[PATCH] perf/kprobe: maxactive for fd-based kprobe (pmu perf_kprobe)
From: Song Liu
Date: Mon Oct 07 2019 - 18:31:34 EST
Enable specifying maxactive for fd based kretprobe. This will be useful
for tracing tools like bcc and bpftrace. [1] discussed the need of this
in bpftrace. Use highest highest 12 bit (bit 52-63) to allow maximal
maxactive of 4095.
[1] https://github.com/iovisor/bpftrace/issues/835
Signed-off-by: Song Liu <songliubraving@xxxxxx>
Cc: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
include/linux/trace_events.h | 3 ++-
kernel/events/core.c | 20 ++++++++++++++++----
kernel/trace/trace_event_perf.c | 5 +++--
kernel/trace/trace_kprobe.c | 4 ++--
kernel/trace/trace_probe.h | 2 +-
5 files changed, 24 insertions(+), 10 deletions(-)
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 30a8cdcfd4a4..706d515d2b5e 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -581,7 +581,8 @@ extern void perf_trace_destroy(struct perf_event *event);
extern int perf_trace_add(struct perf_event *event, int flags);
extern void perf_trace_del(struct perf_event *event, int flags);
#ifdef CONFIG_KPROBE_EVENTS
-extern int perf_kprobe_init(struct perf_event *event, bool is_retprobe);
+extern int perf_kprobe_init(struct perf_event *event, bool is_retprobe,
+ int max_active);
extern void perf_kprobe_destroy(struct perf_event *event);
extern int bpf_get_kprobe_info(const struct perf_event *event,
u32 *fd_type, const char **symbol,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 3f0cb82e4fbc..f1b16cda5a9b 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8772,24 +8772,34 @@ static struct pmu perf_tracepoint = {
* PERF_PROBE_CONFIG_IS_RETPROBE if set, create kretprobe/uretprobe
* if not set, create kprobe/uprobe
*
- * The following values specify a reference counter (or semaphore in the
- * terminology of tools like dtrace, systemtap, etc.) Userspace Statically
- * Defined Tracepoints (USDT). Currently, we use 40 bit for the offset.
+ * PERF_UPROBE_REF_CTR_OFFSET_* specify a reference counter (or semaphore
+ * in the terminology of tools like dtrace, systemtap, etc.) Userspace
+ * Statically Defined Tracepoints (USDT). Currently, we use 40 bit for the
+ * offset.
*
* PERF_UPROBE_REF_CTR_OFFSET_BITS # of bits in config as th offset
* PERF_UPROBE_REF_CTR_OFFSET_SHIFT # of bits to shift left
+ *
+ * PERF_KPROBE_MAX_ACTIVE_* defines max_active for kretprobe.
+ * KRETPROBE_MAXACTIVE_MAX is 4096. We allow 4095 here to save a bit.
*/
enum perf_probe_config {
PERF_PROBE_CONFIG_IS_RETPROBE = 1U << 0, /* [k,u]retprobe */
PERF_UPROBE_REF_CTR_OFFSET_BITS = 32,
PERF_UPROBE_REF_CTR_OFFSET_SHIFT = 64 - PERF_UPROBE_REF_CTR_OFFSET_BITS,
+ PERF_KPROBE_MAX_ACTIVE_BITS = 12,
+ PERF_KPROBE_MAX_ACTIVE_SHIFT = 64 - PERF_KPROBE_MAX_ACTIVE_BITS,
};
PMU_FORMAT_ATTR(retprobe, "config:0");
#endif
#ifdef CONFIG_KPROBE_EVENTS
+/* KRETPROBE_MAXACTIVE_MAX is 4096, only allow 4095 here to save a bit */
+PMU_FORMAT_ATTR(max_active, "config:52-63");
+
static struct attribute *kprobe_attrs[] = {
+ &format_attr_max_active.attr,
&format_attr_retprobe.attr,
NULL,
};
@@ -8820,6 +8830,7 @@ static int perf_kprobe_event_init(struct perf_event *event)
{
int err;
bool is_retprobe;
+ int max_active;
if (event->attr.type != perf_kprobe.type)
return -ENOENT;
@@ -8834,7 +8845,8 @@ static int perf_kprobe_event_init(struct perf_event *event)
return -EOPNOTSUPP;
is_retprobe = event->attr.config & PERF_PROBE_CONFIG_IS_RETPROBE;
- err = perf_kprobe_init(event, is_retprobe);
+ max_active = event->attr.config >> PERF_KPROBE_MAX_ACTIVE_SHIFT;
+ err = perf_kprobe_init(event, is_retprobe, max_active);
if (err)
return err;
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index 0892e38ed6fb..da6744ac7bc9 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -240,7 +240,8 @@ void perf_trace_destroy(struct perf_event *p_event)
}
#ifdef CONFIG_KPROBE_EVENTS
-int perf_kprobe_init(struct perf_event *p_event, bool is_retprobe)
+int perf_kprobe_init(struct perf_event *p_event, bool is_retprobe,
+ int max_active)
{
int ret;
char *func = NULL;
@@ -266,7 +267,7 @@ int perf_kprobe_init(struct perf_event *p_event, bool is_retprobe)
tp_event = create_local_trace_kprobe(
func, (void *)(unsigned long)(p_event->attr.kprobe_addr),
- p_event->attr.probe_offset, is_retprobe);
+ p_event->attr.probe_offset, is_retprobe, max_active);
if (IS_ERR(tp_event)) {
ret = PTR_ERR(tp_event);
goto out;
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 324ffbea3556..12088a76e7da 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1556,7 +1556,7 @@ static int unregister_kprobe_event(struct trace_kprobe *tk)
/* create a trace_kprobe, but don't add it to global lists */
struct trace_event_call *
create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
- bool is_return)
+ bool is_return, int max_active)
{
struct trace_kprobe *tk;
int ret;
@@ -1570,7 +1570,7 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
event = func ? func : "DUMMY_EVENT";
tk = alloc_trace_kprobe(KPROBE_EVENT_SYSTEM, event, (void *)addr, func,
- offs, 0 /* maxactive */, 0 /* nargs */,
+ offs, max_active, 0 /* nargs */,
is_return);
if (IS_ERR(tk)) {
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 4ee703728aec..b4368c652749 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -373,7 +373,7 @@ extern int traceprobe_set_print_fmt(struct trace_probe *tp, bool is_return);
#ifdef CONFIG_PERF_EVENTS
extern struct trace_event_call *
create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
- bool is_return);
+ bool is_return, int max_active);
extern void destroy_local_trace_kprobe(struct trace_event_call *event_call);
extern struct trace_event_call *
--
2.17.1