婴儿霉菌感染的表现与应对

nullChapter 1: Kernel OverviewChapter 1: Kernel OverviewObjectivesObjectivesReview development and history of UNIX and Linux. Clarify the nature and extent of the kernel within the context of the operating system proper. Identify operating system design goals and tradeoffs. Review established architectural approaches for implementing an operating system. Introduce the notion of the “core” Linux kernel. Understand the Linux approach to hardware (architecture) abstraction and independence. Kernel Version Explore the layout of the Linux source code tree. Source lines of codeHistoryHistoryUNIX: 1969 Thompson & Ritchie AT&T Bell Labs BSD: 1978 Berkeley Software Distribution Commercial Vendors: Sun, HP, IBM, SGI, DEC GNU: 1984 Richard Stallman, FSF www.gnu.org gcc gdb emacs GPL GNU Public License POSIX: 1986 IEEE Portable Operating System unIX Minix: 1987 Andy Tannenbaum SVR4: 1989 AT&T and SunHistoryHistoryLinux: 1991 Linus Torvalds Intel 386 (i386) Stable version history Version 1.0 of March 1994 supported only UP i386 machines. Version 1.2 of March 1995 added support for Alpha, Sparc and MIPS. Version 2.0 of June 1996 included SMP support and added support for more processors. Version 2.2 of January 1999 Version 2.4.0 of January 2001 Version 2.6 - current (December 17, 2003 to the present) Open Source: GPL, LGPL, Cathedral and the Bazaar Linux FeaturesLinux Features“UNIX-like” operating system “aims at” standards compliance “all the features you would expect in a modern UNIX” preemptive multitasking virtual memory (protected memory, paging) shared libraries demand loading, dynamic kernel modules shared copy-on-write executables TCP/IP networking other features: free OS SMP support, large memory, large files advanced filesystems efficient, stable, highly portable, supports most device hardware active development community, support, documentation GUIs, applications What’s a Kernel?What’s a Kernel? aka: executive, system monitor, nucleus controls and mediates access to hardware implements and supports fundamental abstractions processes, files, devices, users, net, etc. schedules “fair” sharing of system resources memory, cpu, disk, descriptors, etc. enforces security and protection responds to user requests for service (system calls) performs routine maintenance, system checks, etc. Kernel Design GoalsKernel Design Goalsperformance: efficiency, speed utilize resources to capacity, low overhead, code size stability: robustness, resilience uptime, graceful degradation capability: features, flexibility, compatibility security, protection protect users from each other, secure system from bad guys portability clarity extensibilityDesign TradeoffsDesign Tradeoffsefficiency vs. protection more checks, more overhead clarity vs. compatibility ugly implementation of “broken” standards (e.g. signals) flexibility vs. security the more you can do, the more potential security holes! not all are antagonistic portability tends to enhance code clarity The fundamental architecture of the GNU/LinuxThe fundamental architecture of the GNU/LinuxStephen Tweedie’s DiagramStephen Tweedie’s DiagramSchedulerTrapsVMSyscallsUser ProcessesProcess ManagerVFSSocket ManagerMemory AllocatorMath SupportNetwork ProtocolsFile SystemsIO RequestorPacket RequestorChar DevicesBlock DevicesNet DevicesVahalia’s DiagramVahalia’s Diagramfrom Unix Internals: The New Frontiers Uresh Vahalia / Prentice-Hall 1996core utilitiesvirtual memory frameworkvnode/vfs interfaceexec switchblock device switchscheduler frameworkSTREAMSdisktapenetworkttyNFSFFSs5fselfa.outcofffiledeviceanonymoustime-sharingreal-timesystem“Core” Kernel“Core” KernelApplicationsSystem Libraries (libc)System Call InterfaceHardwareArchitecture-Dependent CodeI/O RelatedProcess RelatedSchedulerMemory ManagementIPCFile SystemsNetworkingDevice DriversModulesArchitectural ApproachesArchitectural ApproachesMonolithic Linux is a modular, UNIX-like monolithic kernel micro-kernel virtual machineIsolating Hardware DependenciesIsolating Hardware Dependenciesarchitecture (cpu) dependent (/arch) independent (everything else) abstract dependencies behind functions and macros example: in schedule(), switch_to(prev,next) was called link appropriate version at compile-time device-dependencies isolated in device drivers provide general abstractions that map to reality e.g. three-level page tables tradeoff: exploiting special hardware featuresLinux Kernel Versions Linux Kernel Versions Linux kernels come in two flavors: stable or development. Three numbers, each separated by a dot, represent Linux kernels. The first value is the major release, the second is the minor release, and the third is the revision. The minor release also determines whether the kernel is a stable or development kernel; an even number is stable, whereas an odd number is development. example: 2.4.20 2.5.47 Linux Kernel Versions Linux Kernel Versions Now, the development of the 2.6 kernel without introducing a 2.7 development series in the near future. The current 2.6 maintainer system that exists between Linus Torvalds and Andrew Morton is working out exceedingly well. - As soon as a new kernel is released a two weeks window is open, during this period of time maintainers can submit big diffs to Linus, usually the patches that have already been included in the -mm kernel for a few weeks. Linux Kernel Versions Linux Kernel Versions - After two weeks a -rc1 kernel is released it is now possible to push only patches that do not include new features that could affect the stability of the whole kernel. A new -rc is released whenever Linus deems the current git tree to be in a reasonably sane state adequate for testing. The goal is to release a new -rc kernel every week. Process continues until the kernel is considered "ready", the process should last around 6 weeks. 2.6.x.y -stable kernel tree Kernels with 4 digit versions are -stable kernels. They contain relatively small and critical fixes for security problems or significant regressions discovered in a given 2.6.x kernel. How to get source codeHow to get source codelxr.linux.no is a nice web-based source browser official home of the Linux kernel http://www.kernel.org http://www.kernel.org/pub/linux/kernel/v2.6/ The kernel tarball is distributed in both GNU zip (gzip) and bzip2 format. Bzip2 is the default and preferred format. The Linux kernel tarball in bzip2 format is named linux-x.y.z.tar.bz2. After downloading the source, uncompressing and untarring it is simple. For bzip2, run $ tar xvjf linux-x.y.z.tar.bz2 If it is compressed with GNU zip, run $ tar xvzf linux-x.y.z.tar.gz This uncompresses and untars the source to the directory linux-x.y.z Source Tree LayoutSource Tree Layoutlinux/archlinux/archsubdirectories for each current port , architecture dependent source subtrees. each contains kernel, lib, mm, boot and other directories whose contents override code stubs in architecture independent code lib contains highly-optimized common utility routines such as memcpy, checksums, etc. some architectures of 2.6: alpha, arm, i386, ia64, m68k, mips, mips64 ppc, s390, sh, sparc, sparc64 linux/driverslinux/driverslargest amount of code in the kernel tree device, bus, platform and general directories drivers/char – n_tty.c is the default line discipline drivers/block – elevator.c, genhd.c, linear.c, ll_rw_blk.c, raidN.c drivers/net –specific drivers and general routines Space.c and net_init.c drivers/scsi – scsi_*.c files are generic; sd.c (disk), sr.c (CD-ROM), st.c (tape), sg.c (generic) general: cdrom, ide, isdn, parport, pcmcia, pnp, sound, telephony, video buses –i2c, nubus, pci, sbus, tc, usb platforms – acorn, macintosh, s390, sgilinux/fslinux/fscontains: virtual filesystem (VFS) framework subdirectories for actual filesystems vfs-related files: exec.c, binfmt_*.c - files for mapping new process images devices.c, blk_dev.c – device registration, block device support super.c, filesystems.c inode.c, dcache.c, namei.c, buffer.c, file_table.c open.c, read_write.c, select.c, pipe.c, fifo.c fcntl.c, ioctl.c, locks.c, dquot.c, stat.clinux/includelinux/includeinclude/asm-* architecture-dependent include subdirectories include/linux header info needed both by the kernel and user apps usually linked to /usr/include/linux kernel-only portions guarded by #ifdefs #ifdef __KERNEL__ /* kernel stuff */ #endif other directories: math-emu net pcmcia scsi videolinux/ipclinux/ipcSystem V IPC facilities if disabled at compile-time, util.c exports stubs that simply return –ENOSYS one file for each facility: sem.c – semaphores shm.c – shared memory msg.c – message queueslinux/kernellinux/kernelthe core kernel code sched.c – “the main kernel file” scheduler, wait queues, timers, alarms, task queues process control fork.c, exec.c, signal.c, exit.c acct.c, capability.c, exec_domain.c kernel module support kmod.c, ksyms.c, module.c other operations time.c, resource.c, dma.c, softirq.c, itimer.c printk.c, info.c, panic.c, sysctl.c, sys.c linux/mmlinux/mmpaging and swapping swap.c, swapfile.c (paging devices), swap_state.c (cache) vmscan.c – paging policies, kwapd page_io.c – low-level page transfer allocation and deallocation slab.c – slab allocator page_alloc.c – page-based allocator zone allocator vmalloc.c – kernel virtual-memory allocator memory mapping memory.c – paging, fault-handling, page table code filemap.c – file mapping mmap.c, mremap.c, mlock.c, mprotect.clinux/netlinux/netcore sock.c sk_buffer.c dst.c etc. ipv4 ipv6 x.25 decnet bluetooth ethernet ipx irda (Infrared Data Association ) Source lines of code Source lines of code http://encyclopedia.thefreedictionary.com/source%20lines%20of%20code This study found that Debian GNU/Linux 2.2 included over 55,000,000 SLOC, and if developed in a conventional proprietary way would have required 14,005 person-years and cost $1.9 billion USD to develop. nullJanuary 25, 1999 - Linux 2.2.0 was released (1,800,847 lines of code). January 4, 2001 - Linux 2.4.0 was released (3,377,902 lines of code). December 17, 2003 - Linux 2.6.0 was released (5,929,913 lines of code).Most active 2.6.35 employers (July 14, 2010 )Most active 2.6.35 employers (July 14, 2010 )TextbookTextbook Understanding the Linux Kernel, 3rd Edition 东南大学出版社 Author : Daniel P.Bovet,Marco Cesati ISBN 7564102764 Price ：98.00 中文译本 深入理解Linux内核（第三版） 【译　　者】陈莉君;张琼声;张宏伟 【出 版 社】 中国电力出版社    【 号】 9787508353944 价格 98.00TextbookTextbookLinux内核与实现（英文影印版）（第2版） 　 【原 书 名】 Linux Kernel Development (2nd Edition) 【作　　者】（美）Robert Love 【出 版 社】 机械工业出版社　 【书 号】 7111175751 【出版日期】 2006年1月 市场价 ：￥40.00 Linux内核设计与实现（第2版） 【作　　者】（美）Robert Love 【译　　者】 陈莉君 康华 张波 【出 版 社】 机械工业出版社 【书 号】 7111178653 【出版日期】 2006年1月　市场价 ：￥38.00