Re: [PATCH v7 21/36] function_graph: Add selftest for passing local variables

Masami Hiramatsu
2024-02-16T08:41:08Z

On Thu, 15 Feb 2024 10:02:54 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Wed, 7 Feb 2024 00:11:22 +0900
> "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:
>
> > From: Steven Rostedt (VMware) <rostedt@goodmis.org>
> >
> > Add boot up selftest that passes variables from a function entry to a
> > function exit, and make sure that they do get passed around.
> >
> > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> > ---
> > Changes in v2:
> > - Add reserved size test.
> > - Use pr_*() instead of printk(KERN_*).
> > ---
> > kernel/trace/trace_selftest.c | 169 +++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 169 insertions(+)
> >
> > diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
> > index f0758afa2f7d..4d86cd4c8c8c 100644
> > --- a/kernel/trace/trace_selftest.c
> > +++ b/kernel/trace/trace_selftest.c
> > @@ -756,6 +756,173 @@ trace_selftest_startup_function(struct tracer *trace, struct trace_array *tr)
> >
> > #ifdef CONFIG_FUNCTION_GRAPH_TRACER
> >
> > +#ifdef CONFIG_DYNAMIC_FTRACE
> > +
> > +#define BYTE_NUMBER 123
> > +#define SHORT_NUMBER 12345
> > +#define WORD_NUMBER 1234567890
> > +#define LONG_NUMBER 1234567890123456789LL
> > +
> > +static int fgraph_store_size __initdata;
> > +static const char *fgraph_store_type_name __initdata;
> > +static char *fgraph_error_str __initdata;
> > +static char fgraph_error_str_buf[128] __initdata;
> > +
> > +static __init int store_entry(struct ftrace_graph_ent *trace,
> > + struct fgraph_ops *gops)
> > +{
> > + const char *type = fgraph_store_type_name;
> > + int size = fgraph_store_size;
> > + void *p;
> > +
> > + p = fgraph_reserve_data(gops->idx, size);
> > + if (!p) {
> > + snprintf(fgraph_error_str_buf, sizeof(fgraph_error_str_buf),
> > + "Failed to reserve %s\n", type);
> > + fgraph_error_str = fgraph_error_str_buf;
> > + return 0;
> > + }
> > +
> > + switch (fgraph_store_size) {
> > + case 1:
> > + *(char *)p = BYTE_NUMBER;
> > + break;
> > + case 2:
> > + *(short *)p = SHORT_NUMBER;
> > + break;
> > + case 4:
> > + *(int *)p = WORD_NUMBER;
> > + break;
> > + case 8:
> > + *(long long *)p = LONG_NUMBER;
> > + break;
> > + }
> > +
>
> What would be an interesting test is to run all versions together. That is,
> to attach a callback that stores a byte, a callback that stores a short, a
> callback that stores a word and a callback that stores a long, and attach
> them all to the same function.
>
> I guess we can add that as a separate patch.

Would you mean we should have different callbacks which stores the different
size of data instead of using switch()?

Thank you,

>
> -- Steve
>
>
> > + return 1;
> > +}
> > +

--
Masami Hiramatsu (Google) <mhiramat@kernel.org>