Re: [PATCH v14 04/19] function_graph: Replace fgraph_ret_regs with ftrace_regs

Will Deacon
2024-09-17T09:55:44Z

On Sun, Sep 15, 2024 at 05:11:44AM -0400, Steven Rostedt wrote:
> On Fri, 13 Sep 2024 00:08:51 +0900
> "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:
>
> > From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> >
> > Use ftrace_regs instead of fgraph_ret_regs for tracing return value
> > on function_graph tracer because of simplifying the callback interface.
> >
> > The CONFIG_HAVE_FUNCTION_GRAPH_RETVAL is also replaced by
> > CONFIG_HAVE_FUNCTION_GRAPH_FREGS.
> >
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> > ---
> > Changes in v8:
> > - Newly added.
> > ---
> > arch/arm64/Kconfig | 1 +
> > arch/arm64/include/asm/ftrace.h | 23 ++++++-----------------
> > arch/arm64/kernel/asm-offsets.c | 12 ------------
> > arch/arm64/kernel/entry-ftrace.S | 32 ++++++++++++++++++--------------

The arm64 part looks good to me, although passing a partially-populated
struct out of asm feels like it's going to cause us hard-to-debug
problems down the line if any of those extra fields get used. How hard
would it be to poison the unpopulated members of 'ftrace_regs'?

Will