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

[Will Deacon]

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 at kernel.org> wrote:
> 
> > From: Masami Hiramatsu (Google) <mhiramat at 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 at 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