diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index 6fdf073093a6..c0cf8dff694e 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -121,6 +121,7 @@ perf-y += mem-events.o
 perf-y += vsprintf.o
 perf-y += units.o
 perf-y += time-utils.o
+perf-y += expr-flex.o
 perf-y += expr-bison.o
 perf-y += expr.o
 perf-y += branch.o
@@ -190,9 +191,13 @@ $(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-flex.c: util/expr.l $(OUTPUT)util/expr-bison.c
+	$(call rule_mkdir)
+	$(Q)$(call echo-cmd,flex)$(FLEX) -o $@ --header-file=$(OUTPUT)util/expr-flex.h $(PARSER_DEBUG_FLEX) util/expr.l
+
 $(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__
+	$(Q)$(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)
@@ -204,12 +209,14 @@ $(OUTPUT)util/pmu-bison.c: util/pmu.y
 
 CFLAGS_parse-events-flex.o  += -w
 CFLAGS_pmu-flex.o           += -w
+CFLAGS_expr-flex.o          += -w
 CFLAGS_parse-events-bison.o += -DYYENABLE_NLS=0 -w
 CFLAGS_pmu-bison.o          += -DYYENABLE_NLS=0 -DYYLTYPE_IS_TRIVIAL=0 -w
 CFLAGS_expr-bison.o         += -DYYENABLE_NLS=0 -DYYLTYPE_IS_TRIVIAL=0 -w
 
 $(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
 
 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))"
@@ -217,6 +224,7 @@ CFLAGS_rbtree.o        += -Wno-unused-parameter -DETC_PERFCONFIG="BUILD_STR($(ET
 CFLAGS_libstring.o     += -Wno-unused-parameter -DETC_PERFCONFIG="BUILD_STR($(ETC_PERFCONFIG_SQ))"
 CFLAGS_hweight.o       += -Wno-unused-parameter -DETC_PERFCONFIG="BUILD_STR($(ETC_PERFCONFIG_SQ))"
 CFLAGS_parse-events.o  += -Wno-redundant-decls
+CFLAGS_expr.o          += -Wno-redundant-decls
 CFLAGS_header.o        += -include $(OUTPUT)PERF-VERSION-FILE
 
 $(OUTPUT)util/kallsyms.o: ../lib/symbol/kallsyms.c FORCE
diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
index 816b23b2068a..b39fd39f10ec 100644
--- a/tools/perf/util/expr.c
+++ b/tools/perf/util/expr.c
@@ -1,6 +1,14 @@
 // SPDX-License-Identifier: GPL-2.0
+#include <stdbool.h>
 #include <assert.h>
 #include "expr.h"
+#include "expr-bison.h"
+#define YY_EXTRA_TYPE int
+#include "expr-flex.h"
+
+#ifdef PARSER_DEBUG
+extern int expr_debug;
+#endif
 
 /* Caller must make sure id is allocated */
 void expr__add_id(struct parse_ctx *ctx, const char *name, double val)
@@ -17,3 +25,88 @@ void expr__ctx_init(struct parse_ctx *ctx)
 {
 	ctx->num_ids = 0;
 }
+
+static int
+__expr__parse(double *val, struct parse_ctx *ctx, const char *expr,
+	      int start)
+{
+	YY_BUFFER_STATE buffer;
+	void *scanner;
+	int ret;
+
+	ret = expr_lex_init_extra(start, &scanner);
+	if (ret)
+		return ret;
+
+	buffer = expr__scan_string(expr, scanner);
+
+#ifdef PARSER_DEBUG
+	expr_debug = 1;
+#endif
+
+	ret = expr_parse(val, ctx, scanner);
+
+	expr__flush_buffer(buffer, scanner);
+	expr__delete_buffer(buffer, scanner);
+	expr_lex_destroy(scanner);
+	return ret;
+}
+
+int expr__parse(double *final_val, struct parse_ctx *ctx, const char **pp)
+{
+	return __expr__parse(final_val, ctx, *pp, EXPR_PARSE);
+}
+
+static bool
+already_seen(const char *val, const char *one, const char **other,
+	     int num_other)
+{
+	int i;
+
+	if (one && !strcasecmp(one, val))
+		return true;
+	for (i = 0; i < num_other; i++)
+		if (!strcasecmp(other[i], val))
+			return true;
+	return false;
+}
+
+int expr__find_other(const char *p, const char *one, const char ***other,
+		     int *num_other)
+{
+	int err, i = 0, j = 0;
+	struct parse_ctx ctx;
+
+	expr__ctx_init(&ctx);
+	err = __expr__parse(NULL, &ctx, p, EXPR_OTHER);
+	if (err)
+		return -1;
+
+	*other = malloc((ctx.num_ids + 1) * sizeof(char *));
+	if (!*other)
+		return -ENOMEM;
+
+	for (i = 0, j = 0; i < ctx.num_ids; i++) {
+		const char *str = ctx.ids[i].name;
+
+		if (already_seen(str, one, *other, j))
+			continue;
+
+		str = strdup(str);
+		if (!str)
+			goto out;
+		(*other)[j++] = str;
+	}
+	(*other)[j] = NULL;
+
+out:
+	if (i != ctx.num_ids) {
+		while (--j)
+			free((char *) (*other)[i]);
+		free(*other);
+		err = -1;
+	}
+
+	*num_other = j;
+	return err;
+}
diff --git a/tools/perf/util/expr.h b/tools/perf/util/expr.h
index 046160831f90..9332796e6649 100644
--- a/tools/perf/util/expr.h
+++ b/tools/perf/util/expr.h
@@ -17,9 +17,7 @@ struct parse_ctx {
 
 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);
 
diff --git a/tools/perf/util/expr.l b/tools/perf/util/expr.l
new file mode 100644
index 000000000000..1928f2a3dddc
--- /dev/null
+++ b/tools/perf/util/expr.l
@@ -0,0 +1,114 @@
+%option prefix="expr_"
+%option reentrant
+%option bison-bridge
+
+%{
+#include <linux/compiler.h>
+#include "expr.h"
+#include "expr-bison.h"
+
+char *expr_get_text(yyscan_t yyscanner);
+YYSTYPE *expr_get_lval(yyscan_t yyscanner);
+
+static int __value(YYSTYPE *yylval, char *str, int base, int token)
+{
+	u64 num;
+
+	errno = 0;
+	num = strtoull(str, NULL, base);
+	if (errno)
+		return EXPR_ERROR;
+
+	yylval->num = num;
+	return token;
+}
+
+static int value(yyscan_t scanner, int base)
+{
+	YYSTYPE *yylval = expr_get_lval(scanner);
+	char *text = expr_get_text(scanner);
+
+	return __value(yylval, text, base, NUMBER);
+}
+
+/*
+ * Allow @ instead of / to be able to specify pmu/event/ without
+ * conflicts with normal division.
+ */
+static char *normalize(char *str)
+{
+	char *ret = str;
+	char *dst = str;
+
+	while (*str) {
+		if (*str == '@')
+			*dst++ = '/';
+		else if (*str == '\\')
+			*dst++ = *++str;
+		else
+			*dst++ = *str;
+		str++;
+	}
+
+	*dst = 0x0;
+	return ret;
+}
+
+static int str(yyscan_t scanner, int token)
+{
+	YYSTYPE *yylval = expr_get_lval(scanner);
+	char *text = expr_get_text(scanner);
+
+	yylval->str = normalize(strdup(text));
+	if (!yylval->str)
+		return EXPR_ERROR;
+
+	yylval->str = normalize(yylval->str);
+	return token;
+}
+%}
+
+number		[0-9]+
+
+sch		[-,=]
+spec		\\{sch}
+sym		[0-9a-zA-Z_\.:@]+
+symbol		{spec}*{sym}*{spec}*{sym}*
+
+%%
+	{
+		int start_token;
+
+		start_token = parse_events_get_extra(yyscanner);
+
+		if (start_token) {
+			parse_events_set_extra(NULL, yyscanner);
+			return start_token;
+		}
+	}
+
+max		{ return MAX; }
+min		{ return MIN; }
+if		{ return IF; }
+else		{ return ELSE; }
+#smt_on		{ return SMT_ON; }
+{number}	{ return value(yyscanner, 10); }
+{symbol}	{ return str(yyscanner, ID); }
+"|"		{ return '|'; }
+"^"		{ return '^'; }
+"&"		{ return '&'; }
+"-"		{ return '-'; }
+"+"		{ return '+'; }
+"*"		{ return '*'; }
+"/"		{ return '/'; }
+"%"		{ return '%'; }
+"("		{ return '('; }
+")"		{ return ')'; }
+","		{ return ','; }
+.		{ }
+%%
+
+int expr_wrap(void *scanner __maybe_unused)
+{
+	return 1;
+}
diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y
index 7cea8b7c3a5c..4720cbe79357 100644
--- a/tools/perf/util/expr.y
+++ b/tools/perf/util/expr.y
@@ -1,5 +1,7 @@
 /* Simple expression parser */
 %{
+#define YYDEBUG 1
+#include <stdio.h>
 #include "util.h"
 #include "util/debug.h"
 #include <stdlib.h> // strtod()
@@ -8,23 +10,23 @@
 #include "smt.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 }
+%parse-param {void *scanner}
+%lex-param {void* scanner}
 
 %union {
-	double num;
-	char id[MAXIDLEN+1];
+	double	 num;
+	char	*str;
 }
 
+%token EXPR_PARSE EXPR_OTHER EXPR_ERROR
 %token <num> NUMBER
-%token <id> ID
+%token <str> ID
 %token MIN MAX IF ELSE SMT_ON
 %left MIN MAX IF
 %left '|'
@@ -36,11 +38,9 @@
 %type <num> expr if_expr
 
 %{
-static int expr__lex(YYSTYPE *res, const char **pp);
-
-static void expr__error(double *final_val __maybe_unused,
+static void expr_error(double *final_val __maybe_unused,
 		       struct parse_ctx *ctx __maybe_unused,
-		       const char **pp __maybe_unused,
+		       void *scanner,
 		       const char *s)
 {
 	pr_debug("%s\n", s);
@@ -62,6 +62,27 @@ static int lookup_id(struct parse_ctx *ctx, char *id, double *val)
 %}
 %%
 
+start:
+EXPR_PARSE all_expr
+|
+EXPR_OTHER all_other
+
+all_other: all_other other
+|
+
+other: ID
+{
+	if (ctx->num_ids + 1 >= EXPR_MAX_OTHER) {
+		pr_err("failed: way too many variables");
+		YYABORT;
+	}
+
+	ctx->ids[ctx->num_ids++].name = $1;
+}
+|
+MIN | MAX | IF | ELSE | SMT_ON | NUMBER | '|' | '^' | '&' | '-' | '+' | '*' | '/' | '%' | '(' | ')'
+
+
 all_expr: if_expr			{ *final_val = $1; }
 	;
 
@@ -92,131 +113,3 @@ expr:	  NUMBER
 	;
 
 %%
-
-static int expr__symbol(YYSTYPE *res, const char *p, const char **pp)
-{
-	char *dst = res->id;
-	const char *s = p;
-
-	if (*p == '#')
-		*dst++ = *p++;
-
-	while (isalnum(*p) || *p == '_' || *p == '.' || *p == ':' || *p == '@' || *p == '\\') {
-		if (p - s >= MAXIDLEN)
-			return -1;
-		/*
-		 * Allow @ instead of / to be able to specify pmu/event/ without
-		 * conflicts with normal division.
-		 */
-		if (*p == '@')
-			*dst++ = '/';
-		else if (*p == '\\')
-			*dst++ = *++p;
-		else
-			*dst++ = *p;
-		p++;
-	}
-	*dst = 0;
-	*pp = p;
-	dst = res->id;
-	switch (dst[0]) {
-	case 'm':
-		if (!strcmp(dst, "min"))
-			return MIN;
-		if (!strcmp(dst, "max"))
-			return MAX;
-		break;
-	case 'i':
-		if (!strcmp(dst, "if"))
-			return IF;
-		break;
-	case 'e':
-		if (!strcmp(dst, "else"))
-			return ELSE;
-		break;
-	case '#':
-		if (!strcasecmp(dst, "#smt_on"))
-			return SMT_ON;
-		break;
-	}
-	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 '#':
-	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;
-}
-
-static bool already_seen(const char *val, const char *one, const char **other,
-			 int num_other)
-{
-	int i;
-
-	if (one && !strcasecmp(one, val))
-		return true;
-	for (i = 0; i < num_other; i++)
-		if (!strcasecmp(other[i], val))
-			return true;
-	return false;
-}
-
-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 && !already_seen(val.id, one, *other, num_other)) {
-			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;
-}