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

Namhyung Kim
2023-02-19T06:13:45Z

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.

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