Re: [PATCH v7 23/36] function_graph: Add a new exit handler with parent_ip and ftrace_regs

Masami Hiramatsu
2024-02-16T08:51:14Z

On Thu, 15 Feb 2024 11:04:04 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Wed, 7 Feb 2024 00:11:44 +0900
> "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:
>
> > diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
> > index c88bf47f46da..a061f8832b20 100644
> > --- a/arch/x86/include/asm/ftrace.h
> > +++ b/arch/x86/include/asm/ftrace.h
> > @@ -72,6 +72,8 @@ arch_ftrace_get_regs(struct ftrace_regs *fregs)
> > override_function_with_return(&(fregs)->regs)
> > #define ftrace_regs_query_register_offset(name) \
> > regs_query_register_offset(name)
> > +#define ftrace_regs_get_frame_pointer(fregs) \
> > + frame_pointer(&(fregs)->regs)
> >
>
> Doesn't the above belong in the next patch that implements this for x86?

Yes, thanks for pointing it!

>
> > struct ftrace_ops;
> > #define ftrace_graph_func ftrace_graph_func
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index 65d4d4b68768..da2a23f5a9ed 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -43,7 +43,9 @@ struct dyn_ftrace;
> >
> > char *arch_ftrace_match_adjust(char *str, const char *search);
> >
> > -#ifdef CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
> > +#ifdef CONFIG_HAVE_FUNCTION_GRAPH_FREGS
> > +unsigned long ftrace_return_to_handler(struct ftrace_regs *fregs);
> > +#elif defined(CONFIG_HAVE_FUNCTION_GRAPH_RETVAL)
> > struct fgraph_ret_regs;
> > unsigned long ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs);
> > #else
> > @@ -157,6 +159,7 @@ struct ftrace_regs {
> > #define ftrace_regs_set_instruction_pointer(fregs, ip) do { } while (0)
> > #endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
> >
> > +
>
> spurious newline.

OK, I'll remove.

>
> > static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs)
> > {
> > if (!fregs)
> > @@ -1067,6 +1070,10 @@ typedef int (*trace_func_graph_regs_ent_t)(unsigned long func,
> > unsigned long parent_ip,
> > struct ftrace_regs *fregs,
> > struct fgraph_ops *); /* entry w/ regs */
> > +typedef void (*trace_func_graph_regs_ret_t)(unsigned long func,
> > + unsigned long parent_ip,
> > + struct ftrace_regs *,
> > + struct fgraph_ops *); /* return w/ regs */
> >
> > extern int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace, struct fgraph_ops *gops);
> >
> > @@ -1076,6 +1083,7 @@ struct fgraph_ops {
> > trace_func_graph_ent_t entryfunc;
> > trace_func_graph_ret_t retfunc;
> > trace_func_graph_regs_ent_t entryregfunc;
> > + trace_func_graph_regs_ret_t retregfunc;
> > struct ftrace_ops ops; /* for the hash lists */
> > void *private;
> > int idx;
> > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
> > index 61c541c36596..308b3bec01b1 100644
> > --- a/kernel/trace/Kconfig
> > +++ b/kernel/trace/Kconfig
> > @@ -34,6 +34,9 @@ config HAVE_FUNCTION_GRAPH_TRACER
> > config HAVE_FUNCTION_GRAPH_RETVAL
> > bool
> >
> > +config HAVE_FUNCTION_GRAPH_FREGS
> > + bool
> > +
> > config HAVE_DYNAMIC_FTRACE
> > bool
> > help
> > @@ -232,7 +235,7 @@ config FUNCTION_GRAPH_TRACER
> >
> > config FUNCTION_GRAPH_RETVAL
> > bool "Kernel Function Graph Return Value"
> > - depends on HAVE_FUNCTION_GRAPH_RETVAL
> > + depends on HAVE_FUNCTION_GRAPH_RETVAL || HAVE_FUNCTION_GRAPH_FREGS
> > depends on FUNCTION_GRAPH_TRACER
> > default n
> > help
> > diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
> > index 459912ca72e0..12e5f108e242 100644
> > --- a/kernel/trace/fgraph.c
> > +++ b/kernel/trace/fgraph.c
> > @@ -752,8 +752,8 @@ int function_graph_enter_ops(unsigned long ret, unsigned long func,
> >
> > /* Retrieve a function return address to the trace stack on thread info.*/
> > static struct ftrace_ret_stack *
> > -ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
> > - unsigned long frame_pointer, int *index)
> > +ftrace_pop_return_trace(unsigned long *ret, unsigned long frame_pointer,
> > + int *index)
> > {
> > struct ftrace_ret_stack *ret_stack;
> >
> > @@ -798,10 +798,6 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
> >
> > *index += FGRAPH_RET_INDEX;
> > *ret = ret_stack->ret;
> > - trace->func = ret_stack->func;
> > - trace->calltime = ret_stack->calltime;
> > - trace->overrun = atomic_read(&current->trace_overrun);
> > - trace->depth = current->curr_ret_depth;
>
> There's a lot of information stored in the trace structure. Why not pass
> that to the new retregfunc?
>
> Then you don't need to separate this code out.

Sorry, I couldn't catch what you meant, Would you mean to call
ftrace_pop_return_trace() before calling retregfunc()?? because some of the
information are found from ret_stack, which is poped from shadow stack.

>
> > /*
> > * We still want to trace interrupts coming in if
> > * max_depth is set to 1. Make sure the decrement is
> > @@ -840,21 +836,42 @@ static struct notifier_block ftrace_suspend_notifier = {
> > /* fgraph_ret_regs is not defined without CONFIG_FUNCTION_GRAPH_RETVAL */
> > struct fgraph_ret_regs;
> >
> > +static void fgraph_call_retfunc(struct ftrace_regs *fregs,
> > + struct fgraph_ret_regs *ret_regs,
> > + struct ftrace_ret_stack *ret_stack,
> > + struct fgraph_ops *gops)
> > +{
> > + struct ftrace_graph_ret trace;
> > +
> > + trace.func = ret_stack->func;
> > + trace.calltime = ret_stack->calltime;
> > + trace.overrun = atomic_read(&current->trace_overrun);
> > + trace.depth = current->curr_ret_depth;
> > + trace.rettime = trace_clock_local();
> > +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
> > + if (fregs)
> > + trace.retval = ftrace_regs_get_return_value(fregs);
> > + else
> > + trace.retval = fgraph_ret_regs_return_value(ret_regs);
> > +#endif
> > + gops->retfunc(&trace, gops);
> > +}
> > +
> > /*
> > * Send the trace to the ring-buffer.
> > * @return the original return address.
> > */
> > -static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs,
> > +static unsigned long __ftrace_return_to_handler(struct ftrace_regs *fregs,
> > + struct fgraph_ret_regs *ret_regs,
> > unsigned long frame_pointer)
> > {
> > struct ftrace_ret_stack *ret_stack;
> > - struct ftrace_graph_ret trace;
> > unsigned long bitmap;
> > unsigned long ret;
> > int index;
> > int i;
> >
> > - ret_stack = ftrace_pop_return_trace(&trace, &ret, frame_pointer, &index);
> > + ret_stack = ftrace_pop_return_trace(&ret, frame_pointer, &index);
> >
> > if (unlikely(!ret_stack)) {
> > ftrace_graph_stop();
> > @@ -863,10 +880,8 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
> > return (unsigned long)panic;
> > }
> >
> > - trace.rettime = trace_clock_local();
> > -#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
> > - trace.retval = fgraph_ret_regs_return_value(ret_regs);
> > -#endif
> > + if (fregs)
> > + ftrace_regs_set_instruction_pointer(fregs, ret);
> >
> > bitmap = get_fgraph_index_bitmap(current, index);
> > for (i = 0; i < FGRAPH_ARRAY_SIZE; i++) {
> > @@ -877,7 +892,10 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
> > if (gops == &fgraph_stub)
> > continue;
> >
> > - gops->retfunc(&trace, gops);
> > + if (gops->retregfunc)
> > + gops->retregfunc(ret_stack->func, ret, fregs, gops);
> > + else
> > + fgraph_call_retfunc(fregs, ret_regs, ret_stack, gops);
> > }
> >
> > /*
> > @@ -892,20 +910,22 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
> > return ret;
> > }
> >
> > -/*
> > - * After all architecures have selected HAVE_FUNCTION_GRAPH_RETVAL, we can
> > - * leave only ftrace_return_to_handler(ret_regs).
> > - */
> > -#ifdef CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
> > +#ifdef CONFIG_HAVE_FUNCTION_GRAPH_FREGS
> > +unsigned long ftrace_return_to_handler(struct ftrace_regs *fregs)
> > +{
> > + return __ftrace_return_to_handler(fregs, NULL,
> > + ftrace_regs_get_frame_pointer(fregs));
> > +}
> > +#elif defined(CONFIG_HAVE_FUNCTION_GRAPH_RETVAL)
> > unsigned long ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs)
> > {
> > - return __ftrace_return_to_handler(ret_regs,
> > + return __ftrace_return_to_handler(NULL, ret_regs,
> > fgraph_ret_regs_frame_pointer(ret_regs));
> > }
> > #else
> > unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
> > {
> > - return __ftrace_return_to_handler(NULL, frame_pointer);
> > + return __ftrace_return_to_handler(NULL, NULL, frame_pointer);
> > }
> > #endif
> >
> > @@ -1262,9 +1282,15 @@ int register_ftrace_graph(struct fgraph_ops *gops)
> > int ret = 0;
> > int i;
> >
> > - if (gops->entryfunc && gops->entryregfunc)
> > + if ((gops->entryfunc && gops->entryregfunc) ||
> > + (gops->retfunc && gops->retregfunc))
> > return -EINVAL;
>
> With a union, you don't need this.

Indeed.

>
> Now, is it possible to have a entryregfunc and a retfunc, or a entryfunc
> and a retregfunc?

It is possisble, but may not give any benefit.

Thank you,

>
> -- Steve
>
> >
> > +#ifndef CONFIG_HAVE_FUNCTION_GRAPH_FREGS
> > + if (gops->retregfunc)
> > + return -EOPNOTSUPP;
> > +#endif
> > +
> > mutex_lock(&ftrace_lock);
> >
> > if (!gops->ops.func) {
>

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