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Date: Thu, 10 Jan 2019 15:55:24 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Song Liu <songliubraving@...com>
Cc: lkml <linux-kernel@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"peterz@...radead.org" <peterz@...radead.org>,
"ast@...nel.org" <ast@...nel.org>,
"daniel@...earbox.net" <daniel@...earbox.net>,
Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH v6 perf, bpf-next 1/7] perf, bpf: Introduce
PERF_RECORD_KSYMBOL
Em Thu, Jan 10, 2019 at 06:40:37PM +0000, Song Liu escreveu:
>
>
> > On Jan 10, 2019, at 10:24 AM, Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
> >
> > Em Wed, Jan 09, 2019 at 11:21:05AM -0800, Song Liu escreveu:
> >> For better performance analysis of dynamically JITed and loaded kernel
> >> functions, such as BPF programs, this patch introduces
> >> PERF_RECORD_KSYMBOL, a new perf_event_type that exposes kernel symbol
> >> register/unregister information to user space.
> >>
> >> The following data structure is used for PERF_RECORD_KSYMBOL.
> >>
> >> /*
> >> * struct {
> >> * struct perf_event_header header;
> >> * u64 addr;
> >> * u32 len;
> >> * u16 ksym_type;
> >> * u16 flags;
> >> * char name[];
> >> * struct sample_id sample_id;
> >> * };
> >> */
> >
> > So, I couldn't find where this gets used, the intention here is just to
> > add the interfaces and afterwards is that you will wire this up? I would
> > like to test the whole shebang to see it working.
>
> I guess you meant PERF_RECORD_BPF_EVENT not being used?
>
> PERF_RECORD_KSYMBOL is used by BPF in 3/7 and 5/7. I tested
Oops, I didn't look at 3/7, just read its cset summary line and as it
says:
Subject: [PATCH v6 perf, bpf-next 3/7] perf, bpf: introduce PERF_RECORD_BPF_EVENT
I didn't thought it was related, perhaps break it down into one that
states that it is wiring up PERF_RECORD_KSYMBOL, and at that point we
could just test it, getting the notifications for new kallsyms related
to BPF?
> PERF_RECORD_BPF_EVENT with dump_trace. As we separate RECORD_KSYMBOL from
> RECORD_BPF_EVENT, user space won't use BPF_EVENT until annotation support.
Right, so why not just introduce PERF_RECORD_KSYMBOL, make it be used by
tooling, etc, then move on to PERF_RECORD_BPF_EVENT?
- Arnaldo
> Thanks,
> Song
>
> >> Signed-off-by: Song Liu <songliubraving@...com>
> >> ---
> >> include/linux/perf_event.h | 13 +++++
> >> include/uapi/linux/perf_event.h | 26 ++++++++-
> >> kernel/events/core.c | 98 ++++++++++++++++++++++++++++++++-
> >> 3 files changed, 135 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> >> index 1d5c551a5add..6b5f08db5ef3 100644
> >> --- a/include/linux/perf_event.h
> >> +++ b/include/linux/perf_event.h
> >> @@ -1113,6 +1113,13 @@ static inline void perf_event_task_sched_out(struct task_struct *prev,
> >> }
> >>
> >> extern void perf_event_mmap(struct vm_area_struct *vma);
> >> +
> >> +/* callback function to generate ksymbol name */
> >> +typedef int (perf_ksymbol_get_name_f)(char *name, int name_len, void *data);
> >> +extern void perf_event_ksymbol(u16 ksym_type, u64 addr, u32 len,
> >> + bool unregister,
> >> + perf_ksymbol_get_name_f get_name, void *data);
> >> +
> >> extern struct perf_guest_info_callbacks *perf_guest_cbs;
> >> extern int perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *callbacks);
> >> extern int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *callbacks);
> >> @@ -1333,6 +1340,12 @@ static inline int perf_unregister_guest_info_callbacks
> >> (struct perf_guest_info_callbacks *callbacks) { return 0; }
> >>
> >> static inline void perf_event_mmap(struct vm_area_struct *vma) { }
> >> +
> >> +typedef int (perf_ksymbol_get_name_f)(char *name, int name_len, void *data);
> >> +static inline void perf_event_ksymbol(u16 ksym_type, u64 addr, u32 len,
> >> + bool unregister,
> >> + perf_ksymbol_get_name_f get_name,
> >> + void *data) { }
> >> static inline void perf_event_exec(void) { }
> >> static inline void perf_event_comm(struct task_struct *tsk, bool exec) { }
> >> static inline void perf_event_namespaces(struct task_struct *tsk) { }
> >> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> >> index 9de8780ac8d9..68c4da0227c5 100644
> >> --- a/include/uapi/linux/perf_event.h
> >> +++ b/include/uapi/linux/perf_event.h
> >> @@ -372,7 +372,8 @@ struct perf_event_attr {
> >> context_switch : 1, /* context switch data */
> >> write_backward : 1, /* Write ring buffer from end to beginning */
> >> namespaces : 1, /* include namespaces data */
> >> - __reserved_1 : 35;
> >> + ksymbol : 1, /* include ksymbol events */
> >> + __reserved_1 : 34;
> >>
> >> union {
> >> __u32 wakeup_events; /* wakeup every n events */
> >> @@ -965,9 +966,32 @@ enum perf_event_type {
> >> */
> >> PERF_RECORD_NAMESPACES = 16,
> >>
> >> + /*
> >> + * Record ksymbol register/unregister events:
> >> + *
> >> + * struct {
> >> + * struct perf_event_header header;
> >> + * u64 addr;
> >> + * u32 len;
> >> + * u16 ksym_type;
> >> + * u16 flags;
> >> + * char name[];
> >> + * struct sample_id sample_id;
> >> + * };
> >> + */
> >> + PERF_RECORD_KSYMBOL = 17,
> >> +
> >> PERF_RECORD_MAX, /* non-ABI */
> >> };
> >>
> >> +enum perf_record_ksymbol_type {
> >> + PERF_RECORD_KSYMBOL_TYPE_UNKNOWN = 0,
> >> + PERF_RECORD_KSYMBOL_TYPE_BPF = 1,
> >> + PERF_RECORD_KSYMBOL_TYPE_MAX /* non-ABI */
> >> +};
> >> +
> >> +#define PERF_RECORD_KSYMBOL_FLAGS_UNREGISTER (1 << 0)
> >> +
> >> #define PERF_MAX_STACK_DEPTH 127
> >> #define PERF_MAX_CONTEXTS_PER_STACK 8
> >>
> >> diff --git a/kernel/events/core.c b/kernel/events/core.c
> >> index 3cd13a30f732..ef27f2776999 100644
> >> --- a/kernel/events/core.c
> >> +++ b/kernel/events/core.c
> >> @@ -385,6 +385,7 @@ static atomic_t nr_namespaces_events __read_mostly;
> >> static atomic_t nr_task_events __read_mostly;
> >> static atomic_t nr_freq_events __read_mostly;
> >> static atomic_t nr_switch_events __read_mostly;
> >> +static atomic_t nr_ksymbol_events __read_mostly;
> >>
> >> static LIST_HEAD(pmus);
> >> static DEFINE_MUTEX(pmus_lock);
> >> @@ -4235,7 +4236,7 @@ static bool is_sb_event(struct perf_event *event)
> >>
> >> if (attr->mmap || attr->mmap_data || attr->mmap2 ||
> >> attr->comm || attr->comm_exec ||
> >> - attr->task ||
> >> + attr->task || attr->ksymbol ||
> >> attr->context_switch)
> >> return true;
> >> return false;
> >> @@ -4305,6 +4306,8 @@ static void unaccount_event(struct perf_event *event)
> >> dec = true;
> >> if (has_branch_stack(event))
> >> dec = true;
> >> + if (event->attr.ksymbol)
> >> + atomic_dec(&nr_ksymbol_events);
> >>
> >> if (dec) {
> >> if (!atomic_add_unless(&perf_sched_count, -1, 1))
> >> @@ -7650,6 +7653,97 @@ static void perf_log_throttle(struct perf_event *event, int enable)
> >> perf_output_end(&handle);
> >> }
> >>
> >> +/*
> >> + * ksymbol register/unregister tracking
> >> + */
> >> +
> >> +struct perf_ksymbol_event {
> >> + const char *name;
> >> + int name_len;
> >> + struct {
> >> + struct perf_event_header header;
> >> + u64 addr;
> >> + u32 len;
> >> + u16 ksym_type;
> >> + u16 flags;
> >> + } event_id;
> >> +};
> >> +
> >> +static int perf_event_ksymbol_match(struct perf_event *event)
> >> +{
> >> + return event->attr.ksymbol;
> >> +}
> >> +
> >> +static void perf_event_ksymbol_output(struct perf_event *event, void *data)
> >> +{
> >> + struct perf_ksymbol_event *ksymbol_event = data;
> >> + struct perf_output_handle handle;
> >> + struct perf_sample_data sample;
> >> + int ret;
> >> +
> >> + if (!perf_event_ksymbol_match(event))
> >> + return;
> >> +
> >> + perf_event_header__init_id(&ksymbol_event->event_id.header,
> >> + &sample, event);
> >> + ret = perf_output_begin(&handle, event,
> >> + ksymbol_event->event_id.header.size);
> >> + if (ret)
> >> + return;
> >> +
> >> + perf_output_put(&handle, ksymbol_event->event_id);
> >> + __output_copy(&handle, ksymbol_event->name, ksymbol_event->name_len);
> >> + perf_event__output_id_sample(event, &handle, &sample);
> >> +
> >> + perf_output_end(&handle);
> >> +}
> >> +
> >> +void perf_event_ksymbol(u16 ksym_type, u64 addr, u32 len, bool unregister,
> >> + perf_ksymbol_get_name_f get_name, void *data)
> >> +{
> >> + struct perf_ksymbol_event ksymbol_event;
> >> + char name[KSYM_NAME_LEN];
> >> + u16 flags = 0;
> >> + int name_len;
> >> +
> >> + if (!atomic_read(&nr_ksymbol_events))
> >> + return;
> >> +
> >> + if (ksym_type >= PERF_RECORD_KSYMBOL_TYPE_MAX ||
> >> + ksym_type == PERF_RECORD_KSYMBOL_TYPE_UNKNOWN)
> >> + goto err;
> >> +
> >> + get_name(name, KSYM_NAME_LEN, data);
> >> + name_len = strlen(name) + 1;
> >> + while (!IS_ALIGNED(name_len, sizeof(u64)))
> >> + name[name_len++] = '\0';
> >> + BUILD_BUG_ON(KSYM_NAME_LEN % sizeof(u64));
> >> +
> >> + if (unregister)
> >> + flags |= PERF_RECORD_KSYMBOL_FLAGS_UNREGISTER;
> >> +
> >> + ksymbol_event = (struct perf_ksymbol_event){
> >> + .name = name,
> >> + .name_len = name_len,
> >> + .event_id = {
> >> + .header = {
> >> + .type = PERF_RECORD_KSYMBOL,
> >> + .size = sizeof(ksymbol_event.event_id) +
> >> + name_len,
> >> + },
> >> + .addr = addr,
> >> + .len = len,
> >> + .ksym_type = ksym_type,
> >> + .flags = flags,
> >> + },
> >> + };
> >> +
> >> + perf_iterate_sb(perf_event_ksymbol_output, &ksymbol_event, NULL);
> >> + return;
> >> +err:
> >> + WARN_ONCE(1, "%s: Invalid KSYMBOL type 0x%x\n", __func__, ksym_type);
> >> +}
> >> +
> >> void perf_event_itrace_started(struct perf_event *event)
> >> {
> >> event->attach_state |= PERF_ATTACH_ITRACE;
> >> @@ -9900,6 +9994,8 @@ static void account_event(struct perf_event *event)
> >> inc = true;
> >> if (is_cgroup_event(event))
> >> inc = true;
> >> + if (event->attr.ksymbol)
> >> + atomic_inc(&nr_ksymbol_events);
> >>
> >> if (inc) {
> >> /*
> >> --
> >> 2.17.1
> >
> > --
> >
> > - Arnaldo
--
- Arnaldo
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