Re: [PATCH 02/10] perf bpf filter: Implement event sample filtering

From: Namhyung Kim
Date: Wed Mar 15 2023 - 12:51:20 EST

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On Wed, Mar 15, 2023 at 9:39 AM Arnaldo Carvalho de Melo
<acme@xxxxxxxxxx> wrote:
>
> 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.
> > >
> > > 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.
> > >
> > > Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> > > Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> >
> >
> > I'm noticing this while building on a debian:11 container:
> >
> > 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_filter.skel.h] Error 254
> > make[2]: *** Deleting file '/tmp/build/perf/util/bpf_skel/sample_filter.skel.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

Hmm.. I thought extern symbols with__ksym are runtime
dependencies and it should build on old kernels too.

BPF folks, any suggestions?

Thanks,
Namhyung

>
> 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_filter.skel.h] Error 254
> make[2]: *** Deleting file '/tmp/build/perf/util/bpf_skel/sample_filter.skel.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=http://192.168.86.10/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) 12.2.0 , Debian clang version 14.0.6
> BUILD_TARBALL_HEAD=d34a77f6cd75d2a75c64e78f3d949a12903a7cf0
>
> 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= CROSS_COMPILE= EXTRA_CFLAGS= -C tools/perf O=/tmp/build/perf CC=clang
>
> and:
>
> COLLECT_GCC=gcc
> COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/12/lto-wrapper
> OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
> OFFLOAD_TARGET_DEFAULT=1
> Target: x86_64-linux-gnu
> Configured with: ../src/configure -v --with-pkgversion='Debian 12.2.0-14' --with-bugurl=file:///usr/share/doc/gcc-12/README.Bugs --enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,m2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-12 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib --enable-libphobos-checking=release --with-target-system-zlib=auto --enable-objc-gc=auto --enable-multiarch --disable-werror --enable-cet --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-offload-targets=nvptx-none=/build/gcc-12-bTRWOB/gcc-12-12.2.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-12-bTRWOB/gcc-12-12.2.0/debian/tmp-gcn/usr --enable-offload-defaulted --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
> Thread model: posix
> Supported LTO compression algorithms: zlib zstd
> gcc version 12.2.0 (Debian 12.2.0-14)
> + make ARCH= CROSS_COMPILE= EXTRA_CFLAGS= -C tools/perf O=/tmp/build/perf
> make: Entering directory '/git/perf-6.3.0-rc1/tools/perf'
>
>
> >
> > > ---
> > > 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
> > >
> > > 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 := $(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 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>
> > >
> > > +#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_and_load();
> > > + if (!skel) {
> > > + 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 93a0d3de038c..eb8e1ac43cdf 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;
> > > + 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 *kctx,
> > > + struct perf_bpf_filter_entry *entry)
> > > +{
> > > + struct perf_sample_data___new *data = (void *)kctx->data;
> > > +
> > > + if (!bpf_core_field_exists(data->sample_flags) ||
> > > + (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 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;
> > >
> > > - /* 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;
> > > @@ -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;
> > > --
> > > 2.40.0.rc1.284.g88254d51c5-goog
> > >
> >
> > --
> >
> > - Arnaldo
>
> --
>
> - Arnaldo

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