Re: [PATCH 07/13] perf, tools: Add a simple expression parser for JSON

From: Arnaldo Carvalho de Melo
Date: Tue Mar 21 2017 - 15:19:09 EST

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In reply to: Arnaldo Carvalho de Melo: "Re: [PATCH 07/13] perf, tools: Add a simple expression parser for JSON"
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Em Tue, Mar 21, 2017 at 04:14:23PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Mar 20, 2017 at 01:17:05PM -0700, Andi Kleen escreveu:
> > From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> >
> > Add a simple expression parser good enough to parse JSON relation
> > expressions. The parser is implemented using bison.
>
> Renaming 'foo_expr' to 'foo_json_expr', as 'expr' is _way_ too
> generic...

I retract that, it is used with JSON, but isn't strictly tied to it,
keeping as is, nevermind.

- Arnaldo

> - Arnaldo
>
> > This is just intended as an simple parser for internal usage
> > in the event lists, not the beginning of a "perf scripting language"
> >
> > v2: Use expr__ prefix instead of expr_
> > Support multiple free variables for parser
> > Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> > ---
> > tools/perf/tests/Build | 1 +
> > tools/perf/tests/builtin-test.c | 4 +
> > tools/perf/tests/expr.c | 55 +++++++++++++
> > tools/perf/tests/tests.h | 1 +
> > tools/perf/util/Build | 5 ++
> > tools/perf/util/expr.h | 25 ++++++
> > tools/perf/util/expr.y | 173 ++++++++++++++++++++++++++++++++++++++++
> > 7 files changed, 264 insertions(+)
> > create mode 100644 tools/perf/tests/expr.c
> > create mode 100644 tools/perf/util/expr.h
> > create mode 100644 tools/perf/util/expr.y
> >
> > diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
> > index 1cb3d9b540e9..af58ebc243ef 100644
> > --- a/tools/perf/tests/Build
> > +++ b/tools/perf/tests/Build
> > @@ -38,6 +38,7 @@ perf-y += cpumap.o
> > perf-y += stat.o
> > perf-y += event_update.o
> > perf-y += event-times.o
> > +perf-y += expr.o
> > perf-y += backward-ring-buffer.o
> > perf-y += sdt.o
> > perf-y += is_printable_array.o
> > diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
> > index 83c4669cbc5b..86822969e8a8 100644
> > --- a/tools/perf/tests/builtin-test.c
> > +++ b/tools/perf/tests/builtin-test.c
> > @@ -44,6 +44,10 @@ static struct test generic_tests[] = {
> > .func = test__parse_events,
> > },
> > {
> > + .desc = "Simple expression parser",
> > + .func = test__expr,
> > + },
> > + {
> > .desc = "PERF_RECORD_* events & perf_sample fields",
> > .func = test__PERF_RECORD,
> > },
> > diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
> > new file mode 100644
> > index 000000000000..554695c06c5b
> > --- /dev/null
> > +++ b/tools/perf/tests/expr.c
> > @@ -0,0 +1,55 @@
> > +#include "util/debug.h"
> > +#include "util/expr.h"
> > +#include "tests.h"
> > +
> > +static int test(struct parse_ctx *ctx, const char *e, double val2)
> > +{
> > + double val;
> > +
> > + if (expr__parse(&val, ctx, &e))
> > + TEST_ASSERT_VAL("parse test failed", 0);
> > + TEST_ASSERT_VAL("unexpected value", val == val2);
> > + return 0;
> > +}
> > +
> > +int test__expr(int subtest __maybe_unused)
> > +{
> > + const char *p;
> > + const char **other;
> > + double val;
> > + int ret;
> > + struct parse_ctx ctx;
> > + int num_other;
> > +
> > + expr__ctx_init(&ctx);
> > + expr__add_id(&ctx, "FOO", 1);
> > + expr__add_id(&ctx, "BAR", 2);
> > +
> > + ret = test(&ctx, "1+1", 2);
> > + ret |= test(&ctx, "FOO+BAR", 3);
> > + ret |= test(&ctx, "(BAR/2)%2", 1);
> > + ret |= test(&ctx, "1 - -4", 5);
> > + ret |= test(&ctx, "(FOO-1)*2 + (BAR/2)%2 - -4", 5);
> > +
> > + if (ret)
> > + return ret;
> > +
> > + p = "FOO/0";
> > + ret = expr__parse(&val, &ctx, &p);
> > + TEST_ASSERT_VAL("division by zero", ret == 1);
> > +
> > + p = "BAR/";
> > + ret = expr__parse(&val, &ctx, &p);
> > + TEST_ASSERT_VAL("missing operand", ret == 1);
> > +
> > + TEST_ASSERT_VAL("find other",
> > + expr__find_other("FOO + BAR + BAZ + BOZO", "FOO", &other, &num_other) == 0);
> > + TEST_ASSERT_VAL("find other", num_other == 3);
> > + TEST_ASSERT_VAL("find other", !strcmp(other[0], "BAR"));
> > + TEST_ASSERT_VAL("find other", !strcmp(other[1], "BAZ"));
> > + TEST_ASSERT_VAL("find other", !strcmp(other[2], "BOZO"));
> > + TEST_ASSERT_VAL("find other", other[3] == NULL);
> > + free((void *)other);
> > +
> > + return 0;
> > +}
> > diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
> > index 1fa9b9d83aa5..631859629403 100644
> > --- a/tools/perf/tests/tests.h
> > +++ b/tools/perf/tests/tests.h
> > @@ -62,6 +62,7 @@ int test__sample_parsing(int subtest);
> > int test__keep_tracking(int subtest);
> > int test__parse_no_sample_id_all(int subtest);
> > int test__dwarf_unwind(int subtest);
> > +int test__expr(int subtest);
> > int test__hists_filter(int subtest);
> > int test__mmap_thread_lookup(int subtest);
> > int test__thread_mg_share(int subtest);
> > diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> > index fb4f42f1bb38..0b98534a9ea1 100644
> > --- a/tools/perf/util/Build
> > +++ b/tools/perf/util/Build
> > @@ -90,6 +90,7 @@ libperf-y += mem-events.o
> > libperf-y += vsprintf.o
> > libperf-y += drv_configs.o
> > libperf-y += time-utils.o
> > +libperf-y += expr-bison.o
> >
> > libperf-$(CONFIG_LIBBPF) += bpf-loader.o
> > libperf-$(CONFIG_BPF_PROLOGUE) += bpf-prologue.o
> > @@ -142,6 +143,10 @@ $(OUTPUT)util/parse-events-bison.c: util/parse-events.y
> > $(call rule_mkdir)
> > $(Q)$(call echo-cmd,bison)$(BISON) -v util/parse-events.y -d $(PARSER_DEBUG_BISON) -o $@ -p parse_events_
> >
> > +$(OUTPUT)util/expr-bison.c: util/expr.y
> > + $(call rule_mkdir)
> > + $(Q)$(call echo-cmd,bison)$(BISON) -v util/expr.y -d $(PARSER_DEBUG_BISON) -o $@ -p expr__
> > +
> > $(OUTPUT)util/pmu-flex.c: util/pmu.l $(OUTPUT)util/pmu-bison.c
> > $(call rule_mkdir)
> > $(Q)$(call echo-cmd,flex)$(FLEX) -o $@ --header-file=$(OUTPUT)util/pmu-flex.h util/pmu.l
> > diff --git a/tools/perf/util/expr.h b/tools/perf/util/expr.h
> > new file mode 100644
> > index 000000000000..9c2760a1a96e
> > --- /dev/null
> > +++ b/tools/perf/util/expr.h
> > @@ -0,0 +1,25 @@
> > +#ifndef PARSE_CTX_H
> > +#define PARSE_CTX_H 1
> > +
> > +#define EXPR_MAX_OTHER 8
> > +#define MAX_PARSE_ID EXPR_MAX_OTHER
> > +
> > +struct parse_id {
> > + const char *name;
> > + double val;
> > +};
> > +
> > +struct parse_ctx {
> > + int num_ids;
> > + struct parse_id ids[MAX_PARSE_ID];
> > +};
> > +
> > +void expr__ctx_init(struct parse_ctx *ctx);
> > +void expr__add_id(struct parse_ctx *ctx, const char *id, double val);
> > +#ifndef IN_EXPR_Y
> > +int expr__parse(double *final_val, struct parse_ctx *ctx, const char **pp);
> > +#endif
> > +int expr__find_other(const char *p, const char *one, const char ***other,
> > + int *num_other);
> > +
> > +#endif
> > diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y
> > new file mode 100644
> > index 000000000000..a8daa7a93605
> > --- /dev/null
> > +++ b/tools/perf/util/expr.y
> > @@ -0,0 +1,173 @@
> > +/* Simple expression parser */
> > +%{
> > +#include "util.h"
> > +#include "util/debug.h"
> > +#define IN_EXPR_Y 1
> > +#include "expr.h"
> > +#include <string.h>
> > +
> > +#define MAXIDLEN 256
> > +%}
> > +
> > +%define api.pure full
> > +%parse-param { double *final_val }
> > +%parse-param { struct parse_ctx *ctx }
> > +%parse-param { const char **pp }
> > +%lex-param { const char **pp }
> > +
> > +%union {
> > + double num;
> > + char id[MAXIDLEN+1];
> > +}
> > +
> > +%token <num> NUMBER
> > +%token <id> ID
> > +%left '|'
> > +%left '^'
> > +%left '&'
> > +%left '-' '+'
> > +%left '*' '/' '%'
> > +%left NEG NOT
> > +%type <num> expr
> > +
> > +%{
> > +static int expr__lex(YYSTYPE *res, const char **pp);
> > +
> > +static void expr__error(double *final_val __maybe_unused,
> > + struct parse_ctx *ctx __maybe_unused,
> > + const char **pp __maybe_unused,
> > + const char *s)
> > +{
> > + pr_debug("%s\n", s);
> > +}
> > +
> > +static int lookup_id(struct parse_ctx *ctx, char *id, double *val)
> > +{
> > + int i;
> > +
> > + for (i = 0; i < ctx->num_ids; i++) {
> > + if (!strcasecmp(ctx->ids[i].name, id)) {
> > + *val = ctx->ids[i].val;
> > + return 0;
> > + }
> > + }
> > + return -1;
> > +}
> > +
> > +%}
> > +%%
> > +
> > +all_expr: expr { *final_val = $1; }
> > + ;
> > +
> > +expr: NUMBER
> > + | ID { if (lookup_id(ctx, $1, &$$) < 0) {
> > + pr_debug("%s not found", $1);
> > + YYABORT;
> > + }
> > + }
> > + | expr '+' expr { $$ = $1 + $3; }
> > + | expr '-' expr { $$ = $1 - $3; }
> > + | expr '*' expr { $$ = $1 * $3; }
> > + | expr '/' expr { if ($3 == 0) YYABORT; $$ = $1 / $3; }
> > + | expr '%' expr { if ((long)$3 == 0) YYABORT; $$ = (long)$1 % (long)$3; }
> > + | '-' expr %prec NEG { $$ = -$2; }
> > + | '(' expr ')' { $$ = $2; }
> > + ;
> > +
> > +%%
> > +
> > +static int expr__symbol(YYSTYPE *res, const char *p, const char **pp)
> > +{
> > + char *dst = res->id;
> > + const char *s = p;
> > +
> > + while (isalnum(*p) || *p == '_' || *p == '.') {
> > + if (p - s >= MAXIDLEN)
> > + return -1;
> > + *dst++ = *p++;
> > + }
> > + *dst = 0;
> > + *pp = p;
> > + return ID;
> > +}
> > +
> > +static int expr__lex(YYSTYPE *res, const char **pp)
> > +{
> > + int tok;
> > + const char *s;
> > + const char *p = *pp;
> > +
> > + while (isspace(*p))
> > + p++;
> > + s = p;
> > + switch (*p++) {
> > + case 'a' ... 'z':
> > + case 'A' ... 'Z':
> > + return expr__symbol(res, p - 1, pp);
> > + case '0' ... '9': case '.':
> > + res->num = strtod(s, (char **)&p);
> > + tok = NUMBER;
> > + break;
> > + default:
> > + tok = *s;
> > + break;
> > + }
> > + *pp = p;
> > + return tok;
> > +}
> > +
> > +/* Caller must make sure id is allocated */
> > +void expr__add_id(struct parse_ctx *ctx, const char *name, double val)
> > +{
> > + int idx;
> > + assert(ctx->num_ids < MAX_PARSE_ID);
> > + idx = ctx->num_ids++;
> > + ctx->ids[idx].name = name;
> > + ctx->ids[idx].val = val;
> > +}
> > +
> > +void expr__ctx_init(struct parse_ctx *ctx)
> > +{
> > + ctx->num_ids = 0;
> > +}
> > +
> > +int expr__find_other(const char *p, const char *one, const char ***other,
> > + int *num_otherp)
> > +{
> > + const char *orig = p;
> > + int err = -1;
> > + int num_other;
> > +
> > + *other = malloc((EXPR_MAX_OTHER + 1) * sizeof(char *));
> > + if (!*other)
> > + return -1;
> > +
> > + num_other = 0;
> > + for (;;) {
> > + YYSTYPE val;
> > + int tok = expr__lex(&val, &p);
> > + if (tok == 0) {
> > + err = 0;
> > + break;
> > + }
> > + if (tok == ID && strcasecmp(one, val.id)) {
> > + if (num_other >= EXPR_MAX_OTHER - 1) {
> > + pr_debug("Too many extra events in %s\n", orig);
> > + break;
> > + }
> > + (*other)[num_other] = strdup(val.id);
> > + if (!(*other)[num_other])
> > + return -1;
> > + num_other++;
> > + }
> > + }
> > + (*other)[num_other] = NULL;
> > + *num_otherp = num_other;
> > + if (err) {
> > + *num_otherp = 0;
> > + free(*other);
> > + *other = NULL;
> > + }
> > + return err;
> > +}
> > --
> > 2.9.3

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