perf core: Per event callchain limit
Additionally to being able to control the system wide maximum depth via
/proc/sys/kernel/perf_event_max_stack, now we are able to ask for
different depths per event, using perf_event_attr.sample_max_stack for
that.
This uses an u16 hole at the end of perf_event_attr, that, when
perf_event_attr.sample_type has the PERF_SAMPLE_CALLCHAIN, if
sample_max_stack is zero, means use perf_event_max_stack, otherwise
it'll be bounds checked under callchain_mutex.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Zefan Li <lizefan@huawei.com>
Link: http://lkml.kernel.org/n/tip-kolmn1yo40p7jhswxwrc7rrd@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 6b87be9..0e43355 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1076,7 +1076,7 @@
extern struct perf_callchain_entry *
get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
u32 max_stack, bool crosstask, bool add_mark);
-extern int get_callchain_buffers(void);
+extern int get_callchain_buffers(int max_stack);
extern void put_callchain_buffers(void);
extern int sysctl_perf_event_max_stack;
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 36ce552..c66a485 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -276,6 +276,9 @@
/*
* Hardware event_id to monitor via a performance monitoring event:
+ *
+ * @sample_max_stack: Max number of frame pointers in a callchain,
+ * should be < /proc/sys/kernel/perf_event_max_stack
*/
struct perf_event_attr {
@@ -385,7 +388,8 @@
* Wakeup watermark for AUX area
*/
__u32 aux_watermark;
- __u32 __reserved_2; /* align to __u64 */
+ __u16 sample_max_stack;
+ __u16 __reserved_2; /* align to __u64 */
};
#define perf_flags(attr) (*(&(attr)->read_format + 1))
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index a82d760..f1de5c1 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -99,7 +99,7 @@
if (err)
goto free_smap;
- err = get_callchain_buffers();
+ err = get_callchain_buffers(sysctl_perf_event_max_stack);
if (err)
goto free_smap;
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index 179ef46..e9fdb52 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -104,7 +104,7 @@
return -ENOMEM;
}
-int get_callchain_buffers(void)
+int get_callchain_buffers(int event_max_stack)
{
int err = 0;
int count;
@@ -121,6 +121,15 @@
/* If the allocation failed, give up */
if (!callchain_cpus_entries)
err = -ENOMEM;
+ /*
+ * If requesting per event more than the global cap,
+ * return a different error to help userspace figure
+ * this out.
+ *
+ * And also do it here so that we have &callchain_mutex held.
+ */
+ if (event_max_stack > sysctl_perf_event_max_stack)
+ err = -EOVERFLOW;
goto exit;
}
@@ -174,11 +183,12 @@
bool user = !event->attr.exclude_callchain_user;
/* Disallow cross-task user callchains. */
bool crosstask = event->ctx->task && event->ctx->task != current;
+ const u32 max_stack = event->attr.sample_max_stack;
if (!kernel && !user)
return NULL;
- return get_perf_callchain(regs, 0, kernel, user, sysctl_perf_event_max_stack, crosstask, true);
+ return get_perf_callchain(regs, 0, kernel, user, max_stack, crosstask, true);
}
struct perf_callchain_entry *
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 050a290..79363f2 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8843,7 +8843,7 @@
if (!event->parent) {
if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) {
- err = get_callchain_buffers();
+ err = get_callchain_buffers(attr->sample_max_stack);
if (err)
goto err_addr_filters;
}
@@ -9165,6 +9165,9 @@
return -EINVAL;
}
+ if (!attr.sample_max_stack)
+ attr.sample_max_stack = sysctl_perf_event_max_stack;
+
/*
* In cgroup mode, the pid argument is used to pass the fd
* opened to the cgroup directory in cgroupfs. The cpu argument