stap 命令-ag真人官方网

systemtap accepts script as command line option or external file, for example:

• command-line script is passed with -e option
  # stap -e 'probe syscall.write { printf("%d\n", $fd); }' [arguments]
• external file as first argument:
  # stap syscalls. [arguments]

systemtap command line arguments may be passed to a script, but it distingushes their types: numerical arguments are accessible with $ prefix: $1, $2 ... $n while string arguments have @ prefix: @1, @2 ... @n

here are some useful stap(1) options:

• -l probespec accepts probe specifier without probe keyword (but with wildcards) and prints all matching probe names (more on wildcards in [probes][lang/probes]). -l will also print probe arguments and their types. for example:
  # stap -l 'scsi.*'
• -v -- increases verbosity of systemtap. the more letters you passed, the more diagnostic information will be printed. if only one -v was passed, stap will report only finishing of each stage.
• -p stage -- ends stap process after stage, represented with a number starting with 1 (parse).
• -k -- stap tool won't delete systemtap temporary files created during compilation (sources and kernel modules kept in /tmp/stapxxxx directory),
• -g -- enables guru-mode, that allows to bind to blacklisted probes and write into kernel memory along with using embedded c in your scripts. generally speaking, it allows dangerous actions.
• -c command and -x pid -- like those in dtrace, they allow to bind systemtap to a specific process
• -o file -- redirects output to a file. if it already exists, systemtap rewrites it.
• -m name -- when compiling a module, give it meaningful name instead of stap_.

when systemtap needs to resolve address into a symbol (for example, instruction pointer to a corresponding function name), it doesn't look into libraries or kernel modules.

here are some useful command-line options that enable that:

• -d modulepath -- enables symbol resolving for a specific library or kernel module. note that in case it is not provided, stap will print a warning with corresponding -d option.
• --ldd -- for tracing process -- use ldd to add all linked libraries for a resolving.
• --all-modules -- enable resolving for all kernel modules

systemtap example

here is sample systemtap script:

#!/usr/sbin/stap

probe syscall.write { if(pid() target())

printf("written %d bytes", $count); }

save it to test.stp and run like this:

root@host# stap /root/test.stp -c "dd if=/dev/zero of=/dev/null count=1"

_q__: run systemtap with following options: # stap -vv -k -p4 /root/test.stp, find generated directory in /tmp and look into created c source.

q: calculate number of probes in a syscall provider and number of variables provided by syscall.write probe:

运行systemtap。

运行systemtap首先需要root权限。

运行systemtap有三种形式：

1． 从文档(通常以.stp作为文档名后缀)中读入并运行脚本：stap [选项] 文档名。

2． 从标准输入中读入并运行脚本： stap [选项]。

3． 运行命令行中的脚本：stap [选项] -e 脚本。

4． 直接运行脚本文档(需要可执行属性并且第一行加上#!/usr/bin/stap)：./脚本文档名用"ctrl c"中止systemtap的运行。

systemtap的选项还在不断的扩展和更新中，其中最常用的选项包括：

-v -- 打印中间信息；

-p num -- 运行完pass num后停止(缺省是运行到pass 5)；

-k -- 运行结束后保留临时文档不删除；

-b -- 使用relayfs文档系统来将数据从内核空间传输到用户空间；

-m -- 仅当使用-b选项时有效，运行结束时不合并每个cpu的单独数据文档；

-o file -- 输出到文档，而不是输出到标准输出；

-c cmd -- 启动探测后，运行cmd命令，直到命令结束后退出；

-g -- 采用guru模式，允许脚本中嵌入c语句；