How to show kernel side function invocations?

How to show kernel side function invocations?

[Shiyao MA]

Hi,

Suppose I run the command `ls'.

Strace only shows the syscall invocations.

Is it possible to show all the functions invoked at the kernel land
with the help of systemtap?



-- 
Best,
Shiyao

Re: How to show kernel side function invocations?

[Daniel Meir Doron]

Hi,

There are many examples in systemtap to probe kernel side of things. You
can find them here: https://sourceware.org/systemtap/examples/
Here is an example of strace on kernel side:
https://sourceware.org/systemtap/examples/process/strace.stp

There are many options like printing backtrace (
https://sourceware.org/systemtap/examples/profiling/pf4.stp) and so much
more...

Daniel.

On Fri, Mar 30, 2018 at 6:47 PM, Shiyao MA <i@introo.me> wrote:

> Hi,
>
> Suppose I run the command `ls'.
>
> Strace only shows the syscall invocations.
>
> Is it possible to show all the functions invoked at the kernel land
> with the help of systemtap?
>
>
>
> --
> Best,
> Shiyao
>

Re: How to show kernel side function invocations?

[Serhei Makarov]

> Is it possible to show all the functions invoked at the kernel land
> with the help of systemtap?

Out of the existing example scripts, para-callgraph.stp and para-callgraph-verbose.stp seem to do something similar.

- https://sourceware.org/systemtap/examples/general/para-callgraph.txt
- https://sourceware.org/systemtap/examples/general/para-callgraph.stp
- https://sourceware.org/systemtap/examples/general/para-callgraph-verbose.stp

However, you must select a subset of the functions in kernel to probe (just saying kernel.function("*") will not work, unfortunately) and a particular syscall to examine. Since you can choose functions by file and not just by name, it might still be flexible enough to give you a good trace of what is being done during a syscall if you pick the right files. As in the example:

# stap para-callgraph-verbose.stp 'kernel.function("*@fs/proc*.c")' \
'kernel.function("vfs_read")' -c "cat /proc/sys/vm/* || true"

All the best,
      Serhei Makarov