarball-pref clean realclean distclean grade handin-prep handin-check

 1 #
 2 # Makefile fragment for JOS kernel.
 3 # This is NOT a complete makefile;
 4 # you must run GNU make in the top-level directory
 5 # where the GNUmakefile is located.
 6 #
 7 
 8 OBJDIRS += kern
 9 
10 KERN_LDFLAGS := $(LDFLAGS) -T kern/kernel.ld -nostdlib
11 
12 # entry.S must be first, so that it‘s the first code in the text segment!!!
13 #
14 # We also snatch the use of a couple handy source files
15 # from the lib directory, to avoid gratuitous code duplication.
# 需要编译的源文件.
16 KERN_SRCFILES :=    kern/entry.S 17             kern/entrypgdir.c 18             kern/init.c 19             kern/console.c 20             kern/monitor.c 21             kern/pmap.c 22             kern/env.c 23             kern/kclock.c 24             kern/picirq.c 25             kern/printf.c 26             kern/trap.c 27             kern/trapentry.S 28             kern/sched.c 29             kern/syscall.c 30             kern/kdebug.c 31             lib/printfmt.c 32             lib/readline.c 33             lib/string.c
34 
35 # Only build files if they exist.
# wildcard：扩展通配符
36 KERN_SRCFILES := $(wildcard $(KERN_SRCFILES))
37 
38 # Binary program images to embed within the kernel.
39 KERN_BINFILES := 
40 
41 KERN_OBJFILES := $(patsubst %.c, $(OBJDIR)/%.o, $(KERN_SRCFILES))
42 KERN_OBJFILES := $(patsubst %.S, $(OBJDIR)/%.o, $(KERN_OBJFILES))
43 KERN_OBJFILES := $(patsubst $(OBJDIR)/lib/%, $(OBJDIR)/kern/%, $(KERN_OBJFILES))
44 
45 KERN_BINFILES := $(patsubst %, $(OBJDIR)/%, $(KERN_BINFILES))
46 
47 # How to build kernel object files
# 48-61，把kern下的.c和.S, lib/下的.c编译成.o 放在kern目录下
# V如果是 @ ,表示这句只执行不显示.
48 $(OBJDIR)/kern/%.o: kern/%.c $(OBJDIR)/.vars.KERN_CFLAGS
49     @echo + cc $<
50     @mkdir -p $(@D)
51     $(V)$(CC) -nostdinc $(KERN_CFLAGS) -c -o $@ $<
52 
53 $(OBJDIR)/kern/%.o: kern/%.S $(OBJDIR)/.vars.KERN_CFLAGS
54     @echo + as $<
55     @mkdir -p $(@D)
56     $(V)$(CC) -nostdinc $(KERN_CFLAGS) -c -o $@ $<
57 
58 $(OBJDIR)/kern/%.o: lib/%.c $(OBJDIR)/.vars.KERN_CFLAGS
59     @echo + cc $<
60     @mkdir -p $(@D)
61     $(V)$(CC) -nostdinc $(KERN_CFLAGS) -c -o $@ $<
62 
63 # Special flags for kern/init
64 $(OBJDIR)/kern/init.o: override KERN_CFLAGS+=$(INIT_CFLAGS)
65 $(OBJDIR)/kern/init.o: $(OBJDIR)/.vars.INIT_CFLAGS
66 
67 # How to build the kernel itself
# 71: 把编译产物用ld命令连接成kernel
# 72: 将kernel反汇编
# 73: 到处符号表
68 $(OBJDIR)/kern/kernel: $(KERN_OBJFILES) $(KERN_BINFILES) kern/kernel.ld 69       $(OBJDIR)/.vars.KERN_LDFLAGS
70     @echo + ld $@
71     $(V)$(LD) -o $@ $(KERN_LDFLAGS) $(KERN_OBJFILES) $(GCC_LIB) -b binary $(KERN_BINFILES)
72     $(V)$(OBJDUMP) -S $@ > $@.asm
73     $(V)$(NM) -n $@ > $@.sym
74 
75 # How to build the kernel disk image

# 上面的kernel仅是elf文件, 此处将boot，kernel导成镜像.
76 $(OBJDIR)/kern/kernel.img: $(OBJDIR)/kern/kernel $(OBJDIR)/boot/boot
77     @echo + mk $@
78     $(V)dd if=/dev/zero of=$(OBJDIR)/kern/kernel.img~ count=10000 2>/dev/null
79     $(V)dd if=$(OBJDIR)/boot/boot of=$(OBJDIR)/kern/kernel.img~ conv=notrunc 2>/dev/null
80     $(V)dd if=$(OBJDIR)/kern/kernel of=$(OBJDIR)/kern/kernel.img~ seek=1 conv=notrunc 2>/dev/null
81     $(V)mv $(OBJDIR)/kern/kernel.img~ $(OBJDIR)/kern/kernel.img
82 
83 all: $(OBJDIR)/kern/kernel.img
84 
85 grub: $(OBJDIR)/jos-grub
86 
87 $(OBJDIR)/jos-grub: $(OBJDIR)/kern/kernel
88     @echo + oc $@
89     $(V)$(OBJCOPY) --adjust-vma=0x10000000 $^ $@

 1 #
 2 # Makefile fragment for the JOS kernel.
 3 # This is NOT a complete makefile;
 4 # you must run GNU make in the top-level directory
 5 # where the GNUmakefile is located.
 6 #
 7 
 8 OBJDIRS += boot
 9 
10 BOOT_OBJS := $(OBJDIR)/boot/boot.o $(OBJDIR)/boot/main.o
11 
12 $(OBJDIR)/boot/%.o: boot/%.c
13     @echo + cc -Os $<
14     @mkdir -p $(@D)
15     $(V)$(CC) -nostdinc $(KERN_CFLAGS) -Os -c -o $@ $<
16 
17 $(OBJDIR)/boot/%.o: boot/%.S
18     @echo + as $<
19     @mkdir -p $(@D)
20     $(V)$(CC) -nostdinc $(KERN_CFLAGS) -c -o $@ $<
21 
22 $(OBJDIR)/boot/main.o: boot/main.c
23     @echo + cc -Os $<
24     $(V)$(CC) -nostdinc $(KERN_CFLAGS) -Os -c -o $(OBJDIR)/boot/main.o boot/main.c
25 
# 将目标文件连接成elf文件.
# -e start: 入口函数为start.
# -Ttext 0x7C00：代码段入口地址为0x7C00. BIOS加电自检后会自动跳到次地址来执行,相当于开机后软件第一条指令地址.
26 $(OBJDIR)/boot/boot: $(BOOT_OBJS)
27     @echo + ld boot/boot
28     $(V)$(LD) $(LDFLAGS) -N -e start -Ttext 0x7C00 -o $@.out $^
29     $(V)$(OBJDUMP) -S $@.out >$@.asm
30     $(V)$(OBJCOPY) -S -O binary -j .text $@.out $@
31     $(V)perl boot/sign.pl $(OBJDIR)/boot/boot