Commit f83ac754 authored by pengdonglin's avatar pengdonglin Committed by Steven Rostedt (Google)
Browse files

function_graph: Enable funcgraph-args and funcgraph-retaddr to work simultaneously 

Currently, the funcgraph-args and funcgraph-retaddr features are
mutually exclusive. This patch resolves this limitation by allowing
funcgraph-retaddr to have an args array.

To verify the change, use perf to trace vfs_write with both options
enabled:

Before:
 # perf ftrace -G vfs_write --graph-opts args,retaddr
   ......
   down_read() { /* <-n_tty_write+0xa3/0x540 */
     __cond_resched(); /* <-down_read+0x12/0x160 */
     preempt_count_add(); /* <-down_read+0x3b/0x160 */
     preempt_count_sub(); /* <-down_read+0x8b/0x160 */
   }

After:
 # perf ftrace -G vfs_write --graph-opts args,retaddr
   ......
   down_read(sem=0xffff8880100bea78) { /* <-n_tty_write+0xa3/0x540 */
     __cond_resched(); /* <-down_read+0x12/0x160 */
     preempt_count_add(val=1); /* <-down_read+0x3b/0x160 */
     preempt_count_sub(val=1); /* <-down_read+0x8b/0x160 */
   }

Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Xiaoqin Zhang <zhangxiaoqin@xiaomi.com>
Link: https://patch.msgid.link/20251125093425.2563849-1-dolinux.peng@gmail.com


Signed-off-by: default avatarpengdonglin <pengdonglin@xiaomi.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 20e71683

include/linux/ftrace.h

+2 −5
Original line number Diff line number Diff line
@@ -1126,17 +1126,14 @@ static inline void ftrace_init(void) { } 
 */

struct ftrace_graph_ent {

	unsigned long func; /* Current function */

	int depth;

	unsigned long depth;

} __packed;



/*

 * Structure that defines an entry function trace with retaddr.

 * It's already packed but the attribute "packed" is needed

 * to remove extra padding at the end.

 */

struct fgraph_retaddr_ent {

	unsigned long func; /* Current function */

	int depth;

	struct ftrace_graph_ent ent;

	unsigned long retaddr;  /* Return address */

} __packed;

kernel/trace/trace.h

+23 −1
Original line number Diff line number Diff line
@@ -964,7 +964,8 @@ extern int __trace_graph_entry(struct trace_array *tr, 
extern int __trace_graph_retaddr_entry(struct trace_array *tr,

				struct ftrace_graph_ent *trace,

				unsigned int trace_ctx,

				unsigned long retaddr);

				unsigned long retaddr,

				struct ftrace_regs *fregs);

extern void __trace_graph_return(struct trace_array *tr,

				 struct ftrace_graph_ret *trace,

				 unsigned int trace_ctx,
@@ -2276,4 +2277,25 @@ static inline int rv_init_interface(void) 
 */

#define FTRACE_TRAMPOLINE_MARKER  ((unsigned long) INT_MAX)



/*

 * This is used to get the address of the args array based on

 * the type of the entry.

 */

#define FGRAPH_ENTRY_ARGS(e)						\

	({								\

		unsigned long *_args;					\

		struct ftrace_graph_ent_entry *_e = e;			\

									\

		if (IS_ENABLED(CONFIG_FUNCTION_GRAPH_RETADDR) &&	\

			e->ent.type == TRACE_GRAPH_RETADDR_ENT) {	\

			struct fgraph_retaddr_ent_entry *_re;		\

									\

			_re = (typeof(_re))_e;				\

			_args = _re->args;				\

		} else {						\

			_args = _e->args;				\

		}							\

		_args;							\

	})



#endif /* _LINUX_KERNEL_TRACE_H */

kernel/trace/trace_entries.h

+8 −7
Original line number Diff line number Diff line
@@ -80,11 +80,11 @@ FTRACE_ENTRY(funcgraph_entry, ftrace_graph_ent_entry, 
	F_STRUCT(

		__field_struct(	struct ftrace_graph_ent,	graph_ent	)

		__field_packed(	unsigned long,	graph_ent,	func		)

		__field_packed(	unsigned int,	graph_ent,	depth		)

		__field_packed(	unsigned long,	graph_ent,	depth		)

		__dynamic_array(unsigned long,	args				)

	),



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

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

);



#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
@@ -95,13 +95,14 @@ FTRACE_ENTRY_PACKED(fgraph_retaddr_entry, fgraph_retaddr_ent_entry, 
	TRACE_GRAPH_RETADDR_ENT,



	F_STRUCT(

		__field_struct(	struct fgraph_retaddr_ent,	graph_ent	)

		__field_packed(	unsigned long,	graph_ent,	func		)

		__field_packed(	unsigned int,	graph_ent,	depth		)

		__field_packed(	unsigned long,	graph_ent,	retaddr		)

		__field_struct(	struct fgraph_retaddr_ent,	graph_rent	)

		__field_packed(	unsigned long,	graph_rent.ent,	func		)

		__field_packed(	unsigned long,	graph_rent.ent,	depth		)

		__field_packed(	unsigned long,	graph_rent,	retaddr		)

		__dynamic_array(unsigned long,	args				)

	),



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

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

		(void *)__entry->retaddr)

);

kernel/trace/trace_functions_graph.c

+47 −24
Original line number Diff line number Diff line
@@ -36,14 +36,19 @@ struct fgraph_ent_args { 
	unsigned long			args[FTRACE_REGS_MAX_ARGS];

};



struct fgraph_retaddr_ent_args {

	struct fgraph_retaddr_ent_entry	ent;

	/* Force the sizeof of args[] to have FTRACE_REGS_MAX_ARGS entries */

	unsigned long			args[FTRACE_REGS_MAX_ARGS];

};



struct fgraph_data {

	struct fgraph_cpu_data __percpu *cpu_data;



	/* Place to preserve last processed entry. */

	union {

		struct fgraph_ent_args		ent;

		/* TODO allow retaddr to have args */

		struct fgraph_retaddr_ent_entry	rent;

		struct fgraph_retaddr_ent_args	rent;

	};

	struct ftrace_graph_ret_entry	ret;

	int				failed;
@@ -160,20 +165,32 @@ int __trace_graph_entry(struct trace_array *tr, 
int __trace_graph_retaddr_entry(struct trace_array *tr,

				struct ftrace_graph_ent *trace,

				unsigned int trace_ctx,

				unsigned long retaddr)

				unsigned long retaddr,

				struct ftrace_regs *fregs)

{

	struct ring_buffer_event *event;

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

	struct fgraph_retaddr_ent_entry *entry;

	int size;



	/* 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_RETADDR_ENT,

					  sizeof(*entry), trace_ctx);

					  size, trace_ctx);

	if (!event)

		return 0;

	entry	= ring_buffer_event_data(event);

	entry->graph_ent.func = trace->func;

	entry->graph_ent.depth = trace->depth;

	entry->graph_ent.retaddr = retaddr;

	entry->graph_rent.ent = *trace;

	entry->graph_rent.retaddr = retaddr;



#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;
@@ -182,7 +199,8 @@ int __trace_graph_retaddr_entry(struct trace_array *tr, 
int __trace_graph_retaddr_entry(struct trace_array *tr,

				struct ftrace_graph_ent *trace,

				unsigned int trace_ctx,

				unsigned long retaddr)

				unsigned long retaddr,

				struct ftrace_regs *fregs)

{

	return 1;

}
@@ -267,7 +285,8 @@ static int graph_entry(struct ftrace_graph_ent *trace, 
	if (IS_ENABLED(CONFIG_FUNCTION_GRAPH_RETADDR) &&

	    tracer_flags_is_set(tr, TRACE_GRAPH_PRINT_RETADDR)) {

		unsigned long retaddr = ftrace_graph_top_ret_addr(current);

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

		ret = __trace_graph_retaddr_entry(tr, trace, trace_ctx,

						  retaddr, fregs);

	} else {

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

	}
@@ -654,13 +673,9 @@ get_return_for_leaf(struct trace_iterator *iter, 
			 * Save current and next entries for later reference

			 * if the output fails.

			 */

			if (unlikely(curr->ent.type == TRACE_GRAPH_RETADDR_ENT)) {

				data->rent = *(struct fgraph_retaddr_ent_entry *)curr;

			} else {

				int size = min((int)sizeof(data->ent), (int)iter->ent_size);

			int size = min_t(int, sizeof(data->rent), iter->ent_size);



				memcpy(&data->ent, curr, size);

			}

			memcpy(&data->rent, curr, size);

			/*

			 * If the next event is not a return type, then

			 * we only care about what type it is. Otherwise we can
@@ -838,7 +853,7 @@ static void print_graph_retaddr(struct trace_seq *s, struct fgraph_retaddr_ent_e 
		trace_seq_puts(s, " /*");



	trace_seq_puts(s, " <-");

	seq_print_ip_sym_offset(s, entry->graph_ent.retaddr, trace_flags);

	seq_print_ip_sym_offset(s, entry->graph_rent.retaddr, trace_flags);



	if (comment)

		trace_seq_puts(s, " */");
@@ -984,7 +999,7 @@ print_graph_entry_leaf(struct trace_iterator *iter, 
		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);

			print_function_args(s, FGRAPH_ENTRY_ARGS(entry), ret_func);

			trace_seq_putc(s, ';');

		} else

			trace_seq_puts(s, "();");
@@ -1036,7 +1051,7 @@ print_graph_entry_nested(struct trace_iterator *iter, 
	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);

		print_function_args(s, FGRAPH_ENTRY_ARGS(entry), func);

	else

		trace_seq_puts(s, "()");
@@ -1218,11 +1233,14 @@ print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s, 
	/*

	 * 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.

	 * This function is shared by ftrace_graph_ent_entry and

	 * fgraph_retaddr_ent_entry, the size of the latter one

	 * is larger, but it is very small and can be safely saved

	 * at the stack.

	 */

	struct ftrace_graph_ent_entry *entry;

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

	struct fgraph_retaddr_ent_entry *rentry;

	u8 save_buf[sizeof(*rentry) + 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))
@@ -1451,12 +1469,17 @@ print_graph_function_flags(struct trace_iterator *iter, u32 flags) 
	}

#ifdef CONFIG_FUNCTION_GRAPH_RETADDR

	case TRACE_GRAPH_RETADDR_ENT: {

		struct fgraph_retaddr_ent_entry saved;

		/*

		 * ftrace_graph_ent_entry and fgraph_retaddr_ent_entry have

		 * similar functions and memory layouts. The only difference

		 * is that the latter one has an extra retaddr member, so

		 * they can share most of the logic.

		 */

		struct fgraph_retaddr_ent_entry *rfield;



		trace_assign_type(rfield, entry);

		saved = *rfield;

		return print_graph_entry((struct ftrace_graph_ent_entry *)&saved, s, iter, flags);

		return print_graph_entry((struct ftrace_graph_ent_entry *)rfield,

					  s, iter, flags);

	}

#endif

	case TRACE_GRAPH_RET: {