[PATCH net-next 0/3] bpf_perf_event_output helper

[PATCH net-next 0/3] bpf_perf_event_output helper

[Alexei Starovoitov]

Over the last year there were multiple attempts to let eBPF programs
output data into perf events by He Kuang and Wangnan.
The last one was:
https://lkml.org/lkml/2015/7/20/736
It was almost perfect with exception that all bpf programs would sent
data into one global perf_event.
This patch set takes different approach by letting user space
open independent PERF_COUNT_SW_BPF_OUTPUT events, so that program
output won't collide.

Wangnan is working on corresponding perf patches.

Alexei Starovoitov (3):
  perf: pad raw data samples automatically
  bpf: introduce bpf_perf_event_output() helper
  samples: bpf: add bpf_perf_event_output example

 include/uapi/linux/bpf.h        |   11 +++
 include/uapi/linux/perf_event.h |    1 +
 kernel/bpf/arraymap.c           |    2 +
 kernel/bpf/verifier.c           |    3 +-
 kernel/events/core.c            |   15 ++-
 kernel/trace/bpf_trace.c        |   46 +++++++++
 samples/bpf/Makefile            |    7 ++
 samples/bpf/bpf_helpers.h       |    2 +
 samples/bpf/trace_output_kern.c |   31 +++++++
 samples/bpf/trace_output_user.c |  196 +++++++++++++++++++++++++++++++++++++++
 10 files changed, 308 insertions(+), 6 deletions(-)
 create mode 100644 samples/bpf/trace_output_kern.c
 create mode 100644 samples/bpf/trace_output_user.c

-- 
1.7.9.5

[PATCH net-next 1/3] perf: pad raw data samples automatically

[Alexei Starovoitov]

Instead of WARN_ON in perf_event_output() on unpaded raw samples,
pad them automatically.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 kernel/events/core.c |   15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index b11756f9b6dc..64754bfecd70 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5286,9 +5286,15 @@ void perf_output_sample(struct perf_output_handle *handle,
 
 	if (sample_type & PERF_SAMPLE_RAW) {
 		if (data->raw) {
-			perf_output_put(handle, data->raw->size);
-			__output_copy(handle, data->raw->data,
-					   data->raw->size);
+			u32 raw_size = data->raw->size;
+			u32 real_size = round_up(raw_size + sizeof(u32),
+						 sizeof(u64)) - sizeof(u32);
+			u64 zero = 0;
+
+			perf_output_put(handle, real_size);
+			__output_copy(handle, data->raw->data, raw_size);
+			if (real_size - raw_size)
+				__output_copy(handle, &zero, real_size - raw_size);
 		} else {
 			struct {
 				u32	size;
@@ -5420,8 +5426,7 @@ void perf_prepare_sample(struct perf_event_header *header,
 		else
 			size += sizeof(u32);
 
-		WARN_ON_ONCE(size & (sizeof(u64)-1));
-		header->size += size;
+		header->size += round_up(size, sizeof(u64));
 	}
 
 	if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
-- 
1.7.9.5

[PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Alexei Starovoitov]

This helper is used to send raw data from eBPF program into
special PERF_TYPE_SOFTWARE/PERF_COUNT_SW_BPF_OUTPUT perf_event.
User space needs to perf_event_open() it (either for one or all cpus) and
store FD into perf_event_array (similar to bpf_perf_event_read() helper)
before eBPF program can send data into it.

Today the programs triggered by kprobe collect the data and either store
it into the maps or print it via bpf_trace_printk() where latter is the debug
facility and not suitable to stream the data. This new helper replaces
such bpf_trace_printk() usage and allows programs to have dedicated
channel into user space for post-processing of the raw data collected.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 include/uapi/linux/bpf.h        |   11 ++++++++++
 include/uapi/linux/perf_event.h |    1 +
 kernel/bpf/arraymap.c           |    2 ++
 kernel/bpf/verifier.c           |    3 ++-
 kernel/trace/bpf_trace.c        |   46 +++++++++++++++++++++++++++++++++++++++
 5 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 564f1f091991..2e032426cfb7 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -287,6 +287,17 @@ enum bpf_func_id {
 	 * Return: realm if != 0
 	 */
 	BPF_FUNC_get_route_realm,
+
+	/**
+	 * bpf_perf_event_output(ctx, map, index, data, size) - output perf raw sample
+	 * @ctx: struct pt_regs*
+	 * @map: pointer to perf_event_array map
+	 * @index: index of event in the map
+	 * @data: data on stack to be output as raw data
+	 * @size: size of data
+	 * Return: 0 on success
+	 */
+	BPF_FUNC_perf_event_output,
 	__BPF_FUNC_MAX_ID,
 };
 
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 2881145cda86..d3c417615361 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -110,6 +110,7 @@ enum perf_sw_ids {
 	PERF_COUNT_SW_ALIGNMENT_FAULTS		= 7,
 	PERF_COUNT_SW_EMULATION_FAULTS		= 8,
 	PERF_COUNT_SW_DUMMY			= 9,
+	PERF_COUNT_SW_BPF_OUTPUT		= 10,
 
 	PERF_COUNT_SW_MAX,			/* non-ABI */
 };
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index f2d9e698c753..e3cfe46b074f 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -295,6 +295,8 @@ static void *perf_event_fd_array_get_ptr(struct bpf_map *map, int fd)
 		return (void *)attr;
 
 	if (attr->type != PERF_TYPE_RAW &&
+	    !(attr->type == PERF_TYPE_SOFTWARE &&
+	      attr->config == PERF_COUNT_SW_BPF_OUTPUT) &&
 	    attr->type != PERF_TYPE_HARDWARE) {
 		perf_event_release_kernel(event);
 		return ERR_PTR(-EINVAL);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1d6b97be79e1..b56cf51f8d42 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -245,6 +245,7 @@ static const struct {
 } func_limit[] = {
 	{BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call},
 	{BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read},
+	{BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_output},
 };
 
 static void print_verifier_state(struct verifier_env *env)
@@ -910,7 +911,7 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id)
 		 * don't allow any other map type to be passed into
 		 * the special func;
 		 */
-		if (bool_map != bool_func)
+		if (bool_func && bool_map != bool_func)
 			return -EINVAL;
 	}
 
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 0fe96c7c8803..47febbe7998e 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -215,6 +215,50 @@ const struct bpf_func_proto bpf_perf_event_read_proto = {
 	.arg2_type	= ARG_ANYTHING,
 };
 
+static u64 bpf_perf_event_output(u64 r1, u64 r2, u64 index, u64 r4, u64 size)
+{
+	struct pt_regs *regs = (struct pt_regs *) (long) r1;
+	struct bpf_map *map = (struct bpf_map *) (long) r2;
+	struct bpf_array *array = container_of(map, struct bpf_array, map);
+	void *data = (void *) (long) r4;
+	struct perf_sample_data sample_data;
+	struct perf_event *event;
+	struct perf_raw_record raw = {
+		.size = size,
+		.data = data,
+	};
+
+	if (unlikely(index >= array->map.max_entries))
+		return -E2BIG;
+
+	event = (struct perf_event *)array->ptrs[index];
+	if (unlikely(!event))
+		return -ENOENT;
+
+	if (unlikely(event->attr.type != PERF_TYPE_SOFTWARE ||
+		     event->attr.config != PERF_COUNT_SW_BPF_OUTPUT))
+		return -EINVAL;
+
+	if (unlikely(event->oncpu != smp_processor_id()))
+		return -EOPNOTSUPP;
+
+	perf_sample_data_init(&sample_data, 0, 0);
+	sample_data.raw = &raw;
+	perf_event_output(event, &sample_data, regs);
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_perf_event_output_proto = {
+	.func		= bpf_perf_event_output,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_CONST_MAP_PTR,
+	.arg3_type	= ARG_ANYTHING,
+	.arg4_type	= ARG_PTR_TO_STACK,
+	.arg5_type	= ARG_CONST_STACK_SIZE,
+};
+
 static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
 {
 	switch (func_id) {
@@ -242,6 +286,8 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
 		return &bpf_get_smp_processor_id_proto;
 	case BPF_FUNC_perf_event_read:
 		return &bpf_perf_event_read_proto;
+	case BPF_FUNC_perf_event_output:
+		return &bpf_perf_event_output_proto;
 	default:
 		return NULL;
 	}
-- 
1.7.9.5

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[He Kuang]

hi, Alexei

I've tested the sample in next patch and it works well. I think more work on
the perf side needs to be done for parsing PERF_COUNT_SW_BPF_OUTPUT event type,
are you working on that?

Thank you.

On 2015/10/21 11:02, Alexei Starovoitov wrote:
> This helper is used to send raw data from eBPF program into
> special PERF_TYPE_SOFTWARE/PERF_COUNT_SW_BPF_OUTPUT perf_event.
> User space needs to perf_event_open() it (either for one or all cpus) and
> store FD into perf_event_array (similar to bpf_perf_event_read() helper)
> before eBPF program can send data into it.
>
> Today the programs triggered by kprobe collect the data and either store
> it into the maps or print it via bpf_trace_printk() where latter is the debug
> facility and not suitable to stream the data. This new helper replaces
> such bpf_trace_printk() usage and allows programs to have dedicated
> channel into user space for post-processing of the raw data collected.
>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> ---
>   include/uapi/linux/bpf.h        |   11 ++++++++++
>   include/uapi/linux/perf_event.h |    1 +
>   kernel/bpf/arraymap.c           |    2 ++
>   kernel/bpf/verifier.c           |    3 ++-
>   kernel/trace/bpf_trace.c        |   46 +++++++++++++++++++++++++++++++++++++++
>   5 files changed, 62 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 564f1f091991..2e032426cfb7 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -287,6 +287,17 @@ enum bpf_func_id {
>   	 * Return: realm if != 0
>   	 */
>   	BPF_FUNC_get_route_realm,
> +
> +	/**
> +	 * bpf_perf_event_output(ctx, map, index, data, size) - output perf raw sample
> +	 * @ctx: struct pt_regs*
> +	 * @map: pointer to perf_event_array map
> +	 * @index: index of event in the map
> +	 * @data: data on stack to be output as raw data
> +	 * @size: size of data
> +	 * Return: 0 on success
> +	 */
> +	BPF_FUNC_perf_event_output,
>   	__BPF_FUNC_MAX_ID,
>   };
>
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index 2881145cda86..d3c417615361 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -110,6 +110,7 @@ enum perf_sw_ids {
>   	PERF_COUNT_SW_ALIGNMENT_FAULTS		= 7,
>   	PERF_COUNT_SW_EMULATION_FAULTS		= 8,
>   	PERF_COUNT_SW_DUMMY			= 9,
> +	PERF_COUNT_SW_BPF_OUTPUT		= 10,
>
>   	PERF_COUNT_SW_MAX,			/* non-ABI */
>   };
> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> index f2d9e698c753..e3cfe46b074f 100644
> --- a/kernel/bpf/arraymap.c
> +++ b/kernel/bpf/arraymap.c
> @@ -295,6 +295,8 @@ static void *perf_event_fd_array_get_ptr(struct bpf_map *map, int fd)
>   		return (void *)attr;
>
>   	if (attr->type != PERF_TYPE_RAW &&
> +	    !(attr->type == PERF_TYPE_SOFTWARE &&
> +	      attr->config == PERF_COUNT_SW_BPF_OUTPUT) &&
>   	    attr->type != PERF_TYPE_HARDWARE) {
>   		perf_event_release_kernel(event);
>   		return ERR_PTR(-EINVAL);
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 1d6b97be79e1..b56cf51f8d42 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -245,6 +245,7 @@ static const struct {
>   } func_limit[] = {
>   	{BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call},
>   	{BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read},
> +	{BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_output},
>   };
>
>   static void print_verifier_state(struct verifier_env *env)
> @@ -910,7 +911,7 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id)
>   		 * don't allow any other map type to be passed into
>   		 * the special func;
>   		 */
> -		if (bool_map != bool_func)
> +		if (bool_func && bool_map != bool_func)
>   			return -EINVAL;
>   	}
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 0fe96c7c8803..47febbe7998e 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -215,6 +215,50 @@ const struct bpf_func_proto bpf_perf_event_read_proto = {
>   	.arg2_type	= ARG_ANYTHING,
>   };
>
> +static u64 bpf_perf_event_output(u64 r1, u64 r2, u64 index, u64 r4, u64 size)
> +{
> +	struct pt_regs *regs = (struct pt_regs *) (long) r1;
> +	struct bpf_map *map = (struct bpf_map *) (long) r2;
> +	struct bpf_array *array = container_of(map, struct bpf_array, map);
> +	void *data = (void *) (long) r4;
> +	struct perf_sample_data sample_data;
> +	struct perf_event *event;
> +	struct perf_raw_record raw = {
> +		.size = size,
> +		.data = data,
> +	};
> +
> +	if (unlikely(index >= array->map.max_entries))
> +		return -E2BIG;
> +
> +	event = (struct perf_event *)array->ptrs[index];
> +	if (unlikely(!event))
> +		return -ENOENT;
> +
> +	if (unlikely(event->attr.type != PERF_TYPE_SOFTWARE ||
> +		     event->attr.config != PERF_COUNT_SW_BPF_OUTPUT))
> +		return -EINVAL;
> +
> +	if (unlikely(event->oncpu != smp_processor_id()))
> +		return -EOPNOTSUPP;
> +
> +	perf_sample_data_init(&sample_data, 0, 0);
> +	sample_data.raw = &raw;
> +	perf_event_output(event, &sample_data, regs);
> +	return 0;
> +}
> +
> +static const struct bpf_func_proto bpf_perf_event_output_proto = {
> +	.func		= bpf_perf_event_output,
> +	.gpl_only	= false,
> +	.ret_type	= RET_INTEGER,
> +	.arg1_type	= ARG_PTR_TO_CTX,
> +	.arg2_type	= ARG_CONST_MAP_PTR,
> +	.arg3_type	= ARG_ANYTHING,
> +	.arg4_type	= ARG_PTR_TO_STACK,
> +	.arg5_type	= ARG_CONST_STACK_SIZE,
> +};
> +
>   static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
>   {
>   	switch (func_id) {
> @@ -242,6 +286,8 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
>   		return &bpf_get_smp_processor_id_proto;
>   	case BPF_FUNC_perf_event_read:
>   		return &bpf_perf_event_read_proto;
> +	case BPF_FUNC_perf_event_output:
> +		return &bpf_perf_event_output_proto;
>   	default:
>   		return NULL;
>   	}
>

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Wangnan (F)]

On 2015/10/21 18:01, He Kuang wrote:
> hi, Alexei
>
> I've tested the sample in next patch and it works well. I think more 
> work on
> the perf side needs to be done for parsing PERF_COUNT_SW_BPF_OUTPUT 
> event type,
> are you working on that?
>
> Thank you.

We need to add something into parse-event.y/l to let it know the new 
software event.
We can do this simple task. However, as I gussed before, perf is unable 
to print
this new event so there is some work need to be done to let 'perf 
report' and
'perf script' know it.

One thing I can still remember is finding a way to inject format 
information through
those output so 'perf script' and 'perf data convert --to-ctf' can 
decode the raw data
without extra work. Can you remember that we have discussed a solution 
which connects
debuginfo and output raw data using a builtin function in LLVM/clang? We 
already have
clang/LLVM patch on it, but on perf side I haven't do start working on 
it. I think we can
make perf output raw data hexadamically at first.

I'll do the above work and put related patch at the end of my eBPF 
patchset because
they shouldn't be merged until this patchset upstreamed.

Thank you.

>
> On 2015/10/21 11:02, Alexei Starovoitov wrote:
>> This helper is used to send raw data from eBPF program into
>> special PERF_TYPE_SOFTWARE/PERF_COUNT_SW_BPF_OUTPUT perf_event.
>> User space needs to perf_event_open() it (either for one or all cpus) 
>> and
>> store FD into perf_event_array (similar to bpf_perf_event_read() helper)
>> before eBPF program can send data into it.
>>
>> Today the programs triggered by kprobe collect the data and either store
>> it into the maps or print it via bpf_trace_printk() where latter is 
>> the debug
>> facility and not suitable to stream the data. This new helper replaces
>> such bpf_trace_printk() usage and allows programs to have dedicated
>> channel into user space for post-processing of the raw data collected.
>>
>> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
>> ---
>>   include/uapi/linux/bpf.h        |   11 ++++++++++
>>   include/uapi/linux/perf_event.h |    1 +
>>   kernel/bpf/arraymap.c           |    2 ++
>>   kernel/bpf/verifier.c           |    3 ++-
>>   kernel/trace/bpf_trace.c        |   46 
>> +++++++++++++++++++++++++++++++++++++++
>>   5 files changed, 62 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index 564f1f091991..2e032426cfb7 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
>> @@ -287,6 +287,17 @@ enum bpf_func_id {
>>        * Return: realm if != 0
>>        */
>>       BPF_FUNC_get_route_realm,
>> +
>> +    /**
>> +     * bpf_perf_event_output(ctx, map, index, data, size) - output 
>> perf raw sample
>> +     * @ctx: struct pt_regs*
>> +     * @map: pointer to perf_event_array map
>> +     * @index: index of event in the map
>> +     * @data: data on stack to be output as raw data
>> +     * @size: size of data
>> +     * Return: 0 on success
>> +     */
>> +    BPF_FUNC_perf_event_output,
>>       __BPF_FUNC_MAX_ID,
>>   };
>>
>> diff --git a/include/uapi/linux/perf_event.h 
>> b/include/uapi/linux/perf_event.h
>> index 2881145cda86..d3c417615361 100644
>> --- a/include/uapi/linux/perf_event.h
>> +++ b/include/uapi/linux/perf_event.h
>> @@ -110,6 +110,7 @@ enum perf_sw_ids {
>>       PERF_COUNT_SW_ALIGNMENT_FAULTS        = 7,
>>       PERF_COUNT_SW_EMULATION_FAULTS        = 8,
>>       PERF_COUNT_SW_DUMMY            = 9,
>> +    PERF_COUNT_SW_BPF_OUTPUT        = 10,
>>
>>       PERF_COUNT_SW_MAX,            /* non-ABI */
>>   };
>> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
>> index f2d9e698c753..e3cfe46b074f 100644
>> --- a/kernel/bpf/arraymap.c
>> +++ b/kernel/bpf/arraymap.c
>> @@ -295,6 +295,8 @@ static void *perf_event_fd_array_get_ptr(struct 
>> bpf_map *map, int fd)
>>           return (void *)attr;
>>
>>       if (attr->type != PERF_TYPE_RAW &&
>> +        !(attr->type == PERF_TYPE_SOFTWARE &&
>> +          attr->config == PERF_COUNT_SW_BPF_OUTPUT) &&
>>           attr->type != PERF_TYPE_HARDWARE) {
>>           perf_event_release_kernel(event);
>>           return ERR_PTR(-EINVAL);
>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
>> index 1d6b97be79e1..b56cf51f8d42 100644
>> --- a/kernel/bpf/verifier.c
>> +++ b/kernel/bpf/verifier.c
>> @@ -245,6 +245,7 @@ static const struct {
>>   } func_limit[] = {
>>       {BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call},
>>       {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read},
>> +    {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_output},
>>   };
>>
>>   static void print_verifier_state(struct verifier_env *env)
>> @@ -910,7 +911,7 @@ static int check_map_func_compatibility(struct 
>> bpf_map *map, int func_id)
>>            * don't allow any other map type to be passed into
>>            * the special func;
>>            */
>> -        if (bool_map != bool_func)
>> +        if (bool_func && bool_map != bool_func)
>>               return -EINVAL;
>>       }
>>
>> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
>> index 0fe96c7c8803..47febbe7998e 100644
>> --- a/kernel/trace/bpf_trace.c
>> +++ b/kernel/trace/bpf_trace.c
>> @@ -215,6 +215,50 @@ const struct bpf_func_proto 
>> bpf_perf_event_read_proto = {
>>       .arg2_type    = ARG_ANYTHING,
>>   };
>>
>> +static u64 bpf_perf_event_output(u64 r1, u64 r2, u64 index, u64 r4, 
>> u64 size)
>> +{
>> +    struct pt_regs *regs = (struct pt_regs *) (long) r1;
>> +    struct bpf_map *map = (struct bpf_map *) (long) r2;
>> +    struct bpf_array *array = container_of(map, struct bpf_array, map);
>> +    void *data = (void *) (long) r4;
>> +    struct perf_sample_data sample_data;
>> +    struct perf_event *event;
>> +    struct perf_raw_record raw = {
>> +        .size = size,
>> +        .data = data,
>> +    };
>> +
>> +    if (unlikely(index >= array->map.max_entries))
>> +        return -E2BIG;
>> +
>> +    event = (struct perf_event *)array->ptrs[index];
>> +    if (unlikely(!event))
>> +        return -ENOENT;
>> +
>> +    if (unlikely(event->attr.type != PERF_TYPE_SOFTWARE ||
>> +             event->attr.config != PERF_COUNT_SW_BPF_OUTPUT))
>> +        return -EINVAL;
>> +
>> +    if (unlikely(event->oncpu != smp_processor_id()))
>> +        return -EOPNOTSUPP;
>> +
>> +    perf_sample_data_init(&sample_data, 0, 0);
>> +    sample_data.raw = &raw;
>> +    perf_event_output(event, &sample_data, regs);
>> +    return 0;
>> +}
>> +
>> +static const struct bpf_func_proto bpf_perf_event_output_proto = {
>> +    .func        = bpf_perf_event_output,
>> +    .gpl_only    = false,
>> +    .ret_type    = RET_INTEGER,
>> +    .arg1_type    = ARG_PTR_TO_CTX,
>> +    .arg2_type    = ARG_CONST_MAP_PTR,
>> +    .arg3_type    = ARG_ANYTHING,
>> +    .arg4_type    = ARG_PTR_TO_STACK,
>> +    .arg5_type    = ARG_CONST_STACK_SIZE,
>> +};
>> +
>>   static const struct bpf_func_proto *kprobe_prog_func_proto(enum 
>> bpf_func_id func_id)
>>   {
>>       switch (func_id) {
>> @@ -242,6 +286,8 @@ static const struct bpf_func_proto 
>> *kprobe_prog_func_proto(enum bpf_func_id func
>>           return &bpf_get_smp_processor_id_proto;
>>       case BPF_FUNC_perf_event_read:
>>           return &bpf_perf_event_read_proto;
>> +    case BPF_FUNC_perf_event_output:
>> +        return &bpf_perf_event_output_proto;
>>       default:
>>           return NULL;
>>       }
>>
>

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Alexei Starovoitov]

On 10/21/15 4:05 AM, Wangnan (F) wrote:
> I think we can
> make perf output raw data hexadamically at first.

that would be my suggestion as well.
print it as hex first and when llvm type info is available you can teach
perf to be smarter.
We're working on support for this feature in iovisor/bcc
without requiring extra llvm work, since we can generate
python classes on the fly from C code of bpf program.

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Peter Zijlstra]

On Tue, Oct 20, 2015 at 08:02:34PM -0700, Alexei Starovoitov wrote:
> This helper is used to send raw data from eBPF program into
> special PERF_TYPE_SOFTWARE/PERF_COUNT_SW_BPF_OUTPUT perf_event.
> User space needs to perf_event_open() it (either for one or all cpus) and
> store FD into perf_event_array (similar to bpf_perf_event_read() helper)
> before eBPF program can send data into it.
> 

> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index 2881145cda86..d3c417615361 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -110,6 +110,7 @@ enum perf_sw_ids {
>  	PERF_COUNT_SW_ALIGNMENT_FAULTS		= 7,
>  	PERF_COUNT_SW_EMULATION_FAULTS		= 8,
>  	PERF_COUNT_SW_DUMMY			= 9,
> +	PERF_COUNT_SW_BPF_OUTPUT		= 10,
>  
>  	PERF_COUNT_SW_MAX,			/* non-ABI */
>  };

Do you really need the new type? Can't you use DUMMY for this?

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Alexei Starovoitov]

On 10/21/15 5:06 AM, Peter Zijlstra wrote:
>>   	PERF_COUNT_SW_DUMMY			= 9,
>> >+	PERF_COUNT_SW_BPF_OUTPUT		= 10,
>> >
>> >  	PERF_COUNT_SW_MAX,			/* non-ABI */
>> >  };
> Do you really need the new type? Can't you use DUMMY for this?

It works fine with dummy, but user space code looked odd when
it perf_event_open-s dummy events and starts reading them.
So I thought either to add alias:
PERF_COUNT_SW_BPF_OUTPUT = PERF_COUNT_SW_DUMMY
or
add new number like I did above.
New number is cheap and I saw that dummy used for probing,
so went with new number to disambiguate.

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Peter Zijlstra]

On Wed, Oct 21, 2015 at 10:26:21AM -0700, Alexei Starovoitov wrote:
> On 10/21/15 5:06 AM, Peter Zijlstra wrote:
> >>  	PERF_COUNT_SW_DUMMY			= 9,
> >>>+	PERF_COUNT_SW_BPF_OUTPUT		= 10,
> >>>
> >>>  	PERF_COUNT_SW_MAX,			/* non-ABI */
> >>>  };
> >Do you really need the new type? Can't you use DUMMY for this?
> 
> It works fine with dummy, but user space code looked odd when
> it perf_event_open-s dummy events and starts reading them.
> So I thought either to add alias:
> PERF_COUNT_SW_BPF_OUTPUT = PERF_COUNT_SW_DUMMY
> or
> add new number like I did above.
> New number is cheap and I saw that dummy used for probing,
> so went with new number to disambiguate.

Ah, ok. It wasn't clear to me why you needed another number.

The SW numbers add some extra (unused) data size to the kernel as a
number of arrays are sized by them, but one more should not hurt (too)
much.

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Peter Zijlstra]

On Tue, Oct 20, 2015 at 08:02:34PM -0700, Alexei Starovoitov wrote:
> +++ b/kernel/trace/bpf_trace.c
> @@ -215,6 +215,50 @@ const struct bpf_func_proto bpf_perf_event_read_proto = {
>  	.arg2_type	= ARG_ANYTHING,
>  };
>  
> +static u64 bpf_perf_event_output(u64 r1, u64 r2, u64 index, u64 r4, u64 size)
> +{
> +	struct pt_regs *regs = (struct pt_regs *) (long) r1;
> +	struct bpf_map *map = (struct bpf_map *) (long) r2;
> +	struct bpf_array *array = container_of(map, struct bpf_array, map);
> +	void *data = (void *) (long) r4;
> +	struct perf_sample_data sample_data;
> +	struct perf_event *event;
> +	struct perf_raw_record raw = {
> +		.size = size,
> +		.data = data,
> +	};
> +
> +	if (unlikely(index >= array->map.max_entries))
> +		return -E2BIG;
> +
> +	event = (struct perf_event *)array->ptrs[index];
> +	if (unlikely(!event))
> +		return -ENOENT;
> +
> +	if (unlikely(event->attr.type != PERF_TYPE_SOFTWARE ||
> +		     event->attr.config != PERF_COUNT_SW_BPF_OUTPUT))
> +		return -EINVAL;
> +
> +	if (unlikely(event->oncpu != smp_processor_id()))
> +		return -EOPNOTSUPP;
> +
> +	perf_sample_data_init(&sample_data, 0, 0);
> +	sample_data.raw = &raw;
> +	perf_event_output(event, &sample_data, regs);
> +	return 0;
> +}

Note that this function also very much requires event to be local.

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Alexei Starovoitov]

On 10/22/15 6:59 AM, Peter Zijlstra wrote:
>> +	if (unlikely(event->oncpu != smp_processor_id()))
>> >+		return -EOPNOTSUPP;
>> >+
>> >+	perf_sample_data_init(&sample_data, 0, 0);
>> >+	sample_data.raw = &raw;
>> >+	perf_event_output(event, &sample_data, regs);
>> >+	return 0;
>> >+}
> Note that this function also very much requires event to be local.

correct. that's why there is a dynamic check above to prevent buggy
programs causing issues.

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Peter Zijlstra]

On Tue, Oct 20, 2015 at 08:02:34PM -0700, Alexei Starovoitov wrote:
> +static const struct bpf_func_proto bpf_perf_event_output_proto = {
> +	.func		= bpf_perf_event_output,
> +	.gpl_only	= false,

Oh ?

> +	.ret_type	= RET_INTEGER,
> +	.arg1_type	= ARG_PTR_TO_CTX,
> +	.arg2_type	= ARG_CONST_MAP_PTR,
> +	.arg3_type	= ARG_ANYTHING,
> +	.arg4_type	= ARG_PTR_TO_STACK,
> +	.arg5_type	= ARG_CONST_STACK_SIZE,
> +};

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Alexei Starovoitov]

On 10/23/15 7:39 AM, Peter Zijlstra wrote:
> On Tue, Oct 20, 2015 at 08:02:34PM -0700, Alexei Starovoitov wrote:
>> >+static const struct bpf_func_proto bpf_perf_event_output_proto = {
>> >+	.func		= bpf_perf_event_output,
>> >+	.gpl_only	= false,
> Oh ?

no particular reason. key helper bpf_probe_read() is gpl, so all
bpf for tracing progs have to be gpl.
If you feel strongly about it, I can change it.

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Peter Zijlstra]

On Fri, Oct 23, 2015 at 08:02:00AM -0700, Alexei Starovoitov wrote:
> On 10/23/15 7:39 AM, Peter Zijlstra wrote:
> >On Tue, Oct 20, 2015 at 08:02:34PM -0700, Alexei Starovoitov wrote:
> >>>+static const struct bpf_func_proto bpf_perf_event_output_proto = {
> >>>+	.func		= bpf_perf_event_output,
> >>>+	.gpl_only	= false,
> >Oh ?
> 
> no particular reason. key helper bpf_probe_read() is gpl, so all
> bpf for tracing progs have to be gpl.
> If you feel strongly about it, I can change it.

All the perf symbols are export GPL, so I suppose this should be true.

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Alexei Starovoitov]

On 10/23/15 9:42 AM, Peter Zijlstra wrote:
> On Fri, Oct 23, 2015 at 08:02:00AM -0700, Alexei Starovoitov wrote:
>> On 10/23/15 7:39 AM, Peter Zijlstra wrote:
>>> On Tue, Oct 20, 2015 at 08:02:34PM -0700, Alexei Starovoitov wrote:
>>>>> +static const struct bpf_func_proto bpf_perf_event_output_proto = {
>>>>> +	.func		= bpf_perf_event_output,
>>>>> +	.gpl_only	= false,
>>> Oh ?
>>
>> no particular reason. key helper bpf_probe_read() is gpl, so all
>> bpf for tracing progs have to be gpl.
>> If you feel strongly about it, I can change it.
>
> All the perf symbols are export GPL, so I suppose this should be true.

ok. will send a patch.

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Wangnan (F)]

On 2015/10/24 1:25, Alexei Starovoitov wrote:
> On 10/23/15 9:42 AM, Peter Zijlstra wrote:
>> On Fri, Oct 23, 2015 at 08:02:00AM -0700, Alexei Starovoitov wrote:
>>> On 10/23/15 7:39 AM, Peter Zijlstra wrote:
>>>> On Tue, Oct 20, 2015 at 08:02:34PM -0700, Alexei Starovoitov wrote:
>>>>>> +static const struct bpf_func_proto bpf_perf_event_output_proto = {
>>>>>> +    .func        = bpf_perf_event_output,
>>>>>> +    .gpl_only    = false,
>>>> Oh ?
>>>
>>> no particular reason. key helper bpf_probe_read() is gpl, so all
>>> bpf for tracing progs have to be gpl.
>>> If you feel strongly about it, I can change it.
>>
>> All the perf symbols are export GPL, so I suppose this should be true.
>
> ok. will send a patch.
>

Can we (or have we already) setup some rules for licensing? Which part
should be GPL? Who has the response to decide it?

Thank you.

Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output() helper

[Alexei Starovoitov]

On 10/25/15 6:46 PM, Wangnan (F) wrote:
> Can we (or have we already) setup some rules for licensing? Which part
> should be GPL? Who has the response to decide it?

in my mind the rules were set long ago. See my other email.

[PATCH net-next 3/3] samples: bpf: add bpf_perf_event_output example

[Alexei Starovoitov]

Performance test and example of bpf_perf_event_output().
kprobe is attached to sys_write() and trivial bpf program streams
pid+cookie into userspace via PERF_COUNT_SW_BPF_OUTPUT event.

Usage:
$ sudo ./bld_x64/samples/bpf/trace_output
recv 2968913 events per sec

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 samples/bpf/Makefile            |    7 ++
 samples/bpf/bpf_helpers.h       |    2 +
 samples/bpf/trace_output_kern.c |   31 +++++++
 samples/bpf/trace_output_user.c |  196 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 236 insertions(+)
 create mode 100644 samples/bpf/trace_output_kern.c
 create mode 100644 samples/bpf/trace_output_user.c

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 63e7d50e6a4f..b30514514e37 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -13,6 +13,7 @@ hostprogs-y += tracex3
 hostprogs-y += tracex4
 hostprogs-y += tracex5
 hostprogs-y += tracex6
+hostprogs-y += trace_output
 hostprogs-y += lathist
 
 test_verifier-objs := test_verifier.o libbpf.o
@@ -27,6 +28,7 @@ tracex3-objs := bpf_load.o libbpf.o tracex3_user.o
 tracex4-objs := bpf_load.o libbpf.o tracex4_user.o
 tracex5-objs := bpf_load.o libbpf.o tracex5_user.o
 tracex6-objs := bpf_load.o libbpf.o tracex6_user.o
+trace_output-objs := bpf_load.o libbpf.o trace_output_user.o
 lathist-objs := bpf_load.o libbpf.o lathist_user.o
 
 # Tell kbuild to always build the programs
@@ -40,6 +42,7 @@ always += tracex3_kern.o
 always += tracex4_kern.o
 always += tracex5_kern.o
 always += tracex6_kern.o
+always += trace_output_kern.o
 always += tcbpf1_kern.o
 always += lathist_kern.o
 
@@ -55,6 +58,7 @@ HOSTLOADLIBES_tracex3 += -lelf
 HOSTLOADLIBES_tracex4 += -lelf -lrt
 HOSTLOADLIBES_tracex5 += -lelf
 HOSTLOADLIBES_tracex6 += -lelf
+HOSTLOADLIBES_trace_output += -lelf -lrt
 HOSTLOADLIBES_lathist += -lelf
 
 # point this to your LLVM backend with bpf support
@@ -64,3 +68,6 @@ $(obj)/%.o: $(src)/%.c
 	clang $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS) \
 		-D__KERNEL__ -Wno-unused-value -Wno-pointer-sign \
 		-O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf -filetype=obj -o $@
+	clang $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS) \
+		-D__KERNEL__ -Wno-unused-value -Wno-pointer-sign \
+		-O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf -filetype=asm -o $@.s
diff --git a/samples/bpf/bpf_helpers.h b/samples/bpf/bpf_helpers.h
index 21aa1b44c30c..b35c21e0b43f 100644
--- a/samples/bpf/bpf_helpers.h
+++ b/samples/bpf/bpf_helpers.h
@@ -37,6 +37,8 @@ static int (*bpf_clone_redirect)(void *ctx, int ifindex, int flags) =
 	(void *) BPF_FUNC_clone_redirect;
 static int (*bpf_redirect)(int ifindex, int flags) =
 	(void *) BPF_FUNC_redirect;
+static int (*bpf_perf_event_output)(void *ctx, void *map, int index, void *data, int size) =
+	(void *) BPF_FUNC_perf_event_output;
 
 /* llvm builtin functions that eBPF C program may use to
  * emit BPF_LD_ABS and BPF_LD_IND instructions
diff --git a/samples/bpf/trace_output_kern.c b/samples/bpf/trace_output_kern.c
new file mode 100644
index 000000000000..8d8d1ec429eb
--- /dev/null
+++ b/samples/bpf/trace_output_kern.c
@@ -0,0 +1,31 @@
+#include <linux/ptrace.h>
+#include <linux/version.h>
+#include <uapi/linux/bpf.h>
+#include "bpf_helpers.h"
+
+struct bpf_map_def SEC("maps") my_map = {
+	.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
+	.key_size = sizeof(int),
+	.value_size = sizeof(u32),
+	.max_entries = 2,
+};
+
+SEC("kprobe/sys_write")
+int bpf_prog1(struct pt_regs *ctx)
+{
+	struct S {
+		u64 pid;
+		u64 cookie;
+	} data;
+
+	memset(&data, 0, sizeof(data));
+	data.pid = bpf_get_current_pid_tgid();
+	data.cookie = 0x12345678;
+
+	bpf_perf_event_output(ctx, &my_map, 0, &data, sizeof(data));
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
+u32 _version SEC("version") = LINUX_VERSION_CODE;
diff --git a/samples/bpf/trace_output_user.c b/samples/bpf/trace_output_user.c
new file mode 100644
index 000000000000..661a7d052f2c
--- /dev/null
+++ b/samples/bpf/trace_output_user.c
@@ -0,0 +1,196 @@
+/* This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <sys/ioctl.h>
+#include <linux/perf_event.h>
+#include <linux/bpf.h>
+#include <errno.h>
+#include <assert.h>
+#include <sys/syscall.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <time.h>
+#include <signal.h>
+#include "libbpf.h"
+#include "bpf_load.h"
+
+static int pmu_fd;
+
+int page_size;
+int page_cnt = 8;
+volatile struct perf_event_mmap_page *header;
+
+typedef void (*print_fn)(void *data, int size);
+
+static int perf_event_mmap(int fd)
+{
+	void *base;
+	int mmap_size;
+
+	page_size = getpagesize();
+	mmap_size = page_size * (page_cnt + 1);
+
+	base = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (base == MAP_FAILED) {
+		printf("mmap err\n");
+		return -1;
+	}
+
+	header = base;
+	return 0;
+}
+
+static int perf_event_poll(int fd)
+{
+	struct pollfd pfd = { .fd = fd, .events = POLLIN };
+
+	return poll(&pfd, 1, 1000);
+}
+
+struct perf_event_sample {
+	struct perf_event_header header;
+	__u32 size;
+	char data[];
+};
+
+void perf_event_read(print_fn fn)
+{
+	__u64 data_tail = header->data_tail;
+	__u64 data_head = header->data_head;
+	__u64 buffer_size = page_cnt * page_size;
+	void *base, *begin, *end;
+	char buf[256];
+
+	asm volatile("" ::: "memory"); /* in real code it should be smp_rmb() */
+	if (data_head == data_tail)
+		return;
+
+	base = ((char *)header) + page_size;
+
+	begin = base + data_tail % buffer_size;
+	end = base + data_head % buffer_size;
+
+	while (begin != end) {
+		struct perf_event_sample *e;
+
+		e = begin;
+		if (begin + e->header.size > base + buffer_size) {
+			long len = base + buffer_size - begin;
+
+			assert(len < e->header.size);
+			memcpy(buf, begin, len);
+			memcpy(buf + len, base, e->header.size - len);
+			e = (void *) buf;
+			begin = base + e->header.size - len;
+		} else if (begin + e->header.size == base + buffer_size) {
+			begin = base;
+		} else {
+			begin += e->header.size;
+		}
+
+		if (e->header.type == PERF_RECORD_SAMPLE) {
+			fn(e->data, e->size);
+		} else if (e->header.type == PERF_RECORD_LOST) {
+			struct {
+				struct perf_event_header header;
+				__u64 id;
+				__u64 lost;
+			} *lost = (void *) e;
+			printf("lost %lld events\n", lost->lost);
+		} else {
+			printf("unknown event type=%d size=%d\n",
+			       e->header.type, e->header.size);
+		}
+	}
+
+	__sync_synchronize(); /* smp_mb() */
+	header->data_tail = data_head;
+}
+
+static __u64 time_get_ns(void)
+{
+	struct timespec ts;
+
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	return ts.tv_sec * 1000000000ull + ts.tv_nsec;
+}
+
+static __u64 start_time;
+
+#define MAX_CNT 100000ll
+
+static void print_bpf_output(void *data, int size)
+{
+	static __u64 cnt;
+	struct {
+		__u64 pid;
+		__u64 cookie;
+	} *e = data;
+
+	if (e->cookie != 0x12345678) {
+		printf("BUG pid %llx cookie %llx sized %d\n",
+		       e->pid, e->cookie, size);
+		kill(0, SIGINT);
+	}
+
+	cnt++;
+
+	if (cnt == MAX_CNT) {
+		printf("recv %lld events per sec\n",
+		       MAX_CNT * 1000000000ll / (time_get_ns() - start_time));
+		kill(0, SIGINT);
+	}
+}
+
+static void test_bpf_perf_event(void)
+{
+	struct perf_event_attr attr = {
+		.sample_type = PERF_SAMPLE_RAW,
+		.type = PERF_TYPE_SOFTWARE,
+		.config = PERF_COUNT_SW_BPF_OUTPUT,
+	};
+	int key = 0;
+
+	pmu_fd = perf_event_open(&attr, -1/*pid*/, 0/*cpu*/, -1/*group_fd*/, 0);
+
+	assert(pmu_fd >= 0);
+	assert(bpf_update_elem(map_fd[0], &key, &pmu_fd, BPF_ANY) == 0);
+	ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0);
+}
+
+int main(int argc, char **argv)
+{
+	char filename[256];
+	FILE *f;
+
+	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+
+	if (load_bpf_file(filename)) {
+		printf("%s", bpf_log_buf);
+		return 1;
+	}
+
+	test_bpf_perf_event();
+
+	if (perf_event_mmap(pmu_fd) < 0)
+		return 1;
+
+	f = popen("taskset 1 dd if=/dev/zero of=/dev/null", "r");
+	(void) f;
+
+	start_time = time_get_ns();
+	for (;;) {
+		perf_event_poll(pmu_fd);
+		perf_event_read(print_bpf_output);
+	}
+
+	return 0;
+}
-- 
1.7.9.5

Re: [PATCH net-next 0/3] bpf_perf_event_output helper

[David Miller]

From: Alexei Starovoitov <ast@plumgrid.com>
Date: Tue, 20 Oct 2015 20:02:32 -0700

> Over the last year there were multiple attempts to let eBPF programs
> output data into perf events by He Kuang and Wangnan.
> The last one was:
> https://lkml.org/lkml/2015/7/20/736
> It was almost perfect with exception that all bpf programs would sent
> data into one global perf_event.
> This patch set takes different approach by letting user space
> open independent PERF_COUNT_SW_BPF_OUTPUT events, so that program
> output won't collide.
> 
> Wangnan is working on corresponding perf patches.

Series applied, thanks.