Re: [PATCH v6 perf, bpf-next 1/7] perf, bpf: Introduce PERF_RECORD_KSYMBOL
From: Song Liu
Date: Thu Jan 10 2019 - 13:41:34 EST
> On Jan 10, 2019, at 10:24 AM, Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> 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.
>
> - Arnaldo
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
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.
Thanks,
Song
>> Signed-off-by: Song Liu <songliubraving@xxxxxx>
>> ---
>> 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