ucore操作系统 lab1 练习一实验报告

练习一：理解通过make生成执行文件的过程。

题目：

列出本实验各练习中对应的OS原理的知识点，并说明本实验中的实现部分如何对应和体现了原理中的基本概念和关键知识点。

在此练习中，大家需要通过静态分析代码来了解：
1.操作系统镜像文件ucore.img是如何一步一步生成的？(需要比较详细地解释Makefile中每一条相关命令和命令参数的含义，以及说明命令导致的结果)
2.一个被系统认为是符合规范的硬盘主引导扇区的特征是什么？
补充材料：
如何调试Makefile
当执行make时，一般只会显示输出，不会显示make到底执行了哪些命令。
如想了解make执行了哪些命令，可以执行：
$ make “V=”
要获取更多有关make的信息，可上网查询，并请执行
$ man make

1.操作系统镜像文件ucore.img是如何一步一步生成的？

查看makefile文件

PROJ := challenge
EMPTY   :=
SPACE   := $(EMPTY) $(EMPTY)
SLASH   := /V       := @
#need llvm/cang-3.5+
#USELLVM := 1
# try to infer the correct GCCPREFX
ifndef GCCPREFIX
GCCPREFIX := $(shell if i386-elf-objdump -i 2>&1 | grep '^elf32-i386$$' >/dev/null 2>&1; \then echo 'i386-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-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-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-system-i386 > /dev/null; \then echo 'qemu-system-i386'; exit; \elif which i386-elf-qemu > /dev/null; \then echo 'i386-elf-qemu'; exit; \elif which qemu > /dev/null; \then echo 'qemu'; exit; \else \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 "***" 1>&2; exit 1; fi)
endif# eliminate default suffix rules
.SUFFIXES: .c .S .h# delete target files if there is an error (or make is interrupted)
.DELETE_ON_ERROR:# define compiler and flags
ifndef  USELLVM
HOSTCC      := gcc
HOSTCFLAGS  := -g -Wall -O2
CC      := $(GCCPREFIX)gcc
CFLAGS  := -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc $(DEFS)
CFLAGS  += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
else
HOSTCC      := clang
HOSTCFLAGS  := -g -Wall -O2
CC      := clang
CFLAGS  := -march=i686 -fno-builtin -fno-PIC -Wall -g -m32 -nostdinc $(DEFS)
CFLAGS  += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
endifCTYPE  := c SLD      := $(GCCPREFIX)ld
LDFLAGS := -m $(shell $(LD) -V | grep elf_i386 2>/dev/null | head -n 1)
LDFLAGS += -nostdlibOBJCOPY := $(GCCPREFIX)objcopy
OBJDUMP := $(GCCPREFIX)objdumpCOPY := cp
MKDIR   := mkdir -p
MV      := mv
RM      := rm -f
AWK     := awk
SED     := sed
SH      := sh
TR      := tr
TOUCH   := touch -cOBJDIR  := obj
BINDIR  := binALLOBJS  :=
ALLDEPS :=
TARGETS :=include tools/function.mklistf_cc = $(call listf,$(1),$(CTYPE))# for cc
add_files_cc = $(call add_files,$(1),$(CC),$(CFLAGS) $(3),$(2),$(4))
create_target_cc = $(call create_target,$(1),$(2),$(3),$(CC),$(CFLAGS))# for hostcc
add_files_host = $(call add_files,$(1),$(HOSTCC),$(HOSTCFLAGS),$(2),$(3))
create_target_host = $(call create_target,$(1),$(2),$(3),$(HOSTCC),$(HOSTCFLAGS))cgtype = $(patsubst %.$(2),%.$(3),$(1))
objfile = $(call toobj,$(1))
asmfile = $(call cgtype,$(call toobj,$(1)),o,asm)
outfile = $(call cgtype,$(call toobj,$(1)),o,out)
symfile = $(call cgtype,$(call toobj,$(1)),o,sym)# for match pattern
match = $(shell echo $(2) | $(AWK) '{for(i=1;i<=NF;i++){if(match("$(1)","^"$$(i)"$$")){exit 1;}}}'; echo $$?)# >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
# include kernel/userINCLUDE    += libs/CFLAGS    += $(addprefix -I,$(INCLUDE))LIBDIR   += libs$(call add_files_cc,$(call listf_cc,$(LIBDIR)),libs,)# -------------------------------------------------------------------
# kernelKINCLUDE    += kern/debug/ \kern/driver/ \kern/trap/ \kern/mm/KSRCDIR     += kern/init \kern/libs \kern/debug \kern/driver \kern/trap \kern/mmKCFLAGS       += $(addprefix -I,$(KINCLUDE))$(call add_files_cc,$(call listf_cc,$(KSRCDIR)),kernel,$(KCFLAGS))KOBJS = $(call read_packet,kernel libs)# create kernel target
kernel = $(call totarget,kernel)$(kernel): tools/kernel.ld$(kernel): $(KOBJS)@echo + ld $@$(V)$(LD) $(LDFLAGS) -T tools/kernel.ld -o $@ $(KOBJS)@$(OBJDUMP) -S $@ > $(call asmfile,kernel)@$(OBJDUMP) -t $@ | $(SED) '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > $(call symfile,kernel)$(call create_target,kernel)# -------------------------------------------------------------------# create bootblock
bootfiles = $(call listf_cc,boot)
$(foreach f,$(bootfiles),$(call cc_compile,$(f),$(CC),$(CFLAGS) -Os -nostdinc))bootblock = $(call totarget,bootblock)$(bootblock): $(call toobj,$(bootfiles)) | $(call totarget,sign)@echo + ld $@$(V)$(LD) $(LDFLAGS) -N -e start -Ttext 0x7C00 $^ -o $(call toobj,bootblock)@$(OBJDUMP) -S $(call objfile,bootblock) > $(call asmfile,bootblock)@$(OBJCOPY) -S -O binary $(call objfile,bootblock) $(call outfile,bootblock)@$(call totarget,sign) $(call outfile,bootblock) $(bootblock)$(call create_target,bootblock)# -------------------------------------------------------------------# create 'sign' tools
$(call add_files_host,tools/sign.c,sign,sign)
$(call create_target_host,sign,sign)# -------------------------------------------------------------------# create ucore.img
UCOREIMG    := $(call totarget,ucore.img)$(UCOREIMG): $(kernel) $(bootblock)$(V)dd if=/dev/zero of=$@ count=10000$(V)dd if=$(bootblock) of=$@ conv=notrunc$(V)dd if=$(kernel) of=$@ seek=1 conv=notrunc$(call create_target,ucore.img)# >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>$(call finish_all)IGNORE_ALLDEPS  = clean \dist-clean \grade \touch \print-.+ \handinifeq ($(call match,$(MAKECMDGOALS),$(IGNORE_ALLDEPS)),0)
-include $(ALLDEPS)
endif# files for grade scriptTARGETS: $(TARGETS).DEFAULT_GOAL := TARGETS.PHONY: qemu qemu-nox debug debug-nox
qemu-mon: $(UCOREIMG)$(V)$(QEMU)  -no-reboot -monitor stdio -hda $< -serial null
qemu: $(UCOREIMG)$(V)$(QEMU) -no-reboot -parallel stdio -hda $< -serial null
log: $(UCOREIMG)$(V)$(QEMU) -no-reboot -d int,cpu_reset  -D q.log -parallel stdio -hda $< -serial null
qemu-nox: $(UCOREIMG)$(V)$(QEMU)   -no-reboot -serial mon:stdio -hda $< -nographic
TERMINAL        :=gnome-terminal
debug: $(UCOREIMG)$(V)$(QEMU) -S -s -parallel stdio -hda $< -serial null &$(V)sleep 2$(V)$(TERMINAL) -e "gdb -q -tui -x tools/gdbinit"debug-nox: $(UCOREIMG)$(V)$(QEMU) -S -s -serial mon:stdio -hda $< -nographic &$(V)sleep 2$(V)$(TERMINAL) -e "gdb -q -x tools/gdbinit".PHONY: grade touchGRADE_GDB_IN    := .gdb.in
GRADE_QEMU_OUT  := .qemu.out
HANDIN          := proj$(PROJ)-handin.tar.gzTOUCH_FILES        := kern/trap/trap.cMAKEOPTS        := --quiet --no-print-directorygrade:$(V)$(MAKE) $(MAKEOPTS) clean$(V)$(SH) tools/grade.shtouch:$(V)$(foreach f,$(TOUCH_FILES),$(TOUCH) $(f))print-%:@echo $($(shell echo $(patsubst print-%,%,$@) | $(TR) [a-z] [A-Z])).PHONY: clean dist-clean handin packall tags
clean:$(V)$(RM) $(GRADE_GDB_IN) $(GRADE_QEMU_OUT) cscope* tags-$(RM) -r $(OBJDIR) $(BINDIR)dist-clean: clean-$(RM) $(HANDIN)handin: packall@echo Please visit http://learn.tsinghua.edu.cn and upload $(HANDIN). Thanks!packall: clean@$(RM) -f $(HANDIN)@tar -czf $(HANDIN) `find . -type f -o -type d | grep -v '^\.*$$' | grep -vF '$(HANDIN)'`tags:@echo TAGS ALL$(V)rm -f cscope.files cscope.in.out cscope.out cscope.po.out tags$(V)find . -type f -name "*.[chS]" >cscope.files$(V)cscope -bq $(V)ctags -L cscope.files

总结ucore.img的生成过程

1.设置环境变量、编译选项等，主要先设置了libs和kern目录下的obj文件名，两者合并即为$(KOBJS)。
2.生成kernel文件，
3.生成bootblock，
4.生成sign工具，
5.最后生成ucore.img。

使用 make “V=” 命令查看具体操作。

make "V="

查看具体操作的内容：

+ cc kern/init/init.c
gcc -Ikern/init/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/init/init.c -o obj/kern/init/init.o
+ cc kern/libs/stdio.c
gcc -Ikern/libs/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/libs/stdio.c -o obj/kern/libs/stdio.o
+ cc kern/libs/readline.c
gcc -Ikern/libs/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/libs/readline.c -o obj/kern/libs/readline.o
+ cc kern/debug/panic.c
gcc -Ikern/debug/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/debug/panic.c -o obj/kern/debug/panic.o
+ cc kern/debug/kdebug.c
gcc -Ikern/debug/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/debug/kdebug.c -o obj/kern/debug/kdebug.o
+ cc kern/debug/kmonitor.c
gcc -Ikern/debug/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/debug/kmonitor.c -o obj/kern/debug/kmonitor.o
+ cc kern/driver/clock.c
gcc -Ikern/driver/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/driver/clock.c -o obj/kern/driver/clock.o
+ cc kern/driver/console.c
gcc -Ikern/driver/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/driver/console.c -o obj/kern/driver/console.o
+ cc kern/driver/picirq.c
gcc -Ikern/driver/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/driver/picirq.c -o obj/kern/driver/picirq.o
+ cc kern/driver/intr.c
gcc -Ikern/driver/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/driver/intr.c -o obj/kern/driver/intr.o
+ cc kern/trap/trap.c
gcc -Ikern/trap/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/trap/trap.c -o obj/kern/trap/trap.o
+ cc kern/trap/vectors.S
gcc -Ikern/trap/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/trap/vectors.S -o obj/kern/trap/vectors.o
+ cc kern/trap/trapentry.S
gcc -Ikern/trap/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/trap/trapentry.S -o obj/kern/trap/trapentry.o
+ cc kern/mm/pmm.c
gcc -Ikern/mm/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Ikern/debug/ -Ikern/driver/ -Ikern/trap/ -Ikern/mm/ -c kern/mm/pmm.c -o obj/kern/mm/pmm.o
+ cc libs/string.c
gcc -Ilibs/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/  -c libs/string.c -o obj/libs/string.o
+ cc libs/printfmt.c
gcc -Ilibs/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/  -c libs/printfmt.c -o obj/libs/printfmt.o
+ ld bin/kernel
ld -m    elf_i386 -nostdlib -T tools/kernel.ld -o bin/kernel  obj/kern/init/init.o obj/kern/libs/stdio.o obj/kern/libs/readline.o obj/kern/debug/panic.o obj/kern/debug/kdebug.o obj/kern/debug/kmonitor.o obj/kern/driver/clock.o obj/kern/driver/console.o obj/kern/driver/picirq.o obj/kern/driver/intr.o obj/kern/trap/trap.o obj/kern/trap/vectors.o obj/kern/trap/trapentry.o obj/kern/mm/pmm.o  obj/libs/string.o obj/libs/printfmt.o
+ cc boot/bootasm.S
gcc -Iboot/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Os -nostdinc -c boot/bootasm.S -o obj/boot/bootasm.o
+ cc boot/bootmain.c
gcc -Iboot/ -march=i686 -fno-builtin -fno-PIC -Wall -ggdb -m32 -gstabs -nostdinc  -fno-stack-protector -Ilibs/ -Os -nostdinc -c boot/bootmain.c -o obj/boot/bootmain.o
+ cc tools/sign.c
gcc -Itools/ -g -Wall -O2 -c tools/sign.c -o obj/sign/tools/sign.o
gcc -g -Wall -O2 obj/sign/tools/sign.o -o bin/sign
+ ld bin/bootblock
ld -m    elf_i386 -nostdlib -N -e start -Ttext 0x7C00 obj/boot/bootasm.o obj/boot/bootmain.o -o obj/bootblock.o
'obj/bootblock.out' size: 484 bytes
build 512 bytes boot sector: 'bin/bootblock' success!
dd if=/dev/zero of=bin/ucore.img count=10000
dd if=bin/bootblock of=bin/ucore.img conv=notrunc
dd if=bin/kernel of=bin/ucore.img seek=1 conv=notrunc

每一个指令下都是具体执行的shell命令，gcc就是指使用gcc编译器编译，现在来比较详细地解释Makefile中每一条相关命令和命令参数的含义及其导致的结果。

-I（大写的i）可指定查找include文件的其他位置.例如,如果有些include文件位于比较特殊的地方。

-g 生成gdb的调试信息

-Wall 以最高级别使用GNU编译程序,专门用于显示警告用!

-o 制定目标名称, 默认的时候, gcc 编译出来的文件是 a.out

-march 设置CPU类型，可以选择 i8086, i186, i286, i386, i486,等

-fno-stack-protector 不生成栈溢出保护

-m32 编译生成32位程序

ld -m    elf_i386 -nostdlib -N -e start -Ttext 0x7C00 obj/boot/bootasm.o obj/boot/bootmain.o -o obj/bootblock.o

ld 通过运行C的编译器来运行链接程序生成

dd if=bin/kernel of=bin/ucore.img seek=1 conv=notrunc

使用指定大小拷贝一个文件

2.一个被系统认为是符合规范的硬盘主引导扇区的特征是什么？

查看sign.c文件内容

#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>int
main(int argc, char *argv[]) {struct stat st;if (argc != 3) {fprintf(stderr, "Usage: <input filename> <output filename>\n");return -1;}if (stat(argv[1], &st) != 0) {fprintf(stderr, "Error opening file '%s': %s\n", argv[1], strerror(errno));return -1;}printf("'%s' size: %lld bytes\n", argv[1], (long long)st.st_size);if (st.st_size > 510) {fprintf(stderr, "%lld >> 510!!\n", (long long)st.st_size);return -1;}char buf[512];memset(buf, 0, sizeof(buf));FILE *ifp = fopen(argv[1], "rb");int size = fread(buf, 1, st.st_size, ifp);if (size != st.st_size) {fprintf(stderr, "read '%s' error, size is %d.\n", argv[1], size);return -1;}fclose(ifp);buf[510] = 0x55;buf[511] = 0xAA;FILE *ofp = fopen(argv[2], "wb+");size = fwrite(buf, 1, 512, ofp);if (size != 512) {fprintf(stderr, "write '%s' error, size is %d.\n", argv[2], size);return -1;}fclose(ofp);printf("build 512 bytes boot sector: '%s' success!\n", argv[2]);return 0;
}

从文件中这三行代码我们可以得出答案。

char buf[512]；buf[510] = 0x55;
buf[511] = 0xAA;

答案：

1.大小只有512字节。
2.第510个字节是0x55，第511个字节是0xAA。

lab1 练习二 https://blog.csdn.net/qq_42815549/article/details/103000511