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

From: Steven Rostedt
Date: Thu Feb 15 2024 - 11:03:41 EST

On Wed, 7 Feb 2024 00:11:44 +0900
"Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx> 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?

> 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.

> 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.

> /*
> * 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.

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

-- Steve

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