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;
* u64 len;
* char name[];
* struct sample_id sample_id;
* };
*/
PERF_RECORD_KSYMBOL uses 4 more bits (bit 3-6) in header.misc:
Bit 3 is used to differentiate register vs. unregister. Bit 4-6
encode types of the ksymbol. The following are details of the
assignment of these bits:
Signed-off-by: Song Liu <songliubrav...@fb.com>
---
include/linux/perf_event.h | 12 ++++
include/uapi/linux/perf_event.h | 23 +++++++-
kernel/events/core.c | 98 ++++++++++++++++++++++++++++++++-
3 files changed, 131 insertions(+), 2 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 53c500f0ca79..037863e69bb2 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1113,6 +1113,12 @@ 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(int type, u64 addr, u64 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 +1339,12 @@ 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(int type, u64 addr, u64 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..6c9e327e87ed 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 */
@@ -648,11 +649,18 @@ struct perf_event_mmap_page {
* PERF_RECORD_MISC_COMM_EXEC - PERF_RECORD_COMM event
* PERF_RECORD_MISC_FORK_EXEC - PERF_RECORD_FORK event (perf internal)
* PERF_RECORD_MISC_SWITCH_OUT - PERF_RECORD_SWITCH* events
+ * PERF_RECORD_MISC_KSYMBOL_* - PERF_RECORD_KSYMBOL event
*/
#define PERF_RECORD_MISC_MMAP_DATA (1 << 13)
#define PERF_RECORD_MISC_COMM_EXEC (1 << 13)
#define PERF_RECORD_MISC_FORK_EXEC (1 << 13)
#define PERF_RECORD_MISC_SWITCH_OUT (1 << 13)
+
+#define PERF_RECORD_MISC_KSYMBOL_UNREGISTER (1 << 3)
+#define PERF_RECORD_MISC_KSYMBOL_TYPE_MASK (7 << 4)
+#define PERF_RECORD_MISC_KSYMBOL_TYPE_UNKNOWN (0 << 4)
+#define PERF_RECORD_MISC_KSYMBOL_TYPE_BPF (1 << 4)
+
/*
* These PERF_RECORD_MISC_* flags below are safely reused
* for the following events:
@@ -965,6 +973,19 @@ enum perf_event_type {
*/
PERF_RECORD_NAMESPACES = 16,
+ /*
+ * Record ksymbol register/unregister events:
+ *
+ * struct {
+ * struct perf_event_header header;
+ * u64 addr;
+ * u64 len;
+ * char name[];
+ * struct sample_id sample_id;
+ * };
+ */
+ PERF_RECORD_KSYMBOL = 17,
+
PERF_RECORD_MAX, /* non-ABI */
};
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 84530ab358c3..c0ac6dee367c 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;
+ u64 len;
+ } 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(int ksym_type, u64 addr, u64 len, bool unregister,
+ perf_ksymbol_get_name_f get_name, void *data)
+{
+ struct perf_ksymbol_event ksymbol_event;
+ char name[KSYM_NAME_LEN];
+ int name_len;
+
+ if (!atomic_read(&nr_ksymbol_events))
+ return;
+
+ if (ksym_type & ~PERF_RECORD_MISC_KSYMBOL_TYPE_MASK)
+ goto err;
+
+ switch (ksym_type & PERF_RECORD_MISC_KSYMBOL_TYPE_MASK) {
+ case PERF_RECORD_MISC_KSYMBOL_TYPE_BPF:
+ break;
+ case PERF_RECORD_MISC_KSYMBOL_TYPE_UNKNOWN:
+ default:
+ 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));
+
+ ksymbol_event = (struct perf_ksymbol_event){
+ .name = name,
+ .name_len = name_len,
+ .event_id = {
+ .header = {
+ .type = PERF_RECORD_KSYMBOL,
+ .misc = ksym_type,
+ .size = sizeof(ksymbol_event.event_id) +
+ name_len,
+ },
+ .addr = addr,
+ .len = len,
+ },
+ };
+
+ 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
