Kernel/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2025-01-06 05:06:29 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

perf/bpf: Call BPF handler directly, not through overflow machinery

Browse Source 
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@kernel.org>
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240412015019.7060-5-khuey@kylehuey.com
This commit is contained in:
Kyle Huey 2024-04-11 18:50:16 -07:00 committed by Ingo Molnar
parent 14e40a9578
commit f11f10bfa1
2 changed files with 12 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/perf_event.h
View File

@ -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) \

27
kernel/events/core.c
View File

@ -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
}