Re: [PATCH 2/8] perf bpf filter: Implement event sample filtering

Arnaldo Carvalho de Melo
2023-02-19T11:14:56Z

Em Sat, Feb 18, 2023 at 10:13:23PM -0800, Namhyung Kim escreveu:
> The BPF program will be attached to a perf_event and be triggered when
> it overflows. It'd iterate the filters map and compare the sample
> value according to the expression. If any of them fails, the sample
> would be dropped.
>
> Also it needs to have the corresponding sample data for the expression
> so it compares data->sample_flags with the given value. To access the
> sample data, it uses the bpf_cast_to_kern_ctx() kfunc which was added
> in v6.2 kernel.

CLANG /tmp/build/perf/util/bpf_skel/.tmp/sample_filter.bpf.o
util/bpf_skel/sample_filter.bpf.c:26:19: error: no member named 'sample_flags' in 'struct perf_sample_data'
if ((kctx->data->sample_flags & entry->flags) == 0)
~~~~~~~~~~ ^
1 error generated.
make[2]: *** [Makefile.perf:1078: /tmp/build/perf/util/bpf_skel/.tmp/sample_filter.bpf.o] Error 1
make[1]: *** [Makefile.perf:236: sub-make] Error 2
make: *** [Makefile:113: install-bin] Error 2
make: Leaving directory '/var/home/acme/git/perf/tools/perf'

Performance counter stats for 'make -k BUILD_BPF_SKEL=1 CORESIGHT=1 O=/tmp/build/perf -C tools/perf install-bin':

> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
> tools/perf/Makefile.perf | 2 +-
> tools/perf/util/bpf-filter.c | 71 +++++++++++
> tools/perf/util/bpf-filter.h | 24 ++--
> tools/perf/util/bpf_skel/sample-filter.h | 24 ++++
> tools/perf/util/bpf_skel/sample_filter.bpf.c | 118 +++++++++++++++++++
> tools/perf/util/evsel.h | 7 +-
> 6 files changed, 234 insertions(+), 12 deletions(-)
> create mode 100644 tools/perf/util/bpf_skel/sample-filter.h
> create mode 100644 tools/perf/util/bpf_skel/sample_filter.bpf.c
>
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index bac9272682b7..474af4adea95 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -1047,7 +1047,7 @@ SKELETONS := $(SKEL_OUT)/bpf_prog_profiler.skel.h
> SKELETONS += $(SKEL_OUT)/bperf_leader.skel.h $(SKEL_OUT)/bperf_follower.skel.h
> SKELETONS += $(SKEL_OUT)/bperf_cgroup.skel.h $(SKEL_OUT)/func_latency.skel.h
> SKELETONS += $(SKEL_OUT)/off_cpu.skel.h $(SKEL_OUT)/lock_contention.skel.h
> -SKELETONS += $(SKEL_OUT)/kwork_trace.skel.h
> +SKELETONS += $(SKEL_OUT)/kwork_trace.skel.h $(SKEL_OUT)/sample_filter.skel.h
>
> $(SKEL_TMP_OUT) $(LIBAPI_OUTPUT) $(LIBBPF_OUTPUT) $(LIBPERF_OUTPUT) $(LIBSUBCMD_OUTPUT) $(LIBSYMBOL_OUTPUT):
> $(Q)$(MKDIR) -p $@
> diff --git a/tools/perf/util/bpf-filter.c b/tools/perf/util/bpf-filter.c
> index 6b1148fcfb0e..f47420cf81c9 100644
> --- a/tools/perf/util/bpf-filter.c
> +++ b/tools/perf/util/bpf-filter.c
> @@ -1,10 +1,81 @@
> // SPDX-License-Identifier: GPL-2.0
> #include <stdlib.h>
>
> +#include <bpf/bpf.h>
> +#include <linux/err.h>
> +#include <internal/xyarray.h>
> +
> +#include "util/debug.h"
> +#include "util/evsel.h"
> +
> #include "util/bpf-filter.h"
> #include "util/bpf-filter-flex.h"
> #include "util/bpf-filter-bison.h"
>
> +#include "bpf_skel/sample-filter.h"
> +#include "bpf_skel/sample_filter.skel.h"
> +
> +#define FD(e, x, y) (*(int *)xyarray__entry(e->core.fd, x, y))
> +
> +int perf_bpf_filter__prepare(struct evsel *evsel)
> +{
> + int i, x, y, fd;
> + struct sample_filter_bpf *skel;
> + struct bpf_program *prog;
> + struct bpf_link *link;
> + struct perf_bpf_filter_expr *expr;
> +
> + skel = sample_filter_bpf__open();
> + if (!skel) {
> + pr_err("Failed to open perf sample-filter BPF skeleton\n");
> + return -1;
> + }
> +
> + bpf_map__set_max_entries(skel->maps.filters, MAX_FILTERS);
> +
> + if (sample_filter_bpf__load(skel) < 0) {
> + pr_err("Failed to load perf sample-filter BPF skeleton\n");
> + return -1;
> + }
> +
> + i = 0;
> + fd = bpf_map__fd(skel->maps.filters);
> + list_for_each_entry(expr, &evsel->bpf_filters, list) {
> + struct perf_bpf_filter_entry entry = {
> + .op = expr->op,
> + .flags = expr->sample_flags,
> + .value = expr->val,
> + };
> + bpf_map_update_elem(fd, &i, &entry, BPF_ANY);
> + i++;
> + }
> +
> + prog = skel->progs.perf_sample_filter;
> + for (x = 0; x < xyarray__max_x(evsel->core.fd); x++) {
> + for (y = 0; y < xyarray__max_y(evsel->core.fd); y++) {
> + link = bpf_program__attach_perf_event(prog, FD(evsel, x, y));
> + if (IS_ERR(link)) {
> + pr_err("Failed to attach perf sample-filter program\n");
> + return PTR_ERR(link);
> + }
> + }
> + }
> + evsel->bpf_skel = skel;
> + return 0;
> +}
> +
> +int perf_bpf_filter__destroy(struct evsel *evsel)
> +{
> + struct perf_bpf_filter_expr *expr, *tmp;
> +
> + list_for_each_entry_safe(expr, tmp, &evsel->bpf_filters, list) {
> + list_del(&expr->list);
> + free(expr);
> + }
> + sample_filter_bpf__destroy(evsel->bpf_skel);
> + return 0;
> +}
> +
> struct perf_bpf_filter_expr *perf_bpf_filter_expr__new(unsigned long sample_flags,
> enum perf_bpf_filter_op op,
> unsigned long val)
> diff --git a/tools/perf/util/bpf-filter.h b/tools/perf/util/bpf-filter.h
> index fd5b1164a322..6077930073f9 100644
> --- a/tools/perf/util/bpf-filter.h
> +++ b/tools/perf/util/bpf-filter.h
> @@ -4,15 +4,7 @@
>
> #include <linux/list.h>
>
> -enum perf_bpf_filter_op {
> - PBF_OP_EQ,
> - PBF_OP_NEQ,
> - PBF_OP_GT,
> - PBF_OP_GE,
> - PBF_OP_LT,
> - PBF_OP_LE,
> - PBF_OP_AND,
> -};
> +#include "bpf_skel/sample-filter.h"
>
> struct perf_bpf_filter_expr {
> struct list_head list;
> @@ -21,16 +13,30 @@ struct perf_bpf_filter_expr {
> unsigned long val;
> };
>
> +struct evsel;
> +
> #ifdef HAVE_BPF_SKEL
> struct perf_bpf_filter_expr *perf_bpf_filter_expr__new(unsigned long sample_flags,
> enum perf_bpf_filter_op op,
> unsigned long val);
> int perf_bpf_filter__parse(struct list_head *expr_head, const char *str);
> +int perf_bpf_filter__prepare(struct evsel *evsel);
> +int perf_bpf_filter__destroy(struct evsel *evsel);
> +
> #else /* !HAVE_BPF_SKEL */
> +
> static inline int perf_bpf_filter__parse(struct list_head *expr_head __maybe_unused,
> const char *str __maybe_unused)
> {
> return -ENOSYS;
> }
> +static inline int perf_bpf_filter__prepare(struct evsel *evsel)
> +{
> + return -ENOSYS;
> +}
> +static inline int perf_bpf_filter__destroy(struct evsel *evsel)
> +{
> + return -ENOSYS;
> +}
> #endif /* HAVE_BPF_SKEL*/
> #endif /* PERF_UTIL_BPF_FILTER_H */
> \ No newline at end of file
> diff --git a/tools/perf/util/bpf_skel/sample-filter.h b/tools/perf/util/bpf_skel/sample-filter.h
> new file mode 100644
> index 000000000000..862060bfda14
> --- /dev/null
> +++ b/tools/perf/util/bpf_skel/sample-filter.h
> @@ -0,0 +1,24 @@
> +#ifndef PERF_UTIL_BPF_SKEL_SAMPLE_FILTER_H
> +#define PERF_UTIL_BPF_SKEL_SAMPLE_FILTER_H
> +
> +#define MAX_FILTERS 32
> +
> +/* supported filter operations */
> +enum perf_bpf_filter_op {
> + PBF_OP_EQ,
> + PBF_OP_NEQ,
> + PBF_OP_GT,
> + PBF_OP_GE,
> + PBF_OP_LT,
> + PBF_OP_LE,
> + PBF_OP_AND
> +};
> +
> +/* BPF map entry for filtering */
> +struct perf_bpf_filter_entry {
> + enum perf_bpf_filter_op op;
> + __u64 flags;
> + __u64 value;
> +};
> +
> +#endif /* PERF_UTIL_BPF_SKEL_SAMPLE_FILTER_H */
> \ No newline at end of file
> diff --git a/tools/perf/util/bpf_skel/sample_filter.bpf.c b/tools/perf/util/bpf_skel/sample_filter.bpf.c
> new file mode 100644
> index 000000000000..1aa6a4cacd51
> --- /dev/null
> +++ b/tools/perf/util/bpf_skel/sample_filter.bpf.c
> @@ -0,0 +1,118 @@
> +// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +// Copyright (c) 2023 Google
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_core_read.h>
> +
> +#include "sample-filter.h"
> +
> +/* BPF map that will be filled by user space */
> +struct filters {
> + __uint(type, BPF_MAP_TYPE_ARRAY);
> + __type(key, int);
> + __type(value, struct perf_bpf_filter_entry);
> + __uint(max_entries, MAX_FILTERS);
> +} filters SEC(".maps");
> +
> +int dropped;
> +
> +void *bpf_cast_to_kern_ctx(void *) __ksym;
> +
> +/* helper function to return the given perf sample data */
> +static inline __u64 perf_get_sample(struct bpf_perf_event_data_kern *kctx,
> + struct perf_bpf_filter_entry *entry)
> +{
> + if ((kctx->data->sample_flags & entry->flags) == 0)
> + return 0;
> +
> + switch (entry->flags) {
> + case PERF_SAMPLE_IP:
> + return kctx->data->ip;
> + case PERF_SAMPLE_ID:
> + return kctx->data->id;
> + case PERF_SAMPLE_TID:
> + return kctx->data->tid_entry.tid;
> + case PERF_SAMPLE_CPU:
> + return kctx->data->cpu_entry.cpu;
> + case PERF_SAMPLE_TIME:
> + return kctx->data->time;
> + case PERF_SAMPLE_ADDR:
> + return kctx->data->addr;
> + case PERF_SAMPLE_PERIOD:
> + return kctx->data->period;
> + case PERF_SAMPLE_TRANSACTION:
> + return kctx->data->txn;
> + case PERF_SAMPLE_WEIGHT:
> + return kctx->data->weight.full;
> + case PERF_SAMPLE_PHYS_ADDR:
> + return kctx->data->phys_addr;
> + case PERF_SAMPLE_CODE_PAGE_SIZE:
> + return kctx->data->code_page_size;
> + case PERF_SAMPLE_DATA_PAGE_SIZE:
> + return kctx->data->data_page_size;
> + default:
> + break;
> + }
> + return 0;
> +}
> +
> +/* BPF program to be called from perf event overflow handler */
> +SEC("perf_event")
> +int perf_sample_filter(void *ctx)
> +{
> + struct bpf_perf_event_data_kern *kctx;
> + struct perf_bpf_filter_entry *entry;
> + __u64 sample_data;
> + int i;
> +
> + kctx = bpf_cast_to_kern_ctx(ctx);
> +
> + for (i = 0; i < MAX_FILTERS; i++) {
> + int key = i; /* needed for verifier :( */
> +
> + entry = bpf_map_lookup_elem(&filters, &key);
> + if (entry == NULL)
> + break;
> + sample_data = perf_get_sample(kctx, entry);
> +
> + switch (entry->op) {
> + case PBF_OP_EQ:
> + if (!(sample_data == entry->value))
> + goto drop;
> + break;
> + case PBF_OP_NEQ:
> + if (!(sample_data != entry->value))
> + goto drop;
> + break;
> + case PBF_OP_GT:
> + if (!(sample_data > entry->value))
> + goto drop;
> + break;
> + case PBF_OP_GE:
> + if (!(sample_data >= entry->value))
> + goto drop;
> + break;
> + case PBF_OP_LT:
> + if (!(sample_data < entry->value))
> + goto drop;
> + break;
> + case PBF_OP_LE:
> + if (!(sample_data <= entry->value))
> + goto drop;
> + break;
> + case PBF_OP_AND:
> + if (!(sample_data & entry->value))
> + goto drop;
> + break;
> + }
> + }
> + /* generate sample data */
> + return 1;
> +
> +drop:
> + __sync_fetch_and_add(&dropped, 1);
> + return 0;
> +}
> +
> +char LICENSE[] SEC("license") = "Dual BSD/GPL";
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index 24cb807ef6ce..6845642485ec 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -151,8 +151,10 @@ struct evsel {
> */
> struct bpf_counter_ops *bpf_counter_ops;
>
> - /* for perf-stat -b */
> - struct list_head bpf_counter_list;
> + union {
> + struct list_head bpf_counter_list; /* for perf-stat -b */
> + struct list_head bpf_filters; /* for perf-record --filter */
> + };
>
> /* for perf-stat --use-bpf */
> int bperf_leader_prog_fd;
> @@ -160,6 +162,7 @@ struct evsel {
> union {
> struct bperf_leader_bpf *leader_skel;
> struct bperf_follower_bpf *follower_skel;
> + void *bpf_skel;
> };
> unsigned long open_flags;
> int precise_ip_original;
> --
> 2.39.2.637.g21b0678d19-goog
>

--

- Arnaldo