Re: [PATCH 03/19] x86/ftrace: Make function graph use ftrace directly

Jiri Olsa
2021-06-08T18:54:14Z

On Tue, Jun 08, 2021 at 11:35:58AM -0700, Andrii Nakryiko wrote:

SNIP

> > diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
> > index b8a0d1d564fb..58e96b45e9da 100644
> > --- a/kernel/trace/fgraph.c
> > +++ b/kernel/trace/fgraph.c
> > @@ -115,6 +115,7 @@ int function_graph_enter(unsigned long ret, unsigned long func,
> > {
> > struct ftrace_graph_ent trace;
> >
> > +#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
> > /*
> > * Skip graph tracing if the return location is served by direct trampoline,
> > * since call sequence and return addresses are unpredictable anyway.
> > @@ -124,6 +125,7 @@ int function_graph_enter(unsigned long ret, unsigned long func,
> > if (ftrace_direct_func_count &&
> > ftrace_find_rec_direct(ret - MCOUNT_INSN_SIZE))
> > return -EBUSY;
> > +#endif
> > trace.func = func;
> > trace.depth = ++current->curr_ret_depth;
> >
> > @@ -333,10 +335,10 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
> > #endif /* HAVE_FUNCTION_GRAPH_RET_ADDR_PTR */
> >
> > static struct ftrace_ops graph_ops = {
> > - .func = ftrace_stub,
> > + .func = ftrace_graph_func,
> > .flags = FTRACE_OPS_FL_INITIALIZED |
> > - FTRACE_OPS_FL_PID |
> > - FTRACE_OPS_FL_STUB,
> > + FTRACE_OPS_FL_PID
> > + FTRACE_OPS_GRAPH_STUB,
>
> nit: this looks so weird... Why not define FTRACE_OPS_GRAPH_STUB as
> zero in case of #ifdef ftrace_graph_func? Then it will be natural and
> correctly looking | FTRACE_OPS_GRAPH_STUB?

ok, I can change that

thanks,
jirka

>
> > #ifdef FTRACE_GRAPH_TRAMP_ADDR
> > .trampoline = FTRACE_GRAPH_TRAMP_ADDR,
> > /* trampoline_size is only needed for dynamically allocated tramps */
> > --
> > 2.31.1
> >
>