GeekOS源代码学习(0)
发布时间:2020-12-16 00:26:11 所属栏目:大数据 来源:网络整理
导读:我使用的是geekos-0.3.0,从 这里下载。 doc目录下的hacking.pdf有详细的运行说明,只有40页,英文也很简单,稍微仔细的看一下。 我们开始 建立project0 $startProject project0 ./geekos-0.3.0/src 这样在当下目录下生成了project0目录 $cd ./project0/buil
我使用的是geekos-0.3.0,从 这里下载。 doc目录下的hacking.pdf有详细的运行说明,只有40页,英文也很简单,稍微仔细的看一下。 我们开始 建立project0 $startProject project0 ./geekos-0.3.0/src 这样在当下目录下生成了project0目录 $cd ./project0/build $make depend $make 编译文件,最后生成了fd.img软盘映像文件。 $file fd.img fd.img: Linux kernel 好,先来试试看再说。 使用在我的上篇文章《sagalinux学习之/boot目录》中的bochsrc,只要改一下软盘名字就好了。 先来看看效果!! 哈哈,看到了吧。 带蓝色背景的字是你需要完成的任务。 pdf上的共有7个project,每一个都会让你完成一个任务,最终任务完成之后,就是一个真正的小型的类unix OS了。。。激动。。。project0要求你完成键盘输入的响应,其实源代码函数都已经写好了,只要你调用一下函数就行了。 不管project0,我先read the f**king source code... 来看一下Makefile,对整体有个结构上的理解 $vi ./build/Makefile Makefile? # Makefile for GeekOS kernel,userspace,and tools # Copyright (c) 2004,2005 David H. Hovemeyer <daveho@cs.umd.edu> # $Revision: 1.45 $ # This is free software. You are permitted to use,# redistribute,and modify it as specified in the file "COPYING". # Required software to build GeekOS: # - GNU Make (http://www.gnu.org/software/make) # - gcc 2.95.2 generating code for target (i386/ELF) and host platforms # - nasm (http://nasm.sourceforge.net) # - Perl5,AWK (any version),egrep # # Cygwin (http://cygwin.com) may be used to build GeekOS. # Make sure that gcc,binutils,nasm,and perl are installed. # NOTES: # - This makefile has been written carefully to work correctly # with the -j (parallel make) option. I regularly use "make -j 2" # to speed the build process on 2 processor systems. PROJECT_ROOT := .. VPATH := $(PROJECT_ROOT)/src # Figure out if we're compiling with cygwin,http://cygwin.com SYSTEM_NAME := $(shell uname -s) ifeq ($(findstring CYGWIN,$(SYSTEM_NAME)),CYGWIN) SYM_PFX := _ EXTRA_C_OPTS := -DNEED_UNDERSCORE -DGNU_WIN32 EXTRA_NASM_OPTS := -DNEED_UNDERSCORE NON_ELF_SYSTEM := yes EXTRA_CC_USER_OPTS := -Dmain=geekos_main endif # ---------------------------------------------------------------------- # Configuration - # Various options specifying how GeekOS should be built,# what source files to build,which user programs to build,# etc. This is generally the only section of the makefile # that will need to be modified. # ---------------------------------------------------------------------- # List of targets to build by default. # These targets encompass everything needed to boot # and run GeekOS. ALL_TARGETS := fd.img # Kernel source files KERNEL_C_SRCS := idt.c int.c trap.c irq.c io.c keyboard.c screen.c timer.c mem.c crc32.c gdt.c tss.c segment.c bget.c malloc.c synch.c kthread.c main.c # Kernel object files built from C source files,将KERNEL_C_SRCS中的xxx.c文件替换成xxx.o并移至当前的geekos目录下 KERNEL_C_OBJS := $(KERNEL_C_SRCS:%.c=geekos/%.o) # Kernel assembly files KERNEL_ASM_SRCS := lowlevel.asm # Kernel object files build from assembler source files KERNEL_ASM_OBJS := $(KERNEL_ASM_SRCS:%.asm=geekos/%.o) # All kernel object files,所有的内核目标文件 KERNEL_OBJS := $(KERNEL_C_OBJS) $(KERNEL_ASM_OBJS) # Common library source files.库文件 # This library is linked into both the kernel and user programs. # It provides string functions and generic printf()-style # formatted output. COMMON_C_SRCS := fmtout.c string.c memmove.c # Common library object files. COMMON_C_OBJS := $(COMMON_C_SRCS:%.c=common/%.o) # Base address of kernel,内核在内存中的基址 KERNEL_BASE_ADDR := 0x00010000 # Kernel entry point function,设置内核入口 KERNEL_ENTRY = $(SYM_PFX)Main # ---------------------------------------------------------------------- # Tools - # This section defines programs that are used to build GeekOS. # ---------------------------------------------------------------------- # Uncomment if cross compiling #TARGET_CC_PREFIX := i386-elf- # Target C compiler. gcc 2.95.2 or later should work. TARGET_CC := $(TARGET_CC_PREFIX)gcc # Host C compiler. This is used to compile programs to execute on # the host platform,not the target (x86) platform. On x86/ELF # systems,such as Linux and FreeBSD,it can generally be the same # as the target C compiler. HOST_CC := gcc # Target linker. GNU ld is probably to only one that will work.各种工具 TARGET_LD := $(TARGET_CC_PREFIX)ld # Target archiver TARGET_AR := $(TARGET_CC_PREFIX)ar # Target ranlib TARGET_RANLIB := $(TARGET_CC_PREFIX)ranlib # Target nm TARGET_NM := $(TARGET_CC_PREFIX)nm # Target objcopy TARGET_OBJCOPY := $(TARGET_CC_PREFIX)objcopy # Nasm (http://nasm.sourceforge.net) NASM := nasm # Tool to build PFAT filesystem images. BUILDFAT := tools/builtFat.exe # Perl5 or later PERL := perl # Pad a file so its size is a multiple of some unit (i.e.,sector size),以0填充文件使之达到要求的大小 PAD := $(PERL) $(PROJECT_ROOT)/scripts/pad # Create a file filled with zeroes.,创建一个内容为‘0’的文件 ZEROFILE := $(PERL) $(PROJECT_ROOT)/scripts/zerofile # Calculate size of file in sectors,以扇区计算文件 NUMSECS := $(PERL) $(PROJECT_ROOT)/scripts/numsecs # ---------------------------------------------------------------------- # Definitions - # Options passed to the tools. # ---------------------------------------------------------------------- # Flags used for all C source files,消除编译器对栈的检查 GENERAL_OPTS := -O -Wall -fno-stack-protector $(EXTRA_C_OPTS) CC_GENERAL_OPTS := $(GENERAL_OPTS) # Flags used for kernel C source files CC_KERNEL_OPTS := -g -DGEEKOS -I$(PROJECT_ROOT)/include # Flags user for kernel assembly files NASM_KERNEL_OPTS := -I$(PROJECT_ROOT)/src/geekos/ -f elf $(EXTRA_NASM_OPTS) # Flags used for common library and libc source files CC_USER_OPTS := -I$(PROJECT_ROOT)/include -I$(PROJECT_ROOT)/include/libc $(EXTRA_CC_USER_OPTS) # Flags passed to objcopy program (strip unnecessary sections from kernel.exe) OBJCOPY_FLAGS := -R .dynamic -R .note -R .comment # ---------------------------------------------------------------------- # Rules - # Describes how to compile the source files. # ---------------------------------------------------------------------- # Compilation of kernel C source files #geekos/下的.o目标文件依赖.c源文件 geekos/%.o : geekos/%.c $(TARGET_CC) -c $(CC_GENERAL_OPTS) $(CC_KERNEL_OPTS) $< -o geekos/$*.o # Compilation of kernel assembly source files geekos/%.o : geekos/%.asm $(NASM) $(NASM_KERNEL_OPTS) $< -o geekos/$*.o geekos/%.o : geekos/%.S $(TARGET_CC) -c $(CC_GENERAL_OPTS) $(CC_KERNEL_OPTS) $< -o geekos/$*.o # Compilation of common library C source files common/%.o : common/%.c $(TARGET_CC) -c $(CC_GENERAL_OPTS) $(CC_USER_OPTS) $< -o common/$*.o # ---------------------------------------------------------------------- # Targets - # Specifies files to be built # ---------------------------------------------------------------------- # Default target - see definition of ALL_TARGETS in Configuration section all : $(ALL_TARGETS) # Standard floppy image - just boots the kernel fd.img : geekos/fd_boot.bin geekos/setup.bin geekos/kernel.bin cat geekos/fd_boot.bin geekos/setup.bin geekos/kernel.bin > $@ # Floppy boot sector (first stage boot loader).这里动态的计算setup.bin和kernel.bin占软盘扇区大小并插入到boot.asm中的变量中,以将其载入到内存中 geekos/fd_boot.bin : geekos/setup.bin geekos/kernel.bin $(PROJECT_ROOT)/src/geekos/fd_boot.asm $(NASM) -f bin -I$(PROJECT_ROOT)/src/geekos/ -DNUM_SETUP_SECTORS=`$(NUMSECS) geekos/setup.bin` #NUM_SETUP_SECTORS是fd_boot.asm中的变量名,在这里赋值 -DNUM_KERN_SECTORS=`$(NUMSECS) geekos/kernel.bin` $(PROJECT_ROOT)/src/geekos/fd_boot.asm -o $@ # Setup program (second stage boot loader). geekos/setup.bin : geekos/kernel.exe $(PROJECT_ROOT)/src/geekos/setup.asm $(NASM) -f bin -I$(PROJECT_ROOT)/src/geekos/ -DENTRY_POINT=0x`egrep 'Main$$' geekos/kernel.syms |awk '{print $$1}'` #ENTRY_POINT为内核的代码入口,从setup代码跳入 $(PROJECT_ROOT)/src/geekos/setup.asm -o $@ $(PAD) $@ 512 # Loadable (flat) kernel image. geekos/kernel.bin : geekos/kernel.exe $(TARGET_OBJCOPY) $(OBJCOPY_FLAGS) -S -O binary geekos/kernel.exe geekos/kernel.bin $(PAD) $@ 512 # The kernel executable and symbol map. geekos/kernel.exe : $(KERNEL_OBJS) $(COMMON_C_OBJS) $(TARGET_LD) -o geekos/kernel.exe -Ttext $(KERNEL_BASE_ADDR) -e $(KERNEL_ENTRY) $(KERNEL_OBJS) $(COMMON_C_OBJS) $(TARGET_NM) geekos/kernel.exe > geekos/kernel.syms # Clean build directories of generated files clean : for d in geekos common libc user tools; do (cd $$d && rm -f *); done # Build header file dependencies,so source files are recompiled when # header files they depend on are modified. depend : $(GENERATED_LIBC_SRCS) $(TARGET_CC) -M $(CC_GENERAL_OPTS) $(CC_KERNEL_OPTS) $(KERNEL_C_SRCS:%.c=$(PROJECT_ROOT)/src/geekos/%.c) | $(PERL) -n -e 's,^(S),geekos/$$1,;print' > depend.mak $(TARGET_CC) -M $(CC_GENERAL_OPTS) $(CC_USER_OPTS) $(COMMON_C_SRCS:%.c=$(PROJECT_ROOT)/src/common/%.c) | $(PERL) -n -e 's,common/$$1,;print' >> depend.mak # By default,there are no header file dependencies. depend.mak : touch $@ include depend.mak可以看到和sagalinux类似,生成了fd_boot.bin,setup.bin,kernel.bin文件,并最终通过cat命令生成软盘映像。 我们还是从系统启动开始看起,下一篇来分析./src/geekos/fd_boot.asm和setup.asm源代码。 (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |