Re: [PATCH v6 perf, bpf-next 1/7] perf, bpf: Introduce PERF_RECORD_KSYMBOL

Em Thu, Jan 10, 2019 at 06:40:37PM +0000, Song Liu escreveu:

quoted

On Jan 10, 2019, at 10:24 AM, Arnaldo Carvalho de Melo [off-list ref] wrote:

Em Wed, Jan 09, 2019 at 11:21:05AM -0800, Song Liu escreveu:

quoted

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;
    * };
    */

So, I couldn't find where this gets used, the intention here is just to
add the interfaces and afterwards is that you will wire this up? I would
like to test the whole shebang to see it working.

I guess you meant PERF_RECORD_BPF_EVENT not being used? 

PERF_RECORD_KSYMBOL is used by BPF in 3/7 and 5/7. I tested 

Oops, I didn't look at 3/7, just read its cset summary line and as it
says:

Subject: [PATCH v6 perf, bpf-next 3/7] perf, bpf: introduce PERF_RECORD_BPF_EVENT

I didn't thought it was related, perhaps break it down into one that
states that it is wiring up PERF_RECORD_KSYMBOL, and at that point we
could just test it, getting the notifications for new kallsyms related
to BPF?

PERF_RECORD_BPF_EVENT with dump_trace. As we separate RECORD_KSYMBOL from
RECORD_BPF_EVENT, user space won't use BPF_EVENT until annotation support.  

Right, so why not just introduce PERF_RECORD_KSYMBOL, make it be used by
tooling, etc, then move on to PERF_RECORD_BPF_EVENT?

- Arnaldo
 

Thanks,
Song

quoted

quoted

Signed-off-by: Song Liu <redacted>
---
include/linux/perf_event.h      | 13 +++++
include/uapi/linux/perf_event.h | 26 ++++++++-
kernel/events/core.c            | 98 ++++++++++++++++++++++++++++++++-
3 files changed, 135 insertions(+), 2 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 1d5c551a5add..6b5f08db5ef3 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h

@@ -1113,6 +1113,13 @@ static inline void perf_event_task_sched_out(struct task_struct *prev,

}

extern void perf_event_mmap(struct vm_area_struct *vma);
+
+/* callback function to generate ksymbol name */
+typedef int (perf_ksymbol_get_name_f)(char *name, int name_len, void *data);
+extern void perf_event_ksymbol(u16 ksym_type, u64 addr, u32 len,
+			       bool unregister,
+			       perf_ksymbol_get_name_f get_name, void *data);
+
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);

@@ -1333,6 +1340,12 @@ 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,
+				      perf_ksymbol_get_name_f get_name,
+				      void *data) 			{ }
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)	{ }

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 9de8780ac8d9..68c4da0227c5 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h

@@ -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 */

@@ -965,9 +966,32 @@ 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

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 3cd13a30f732..ef27f2776999 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c

@@ -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))

@@ -7650,6 +7653,97 @@ 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,
+			perf_ksymbol_get_name_f get_name, void *data)
+{
+	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;
+
+	get_name(name, KSYM_NAME_LEN, data);
+	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;

@@ -9900,6 +9994,8 @@ 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) {
		/*
-- 
2.17.1

-- 

- Arnaldo

-- 

- Arnaldo