Re: [PATCH 0/7] add function arguments to ftrace

[Sven Schnelle <svens@linux.ibm.com>]

Sven Schnelle <svens@linux.ibm.com> writes:

> Masami Hiramatsu (Google) <mhiramat@kernel.org> writes:
>
>> On Fri, 6 Sep 2024 10:07:38 -0400
>> Steven Rostedt <rostedt@goodmis.org> wrote:
>>
>>> On Fri, 06 Sep 2024 08:18:02 +0200
>>> Sven Schnelle <svens@linux.ibm.com> wrote:
>>> 
>>> 
>>> > One thing i learned after submitting the series is that struct
>>> > ftrace_regs depends on CONFIG_FUNCTION_TRACER, so it cannot be used
>>> > with the graph tracer.
>>
>> Yeah, this is solved by my series [1].
>>
>> [1] https://patchwork.kernel.org/project/linux-trace-kernel/patch/172398532480.293426.13232399076477198126.stgit@devnote2/
>>
>> So I think this series is easier to apply after my series, which
>> passes fgraph_regs in return handler.
>
> Thanks, i'll rebase my changes on top of your patches then.

While doing so i noticed that i completely forgot about arguments
located on the stack. The current patchset tries to read from the
current kernel stack, which is obviously wrong. So either the tracer
needs to save the stack frame in the ringbuffer (which would be quite
a lot of data), or ftrace only prints arguments located in registers.
Also not nice. Opinions?

Thanks
Sven