一個初學者如何可以在浩瀚的linux海洋裏找到自己的小舟，遨遊其中。我就是在尋覓的其中一員，希望你也是。接觸linux內核，學習源代碼，學習大師
們的傑作，這就是我的原動力，網上太多如何學習linux源代碼的方法，可能適合一部分人，每個人都有自己的方法。而我，經過很常時間的思考，於是下定決
心，先攻破晦澀的英語這關，因爲代碼註釋都是英文。我希望和有興趣的初學者一起完成我們的遨遊，那是無比的快樂和幸福！我英語只過了4級，翻譯得很爛，只
是將我以爲必要的翻譯了，希望有愛好者能有時間將它補充完整，有些地方還翻譯得不好。
來自linux-2.6.36.2/README
Linux kernel release 2.6.xx <http://kernel.org/>
These are the release notes for Linux version 2.6. Read them carefully,
as they tell you what this is all about, explain how to install the
kernel, and what to do if something goes wrong.
WHAT IS LINUX?
Linux is a clone of the operating system Unix, written from scratch by
Linus Torvalds with assistance from a loosely-knit team of hackers across
the Net. It aims towards POSIX and Single UNIX Specification compliance.
It has all the features you would expect in a modern fully-fledged Unix,
including true multitasking, virtual memory, shared libraries, demand
loading, shared copy-on-write executables, proper memory management,
and multistack networking including IPv4 and IPv6.
It is distributed under the GNU General Public License - see the
accompanying COPYING file for more details.
ON WHAT HARDWARE DOES IT RUN?
在什麼機器上可以跑？
Although originally developed first for 32-bit x86-based PCs (386 or higher),
today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,
IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,
Xtensa, AVR32 and Renesas M32R architectures.
Linux is easily portable(方便的) to most general-purpose 32- or 64-bit architectures
as long as they have a paged memory management unit (PMMU) and a port of the
GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
also been ported to a number of architectures without a PMMU, although
functionality is then obviously somewhat（有點） limited.
Linux has also been ported to itself. You can now run the kernel as a
userspace application - this is called UserMode Linux (UML).
linux很容易就可以移植到32或者64位的機器上，只要它們有內存管理單元(PMMU)和一個GNU C編譯工具。
linux也可以移植到一些沒有PMMU的機器上，雖然功能上有點限制。linux也可以移植到自身。你現在就可以
將內核作爲一個用戶空間的應用程序（UML）。
DOCUMENTATION:
- There is a lot of documentation available both in electronic form on
the Internet and in books, both Linux-specific and pertaining to
general UNIX questions. I'd recommend looking into the documentation
subdirectories on any Linux FTP site for the LDP (Linux Documentation
Project) books. This README is not meant to be documentation on the
system: there are much better sources available.
這個文件夾下面包括了許多有用多文件，來自網絡和書的電子版，還有linux和一般性unix的問題。
我推薦去看這個文件夾下面的那些linux FTP站點。此README在系統中並不意味着是完整的說明，站點裏面
有更加好的資源。
- There are various README files in the Documentation/ subdirectory:
these typically contain kernel-specific installation notes for some
drivers for example. See Documentation/00-INDEX for a list of what
is contained in each file. Please read the Changes file, as it
contains information about the problems, which may result by upgrading
your kernel.
在每個子目錄下面都有README文件，包含來內核安裝的提示，比如某些驅動。看一下“Documentation/00-INDEX”
這個子目錄，裏面列出來每個文件。請讀“Changs”這個文件，裏面包含了一些難點信息，可能要導致你內核的升級。
- The Documentation/DocBook/ subdirectory contains several guides for
kernel developers and users. These guides can be rendered in a
number of formats: PostScript (.ps), PDF, HTML, & man-pages, among others.
After installation, "make psdocs", "make pdfdocs", "make htmldocs",
or "make mandocs" will render the documentation in the requested format.
在“Documentation/DocBook/”這個子目錄下包含了內核開發者和使用者的一些嚮導。可以作成.ps、PDF、
HTML等格式，用命令"make psdocs"、“make pdfdocs”、"make htmldocs"或者“make mandocs”。
INSTALLING the kernel source:
- If you install the full sources, put the kernel tarball in a
directory where you have permissions (eg. your home directory) and
unpack it:
如果你想安裝源代碼，請安裝tar打包工具，然後用以下命令：
gzip -cd linux-2.6.XX.tar.gz | tar xvf -
or
bzip2 -dc linux-2.6.XX.tar.bz2 | tar xvf -
Replace "XX" with the version number of the latest kernel.
請用“XX”代替最近內核的版本號。
Do NOT use the /usr/src/linux area! This area has a (usually
incomplete) set of kernel headers that are used by the library header
files. They should match the library, and not get messed up by
whatever the kernel-du-jour happens to be.
不要使用“/usr/src/linux”作爲目錄，因爲這個是內核庫頭文件的目錄。
- You can also upgrade between 2.6.xx releases by patching. Patches are
distributed in the traditional gzip and the newer bzip2 format. To
install by patching, get all the newer patch files, enter the
top level directory of the kernel source (linux-2.6.xx) and execute:
你可以通過patch升級你的發行版。Patches一般都是用gzip和bzip2打包的。爲了安裝補丁，
要得到所有新的patch文件，然後進入內核源代碼的頂級目錄，使用以下命令：
gzip -cd ../patch-2.6.xx.gz | patch -p1
or
bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
(repeat xx for all versions bigger than the version of your current
source tree, _in_order_) and you should be ok. You may want to remove
the backup files (xxx~ or xxx.orig), and make sure that there are no
failed patches (xxx# or xxx.rej). If there are, either you or me has
made a mistake.
（打完補丁後，“xx”會替代當前源代碼樹的版本號），這樣就ok了。你可能還要將一些備份文件刪除掉，
(xxx~ or xxx.orig),確保沒有失敗的patches(xxx# or xxx.rej)。如果有，不是你犯錯了，就是我。
Unlike patches for the 2.6.x kernels, patches for the 2.6.x.y kernels
(also known as the -stable kernels) are not incremental but instead apply
directly to the base 2.6.x kernel. Please read
Documentation/applying-patches.txt for more information.
不像“2.6.x”的內核補丁，“2.6.x.y”的內核補丁不是遞增而是直接急於“2.6.x”內核的。請閱讀“
Documentation/applying-patches.txt”文件，有更多信息。
Alternatively, the script patch-kernel can be used to automate this
process. It determines the current kernel version and applies any
patches found.
這個腳本“patch-kernel”被自動地使用在這個過程中，決定當前內核版本，運用在任何的補丁上。
linux/scripts/patch-kernel linux
The first argument in the command above is the location of the
kernel source. Patches are applied from the current directory, but
an alternative directory can be specified as the second argument.
上面那個放在內核源代碼中。補丁們可以用於當前目錄，而且可以選擇不同的目錄。
- If you are upgrading between releases using the stable series patches
(for example, patch-2.6.xx.y), note that these "dot-releases" are
not incremental and must be applied to the 2.6.xx base tree. For
example, if your base kernel is 2.6.12 and you want to apply the
2.6.12.3 patch, you do not and indeed must not first apply the
2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel
version 2.6.12.2 and want to jump to 2.6.12.3, you must first
reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying
the 2.6.12.3 patch.
You can read more on this in Documentation/applying-patches.txt
- Make sure you have no stale .o files and dependencies lying around:
cd linux
make mrproper
You should now have the sources correctly installed.
SOFTWARE REQUIREMENTS
Compiling and running the 2.6.xx kernels requires up-to-date
versions of various software packages. Consult
Documentation/Changes for the minimum version numbers required
and how to get updates for these packages. Beware that using
excessively old versions of these packages can cause indirect
errors that are very difficult to track down, so don't assume that
you can just update packages when obvious problems arise during
build or operation.
我們編譯和運行內核時，需要一些軟件包，並且這些軟件包要符合內核更新的版本，否則會帶來
很難追蹤的錯誤。
BUILD directory for the kernel:
爲內核建立目錄：
When compiling the kernel all output files will per default be
stored together with the kernel source code.
Using the option "make O=output/dir" allow you to specify an alternate
place for the output files (including .config).
Example:
kernel source code: /usr/src/linux-2.6.N
build directory: /home/name/build/kernel
我們編譯內核時，可以將輸出文件放在一起。
To configure and build the kernel use:
cd /usr/src/linux-2.6.N
make O=/home/name/build/kernel menuconfig
make O=/home/name/build/kernel
sudo make O=/home/name/build/kernel modules_install install
Please note: If the 'O=output/dir' option is used then it must be
used for all invocations of make.
注意：所有的“make”命令都要帶着“0=output/dir”。
CONFIGURING the kernel:
配置內核：
Do not skip this step even if you are only upgrading one minor
version. New configuration options are added in each release, and
odd problems will turn up if the configuration files are not set up
as expected. If you want to carry your existing configuration to a
new version with minimal work, use "make oldconfig", which will
only ask you for the answers to new questions.
不要跳過這個步驟，即使你僅僅只是升級一個小的版本。新的配置選項被增加到每個發行版中。
如果你想盡量用最小的工作量來配置，可以使用“use oldconfig”。
- Alternate configuration commands are:
"make config" Plain text interface.
簡單的文本界面
"make menuconfig" Text based color menus, radiolists & dialogs.
有顏色的文本菜單，按鈕列表和對話框
"make xconfig" X windows (Qt) based configuration tool.
圖形界面（QT）
"make gconfig" X windows (Gtk) based configuration tool.
圖形界面（GTK）
"make oldconfig" Default all questions based on the contents of
your existing ./.config file and asking about
new config symbols.
會默認一些基本內容，問一些新的配置
"make silentoldconfig"
Like above, but avoids cluttering the screen
with questions already answered.
Additionally updates the dependencies.
"make defconfig" Create a ./.config file by using the default
symbol values from either arch/$ARCH/defconfig
or arch/$ARCH/configs/${PLATFORM}_defconfig,
depending on the architecture.
"make ${PLATFORM}_defconfig"
Create a ./.config file by using the default
symbol values from
arch/$ARCH/configs/${PLATFORM}_defconfig.
Use "make help" to get a list of all available
platforms of your architecture.
"make allyesconfig"
Create a ./.config file by setting symbol
values to 'y' as much as possible.
"make allmodconfig"
Create a ./.config file by setting symbol
values to 'm' as much as possible.
"make allnoconfig" Create a ./.config file by setting symbol
values to 'n' as much as possible.
"make randconfig" Create a ./.config file by setting symbol
values to random values.
You can find more information on using the Linux kernel config tools
in Documentation/kbuild/kconfig.txt.
你可以通過“Documentation/kbuild/kconfig.txt”得到更多信息。
NOTES on "make config":
- having unnecessary drivers will make the kernel bigger, and can
under some circumstances lead to problems: probing for a
nonexistent controller card may confuse your other controllers
沒有必要的驅動會使內核變大，在某些環境下可能會導致問題：探測一個不存在的控制器卡可能會
拒絕你另外一些控制器
- compiling the kernel with "Processor type" set higher than 386
will result in a kernel that does NOT work on a 386. The
kernel will detect this on bootup, and give up.
編譯內核時，高於386的處理器在386的機器上無法工作。
- A kernel with math-emulation compiled in will still use the
coprocessor if one is present: the math emulation will just
never get used in that case. The kernel will be slightly larger,
but will work on different machines regardless of whether they
have a math coprocessor or not.
就是說如果內核將數學模擬編譯進去後，不管運行在什麼機器上，即使那個機器上有數學協處理器，
它都會進行模擬。
- the "kernel hacking" configuration details usually result in a
bigger or slower kernel (or both), and can even make the kernel
less stable by configuring some routines to actively try to
break bad code to find kernel problems (kmalloc()). Thus you
should probably answer 'n' to the questions for
"development", "experimental", or "debugging" features.
像“kernel hacking”這樣的選項會導致內核的不穩定。因此最好不要將它們編譯進內核，比如有
"development", "experimental", or "debugging"特徵的。
COMPILING the kernel:
編譯內核：
- Make sure you have at least gcc 3.2 available.
For more information, refer to Documentation/Changes.
最低gcc本版爲3.2，可以參考“Documentation/Changes”文件
Please note that you can still run a.out user programs with this kernel.
- Do a "make" to create a compressed kernel image. It is also
possible to do "make install" if you have lilo installed to suit the
kernel makefiles, but you may want to check your particular lilo setup first.
你可以使用“make”來創建壓縮內核映像，也可以使用“make install”，不過要檢查一下是否安裝來lilo。
To do the actual install you have to be root, but none of the normal
build should require that. Don't take the name of root in vain.
- If you configured any of the parts of the kernel as `modules', you
will also have to do "make modules_install".
如果你將內核配置成了模塊，那麼你得用“make modules_install”。
- Verbose kernel compile/build output:
- 編譯/建立的詳細輸出：
Normally the kernel build system runs in a fairly quiet mode (but not
totally silent). However, sometimes you or other kernel developers need
to see compile, link, or other commands exactly as they are executed.
For this, use "verbose" build mode. This is done by inserting
"V=1" in the "make" command. E.g.:
一般來說內核建立步驟比較簡單啦，然而，有些時候，需要學習一下編譯、鏈接和另外一些命令。
make V=1 all
To have the build system also tell the reason for the rebuild of each
target, use "V=2". The default is "V=0".
- Keep a backup kernel handy in case something goes wrong. This is
especially true for the development releases, since each new release
contains new code which has not been debugged. Make sure you keep a
backup of the modules corresponding to that kernel, as well. If you
are installing a new kernel with the same version number as your
working kernel, make a backup of your modules directory before you
do a "make modules_install".
Alternatively, before compiling, use the kernel config option
"LOCALVERSION" to append a unique suffix to the regular kernel version.
LOCALVERSION can be set in the "General Setup" menu.
就是說讓內核編譯的模塊時，有個備份，如果你不備份，也可以使用“General Setup”菜單下面的
“LOCALVERSION”選項。
- In order to boot your new kernel, you'll need to copy the kernel
image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
to the place where your regular bootable kernel is found.
爲了讓你的新內核啓動，要將內核映像放在boot可以找得到的地方。
- Booting a kernel directly from a floppy without the assistance of a
bootloader such as LILO, is no longer supported.
我們不提倡用軟盤啓動內核在沒有bootloader“LILO”的情況下。
If you boot Linux from the hard drive, chances are you use LILO which
uses the kernel image as specified in the file /etc/lilo.conf. The
kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
/boot/bzImage. To use the new kernel, save a copy of the old image
and copy the new image over the old one. Then, you MUST RERUN LILO
to update the loading map!! If you don't, you won't be able to boot
the new kernel image.
如果用硬盤啓動，你使用LILO，配置文件在“/etc/lilo.conf”，內核映像在"/boot/"目錄下。
爲了使用新的內核，爲舊的內核保存一份拷貝，將新的內核映像覆蓋舊的。然後重新運行一下LILO，更新
加載的map!!否則不能啓動新的內核映像。
Reinstalling LILO is usually a matter of running /sbin/lilo.
You may wish to edit /etc/lilo.conf to specify an entry for your
old kernel image (say, /vmlinux.old) in case the new one does not
work. See the LILO docs for more information.
下載後的LILO程序放在“/sbin/lilo”裏，如果你將它的配置文件“/etc/lilo.conf”配置
成舊內核啓動，那麼新內核就無法工作了，可以查看LILO文檔獲得更多的信息。
After reinstalling LILO, you should be all set. Shutdown the system,
reboot, and enjoy!
重新啓動，即可進入新內核了！
If you ever need to change the default root device, video mode,
ramdisk size, etc. in the kernel image, use the 'rdev' program (or
alternatively the LILO boot options when appropriate). No need to
recompile the kernel to change these parameters.
如果你想改變內核映像的根設備、視頻模式、虛擬盤的大小，可以使用"rdev"程序（或者在
LILO的選項中配置），不需要改變內核參數重新編譯內核。
- Reboot with the new kernel and enjoy.
IF SOMETHING GOES WRONG:
如果出錯了：
- If you have problems that seem to be due to kernel bugs, please check
the file MAINTAINERS to see if there is a particular person associated
with the part of the kernel that you are having trouble with. If there
isn't anyone listed there, then the second best thing is to mail
them to me ([email protected]), and possibly to any other
relevant mailing-list or to the newsgroup.
- In all bug-reports, *please* tell what kernel you are talking about,
how to duplicate the problem, and what your setup is (use your common
sense). If the problem is new, tell me so, and if the problem is
old, please try to tell me when you first noticed it.
- If the bug results in a message like
unable to handle kernel paging request at address C0000010
Oops: 0002
EIP: 0010:XXXXXXXX
eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
ds: xxxx es: xxxx fs: xxxx gs: xxxx
Pid: xx, process nr: xx
xx xx xx xx xx xx xx xx xx xx
or similar kernel debugging information on your screen or in your
system log, please duplicate it *exactly*. The dump may look
incomprehensible to you, but it does contain information that may
help debugging the problem. The text above the dump is also
important: it tells something about why the kernel dumped code (in
the above example it's due to a bad kernel pointer). More information
on making sense of the dump is in Documentation/oops-tracing.txt
- If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
as is, otherwise you will have to use the "ksymoops" program to make
sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
This utility can be downloaded from
ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
Alternately you can do the dump lookup by hand:
- In debugging dumps like the above, it helps enormously if you can
look up what the EIP value means. The hex value as such doesn't help
me or anybody else very much: it will depend on your particular
kernel setup. What you should do is take the hex value from the EIP
line (ignore the "0010:"), and look it up in the kernel namelist to
see which kernel function contains the offending address.
To find out the kernel function name, you'll need to find the system
binary associated with the kernel that exhibited the symptom. This is
the file 'linux/vmlinux'. To extract the namelist and match it against
the EIP from the kernel crash, do:
nm vmlinux | sort | less
This will give you a list of kernel addresses sorted in ascending
order, from which it is simple to find the function that contains the
offending address. Note that the address given by the kernel
debugging messages will not necessarily match exactly with the
function addresses (in fact, that is very unlikely), so you can't
just 'grep' the list: the list will, however, give you the starting
point of each kernel function, so by looking for the function that
has a starting address lower than the one you are searching for but
is followed by a function with a higher address you will find the one
you want. In fact, it may be a good idea to include a bit of
"context" in your problem report, giving a few lines around the
interesting one.
If you for some reason cannot do the above (you have a pre-compiled
kernel image or similar), telling me as much about your setup as
possible will help. Please read the REPORTING-BUGS document for details.
- Alternately, you can use gdb on a running kernel. (read-only; i.e. you
cannot change values or set break points.) To do this, first compile the
kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
You can now use all the usual gdb commands. The command to look up the
point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
with the EIP value.)
gdb'ing a non-running kernel currently fails because gdb (wrongly)
disregards the starting offset for which the kernel is compiled.
