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Commit 76193a94 authored by Song Liu's avatar Song Liu Committed by Arnaldo Carvalho de Melo
Browse files

perf, bpf: Introduce PERF_RECORD_KSYMBOL 



For better performance analysis of dynamically JITed and loaded kernel
functions, such as BPF programs, this patch introduces
PERF_RECORD_KSYMBOL, a new perf_event_type that exposes kernel symbol
register/unregister information to user space.

The following data structure is used for PERF_RECORD_KSYMBOL.

    /*
     * struct {
     *      struct perf_event_header        header;
     *      u64                             addr;
     *      u32                             len;
     *      u16                             ksym_type;
     *      u16                             flags;
     *      char                            name[];
     *      struct sample_id                sample_id;
     * };
     */

Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
Reviewed-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: kernel-team@fb.com
Cc: netdev@vger.kernel.org
Link: http://lkml.kernel.org/r/20190117161521.1341602-2-songliubraving@fb.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 56201969

include/linux/perf_event.h

+8 −0
Original line number Diff line number Diff line
@@ -1122,6 +1122,10 @@ static inline void perf_event_task_sched_out(struct task_struct *prev, 
}



extern void perf_event_mmap(struct vm_area_struct *vma);



extern void perf_event_ksymbol(u16 ksym_type, u64 addr, u32 len,

			       bool unregister, const char *sym);



extern struct perf_guest_info_callbacks *perf_guest_cbs;

extern int perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *callbacks);

extern int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *callbacks);
@@ -1342,6 +1346,10 @@ static inline int perf_unregister_guest_info_callbacks 
(struct perf_guest_info_callbacks *callbacks)				{ return 0; }



static inline void perf_event_mmap(struct vm_area_struct *vma)		{ }



typedef int (perf_ksymbol_get_name_f)(char *name, int name_len, void *data);

static inline void perf_event_ksymbol(u16 ksym_type, u64 addr, u32 len,

				      bool unregister, const char *sym)	{ }

static inline void perf_event_exec(void)				{ }

static inline void perf_event_comm(struct task_struct *tsk, bool exec)	{ }

static inline void perf_event_namespaces(struct task_struct *tsk)	{ }

include/uapi/linux/perf_event.h

+25 −1
Original line number Diff line number Diff line
@@ -372,7 +372,8 @@ struct perf_event_attr { 
				context_switch :  1, /* context switch data */

				write_backward :  1, /* Write ring buffer from end to beginning */

				namespaces     :  1, /* include namespaces data */

				__reserved_1   : 35;

				ksymbol        :  1, /* include ksymbol events */

				__reserved_1   : 34;



	union {

		__u32		wakeup_events;	  /* wakeup every n events */
@@ -963,9 +964,32 @@ enum perf_event_type { 
	 */

	PERF_RECORD_NAMESPACES			= 16,



	/*

	 * Record ksymbol register/unregister events:

	 *

	 * struct {

	 *	struct perf_event_header	header;

	 *	u64				addr;

	 *	u32				len;

	 *	u16				ksym_type;

	 *	u16				flags;

	 *	char				name[];

	 *	struct sample_id		sample_id;

	 * };

	 */

	PERF_RECORD_KSYMBOL			= 17,



	PERF_RECORD_MAX,			/* non-ABI */

};



enum perf_record_ksymbol_type {

	PERF_RECORD_KSYMBOL_TYPE_UNKNOWN	= 0,

	PERF_RECORD_KSYMBOL_TYPE_BPF		= 1,

	PERF_RECORD_KSYMBOL_TYPE_MAX		/* non-ABI */

};



#define PERF_RECORD_KSYMBOL_FLAGS_UNREGISTER	(1 << 0)



#define PERF_MAX_STACK_DEPTH		127

#define PERF_MAX_CONTEXTS_PER_STACK	  8

kernel/events/core.c

+97 −1
Original line number Diff line number Diff line
@@ -385,6 +385,7 @@ static atomic_t nr_namespaces_events __read_mostly; 
static atomic_t nr_task_events __read_mostly;

static atomic_t nr_freq_events __read_mostly;

static atomic_t nr_switch_events __read_mostly;

static atomic_t nr_ksymbol_events __read_mostly;



static LIST_HEAD(pmus);

static DEFINE_MUTEX(pmus_lock);
@@ -4235,7 +4236,7 @@ static bool is_sb_event(struct perf_event *event) 


	if (attr->mmap || attr->mmap_data || attr->mmap2 ||

	    attr->comm || attr->comm_exec ||

	    attr->task ||

	    attr->task || attr->ksymbol ||

	    attr->context_switch)

		return true;

	return false;
@@ -4305,6 +4306,8 @@ static void unaccount_event(struct perf_event *event) 
		dec = true;

	if (has_branch_stack(event))

		dec = true;

	if (event->attr.ksymbol)

		atomic_dec(&nr_ksymbol_events);



	if (dec) {

		if (!atomic_add_unless(&perf_sched_count, -1, 1))
@@ -7653,6 +7656,97 @@ static void perf_log_throttle(struct perf_event *event, int enable) 
	perf_output_end(&handle);

}



/*

 * ksymbol register/unregister tracking

 */



struct perf_ksymbol_event {

	const char	*name;

	int		name_len;

	struct {

		struct perf_event_header        header;

		u64				addr;

		u32				len;

		u16				ksym_type;

		u16				flags;

	} event_id;

};



static int perf_event_ksymbol_match(struct perf_event *event)

{

	return event->attr.ksymbol;

}



static void perf_event_ksymbol_output(struct perf_event *event, void *data)

{

	struct perf_ksymbol_event *ksymbol_event = data;

	struct perf_output_handle handle;

	struct perf_sample_data sample;

	int ret;



	if (!perf_event_ksymbol_match(event))

		return;



	perf_event_header__init_id(&ksymbol_event->event_id.header,

				   &sample, event);

	ret = perf_output_begin(&handle, event,

				ksymbol_event->event_id.header.size);

	if (ret)

		return;



	perf_output_put(&handle, ksymbol_event->event_id);

	__output_copy(&handle, ksymbol_event->name, ksymbol_event->name_len);

	perf_event__output_id_sample(event, &handle, &sample);



	perf_output_end(&handle);

}



void perf_event_ksymbol(u16 ksym_type, u64 addr, u32 len, bool unregister,

			const char *sym)

{

	struct perf_ksymbol_event ksymbol_event;

	char name[KSYM_NAME_LEN];

	u16 flags = 0;

	int name_len;



	if (!atomic_read(&nr_ksymbol_events))

		return;



	if (ksym_type >= PERF_RECORD_KSYMBOL_TYPE_MAX ||

	    ksym_type == PERF_RECORD_KSYMBOL_TYPE_UNKNOWN)

		goto err;



	strlcpy(name, sym, KSYM_NAME_LEN);

	name_len = strlen(name) + 1;

	while (!IS_ALIGNED(name_len, sizeof(u64)))

		name[name_len++] = '\0';

	BUILD_BUG_ON(KSYM_NAME_LEN % sizeof(u64));



	if (unregister)

		flags |= PERF_RECORD_KSYMBOL_FLAGS_UNREGISTER;



	ksymbol_event = (struct perf_ksymbol_event){

		.name = name,

		.name_len = name_len,

		.event_id = {

			.header = {

				.type = PERF_RECORD_KSYMBOL,

				.size = sizeof(ksymbol_event.event_id) +

					name_len,

			},

			.addr = addr,

			.len = len,

			.ksym_type = ksym_type,

			.flags = flags,

		},

	};



	perf_iterate_sb(perf_event_ksymbol_output, &ksymbol_event, NULL);

	return;

err:

	WARN_ONCE(1, "%s: Invalid KSYMBOL type 0x%x\n", __func__, ksym_type);

}



void perf_event_itrace_started(struct perf_event *event)

{

	event->attach_state |= PERF_ATTACH_ITRACE;
@@ -9912,6 +10006,8 @@ static void account_event(struct perf_event *event) 
		inc = true;

	if (is_cgroup_event(event))

		inc = true;

	if (event->attr.ksymbol)

		atomic_inc(&nr_ksymbol_events);



	if (inc) {

		/*