* [PATCH v6 1/7] perf/bpf: Reorder bpf_overflow_handler() ahead of __perf_event_overflow()
[not found] <20240412015019.7060-1-khuey@kylehuey.com>
@ 2024-04-12 1:50 ` Kyle Huey
2024-04-12 1:50 ` [PATCH v6 2/7] perf/bpf: Create bpf_overflow_handler() stub for !CONFIG_BPF_SYSCALL Kyle Huey
` (4 subsequent siblings)
5 siblings, 0 replies; 6+ messages in thread
From: Kyle Huey @ 2024-04-12 1:50 UTC (permalink / raw)
To: Kyle Huey, linux-kernel, Andrii Nakryiko, Jiri Olsa, Namhyung Kim,
Marco Elver, Yonghong Song, Peter Zijlstra, Ingo Molnar,
Arnaldo Carvalho de Melo
Cc: Robert O'Callahan, bpf, Ingo Molnar, Mark Rutland,
Alexander Shishkin, Ian Rogers, Adrian Hunter, linux-perf-users
This will allow __perf_event_overflow() to call bpf_overflow_handler().
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
---
kernel/events/core.c | 183 ++++++++++++++++++++++---------------------
1 file changed, 92 insertions(+), 91 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 724e6d7e128f..ee025125a681 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9544,6 +9544,98 @@ static inline bool sample_is_allowed(struct perf_event *event, struct pt_regs *r
return true;
}
+#ifdef CONFIG_BPF_SYSCALL
+static void 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,
+ .event = event,
+ };
+ struct bpf_prog *prog;
+ int ret = 0;
+
+ ctx.regs = perf_arch_bpf_user_pt_regs(regs);
+ if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1))
+ goto out;
+ rcu_read_lock();
+ prog = READ_ONCE(event->prog);
+ if (prog) {
+ perf_prepare_sample(data, event, regs);
+ ret = bpf_prog_run(prog, &ctx);
+ }
+ rcu_read_unlock();
+out:
+ __this_cpu_dec(bpf_prog_active);
+ if (!ret)
+ return;
+
+ event->orig_overflow_handler(event, data, regs);
+}
+
+static int perf_event_set_bpf_handler(struct perf_event *event,
+ struct bpf_prog *prog,
+ u64 bpf_cookie)
+{
+ if (event->overflow_handler_context)
+ /* hw breakpoint or kernel counter */
+ return -EINVAL;
+
+ if (event->prog)
+ return -EEXIST;
+
+ if (prog->type != BPF_PROG_TYPE_PERF_EVENT)
+ return -EINVAL;
+
+ if (event->attr.precise_ip &&
+ prog->call_get_stack &&
+ (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) ||
+ event->attr.exclude_callchain_kernel ||
+ event->attr.exclude_callchain_user)) {
+ /*
+ * On perf_event with precise_ip, calling bpf_get_stack()
+ * may trigger unwinder warnings and occasional crashes.
+ * bpf_get_[stack|stackid] works around this issue by using
+ * callchain attached to perf_sample_data. If the
+ * perf_event does not full (kernel and user) callchain
+ * attached to perf_sample_data, do not allow attaching BPF
+ * program that calls bpf_get_[stack|stackid].
+ */
+ return -EPROTO;
+ }
+
+ 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;
+}
+
+static void perf_event_free_bpf_handler(struct perf_event *event)
+{
+ struct bpf_prog *prog = event->prog;
+
+ if (!prog)
+ return;
+
+ WRITE_ONCE(event->overflow_handler, event->orig_overflow_handler);
+ event->prog = NULL;
+ bpf_prog_put(prog);
+}
+#else
+static int perf_event_set_bpf_handler(struct perf_event *event,
+ struct bpf_prog *prog,
+ u64 bpf_cookie)
+{
+ return -EOPNOTSUPP;
+}
+
+static void perf_event_free_bpf_handler(struct perf_event *event)
+{
+}
+#endif
+
/*
* Generic event overflow handling, sampling.
*/
@@ -10422,97 +10514,6 @@ static void perf_event_free_filter(struct perf_event *event)
ftrace_profile_free_filter(event);
}
-#ifdef CONFIG_BPF_SYSCALL
-static void 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,
- .event = event,
- };
- struct bpf_prog *prog;
- int ret = 0;
-
- ctx.regs = perf_arch_bpf_user_pt_regs(regs);
- if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1))
- goto out;
- rcu_read_lock();
- prog = READ_ONCE(event->prog);
- if (prog) {
- perf_prepare_sample(data, event, regs);
- ret = bpf_prog_run(prog, &ctx);
- }
- rcu_read_unlock();
-out:
- __this_cpu_dec(bpf_prog_active);
- if (!ret)
- return;
-
- event->orig_overflow_handler(event, data, regs);
-}
-
-static int perf_event_set_bpf_handler(struct perf_event *event,
- struct bpf_prog *prog,
- u64 bpf_cookie)
-{
- if (event->overflow_handler_context)
- /* hw breakpoint or kernel counter */
- return -EINVAL;
-
- if (event->prog)
- return -EEXIST;
-
- if (prog->type != BPF_PROG_TYPE_PERF_EVENT)
- return -EINVAL;
-
- if (event->attr.precise_ip &&
- prog->call_get_stack &&
- (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) ||
- event->attr.exclude_callchain_kernel ||
- event->attr.exclude_callchain_user)) {
- /*
- * On perf_event with precise_ip, calling bpf_get_stack()
- * may trigger unwinder warnings and occasional crashes.
- * bpf_get_[stack|stackid] works around this issue by using
- * callchain attached to perf_sample_data. If the
- * perf_event does not full (kernel and user) callchain
- * attached to perf_sample_data, do not allow attaching BPF
- * program that calls bpf_get_[stack|stackid].
- */
- return -EPROTO;
- }
-
- 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;
-}
-
-static void perf_event_free_bpf_handler(struct perf_event *event)
-{
- struct bpf_prog *prog = event->prog;
-
- if (!prog)
- return;
-
- WRITE_ONCE(event->overflow_handler, event->orig_overflow_handler);
- event->prog = NULL;
- bpf_prog_put(prog);
-}
-#else
-static int perf_event_set_bpf_handler(struct perf_event *event,
- struct bpf_prog *prog,
- u64 bpf_cookie)
-{
- return -EOPNOTSUPP;
-}
-static void perf_event_free_bpf_handler(struct perf_event *event)
-{
-}
-#endif
-
/*
* returns true if the event is a tracepoint, or a kprobe/upprobe created
* with perf_event_open()
--
2.34.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v6 2/7] perf/bpf: Create bpf_overflow_handler() stub for !CONFIG_BPF_SYSCALL
[not found] <20240412015019.7060-1-khuey@kylehuey.com>
2024-04-12 1:50 ` [PATCH v6 1/7] perf/bpf: Reorder bpf_overflow_handler() ahead of __perf_event_overflow() Kyle Huey
@ 2024-04-12 1:50 ` Kyle Huey
2024-04-12 1:50 ` [PATCH v6 3/7] perf/bpf: Remove #ifdef CONFIG_BPF_SYSCALL from struct perf_event members Kyle Huey
` (3 subsequent siblings)
5 siblings, 0 replies; 6+ messages in thread
From: Kyle Huey @ 2024-04-12 1:50 UTC (permalink / raw)
To: Kyle Huey, linux-kernel, Andrii Nakryiko, Jiri Olsa, Namhyung Kim,
Marco Elver, Yonghong Song, Peter Zijlstra, Ingo Molnar,
Arnaldo Carvalho de Melo
Cc: Robert O'Callahan, bpf, Ingo Molnar, Mark Rutland,
Alexander Shishkin, Ian Rogers, Adrian Hunter, linux-perf-users
This will allow __perf_event_overflow() (which is independent of
CONFIG_BPF_SYSCALL) to call bpf_overflow_handler().
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
---
kernel/events/core.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index ee025125a681..a7c2a739a27c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9624,6 +9624,12 @@ static void perf_event_free_bpf_handler(struct perf_event *event)
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 perf_event_set_bpf_handler(struct perf_event *event,
struct bpf_prog *prog,
u64 bpf_cookie)
--
2.34.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v6 3/7] perf/bpf: Remove #ifdef CONFIG_BPF_SYSCALL from struct perf_event members
[not found] <20240412015019.7060-1-khuey@kylehuey.com>
2024-04-12 1:50 ` [PATCH v6 1/7] perf/bpf: Reorder bpf_overflow_handler() ahead of __perf_event_overflow() Kyle Huey
2024-04-12 1:50 ` [PATCH v6 2/7] perf/bpf: Create bpf_overflow_handler() stub for !CONFIG_BPF_SYSCALL Kyle Huey
@ 2024-04-12 1:50 ` Kyle Huey
2024-04-12 1:50 ` [PATCH v6 4/7] perf/bpf: Call bpf handler directly, not through overflow machinery Kyle Huey
` (2 subsequent siblings)
5 siblings, 0 replies; 6+ messages in thread
From: Kyle Huey @ 2024-04-12 1:50 UTC (permalink / raw)
To: Kyle Huey, linux-kernel, Andrii Nakryiko, Jiri Olsa, Namhyung Kim,
Marco Elver, Yonghong Song, Peter Zijlstra, Ingo Molnar,
Arnaldo Carvalho de Melo
Cc: Robert O'Callahan, bpf, Ingo Molnar, Mark Rutland,
Alexander Shishkin, Ian Rogers, Adrian Hunter, linux-perf-users
This will allow __perf_event_overflow() (which is independent of
CONFIG_BPF_SYSCALL) to use struct perf_event's prog to decide whether to
call bpf_overflow_handler().
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
---
include/linux/perf_event.h | 2 --
1 file changed, 2 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index d2a15c0c6f8a..07cd4722dedb 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -809,11 +809,9 @@ struct perf_event {
u64 (*clock)(void);
perf_overflow_handler_t overflow_handler;
void *overflow_handler_context;
-#ifdef CONFIG_BPF_SYSCALL
perf_overflow_handler_t orig_overflow_handler;
struct bpf_prog *prog;
u64 bpf_cookie;
-#endif
#ifdef CONFIG_EVENT_TRACING
struct trace_event_call *tp_event;
--
2.34.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v6 4/7] perf/bpf: Call bpf handler directly, not through overflow machinery
[not found] <20240412015019.7060-1-khuey@kylehuey.com>
` (2 preceding siblings ...)
2024-04-12 1:50 ` [PATCH v6 3/7] perf/bpf: Remove #ifdef CONFIG_BPF_SYSCALL from struct perf_event members Kyle Huey
@ 2024-04-12 1:50 ` Kyle Huey
2024-04-12 1:50 ` [PATCH v6 5/7] perf/bpf: Remove unneeded uses_default_overflow_handler() Kyle Huey
2024-04-12 1:50 ` [PATCH v6 6/7] perf/bpf: Allow a bpf program to suppress all sample side effects Kyle Huey
5 siblings, 0 replies; 6+ messages in thread
From: Kyle Huey @ 2024-04-12 1:50 UTC (permalink / raw)
To: Kyle Huey, linux-kernel, Andrii Nakryiko, Jiri Olsa, Namhyung Kim,
Marco Elver, Yonghong Song, Peter Zijlstra, Ingo Molnar,
Arnaldo Carvalho de Melo
Cc: Robert O'Callahan, bpf, Song Liu, Andrii Nakryiko,
Ingo Molnar, Mark Rutland, Alexander Shishkin, Ian Rogers,
Adrian Hunter, linux-perf-users
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>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
---
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 07cd4722dedb..65ad1294218f 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;
@@ -1355,10 +1354,7 @@ __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 a7c2a739a27c..fd601d509cea 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9545,9 +9545,9 @@ 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,
@@ -9568,10 +9568,8 @@ 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,
@@ -9607,8 +9605,6 @@ 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;
}
@@ -9619,15 +9615,15 @@ 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,
@@ -9711,7 +9707,8 @@ 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;
@@ -11978,13 +11975,11 @@ 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
}
--
2.34.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v6 5/7] perf/bpf: Remove unneeded uses_default_overflow_handler()
[not found] <20240412015019.7060-1-khuey@kylehuey.com>
` (3 preceding siblings ...)
2024-04-12 1:50 ` [PATCH v6 4/7] perf/bpf: Call bpf handler directly, not through overflow machinery Kyle Huey
@ 2024-04-12 1:50 ` Kyle Huey
2024-04-12 1:50 ` [PATCH v6 6/7] perf/bpf: Allow a bpf program to suppress all sample side effects Kyle Huey
5 siblings, 0 replies; 6+ messages in thread
From: Kyle Huey @ 2024-04-12 1:50 UTC (permalink / raw)
To: Kyle Huey, linux-kernel, Andrii Nakryiko, Jiri Olsa, Namhyung Kim,
Marco Elver, Yonghong Song, Peter Zijlstra, Ingo Molnar,
Arnaldo Carvalho de Melo
Cc: Robert O'Callahan, bpf, Will Deacon, Song Liu,
Andrii Nakryiko, Mark Rutland, Russell King, Catalin Marinas,
Ingo Molnar, Alexander Shishkin, Ian Rogers, Adrian Hunter,
linux-arm-kernel, linux-perf-users
Now that struct perf_event's orig_overflow_handler is gone, there's no need
for the functions and macros to support looking past overflow_handler to
orig_overflow_handler.
This patch is solely a refactoring and results in no behavior change.
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
---
arch/arm/kernel/hw_breakpoint.c | 8 ++++----
arch/arm64/kernel/hw_breakpoint.c | 4 ++--
include/linux/perf_event.h | 17 +++--------------
3 files changed, 9 insertions(+), 20 deletions(-)
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index dc0fb7a81371..054e9199f30d 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -626,7 +626,7 @@ int hw_breakpoint_arch_parse(struct perf_event *bp,
hw->address &= ~alignment_mask;
hw->ctrl.len <<= offset;
- if (uses_default_overflow_handler(bp)) {
+ if (is_default_overflow_handler(bp)) {
/*
* Mismatch breakpoints are required for single-stepping
* breakpoints.
@@ -798,7 +798,7 @@ static void watchpoint_handler(unsigned long addr, unsigned int fsr,
* Otherwise, insert a temporary mismatch breakpoint so that
* we can single-step over the watchpoint trigger.
*/
- if (!uses_default_overflow_handler(wp))
+ if (!is_default_overflow_handler(wp))
continue;
step:
enable_single_step(wp, instruction_pointer(regs));
@@ -811,7 +811,7 @@ static void watchpoint_handler(unsigned long addr, unsigned int fsr,
info->trigger = addr;
pr_debug("watchpoint fired: address = 0x%x\n", info->trigger);
perf_bp_event(wp, regs);
- if (uses_default_overflow_handler(wp))
+ if (is_default_overflow_handler(wp))
enable_single_step(wp, instruction_pointer(regs));
}
@@ -886,7 +886,7 @@ static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
info->trigger = addr;
pr_debug("breakpoint fired: address = 0x%x\n", addr);
perf_bp_event(bp, regs);
- if (uses_default_overflow_handler(bp))
+ if (is_default_overflow_handler(bp))
enable_single_step(bp, addr);
goto unlock;
}
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index 2f5755192c2b..722ac45f9f7b 100644
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -655,7 +655,7 @@ static int breakpoint_handler(unsigned long unused, unsigned long esr,
perf_bp_event(bp, regs);
/* Do we need to handle the stepping? */
- if (uses_default_overflow_handler(bp))
+ if (is_default_overflow_handler(bp))
step = 1;
unlock:
rcu_read_unlock();
@@ -734,7 +734,7 @@ static u64 get_distance_from_watchpoint(unsigned long addr, u64 val,
static int watchpoint_report(struct perf_event *wp, unsigned long addr,
struct pt_regs *regs)
{
- int step = uses_default_overflow_handler(wp);
+ int step = is_default_overflow_handler(wp);
struct arch_hw_breakpoint *info = counter_arch_bp(wp);
info->trigger = addr;
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 65ad1294218f..13a2b05cc431 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1339,8 +1339,10 @@ extern int perf_event_output(struct perf_event *event,
struct pt_regs *regs);
static inline bool
-__is_default_overflow_handler(perf_overflow_handler_t overflow_handler)
+is_default_overflow_handler(struct perf_event *event)
{
+ perf_overflow_handler_t overflow_handler = event->overflow_handler;
+
if (likely(overflow_handler == perf_event_output_forward))
return true;
if (unlikely(overflow_handler == perf_event_output_backward))
@@ -1348,19 +1350,6 @@ __is_default_overflow_handler(perf_overflow_handler_t overflow_handler)
return false;
}
-#define is_default_overflow_handler(event) \
- __is_default_overflow_handler((event)->overflow_handler)
-
-#ifdef CONFIG_BPF_SYSCALL
-static inline bool uses_default_overflow_handler(struct perf_event *event)
-{
- return is_default_overflow_handler(event);
-}
-#else
-#define uses_default_overflow_handler(event) \
- is_default_overflow_handler(event)
-#endif
-
extern void
perf_event_header__init_id(struct perf_event_header *header,
struct perf_sample_data *data,
--
2.34.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v6 6/7] perf/bpf: Allow a bpf program to suppress all sample side effects
[not found] <20240412015019.7060-1-khuey@kylehuey.com>
` (4 preceding siblings ...)
2024-04-12 1:50 ` [PATCH v6 5/7] perf/bpf: Remove unneeded uses_default_overflow_handler() Kyle Huey
@ 2024-04-12 1:50 ` Kyle Huey
5 siblings, 0 replies; 6+ messages in thread
From: Kyle Huey @ 2024-04-12 1:50 UTC (permalink / raw)
To: Kyle Huey, linux-kernel, Andrii Nakryiko, Jiri Olsa, Namhyung Kim,
Marco Elver, Yonghong Song, Peter Zijlstra, Ingo Molnar,
Arnaldo Carvalho de Melo
Cc: Robert O'Callahan, bpf, Song Liu, Andrii Nakryiko,
Ingo Molnar, Mark Rutland, Alexander Shishkin, Ian Rogers,
Adrian Hunter, linux-perf-users
Returning zero from a bpf program attached to a perf event already
suppresses any data output. Return early from __perf_event_overflow() in
this case so it will also suppress event_limit accounting, SIGTRAP
generation, and F_ASYNC signalling.
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
---
kernel/events/core.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index fd601d509cea..cd88d1e89eb8 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9658,6 +9658,9 @@ static int __perf_event_overflow(struct perf_event *event,
ret = __perf_event_account_interrupt(event, throttle);
+ if (event->prog && !bpf_overflow_handler(event, data, regs))
+ return ret;
+
/*
* XXX event_limit might not quite work as expected on inherited
* events
@@ -9707,8 +9710,7 @@ static int __perf_event_overflow(struct perf_event *event,
irq_work_queue(&event->pending_irq);
}
- if (!(event->prog && !bpf_overflow_handler(event, data, regs)))
- READ_ONCE(event->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;
--
2.34.1
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