Enable specifying maxactive for fd based kretprobe. This will be useful for tracing tools like bcc and bpftrace (see for example discussion [1]). Use highest 12 bit (bit 52-63) to allow maximal maxactive of 4095. The original patch [2] seems to be fallen through the cracks and wasn't applied. I've merely rebased the work done by Song Liu and verififed it still works. [1]: https://github.com/iovisor/bpftrace/issues/835 [2]: https://lore.kernel.org/all/20191007223111.1142454-1-songliubraving@xxxxxx/ Signed-off-by: Dmitrii Dolgov <9erthalion6@xxxxxxxxx> --- 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 e6e95a9f07a5..7ca453a73252 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -850,7 +850,8 @@ 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 23bb19716ad3..f0e936b3dfc4 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9809,24 +9809,34 @@ 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, }; @@ -9857,6 +9867,7 @@ 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; @@ -9871,7 +9882,8 @@ 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 a114549720d6..129000327809 100644 --- a/kernel/trace/trace_event_perf.c +++ b/kernel/trace/trace_event_perf.c @@ -245,7 +245,8 @@ 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; @@ -271,7 +272,7 @@ 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 47cebef78532..3ad30cfce9c3 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -1784,7 +1784,7 @@ 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) { enum probe_print_type ptype; struct trace_kprobe *tk; @@ -1799,7 +1799,7 @@ 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 92cc149af0fd..26fe21980793 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -376,7 +376,7 @@ extern int traceprobe_set_print_fmt(struct trace_probe *tp, enum probe_print_typ #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 * -- 2.32.0
