stapbpf — systemtap bpf runtime
Synopsis
stapbpf [ Options ] MODULE
Description
The stapbpf program is the BPF back-end of the Systemtap tool. It expects a bpf-elf file produced by the front-end stap tool, when run with --runtime=bpf.
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 needed 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 # (for Fedora/RHEL)
$ apt-get -v systemtap # (for Ubuntu)
Options
The stapbpf 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.
- -h
Print help message.
- -x PID
The '_stp_target' variable will be set to PID.
- -o FILE
Send output to FILE.
Arguments
MODULE is the path of a bpf-elf file produced by the front-end stap tool, when run with --runtime=bpf.
Examples
Here is a very basic example of how to generate a stapbpf module. First, use stap to compile a script. The stap program will report the name of the resulting module in the current working directory.
$ stap --runtime=bpf -p4 -e 'probe begin { printf("Hello World!\n"); exit() }'
stap_28784.bo
Run stapbpf with the pathname to the module as an argument.
$ stapbpf ./stap_28784.bo
Hello World!
If the -p4 option is omitted, stap will invoke stapbpf automatically.
Limitations
This runtime is in an early stage of development and it currently lacks support for a number of features available in the default runtime. A subset of the following probe points is supported:
begin end kernel.* process.* timer.* perf.* procfs.*
In general, probes based on the kprobes, uprobes, tracepoint and perf infrastructures are supported. See stapprobes(3stap) for more information on the probe points and which tracing infrastructures they are based on.
for loops, foreach loops and while loops are usable only in begin and end probes. try statements are not supported.
There is limited support for string operations. String variables and literals are limited to 64 characters, except for printf format strings, which are limited to 256 characters.
A subset of the statistical aggregate functionality is available, with support only for the @count(), @sum(), @avg() extractor functions.
The name of the bpf-elf file produced by the front-end stap tool should not be changed.
Safety and Security
See the stap(1) manual page for additional information on safety and security.
See Also
stap(1), stapprobes(3stap), 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>.