Commit ff5c9c57 authored by Sven Schnelle's avatar Sven Schnelle Committed by Steven Rostedt (Google)
Browse files

ftrace: Add support for function argument to graph tracer 

Wire up the code to print function arguments in the function graph
tracer. This functionality can be enabled/disabled during runtime with
options/funcgraph-args.

Example usage:

6)              | dummy_xmit [dummy](skb = 0x8887c100, dev = 0x872ca000) {
6)              |   consume_skb(skb = 0x8887c100) {
6)              |     skb_release_head_state(skb = 0x8887c100) {
6)  0.178 us    |       sock_wfree(skb = 0x8887c100)
6)  0.627 us    |     }

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Guo Ren <guoren@kernel.org>
Cc: Donglin Peng <dolinux.peng@gmail.com>
Cc: Zheng Yejian <zhengyejian@huaweicloud.com>
Link: https://lore.kernel.org/20250227185822.810321199@goodmis.org


Reviewed-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Co-developed-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarSven Schnelle <svens@linux.ibm.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 533c20b0

kernel/trace/Kconfig

+6 −0
Original line number Diff line number Diff line
@@ -268,6 +268,12 @@ config FUNCTION_TRACE_ARGS 
	depends on HAVE_FUNCTION_ARG_ACCESS_API

	depends on DEBUG_INFO_BTF

	default y

	help

	  If supported with function argument access API and BTF, then

	  the function tracer and function graph tracer will support printing

	  of function arguments. This feature is off by default, and can be

	  enabled via the trace option func-args (for the function tracer) and

	  funcgraph-args (for the function graph tracer)



config DYNAMIC_FTRACE

	bool "enable/disable function tracing dynamically"

kernel/trace/trace.h

+1 −0
Original line number Diff line number Diff line
@@ -897,6 +897,7 @@ static __always_inline bool ftrace_hash_empty(struct ftrace_hash *hash) 
#define TRACE_GRAPH_PRINT_RETVAL        0x800

#define TRACE_GRAPH_PRINT_RETVAL_HEX    0x1000

#define TRACE_GRAPH_PRINT_RETADDR       0x2000

#define TRACE_GRAPH_ARGS		0x4000

#define TRACE_GRAPH_PRINT_FILL_SHIFT	28

#define TRACE_GRAPH_PRINT_FILL_MASK	(0x3 << TRACE_GRAPH_PRINT_FILL_SHIFT)

kernel/trace/trace_entries.h

+4 −3
Original line number Diff line number Diff line
@@ -72,17 +72,18 @@ FTRACE_ENTRY_REG(function, ftrace_entry, 
);



/* Function call entry */

FTRACE_ENTRY_PACKED(funcgraph_entry, ftrace_graph_ent_entry,

FTRACE_ENTRY(funcgraph_entry, ftrace_graph_ent_entry,



	TRACE_GRAPH_ENT,



	F_STRUCT(

		__field_struct(	struct ftrace_graph_ent,	graph_ent	)

		__field_packed(	unsigned long,	graph_ent,	func		)

		__field_packed(	int,		graph_ent,	depth		)

		__field_packed(	unsigned long,	graph_ent,	depth		)

		__dynamic_array(unsigned long,	args				)

	),



	F_printk("--> %ps (%d)", (void *)__entry->func, __entry->depth)

	F_printk("--> %ps (%lu)", (void *)__entry->func, __entry->depth)

);



#ifdef CONFIG_FUNCTION_GRAPH_RETADDR

kernel/trace/trace_functions_graph.c

+113 −32
Original line number Diff line number Diff line
@@ -70,6 +70,10 @@ static struct tracer_opt trace_opts[] = { 
#ifdef CONFIG_FUNCTION_GRAPH_RETADDR

	/* Display function return address ? */

	{ TRACER_OPT(funcgraph-retaddr, TRACE_GRAPH_PRINT_RETADDR) },

#endif

#ifdef CONFIG_FUNCTION_TRACE_ARGS

	/* Display function arguments ? */

	{ TRACER_OPT(funcgraph-args, TRACE_GRAPH_ARGS) },

#endif

	/* Include sleep time (scheduled out) between entry and return */

	{ TRACER_OPT(sleep-time, TRACE_GRAPH_SLEEP_TIME) },
@@ -110,25 +114,43 @@ static void 
print_graph_duration(struct trace_array *tr, unsigned long long duration,

		     struct trace_seq *s, u32 flags);



int __trace_graph_entry(struct trace_array *tr,

				struct ftrace_graph_ent *trace,

				unsigned int trace_ctx)

static int __graph_entry(struct trace_array *tr, struct ftrace_graph_ent *trace,

			 unsigned int trace_ctx, struct ftrace_regs *fregs)

{

	struct ring_buffer_event *event;

	struct trace_buffer *buffer = tr->array_buffer.buffer;

	struct ftrace_graph_ent_entry *entry;

	int size;



	event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT,

					  sizeof(*entry), trace_ctx);

	/* If fregs is defined, add FTRACE_REGS_MAX_ARGS long size words */

	size = sizeof(*entry) + (FTRACE_REGS_MAX_ARGS * !!fregs * sizeof(long));



	event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT, size, trace_ctx);

	if (!event)

		return 0;



	entry = ring_buffer_event_data(event);

	entry->graph_ent = *trace;



#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API

	if (fregs) {

		for (int i = 0; i < FTRACE_REGS_MAX_ARGS; i++)

			entry->args[i] = ftrace_regs_get_argument(fregs, i);

	}

#endif



	trace_buffer_unlock_commit_nostack(buffer, event);



	return 1;

}



int __trace_graph_entry(struct trace_array *tr,

				struct ftrace_graph_ent *trace,

				unsigned int trace_ctx)

{

	return __graph_entry(tr, trace, trace_ctx, NULL);

}



#ifdef CONFIG_FUNCTION_GRAPH_RETADDR

int __trace_graph_retaddr_entry(struct trace_array *tr,

				struct ftrace_graph_ent *trace,
@@ -174,7 +196,7 @@ struct fgraph_times { 
	unsigned long long		sleeptime; /* may be optional! */

};



int trace_graph_entry(struct ftrace_graph_ent *trace,

static int graph_entry(struct ftrace_graph_ent *trace,

		       struct fgraph_ops *gops,

		       struct ftrace_regs *fregs)

{
@@ -246,7 +268,7 @@ int trace_graph_entry(struct ftrace_graph_ent *trace, 
			unsigned long retaddr = ftrace_graph_top_ret_addr(current);

			ret = __trace_graph_retaddr_entry(tr, trace, trace_ctx, retaddr);

		} else {

			ret = __trace_graph_entry(tr, trace, trace_ctx);

			ret = __graph_entry(tr, trace, trace_ctx, fregs);

		}

	}

	preempt_enable_notrace();
@@ -254,6 +276,20 @@ int trace_graph_entry(struct ftrace_graph_ent *trace, 
	return ret;

}



int trace_graph_entry(struct ftrace_graph_ent *trace,

		      struct fgraph_ops *gops,

		      struct ftrace_regs *fregs)

{

	return graph_entry(trace, gops, NULL);

}



static int trace_graph_entry_args(struct ftrace_graph_ent *trace,

				  struct fgraph_ops *gops,

				  struct ftrace_regs *fregs)

{

	return graph_entry(trace, gops, fregs);

}



static void

__trace_graph_function(struct trace_array *tr,

		unsigned long ip, unsigned int trace_ctx)
@@ -418,6 +454,9 @@ static int graph_trace_init(struct trace_array *tr) 
{

	int ret;



	if (tracer_flags_is_set(TRACE_GRAPH_ARGS))

		tr->gops->entryfunc = trace_graph_entry_args;

	else

		tr->gops->entryfunc = trace_graph_entry;



	if (tracing_thresh)
@@ -775,7 +814,7 @@ static void print_graph_retaddr(struct trace_seq *s, struct fgraph_retaddr_ent_e 


static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entry *entry,

				struct ftrace_graph_ret *graph_ret, void *func,

				u32 opt_flags, u32 trace_flags)

				u32 opt_flags, u32 trace_flags, int args_size)

{

	unsigned long err_code = 0;

	unsigned long retval = 0;
@@ -809,7 +848,14 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr 
		if (entry->ent.type != TRACE_GRAPH_RETADDR_ENT)

			print_retaddr = false;



		trace_seq_printf(s, "%ps();", func);

		trace_seq_printf(s, "%ps", func);



		if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {

			print_function_args(s, entry->args, (unsigned long)func);

			trace_seq_putc(s, ';');

		} else

			trace_seq_puts(s, "();");



		if (print_retval || print_retaddr)

			trace_seq_puts(s, " /*");

		else
@@ -836,7 +882,8 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr 


#else



#define print_graph_retval(_seq, _ent, _ret, _func, _opt_flags, _trace_flags) do {} while (0)

#define print_graph_retval(_seq, _ent, _ret, _func, _opt_flags, _trace_flags, args_size) \

	do {} while (0)



#endif
@@ -852,10 +899,14 @@ print_graph_entry_leaf(struct trace_iterator *iter, 
	struct ftrace_graph_ret *graph_ret;

	struct ftrace_graph_ent *call;

	unsigned long long duration;

	unsigned long ret_func;

	unsigned long func;

	int args_size;

	int cpu = iter->cpu;

	int i;



	args_size = iter->ent_size - offsetof(struct ftrace_graph_ent_entry, args);



	graph_ret = &ret_entry->ret;

	call = &entry->graph_ent;

	duration = ret_entry->rettime - ret_entry->calltime;
@@ -887,16 +938,25 @@ print_graph_entry_leaf(struct trace_iterator *iter, 
	for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++)

		trace_seq_putc(s, ' ');



	ret_func = graph_ret->func + iter->tr->text_delta;



	/*

	 * Write out the function return value or return address

	 */

	if (flags & (__TRACE_GRAPH_PRINT_RETVAL | __TRACE_GRAPH_PRINT_RETADDR)) {

		print_graph_retval(s, entry, graph_ret,

				   (void *)graph_ret->func + iter->tr->text_delta,

				   flags, tr->trace_flags);

				   flags, tr->trace_flags, args_size);

	} else {

		trace_seq_printf(s, "%ps();\n", (void *)func);

		trace_seq_printf(s, "%ps", (void *)ret_func);



		if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {

			print_function_args(s, entry->args, ret_func);

			trace_seq_putc(s, ';');

		} else

			trace_seq_puts(s, "();");

	}

	trace_seq_printf(s, "\n");



	print_graph_irq(iter, graph_ret->func, TRACE_GRAPH_RET,

			cpu, iter->ent->pid, flags);
@@ -913,6 +973,7 @@ print_graph_entry_nested(struct trace_iterator *iter, 
	struct fgraph_data *data = iter->private;

	struct trace_array *tr = iter->tr;

	unsigned long func;

	int args_size;

	int i;



	if (data) {
@@ -937,7 +998,17 @@ print_graph_entry_nested(struct trace_iterator *iter, 


	func = call->func + iter->tr->text_delta;



	trace_seq_printf(s, "%ps() {", (void *)func);

	trace_seq_printf(s, "%ps", (void *)func);



	args_size = iter->ent_size - offsetof(struct ftrace_graph_ent_entry, args);



	if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long))

		print_function_args(s, entry->args, func);

	else

		trace_seq_puts(s, "()");



	trace_seq_puts(s, " {");



	if (flags & __TRACE_GRAPH_PRINT_RETADDR  &&

		entry->ent.type == TRACE_GRAPH_RETADDR_ENT)

		print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
@@ -1107,21 +1178,38 @@ print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s, 
			struct trace_iterator *iter, u32 flags)

{

	struct fgraph_data *data = iter->private;

	struct ftrace_graph_ent *call = &field->graph_ent;

	struct ftrace_graph_ent *call;

	struct ftrace_graph_ret_entry *leaf_ret;

	static enum print_line_t ret;

	int cpu = iter->cpu;

	/*

	 * print_graph_entry() may consume the current event,

	 * thus @field may become invalid, so we need to save it.

	 * sizeof(struct ftrace_graph_ent_entry) is very small,

	 * it can be safely saved at the stack.

	 */

	struct ftrace_graph_ent_entry *entry;

	u8 save_buf[sizeof(*entry) + FTRACE_REGS_MAX_ARGS * sizeof(long)];



	/* The ent_size is expected to be as big as the entry */

	if (iter->ent_size > sizeof(save_buf))

		iter->ent_size = sizeof(save_buf);



	entry = (void *)save_buf;

	memcpy(entry, field, iter->ent_size);



	call = &entry->graph_ent;



	if (check_irq_entry(iter, flags, call->func, call->depth))

		return TRACE_TYPE_HANDLED;



	print_graph_prologue(iter, s, TRACE_GRAPH_ENT, call->func, flags);



	leaf_ret = get_return_for_leaf(iter, field);

	leaf_ret = get_return_for_leaf(iter, entry);

	if (leaf_ret)

		ret = print_graph_entry_leaf(iter, field, leaf_ret, s, flags);

		ret = print_graph_entry_leaf(iter, entry, leaf_ret, s, flags);

	else

		ret = print_graph_entry_nested(iter, field, s, cpu, flags);

		ret = print_graph_entry_nested(iter, entry, s, cpu, flags);



	if (data) {

		/*
@@ -1195,7 +1283,8 @@ print_graph_return(struct ftrace_graph_ret_entry *retentry, struct trace_seq *s, 
	 * funcgraph-retval option is enabled.

	 */

	if (flags & __TRACE_GRAPH_PRINT_RETVAL) {

		print_graph_retval(s, NULL, trace, (void *)func, flags, tr->trace_flags);

		print_graph_retval(s, NULL, trace, (void *)func, flags,

				   tr->trace_flags, 0);

	} else {

		/*

		 * If the return function does not have a matching entry,
@@ -1323,16 +1412,8 @@ print_graph_function_flags(struct trace_iterator *iter, u32 flags) 


	switch (entry->type) {

	case TRACE_GRAPH_ENT: {

		/*

		 * print_graph_entry() may consume the current event,

		 * thus @field may become invalid, so we need to save it.

		 * sizeof(struct ftrace_graph_ent_entry) is very small,

		 * it can be safely saved at the stack.

		 */

		struct ftrace_graph_ent_entry saved;

		trace_assign_type(field, entry);

		saved = *field;

		return print_graph_entry(&saved, s, iter, flags);

		return print_graph_entry(field, s, iter, flags);

	}

#ifdef CONFIG_FUNCTION_GRAPH_RETADDR

	case TRACE_GRAPH_RETADDR_ENT: {