Commit a43eec30 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

bpf: introduce bpf_perf_event_output() helper 



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: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fa128e6a

include/uapi/linux/bpf.h

+11 −0
Original line number Diff line number Diff line
@@ -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,

};

include/uapi/linux/perf_event.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */

};

kernel/bpf/arraymap.c

+2 −0
Original line number Diff line number Diff line
@@ -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);

kernel/bpf/verifier.c

+2 −1
Original line number Diff line number Diff line
@@ -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;

	}

kernel/trace/bpf_trace.c

+46 −0
Original line number Diff line number Diff line
@@ -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;

	}

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