[PATCH 08/10] perf, tools: Add a simple expression parser for JSON

Andi Kleen
2017-01-28T02:21:40Z

From: Andi Kleen <ak@linux.intel.com>

Add a simple expression parser good enough to parse JSON relation
expressions. The parser is implemented using bison.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
tools/perf/tests/Build | 1 +
tools/perf/tests/builtin-test.c | 4 ++
tools/perf/tests/expr.c | 48 +++++++++++++
tools/perf/tests/tests.h | 1 +
tools/perf/util/Build | 5 ++
tools/perf/util/expr.h | 23 ++++++
tools/perf/util/expr.y | 156 ++++++++++++++++++++++++++++++++++++++++
7 files changed, 238 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 37e326bfd2dc..db03e853ba7f 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..38e4bb31692c
--- /dev/null
+++ b/tools/perf/tests/expr.c
@@ -0,0 +1,48 @@
+#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;
+ double val;
+ int ret;
+ struct parse_ctx ctx;
+
+ 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", "FOO", &p) == 0);
+ TEST_ASSERT_VAL("find other", !strcmp(p, "BAR"));
+ free((void *)p);
+
+ 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 5da376bc1afc..887642ca609c 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -88,6 +88,7 @@ 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
@@ -140,6 +141,10 @@ $(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..3b99fa282059
--- /dev/null
+++ b/tools/perf/util/expr.h
@@ -0,0 +1,23 @@
+#ifndef PARSE_CTX_H
+#define PARSE_CTX_H 1
+
+#define MAX_PARSE_ID 2
+
+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);
+
+#endif
diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y
new file mode 100644
index 000000000000..9c2c39512b8d
--- /dev/null
+++ b/tools/perf/util/expr.y
@@ -0,0 +1,156 @@
+/* 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", 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)
+{
+ const char *orig = p;
+
+ *other = NULL;
+ for (;;) {
+ YYSTYPE val;
+ int tok = expr_lex(&val, &p);
+ if (tok == 0)
+ break;
+ if (tok == ID && strcasecmp(one, val.id)) {
+ if (*other) {
+ pr_debug("More than one extra identifier in %s\n", orig);
+ return -1;
+ }
+ *other = strdup(val.id);
+ if (!*other)
+ return -1;
+ }
+ }
+ return 0;
+}
--
2.9.3