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Date: Wed, 21 Oct 2015 18:01:05 +0800
From: He Kuang <hekuang@...wei.com>
To: Alexei Starovoitov <ast@...mgrid.com>,
"David S. Miller" <davem@...emloft.net>
CC: Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Wang Nan <wangnan0@...wei.com>,
Arnaldo Carvalho de Melo <acme@...radead.org>,
Daniel Borkmann <daniel@...earbox.net>,
<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 2/3] bpf: introduce bpf_perf_event_output()
helper
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@...nel.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;
> }
>
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