Date:   Wed, 15 Mar 2023 13:39:15 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Namhyung Kim <namhyung@kernel.org>
Cc:     Jiri Olsa <jolsa@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Song Liu <song@kernel.org>,
        Stephane Eranian <eranian@google.com>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        Leo Yan <leo.yan@linaro.org>,
        James Clark <james.clark@arm.com>, Hao Luo <haoluo@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-perf-users@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH 02/10] perf bpf filter: Implement event sample filtering
Message-ID: <ZBH0s5P2KV5bJR3h@kernel.org>
References: <20230314234237.3008956-1-namhyung@kernel.org>
 <20230314234237.3008956-3-namhyung@kernel.org>
 <ZBHxRaP7BC+qDzJ/@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
In-Reply-To: <ZBHxRaP7BC+qDzJ/@kernel.org>
Precedence: bulk

Em Wed, Mar 15, 2023 at 01:24:37PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Tue, Mar 14, 2023 at 04:42:29PM -0700, 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.
> >=20
> > 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.
> >=20
> > Acked-by: Jiri Olsa <jolsa@kernel.org>
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
>=20
>=20
> I'm noticing this while building on a debian:11 container:
>=20
>   GENSKEL /tmp/build/perf/util/bpf_skel/bperf_leader.skel.h
>   GENSKEL /tmp/build/perf/util/bpf_skel/bperf_follower.skel.h
>   GENSKEL /tmp/build/perf/util/bpf_skel/func_latency.skel.h
>   GENSKEL /tmp/build/perf/util/bpf_skel/bpf_prog_profiler.skel.h
>   GENSKEL /tmp/build/perf/util/bpf_skel/kwork_trace.skel.h
>   GENSKEL /tmp/build/perf/util/bpf_skel/sample_filter.skel.h
> libbpf: failed to find BTF for extern 'bpf_cast_to_kern_ctx' [21] section=
: -2
> Error: failed to open BPF object file: No such file or directory
> make[2]: *** [Makefile.perf:1085: /tmp/build/perf/util/bpf_skel/sample_fi=
lter.skel.h] Error 254
> make[2]: *** Deleting file '/tmp/build/perf/util/bpf_skel/sample_filter.s=
kel.h'
> make[2]: *** Waiting for unfinished jobs....
> make[1]: *** [Makefile.perf:236: sub-make] Error 2
> make: *** [Makefile:70: all] Error 2
> make: Leaving directory '/git/perf-6.3.0-rc1/tools/perf'
> + exit 1
> [perfbuilder@five 11]$

Same thing on debian:10

libbpf: failed to find BTF for extern 'bpf_cast_to_kern_ctx' [21] section: =
-2
Error: failed to open BPF object file: No such file or directory
make[2]: *** [Makefile.perf:1085: /tmp/build/perf/util/bpf_skel/sample_filt=
er.skel.h] Error 254
make[2]: *** Deleting file '/tmp/build/perf/util/bpf_skel/sample_filter.ske=
l.h'
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [Makefile.perf:236: sub-make] Error 2
make: *** [Makefile:70: all] Error 2
make: Leaving directory '/git/perf-6.3.0-rc1/tools/perf'
+ exit 1
[perfbuilder@five 10]$

Works with debian:experimental:


[perfbuilder@five experimental]$ export BUILD_TARBALL=3Dhttp://192.168.86.1=
0/perf/perf-6.3.0-rc1.tar.xz
[perfbuilder@five experimental]$ time dm .
   1   147.54 debian:experimental           : Ok   gcc (Debian 12.2.0-14) 1=
2.2.0 , Debian clang version 14.0.6
BUILD_TARBALL_HEAD=3Dd34a77f6cd75d2a75c64e78f3d949a12903a7cf0

Both with:

Debian clang version 14.0.6
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/12
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/12
Candidate multilib: .;@m64
Selected multilib: .;@m64
+ rm -rf /tmp/build/perf
+ mkdir /tmp/build/perf
+ make ARCH=3D CROSS_COMPILE=3D EXTRA_CFLAGS=3D -C tools/perf O=3D/tmp/buil=
d/perf CC=3Dclang

and:

COLLECT_GCC=3Dgcc
COLLECT_LTO_WRAPPER=3D/usr/lib/gcc/x86_64-linux-gnu/12/lto-wrapper
OFFLOAD_TARGET_NAMES=3Dnvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=3D1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion=3D'Debian 12.2.0-14'=
 --with-bugurl=3Dfile:///usr/share/doc/gcc-12/README.Bugs --enable-language=
s=3Dc,ada,c++,go,d,fortran,objc,obj-c++,m2 --prefix=3D/usr --with-gcc-major=
-version-only --program-suffix=3D-12 --program-prefix=3Dx86_64-linux-gnu- -=
-enable-shared --enable-linker-build-id --libexecdir=3D/usr/lib --without-i=
ncluded-gettext --enable-threads=3Dposix --libdir=3D/usr/lib --enable-nls -=
-enable-clocale=3Dgnu --enable-libstdcxx-debug --enable-libstdcxx-time=3Dye=
s --with-default-libstdcxx-abi=3Dnew --enable-gnu-unique-object --disable-v=
table-verify --enable-plugin --enable-default-pie --with-system-zlib --enab=
le-libphobos-checking=3Drelease --with-target-system-zlib=3Dauto --enable-o=
bjc-gc=3Dauto --enable-multiarch --disable-werror --enable-cet --with-arch-=
32=3Di686 --with-abi=3Dm64 --with-multilib-list=3Dm32,m64,mx32 --enable-mul=
tilib --with-tune=3Dgeneric --enable-offload-targets=3Dnvptx-none=3D/build/=
gcc-12-bTRWOB/gcc-12-12.2.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=3D/build/gcc=
-12-bTRWOB/gcc-12-12.2.0/debian/tmp-gcn/usr --enable-offload-defaulted --wi=
thout-cuda-driver --enable-checking=3Drelease --build=3Dx86_64-linux-gnu --=
host=3Dx86_64-linux-gnu --target=3Dx86_64-linux-gnu
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.2.0 (Debian 12.2.0-14)=20
+ make ARCH=3D CROSS_COMPILE=3D EXTRA_CFLAGS=3D -C tools/perf O=3D/tmp/buil=
d/perf
make: Entering directory '/git/perf-6.3.0-rc1/tools/perf'


>=20
> > ---
> >  tools/perf/Makefile.perf                     |   2 +-
> >  tools/perf/util/bpf-filter.c                 |  64 ++++++++++
> >  tools/perf/util/bpf-filter.h                 |  26 ++--
> >  tools/perf/util/bpf_skel/sample-filter.h     |  24 ++++
> >  tools/perf/util/bpf_skel/sample_filter.bpf.c | 126 +++++++++++++++++++
> >  tools/perf/util/evsel.h                      |   7 +-
> >  6 files changed, 236 insertions(+), 13 deletions(-)
> >  create mode 100644 tools/perf/util/bpf_skel/sample-filter.h
> >  create mode 100644 tools/perf/util/bpf_skel/sample_filter.bpf.c
> >=20
> > diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> > index dc9dda09b076..ed6b6a070f79 100644
> > --- a/tools/perf/Makefile.perf
> > +++ b/tools/perf/Makefile.perf
> > @@ -1050,7 +1050,7 @@ SKELETONS :=3D $(SKEL_OUT)/bpf_prog_profiler.skel=
=2Eh
> >  SKELETONS +=3D $(SKEL_OUT)/bperf_leader.skel.h $(SKEL_OUT)/bperf_follo=
wer.skel.h
> >  SKELETONS +=3D $(SKEL_OUT)/bperf_cgroup.skel.h $(SKEL_OUT)/func_latenc=
y.skel.h
> >  SKELETONS +=3D $(SKEL_OUT)/off_cpu.skel.h $(SKEL_OUT)/lock_contention.=
skel.h
> > -SKELETONS +=3D $(SKEL_OUT)/kwork_trace.skel.h
> > +SKELETONS +=3D $(SKEL_OUT)/kwork_trace.skel.h $(SKEL_OUT)/sample_filte=
r.skel.h
> > =20
> >  $(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 c72e35d51240..f20e1bc03778 100644
> > --- a/tools/perf/util/bpf-filter.c
> > +++ b/tools/perf/util/bpf-filter.c
> > @@ -1,10 +1,74 @@
> >  /* SPDX-License-Identifier: GPL-2.0 */
> >  #include <stdlib.h>
> > =20
> > +#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"
> > =20
> > +#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 =3D sample_filter_bpf__open_and_load();
> > +	if (!skel) {
> > +		pr_err("Failed to load perf sample-filter BPF skeleton\n");
> > +		return -1;
> > +	}
> > +
> > +	i =3D 0;
> > +	fd =3D bpf_map__fd(skel->maps.filters);
> > +	list_for_each_entry(expr, &evsel->bpf_filters, list) {
> > +		struct perf_bpf_filter_entry entry =3D {
> > +			.op =3D expr->op,
> > +			.flags =3D expr->sample_flags,
> > +			.value =3D expr->val,
> > +		};
> > +		bpf_map_update_elem(fd, &i, &entry, BPF_ANY);
> > +		i++;
> > +	}
> > +
> > +	prog =3D skel->progs.perf_sample_filter;
> > +	for (x =3D 0; x < xyarray__max_x(evsel->core.fd); x++) {
> > +		for (y =3D 0; y < xyarray__max_y(evsel->core.fd); y++) {
> > +			link =3D 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 =3D 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 s=
ample_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 93a0d3de038c..eb8e1ac43cdf 100644
> > --- a/tools/perf/util/bpf-filter.h
> > +++ b/tools/perf/util/bpf-filter.h
> > @@ -4,15 +4,7 @@
> > =20
> >  #include <linux/list.h>
> > =20
> > -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"
> > =20
> >  struct perf_bpf_filter_expr {
> >  	struct list_head list;
> > @@ -21,16 +13,30 @@ struct perf_bpf_filter_expr {
> >  	unsigned long val;
> >  };
> > =20
> > +struct evsel;
> > +
> >  #ifdef HAVE_BPF_SKEL
> >  struct perf_bpf_filter_expr *perf_bpf_filter_expr__new(unsigned long s=
ample_flags,
> >  						       enum perf_bpf_filter_op op,
> >  						       unsigned long val);
> >  int perf_bpf_filter__parse(struct list_head *expr_head, const char *st=
r);
> > +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;
> > +	return -EOPNOTSUPP;
> > +}
> > +static inline int perf_bpf_filter__prepare(struct evsel *evsel __maybe=
_unused)
> > +{
> > +	return -EOPNOTSUPP;
> > +}
> > +static inline int perf_bpf_filter__destroy(struct evsel *evsel __maybe=
_unused)
> > +{
> > +	return -EOPNOTSUPP;
> >  }
> >  #endif /* HAVE_BPF_SKEL*/
> >  #endif /* PERF_UTIL_BPF_FILTER_H */
> > 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..c07256279c3e
> > --- /dev/null
> > +++ b/tools/perf/util/bpf_skel/sample_filter.bpf.c
> > @@ -0,0 +1,126 @@
> > +// 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;
> > +
> > +/* new kernel perf_sample_data definition */
> > +struct perf_sample_data___new {
> > +	__u64 sample_flags;
> > +} __attribute__((preserve_access_index));
> > +
> > +/* helper function to return the given perf sample data */
> > +static inline __u64 perf_get_sample(struct bpf_perf_event_data_kern *k=
ctx,
> > +				    struct perf_bpf_filter_entry *entry)
> > +{
> > +	struct perf_sample_data___new *data =3D (void *)kctx->data;
> > +
> > +	if (!bpf_core_field_exists(data->sample_flags) ||
> > +	    (data->sample_flags & entry->flags) =3D=3D 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 =3D bpf_cast_to_kern_ctx(ctx);
> > +
> > +	for (i =3D 0; i < MAX_FILTERS; i++) {
> > +		int key =3D i; /* needed for verifier :( */
> > +
> > +		entry =3D bpf_map_lookup_elem(&filters, &key);
> > +		if (entry =3D=3D NULL)
> > +			break;
> > +		sample_data =3D perf_get_sample(kctx, entry);
> > +
> > +		switch (entry->op) {
> > +		case PBF_OP_EQ:
> > +			if (!(sample_data =3D=3D entry->value))
> > +				goto drop;
> > +			break;
> > +		case PBF_OP_NEQ:
> > +			if (!(sample_data !=3D entry->value))
> > +				goto drop;
> > +			break;
> > +		case PBF_OP_GT:
> > +			if (!(sample_data > entry->value))
> > +				goto drop;
> > +			break;
> > +		case PBF_OP_GE:
> > +			if (!(sample_data >=3D entry->value))
> > +				goto drop;
> > +			break;
> > +		case PBF_OP_LT:
> > +			if (!(sample_data < entry->value))
> > +				goto drop;
> > +			break;
> > +		case PBF_OP_LE:
> > +			if (!(sample_data <=3D 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") =3D "Dual BSD/GPL";
> > diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> > index c272c06565c0..68072ec655ce 100644
> > --- a/tools/perf/util/evsel.h
> > +++ b/tools/perf/util/evsel.h
> > @@ -150,8 +150,10 @@ struct evsel {
> >  	 */
> >  	struct bpf_counter_ops	*bpf_counter_ops;
> > =20
> > -	/* 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 */
> > +	};
> > =20
> >  	/* for perf-stat --use-bpf */
> >  	int			bperf_leader_prog_fd;
> > @@ -159,6 +161,7 @@ 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;
> > --=20
> > 2.40.0.rc1.284.g88254d51c5-goog
> >=20
>=20
> --=20
>=20
> - Arnaldo

--=20

- Arnaldo