Re: [PATCH 1/7] perf bpf filter: Introduce basic BPF filter expression

[Ian Rogers <irogers@google.com>]

On Mon, Feb 13, 2023 at 9:05 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> This implements a tiny parser for the filter expressions used for BPF.
> Each expression will be converted to struct perf_bpf_filter_expr and
> be passed to a BPF map.
>
> For now, I'd like to start with the very basic comparisons like EQ or
> GT.  The LHS should be a term for sample data and the RHS is a number.
> The expressions are connected by a comma.  For example,
>
>     period > 10000
>     ip < 0x1000000000000, cpu == 3
>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
>  tools/perf/util/Build        | 16 +++++++++
>  tools/perf/util/bpf-filter.c | 37 +++++++++++++++++++
>  tools/perf/util/bpf-filter.h | 36 +++++++++++++++++++
>  tools/perf/util/bpf-filter.l | 70 ++++++++++++++++++++++++++++++++++++
>  tools/perf/util/bpf-filter.y | 52 +++++++++++++++++++++++++++
>  5 files changed, 211 insertions(+)
>  create mode 100644 tools/perf/util/bpf-filter.c
>  create mode 100644 tools/perf/util/bpf-filter.h
>  create mode 100644 tools/perf/util/bpf-filter.l
>  create mode 100644 tools/perf/util/bpf-filter.y
>
> diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> index 918b501f9bd8..6af73fb5c797 100644
> --- a/tools/perf/util/Build
> +++ b/tools/perf/util/Build
> @@ -154,6 +154,9 @@ perf-$(CONFIG_PERF_BPF_SKEL) += bpf_counter.o
>  perf-$(CONFIG_PERF_BPF_SKEL) += bpf_counter_cgroup.o
>  perf-$(CONFIG_PERF_BPF_SKEL) += bpf_ftrace.o
>  perf-$(CONFIG_PERF_BPF_SKEL) += bpf_off_cpu.o
> +perf-$(CONFIG_PERF_BPF_SKEL) += bpf-filter.o
> +perf-$(CONFIG_PERF_BPF_SKEL) += bpf-filter-flex.o
> +perf-$(CONFIG_PERF_BPF_SKEL) += bpf-filter-bison.o
>
>  ifeq ($(CONFIG_LIBTRACEEVENT),y)
>    perf-$(CONFIG_PERF_BPF_SKEL) += bpf_lock_contention.o
> @@ -266,6 +269,16 @@ $(OUTPUT)util/pmu-bison.c $(OUTPUT)util/pmu-bison.h: util/pmu.y
>         $(Q)$(call echo-cmd,bison)$(BISON) -v $< -d $(PARSER_DEBUG_BISON) $(BISON_FILE_PREFIX_MAP) \
>                 -o $(OUTPUT)util/pmu-bison.c -p perf_pmu_
>
> +$(OUTPUT)util/bpf-filter-flex.c $(OUTPUT)util/bpf-filter-flex.h: util/bpf-filter.l $(OUTPUT)util/bpf-filter-bison.c
> +       $(call rule_mkdir)
> +       $(Q)$(call echo-cmd,flex)$(FLEX) -o $(OUTPUT)util/bpf-filter-flex.c \
> +               --header-file=$(OUTPUT)util/bpf-filter-flex.h $(PARSER_DEBUG_FLEX) $<
> +
> +$(OUTPUT)util/bpf-filter-bison.c $(OUTPUT)util/bpf-filter-bison.h: util/bpf-filter.y
> +       $(call rule_mkdir)
> +       $(Q)$(call echo-cmd,bison)$(BISON) -v $< -d $(PARSER_DEBUG_BISON) $(BISON_FILE_PREFIX_MAP) \
> +               -o $(OUTPUT)util/bpf-filter-bison.c -p perf_bpf_filter_
> +
>  FLEX_GE_26 := $(shell expr $(shell $(FLEX) --version | sed -e  's/flex \([0-9]\+\).\([0-9]\+\)/\1\2/g') \>\= 26)
>  ifeq ($(FLEX_GE_26),1)
>    flex_flags := -Wno-switch-enum -Wno-switch-default -Wno-unused-function -Wno-redundant-decls -Wno-sign-compare -Wno-unused-parameter -Wno-missing-prototypes -Wno-missing-declarations
> @@ -279,6 +292,7 @@ endif
>  CFLAGS_parse-events-flex.o  += $(flex_flags)
>  CFLAGS_pmu-flex.o           += $(flex_flags)
>  CFLAGS_expr-flex.o          += $(flex_flags)
> +CFLAGS_bpf-filter-flex.o    += $(flex_flags)
>
>  bison_flags := -DYYENABLE_NLS=0
>  BISON_GE_35 := $(shell expr $(shell $(BISON) --version | grep bison | sed -e 's/.\+ \([0-9]\+\).\([0-9]\+\)/\1\2/g') \>\= 35)
> @@ -290,10 +304,12 @@ endif
>  CFLAGS_parse-events-bison.o += $(bison_flags)
>  CFLAGS_pmu-bison.o          += -DYYLTYPE_IS_TRIVIAL=0 $(bison_flags)
>  CFLAGS_expr-bison.o         += -DYYLTYPE_IS_TRIVIAL=0 $(bison_flags)
> +CFLAGS_bpf-filter-bison.o   += -DYYLTYPE_IS_TRIVIAL=0 $(bison_flags)
>
>  $(OUTPUT)util/parse-events.o: $(OUTPUT)util/parse-events-flex.c $(OUTPUT)util/parse-events-bison.c
>  $(OUTPUT)util/pmu.o: $(OUTPUT)util/pmu-flex.c $(OUTPUT)util/pmu-bison.c
>  $(OUTPUT)util/expr.o: $(OUTPUT)util/expr-flex.c $(OUTPUT)util/expr-bison.c
> +$(OUTPUT)util/bpf-filter.o: $(OUTPUT)util/bpf-filter-flex.c $(OUTPUT)util/bpf-filter-bison.c
>
>  CFLAGS_bitmap.o        += -Wno-unused-parameter -DETC_PERFCONFIG="BUILD_STR($(ETC_PERFCONFIG_SQ))"
>  CFLAGS_find_bit.o      += -Wno-unused-parameter -DETC_PERFCONFIG="BUILD_STR($(ETC_PERFCONFIG_SQ))"
> diff --git a/tools/perf/util/bpf-filter.c b/tools/perf/util/bpf-filter.c
> new file mode 100644
> index 000000000000..6b1148fcfb0e
> --- /dev/null
> +++ b/tools/perf/util/bpf-filter.c
> @@ -0,0 +1,37 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <stdlib.h>
> +
> +#include "util/bpf-filter.h"
> +#include "util/bpf-filter-flex.h"
> +#include "util/bpf-filter-bison.h"
> +
> +struct perf_bpf_filter_expr *perf_bpf_filter_expr__new(unsigned long sample_flags,
> +                                                      enum perf_bpf_filter_op op,
> +                                                      unsigned long val)
> +{
> +       struct perf_bpf_filter_expr *expr;
> +
> +       expr = malloc(sizeof(*expr));
> +       if (expr != NULL) {
> +               expr->sample_flags = sample_flags;
> +               expr->op = op;
> +               expr->val = val;
> +       }
> +       return expr;
> +}
> +
> +int perf_bpf_filter__parse(struct list_head *expr_head, const char *str)
> +{
> +       YY_BUFFER_STATE buffer;
> +       int ret;
> +
> +       buffer = perf_bpf_filter__scan_string(str);
> +
> +       ret = perf_bpf_filter_parse(expr_head);
> +
> +       perf_bpf_filter__flush_buffer(buffer);
> +       perf_bpf_filter__delete_buffer(buffer);
> +       perf_bpf_filter_lex_destroy();
> +
> +       return ret;
> +}
> \ No newline at end of file
> diff --git a/tools/perf/util/bpf-filter.h b/tools/perf/util/bpf-filter.h
> new file mode 100644
> index 000000000000..fd5b1164a322
> --- /dev/null
> +++ b/tools/perf/util/bpf-filter.h
> @@ -0,0 +1,36 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#ifndef PERF_UTIL_BPF_FILTER_H
> +#define PERF_UTIL_BPF_FILTER_H
> +
> +#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,
> +};
> +
> +struct perf_bpf_filter_expr {
> +       struct list_head list;
> +       enum perf_bpf_filter_op op;
> +       unsigned long sample_flags;
> +       unsigned long val;
> +};
> +
> +#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);
> +#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;
> +}
> +#endif /* HAVE_BPF_SKEL*/
> +#endif /* PERF_UTIL_BPF_FILTER_H */
> \ No newline at end of file
> diff --git a/tools/perf/util/bpf-filter.l b/tools/perf/util/bpf-filter.l
> new file mode 100644
> index 000000000000..34c6a9fd4fa4
> --- /dev/null
> +++ b/tools/perf/util/bpf-filter.l
> @@ -0,0 +1,70 @@
> +%option prefix="perf_bpf_filter_"
> +%option noyywrap
> +
> +%{
> +#include <stdlib.h>
> +#include <linux/perf_event.h>
> +
> +#include "bpf-filter.h"
> +#include "bpf-filter-bison.h"
> +
> +static int sample(unsigned long sample_flag)
> +{
> +       perf_bpf_filter_lval.sample = sample_flag;
> +       return BFT_SAMPLE;
> +}
> +
> +static int operator(enum perf_bpf_filter_op op)
> +{
> +       perf_bpf_filter_lval.op = op;
> +       return BFT_OP;
> +}
> +
> +static int value(int base)
> +{
> +       long num;
> +
> +       errno = 0;
> +       num = strtoul(perf_bpf_filter_text, NULL, base);
> +       if (errno)
> +               return BFT_ERROR;
> +
> +       perf_bpf_filter_lval.num = num;
> +       return BFT_NUM;
> +}
> +
> +%}
> +
> +num_dec                [0-9]+
> +num_hex                0[Xx][0-9a-fA-F]+
> +
> +%%
> +
> +{num_dec}      { return value(10); }
> +{num_hex}      { return value(16); }
> +
> +ip             { return sample(PERF_SAMPLE_IP); }
> +id             { return sample(PERF_SAMPLE_ID); }
> +tid            { return sample(PERF_SAMPLE_TID); }
> +cpu            { return sample(PERF_SAMPLE_CPU); }
> +time           { return sample(PERF_SAMPLE_TIME); }
> +addr           { return sample(PERF_SAMPLE_ADDR); }
> +period         { return sample(PERF_SAMPLE_PERIOD); }
> +txn            { return sample(PERF_SAMPLE_TRANSACTION); }
> +weight         { return sample(PERF_SAMPLE_WEIGHT); }
> +phys_addr      { return sample(PERF_SAMPLE_PHYS_ADDR); }
> +code_pgsz      { return sample(PERF_SAMPLE_CODE_PAGE_SIZE); }
> +data_pgsz      { return sample(PERF_SAMPLE_DATA_PAGE_SIZE); }
> +
> +"=="           { return operator(PBF_OP_EQ); }
> +"!="           { return operator(PBF_OP_NEQ); }
> +">"            { return operator(PBF_OP_GT); }
> +"<"            { return operator(PBF_OP_LT); }
> +">="           { return operator(PBF_OP_GE); }
> +"<="           { return operator(PBF_OP_LE); }
> +"&"            { return operator(PBF_OP_AND); }
> +
> +","            { return ','; }
> +.              { }
> +
> +%%
> diff --git a/tools/perf/util/bpf-filter.y b/tools/perf/util/bpf-filter.y
> new file mode 100644
> index 000000000000..0bf36ec30abf
> --- /dev/null
> +++ b/tools/perf/util/bpf-filter.y
> @@ -0,0 +1,52 @@
> +%parse-param {struct list_head *expr_head}
> +
> +%{
> +
> +#include <stdio.h>
> +#include <string.h>
> +#include <linux/compiler.h>
> +#include <linux/list.h>
> +#include "bpf-filter.h"
> +
> +static void perf_bpf_filter_error(struct list_head *expr __maybe_unused,
> +                                 char const *msg)
> +{
> +       printf("perf_bpf_filter: %s\n", msg);
> +}
> +
> +%}
> +
> +%union
> +{
> +       unsigned long num;
> +       unsigned long sample;
> +       enum perf_bpf_filter_op op;
> +       struct perf_bpf_filter_expr *expr;
> +}
> +
> +%token BFT_SAMPLE BFT_OP BFT_ERROR BFT_NUM
> +%type <expr> filter_term

To avoid memory leaks for parse errors, I think you want here:
%destructor { free($$); } <expr>

Thanks,
Ian

> +%type <sample> BFT_SAMPLE
> +%type <op> BFT_OP
> +%type <num> BFT_NUM
> +
> +%%
> +
> +filter:
> +filter ',' filter_term
> +{
> +       list_add(&$3->list, expr_head);
> +}
> +|
> +filter_term
> +{
> +       list_add(&$1->list, expr_head);
> +}
> +
> +filter_term:
> +BFT_SAMPLE BFT_OP BFT_NUM
> +{
> +       $$ = perf_bpf_filter_expr__new($1, $2, $3);
> +}
> +
> +%%
> --
> 2.39.1.581.gbfd45094c4-goog
>