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Subject[tip:perf/core] perf, bpf: Introduce PERF_RECORD_KSYMBOL
Commit-ID:  76193a94522f1d4edf2447a536f3f796ce56343b
Gitweb: https://git.kernel.org/tip/76193a94522f1d4edf2447a536f3f796ce56343b
Author: Song Liu <songliubraving@fb.com>
AuthorDate: Thu, 17 Jan 2019 08:15:13 -0800
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 21 Jan 2019 17:00:57 -0300

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: Song Liu <songliubraving@fb.com>
Reviewed-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Peter 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: Arnaldo Carvalho de Melo <acme@redhat.com>
---
include/linux/perf_event.h | 8 ++++
include/uapi/linux/perf_event.h | 26 ++++++++++-
kernel/events/core.c | 98 ++++++++++++++++++++++++++++++++++++++++-
3 files changed, 130 insertions(+), 2 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 4eb88065a9b5..136fe0495374 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -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) { }
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index ea19b5d491bf..1dee5c8f166b 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 */
@@ -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

diff --git a/kernel/events/core.c b/kernel/events/core.c
index bc525cd1615c..e04ab5f325cf 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))
@@ -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) {
/*
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