On Sat, 25 Jun 2022 17:24:29 +0200 Dmitrii Dolgov <9erthalion6@xxxxxxxxx> wrote: > From: Song Liu <songliubraving@xxxxxx> > > 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 4 bit (bit 59-63) to allow specifying maxactive by log2. > > 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, verififed it > still works, and modified to allow specifying maxactive by log2 per > suggestion from the discussion thread. > > Note that changes in rethook implementation may render maxactive > obsolete. > > [1]: https://github.com/iovisor/bpftrace/issues/835 > [2]: https://lore.kernel.org/all/20191007223111.1142454-1-songliubraving@xxxxxx/ > > Signed-off-by: Song Liu <songliubraving@xxxxxx> > Signed-off-by: Dmitrii Dolgov <9erthalion6@xxxxxxxxx> This looks good to me. Reviewed-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> Thank you! > --- > Previous discussion: https://lore.kernel.org/bpf/20220615211559.7856-1-9erthalion6@xxxxxxxxx/ > > Changes in v4: > - Allow specifying maxactive by log2 > > Changes in v3: > - Set correct author > > Changes in v2: > - Fix comment about number bits for the offset > > 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..184325ff2656 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 32 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 log2 of 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 = 4, > + PERF_KPROBE_MAX_ACTIVE_SHIFT = 64 - PERF_KPROBE_MAX_ACTIVE_BITS, > }; > > PMU_FORMAT_ATTR(retprobe, "config:0"); > #endif > > #ifdef CONFIG_KPROBE_EVENTS > +/* max_active is specified by log2, to allow larger values if needed */ > +PMU_FORMAT_ATTR(max_active_log2, "config:59-63"); > + > static struct attribute *kprobe_attrs[] = { > + &format_attr_max_active_log2.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_log2; > > 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_log2 = event->attr.config >> PERF_KPROBE_MAX_ACTIVE_SHIFT; > + err = perf_kprobe_init(event, is_retprobe, 1U << max_active_log2); > 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 > -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
