The following commit has been merged into the perf/core branch of tip:
Commit-ID: f11f10bfa1ca23b32020b2073aa13131a27978fe
Gitweb: https://git.kernel.org/tip/f11f10bfa1ca23b32020b2073aa13131a27978fe
Author: Kyle Huey <me@xxxxxxxxxxxx>
AuthorDate: Thu, 11 Apr 2024 18:50:16 -07:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Fri, 12 Apr 2024 11:49:49 +02:00
perf/bpf: Call BPF handler directly, not through overflow machinery
To ultimately allow BPF programs attached to perf events to completely
suppress all of the effects of a perf event overflow (rather than just the
sample output, as they do today), call bpf_overflow_handler() from
__perf_event_overflow() directly rather than modifying struct perf_event's
overflow_handler. Return the BPF program's return value from
bpf_overflow_handler() so that __perf_event_overflow() knows how to
proceed. Remove the now unnecessary orig_overflow_handler from struct
perf_event.
This patch is solely a refactoring and results in no behavior change.
Suggested-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Signed-off-by: Kyle Huey <khuey@xxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Acked-by: Song Liu <song@xxxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240412015019.7060-5-khuey@xxxxxxxxxxxx
---
include/linux/perf_event.h | 6 +-----
kernel/events/core.c | 27 +++++++++++----------------
2 files changed, 12 insertions(+), 21 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 50e01db..2ce2fbc 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -809,7 +809,6 @@ struct perf_event {
u64 (*clock)(void);
perf_overflow_handler_t overflow_handler;
void *overflow_handler_context;
- perf_overflow_handler_t orig_overflow_handler;
struct bpf_prog *prog;
u64 bpf_cookie;
@@ -1361,10 +1360,7 @@ __is_default_overflow_handler(perf_overflow_handler_t overflow_handler)
#ifdef CONFIG_BPF_SYSCALL
static inline bool uses_default_overflow_handler(struct perf_event *event)
{
- if (likely(is_default_overflow_handler(event)))
- return true;
-
- return __is_default_overflow_handler(event->orig_overflow_handler);
+ return is_default_overflow_handler(event);
}
#else
#define uses_default_overflow_handler(event) \
diff --git a/kernel/events/core.c b/kernel/events/core.c
index d3f3f55..c6a6936 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9564,9 +9564,9 @@ static inline bool sample_is_allowed(struct perf_event *event, struct pt_regs *r
}
#ifdef CONFIG_BPF_SYSCALL
-static void bpf_overflow_handler(struct perf_event *event,
- struct perf_sample_data *data,
- struct pt_regs *regs)
+static int bpf_overflow_handler(struct perf_event *event,
+ struct perf_sample_data *data,
+ struct pt_regs *regs)
{
struct bpf_perf_event_data_kern ctx = {
.data = data,
@@ -9587,10 +9587,8 @@ static void bpf_overflow_handler(struct perf_event *event,
rcu_read_unlock();
out:
__this_cpu_dec(bpf_prog_active);
- if (!ret)
- return;
- event->orig_overflow_handler(event, data, regs);
+ return ret;
}
static int perf_event_set_bpf_handler(struct perf_event *event,
@@ -9626,8 +9624,6 @@ static int perf_event_set_bpf_handler(struct perf_event *event,
event->prog = prog;
event->bpf_cookie = bpf_cookie;
- event->orig_overflow_handler = READ_ONCE(event->overflow_handler);
- WRITE_ONCE(event->overflow_handler, bpf_overflow_handler);
return 0;
}
@@ -9638,15 +9634,15 @@ static void perf_event_free_bpf_handler(struct perf_event *event)
if (!prog)
return;
- WRITE_ONCE(event->overflow_handler, event->orig_overflow_handler);
event->prog = NULL;
bpf_prog_put(prog);
}
#else
-static void bpf_overflow_handler(struct perf_event *event,
- struct perf_sample_data *data,
- struct pt_regs *regs)
+static int bpf_overflow_handler(struct perf_event *event,
+ struct perf_sample_data *data,
+ struct pt_regs *regs)
{
+ return 1;
}
static int perf_event_set_bpf_handler(struct perf_event *event,
@@ -9730,7 +9726,8 @@ static int __perf_event_overflow(struct perf_event *event,
irq_work_queue(&event->pending_irq);
}
- READ_ONCE(event->overflow_handler)(event, data, regs);
+ if (!(event->prog && !bpf_overflow_handler(event, data, regs)))
+ READ_ONCE(event->overflow_handler)(event, data, regs);
if (*perf_event_fasync(event) && event->pending_kill) {
event->pending_wakeup = 1;
@@ -11997,13 +11994,11 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
overflow_handler = parent_event->overflow_handler;
context = parent_event->overflow_handler_context;
#if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_EVENT_TRACING)
- if (overflow_handler == bpf_overflow_handler) {
+ if (parent_event->prog) {
struct bpf_prog *prog = parent_event->prog;
bpf_prog_inc(prog);
event->prog = prog;
- event->orig_overflow_handler =
- parent_event->orig_overflow_handler;
}
#endif
}
|