stapdyn — systemtap dyninst runtime
Synopsis
stapdyn [ Options ] MODULE [ MODULE-OPTIONS ]
Description
The stapdyn program is the dyninst back-end of the Systemtap tool. It expects a shared library produced by the front-end stap tool, when run with --dyninst.
Splitting the systemtap tool into a front-end and a back-end allows a user to compile a systemtap script on a development machine that has the debugging information (need to compile the script) and then transfer the resulting shared object to a production machine that doesn't have any development tools or debugging information installed.
Please refer to stappaths (7) for the version number, or run rpm -q systemtap (fedora/red hat) apt-get -v systemtap (ubuntu)
Options
The stapdyn program supports the following options. Any other option prints a list of supported options.
- -v
Verbose mode.
- -V
Print version number and exit.
- -w
Suppress warnings from the script.
- -c CMD
Command CMD will be run and the stapdyn program will exit when CMD does. The '_stp_target' variable will contain the pid for CMD.
- -x PID
The '_stp_target' variable will be set to PID.
- -o FILE
Send output to FILE. If the module uses bulk mode, the output will be in percpu files FILE_x(FILE_cpux in background and bulk mode) where 'x' is the cpu number. This supports strftime(3) formats for FILE.
- -C WHEN
Control coloring of error messages. WHEN must be either "never", "always", or "auto" (i.e. enable only if at a terminal). If the option is missing, then "auto" is assumed. Colors can be modified using the SYSTEMTAP_COLORS environment variable. See the stap(1) manual page for more information on syntax and behaviour.
- var1=val
Sets the value of global variable var1 to val. Global variables contained within a script are treated as options and can be set from the stapdyn command line.
Arguments
MODULE is either a module path or a module name. If it is a module name, the module will be looked for in the following directory (where 'VERSION' is the output of "uname -r"):
/lib/modules/VERSION/systemtap
$ stap --dyninst -p4 -m mod1 -e 'global var1="foo"; probe begin{printf("%s\n", var1); exit()}'
Running this with an additional module argument:
$ stapdyn mod1.so var1="HelloWorld"
HelloWorld
Spaces and exclamation marks currently cannot be passed into global variables this way.
Examples
See the stapex(3stap) manual page for a collection of sample scripts.
Here is a very basic example of how to use stapdyn. First, use stap to compile a script. The stap program will report the pathname to the resulting module.
$ stap --dyninst -p4 -e 'probe begin { printf("Hello World!\n"); exit() }'
/home/user/.systemtap/cache/85/stap_8553d83f78c_265.so
Run stapdyn with the pathname to the module as an argument.
$ stapdyn /home/user/.systemtap/cache/85/stap_8553d83f78c_265.so
Hello World!
Safety and Security
Systemtap, in DynInst mode, is a developer tool, and runs completely unprivileged. The Linux kernel will only permit one's own processes to be accessed, which is enforced by the ptrace(2) system call. See the stap(1) manual page for additional information on safety and security.
See Also
stap(1), stapprobes(3stap), stap-server(8), staprun(8), stapex(3stap)
Bugs
Use the Bugzilla link of the project web page or our mailing list. http://sourceware.org/systemtap/, <systemtap@sourceware.org>.