Date:   Tue, 21 Mar 2017 16:14:23 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Andi Kleen <andi@...stfloor.org>
Cc:     jolsa@...nel.org, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 07/13] perf, tools: Add a simple expression parser for
 JSON

Em Mon, Mar 20, 2017 at 01:17:05PM -0700, Andi Kleen escreveu:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> 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...

- 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@...ux.intel.com>
> ---
>  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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