下载内核后,文档在:Documentation/dynamic-debug-howto.txt

中文版本:http://www.oschina.net/translate/dynamic-debug-howto?print

Introduction 简介
============

This document describes how to use the dynamic debug (dyndbg) feature.

Dynamic debug is designed to allow you to dynamically enable/disable
kernel code to obtain additional kernel information. Currently, if
CONFIG_DYNAMIC_DEBUG is set, then all pr_debug()/dev_dbg() and
print_hex_dump_debug()/print_hex_dump_bytes() calls can be dynamically
enabled per-callsite.

If CONFIG_DYNAMIC_DEBUG is not set, print_hex_dump_debug() is just
shortcut for print_hex_dump(KERN_DEBUG).

For print_hex_dump_debug()/print_hex_dump_bytes(), format string is
its 'prefix_str' argument, if it is constant string; or "hexdump"
in case 'prefix_str' is build dynamically.

Dynamic debug has even more useful features:

* Simple query language allows turning on and off debugging
statements by matching any combination of 0 or 1 of:

- source filename
- function name
- line number (including ranges of line numbers)
- module name
- format string

* Provides a debugfs control file: <debugfs>/dynamic_debug/control
which can be read to display the complete list of known debug
statements, to help guide you

Controlling dynamic debug Behaviour 如何添加动态调试
=====================================================

The behaviour of pr_debug()/dev_dbg()s are controlled via writing to a
control file in the 'debugfs' filesystem. Thus, you must first mount
the debugfs filesystem, in order to make use of this feature.
Subsequently, we refer to the control file as:
<debugfs>/dynamic_debug/control. For example, if you want to enable
printing from source file 'svcsock.c', line 1603 you simply do:

nullarbor:~ # echo 'file svcsock.c line 1603 +p' > <debugfs>/dynamic_debug/control

If you make a mistake with the syntax, the write will fail thus:

nullarbor:~ # echo 'file svcsock.c wtf 1 +p' > <debugfs>/dynamic_debug/control

-bash: echo: write error: Invalid argument

Viewing Dynamic Debug Behaviour  查看已经添加的动态调试
=================================================

You can view the currently configured behaviour of all the debug
statements via:

nullarbor:~ # cat <debugfs>/dynamic_debug/control
# filename:lineno [module]function flags format
/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c: [svcxprt_rdma]svc_rdma_cleanup =_ "SVCRDMA Module Removed, deregister RPC RDMA transport\012"
/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c: [svcxprt_rdma]svc_rdma_init =_ "\011max_inline : %d\012"
/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c: [svcxprt_rdma]svc_rdma_init =_ "\011sq_depth : %d\012"
/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c: [svcxprt_rdma]svc_rdma_init =_ "\011max_requests : %d\012"
...

You can also apply standard Unix text manipulation filters to this
data, e.g.

nullarbor:~ # grep -i rdma <debugfs>/dynamic_debug/control | wc -l
nullarbor:~ # grep -i tcp <debugfs>/dynamic_debug/control | wc -l

The third column shows the currently enabled flags for each debug

statement callsite (see below for definitions of the flags). The
default value, with no flags enabled, is "=_". So you can view all
the debug statement callsites with any non-default flags:

nullarbor:~ # awk '$3 != "=_"' <debugfs>/dynamic_debug/control

# filename:lineno [module]function flags format

/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svcsock.c:1603 [sunrpc]svc_send p "svc_process: st_sendto returned %d\012"

Command Language Reference 动态调试的命令参数
============================================

At the lexical level, a command comprises a sequence of words separated
by spaces or tabs. So these are all equivalent:

nullarbor:~ # echo -c 'file svcsock.c line 1603 +p' > <debugfs>/dynamic_debug/control
nullarbor:~ # echo -c ' file svcsock.c line 1603 +p ' > <debugfs>/dynamic_debug/control
nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > <debugfs>/dynamic_debug/control

Command submissions are bounded by a write() system call.
Multiple commands can be written together, separated by ';' or '\n'.

~# echo "func pnpacpi_get_resources +p; func pnp_assign_mem +p"  > <debugfs>/dynamic_debug/control

If your query set is big, you can batch them too:

~# cat query-batch-file > <debugfs>/dynamic_debug/control

At the syntactical level, a command comprises a sequence of match
specifications, followed by a flags change specification.

command ::= match-spec* flags-spec

The match-spec's are used to choose a subset of the known pr_debug()
callsites to which to apply the flags-spec. Think of them as a query
with implicit ANDs between each pair. Note that an empty list of
match-specs will select all debug statement callsites.

A match specification comprises a keyword, which controls the
attribute of the callsite to be compared, and a value to compare
against. Possible keywords are:

match-spec ::= 'func' string |
'file' string |
'module' string |
'format' string |
'line' line-range line-range ::= lineno |
'-'lineno |
lineno'-' |
lineno'-'lineno
// Note: line-range cannot contain space, e.g.
// "1-30" is valid range but "1 - 30" is not.

lineno ::= unsigned-int

The meanings of each keyword are:

func
The given string is compared against the function name
of each callsite. Example:

func svc_tcp_accept

file
The given string is compared against either the full pathname, the
src-root relative pathname, or the basename of the source file of
each callsite. Examples:

file svcsock.c
file kernel/freezer.c
file /usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svcsock.c

module
The given string is compared against the module name
of each callsite. The module name is the string as
seen in "lsmod", i.e. without the directory or the .ko
suffix and with '-' changed to '_'. Examples:

module sunrpc
module nfsd

format
The given string is searched for in the dynamic debug format
string. Note that the string does not need to match the
entire format, only some part. Whitespace and other
special characters can be escaped using C octal character
escape \ooo notation, e.g. the space character is \040.
Alternatively, the string can be enclosed in double quote
characters (") or single quote characters (').
Examples:

format svcrdma: // many of the NFS/RDMA server pr_debugs
format readahead // some pr_debugs in the readahead cache
format nfsd:\040SETATTR // one way to match a format with whitespace
format "nfsd: SETATTR" // a neater way to match a format with whitespace
format 'nfsd: SETATTR' // yet another way to match a format with whitespace

line
The given line number or range of line numbers is compared
against the line number of each pr_debug() callsite. A single
line number matches the callsite line number exactly. A
range of line numbers matches any callsite between the first
and last line number inclusive. An empty first number means
the first line in the file, an empty line number means the
last number in the file. Examples:

line 1603 // exactly line 1603
line 1600-1605 // the six lines from line 1600 to line 1605
line -1605 // the 1605 lines from line 1 to line 1605
line 1600- // all lines from line 1600 to the end of the file

The flags specification comprises a change operation followed
by one or more flag characters. The change operation is one
of the characters:

  • - remove the given flags
  • + add the given flags
  • = set the flags to the given flags

The flags are:

  • p   enables the pr_debug() callsite.
  • f    Include the function name in the printed message
  • l    Include line number in the printed message
  • m     Include module name in the printed message
  • t    Include thread ID in messages not generated from interrupt context
  • _   No flags are set. (Or'd with others on input)

For print_hex_dump_debug() and print_hex_dump_bytes(), only 'p' flag
have meaning, other flags ignored.

For display, the flags are preceded by '='
(mnemonic: what the flags are currently equal to).

Note the regexp ^[-+=][flmpt_]+$ matches a flags specification.
To clear all flags at once, use "=_" or "-flmpt".

Debug messages during Boot Process 如何在系统启动时显示动态调试信息
=====================================================================================================

To activate debug messages for core code and built-in modules during
the boot process, even before userspace and debugfs exists, use
dyndbg="QUERY", module.dyndbg="QUERY", or ddebug_query="QUERY"
(ddebug_query is obsoleted by dyndbg, and deprecated). QUERY follows
the syntax described above, but must not exceed 1023 characters. Your
bootloader may impose lower limits.

These dyndbg params are processed just after the ddebug tables are
processed, as part of the arch_initcall. Thus you can enable debug
messages in all code run after this arch_initcall via this boot
parameter.

On an x86 system for example ACPI enablement is a subsys_initcall and
dyndbg="file ec.c +p"
will show early Embedded Controller transactions during ACPI setup if
your machine (typically a laptop) has an Embedded Controller.
PCI (or other devices) initialization also is a hot candidate for using
this boot parameter for debugging purposes.

If foo module is not built-in, foo.dyndbg will still be processed at
boot time, without effect, but will be reprocessed when module is
loaded later. dyndbg_query= and bare dyndbg= are only processed at
boot.

Debug Messages at Module Initialization Time 在模块初始化时显示动态调试信息
=============================================================================================================

  When "modprobe foo" is called, modprobe scans /proc/cmdline for
foo.params, strips "foo.", and passes them to the kernel along with
params given in modprobe args or /etc/modprob.d/*.conf files,
in the following order:

1. # parameters given via /etc/modprobe.d/*.conf
         options foo dyndbg=+pt
         options foo dyndbg # defaults to +p

2. # foo.dyndbg as given in boot args, "foo." is stripped and passed
         foo.dyndbg=" func bar +p; func buz +mp"

3. # args to modprobe
        modprobe foo dyndbg==pmf # override previous settings

  These dyndbg queries are applied in order, with last having final say.
This allows boot args to override or modify those from /etc/modprobe.d
(sensible, since 1 is system wide, 2 is kernel or boot specific), and
modprobe args to override both.

  In the foo.dyndbg="QUERY" form, the query must exclude "module foo".
"foo" is extracted from the param-name, and applied to each query in
"QUERY", and only 1 match-spec of each type is allowed.

The dyndbg option is a "fake" module parameter, which means:

- modules do not need to define it explicitly
- every module gets it tacitly, whether they use pr_debug or not
- it doesnt appear in /sys/module/$module/parameters/
To see it, grep the control file, or inspect /proc/cmdline.

  For CONFIG_DYNAMIC_DEBUG kernels, any settings given at boot-time (or
enabled by -DDEBUG flag during compilation) can be disabled later via
the sysfs interface if the debug messages are no longer needed:

echo "module module_name -p" > <debugfs>/dynamic_debug/control

Examples 综合示例
==========================

// enable the message at line 1603 of file svcsock.c
nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > <debugfs>/dynamic_debug/control // enable all the messages in file svcsock.c
nullarbor:~ # echo -n 'file svcsock.c +p' > <debugfs>/dynamic_debug/control // enable all the messages in the NFS server module
nullarbor:~ # echo -n 'module nfsd +p' > <debugfs>/dynamic_debug/control // enable all 12 messages in the function svc_process()
nullarbor:~ # echo -n 'func svc_process +p' > <debugfs>/dynamic_debug/control // disable all 12 messages in the function svc_process()
nullarbor:~ # echo -n 'func svc_process -p' > <debugfs>/dynamic_debug/control // enable messages for NFS calls READ, READLINK, READDIR and READDIR+.
nullarbor:~ # echo -n 'format "nfsd: READ" +p' > <debugfs>/dynamic_debug/control // enable all messages
nullarbor:~ # echo -n '+p' > <debugfs>/dynamic_debug/control // add module, function to all enabled messages
nullarbor:~ # echo -n '+mf' > <debugfs>/dynamic_debug/control // boot-args example, with newlines and comments for readability
Kernel command line: ...
// see whats going on in dyndbg=value processing
dynamic_debug.verbose=
// enable pr_debugs in 2 builtins, #cmt is stripped
dyndbg="module params +p #cmt ; module sys +p"
// enable pr_debugs in 2 functions in a module loaded later
pc87360.dyndbg="func pc87360_init_device +p; func pc87360_find +p"

随机推荐

  1. SQL Server 2000: 维护计划无法执行

    开启“sql server agent”服务,控制面板-->管理工具-->服务

  2. 10月14日上午PHP环境搭建

    第一步:安装wampserver2.5-Apache-2.4.9-Mysql-5.6.17-php5.5.12-64b文件,安装过程中可能会遇到问题,把遇到的问题代码复制粘贴到360人工服务,查找方案 ...

  3. java中getBytes方法可能使图片文件产生的问题

    InputStream is = new FileInputStream(fl); ImageInputStream iis = ImageIO.createImageInputStream(is); ...

  4. Controller与View之间的数据传递

    1)Controller向View传递数据ViewData["message"] = "Hello";//使用ViewData传递数据ViewBag.Time ...

  5. 开箱即用 - Memcache

    废话少说,先上代码C# memcache Demo memcache 是服务器缓存系统,以键值对方式保存数据到内存中,把对象序列化后,理论上可支持所有的数据类型. 使用情景:怎么用都可以,注意的是它只 ...

  6. AngularJS学习篇(十六)

    AngularJS 表单 HTML 控件 以下 HTML input 元素被称为 HTML 控件: input 元素 select 元素 button 元素 textarea 元素 HTML 表单 H ...

  7. Java的家庭记账本程序(I)

    日期:2019.2.26 博客期:037 星期二 Part 1: 今天使用新的"radio"标签,将搜索方式的选则内容更改了,如下图,不过,研究了很久的数据库连接也还是没有成功!嗯 ...

  8. spring注解-“@Scope”

    @Scope可用来指定Spring创建bean的方式 默认为单实例,即@Scope("singleton").IOC容器启动的时候会调用方法创建对象并放到IOC容器中,以后每次获取 ...

  9. C 栈实现队列节点的管理

    栈预先存储节点,队列的malloc/free均有栈模拟,从而保证不频繁的开辟/是否节点内存. #include "com_is_buf.h" #include "com_ ...

  10. shell 网络状态查询 ping curl telnet

    ping curl telnet python -m SimpleHTTPServer