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Date:   Wed, 22 Apr 2020 15:04:29 -0700
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Subject: [PATCH v2 10/11] perf expr: print a debug message for division by zero
From:   Ian Rogers <irogers@google.com>
To:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Kan Liang <kan.liang@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Haiyan Song <haiyanx.song@intel.com>,
        Jin Yao <yao.jin@linux.intel.com>,
        Song Liu <songliubraving@fb.com>,
        Ravi Bangoria <ravi.bangoria@linux.ibm.com>,
        John Garry <john.garry@huawei.com>,
        Leo Yan <leo.yan@linaro.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Paul Clarke <pc@us.ibm.com>, linux-kernel@vger.kernel.org,
        linux-perf-users@vger.kernel.org
Cc:     Stephane Eranian <eranian@google.com>,
        Ian Rogers <irogers@google.com>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

If an expression yields 0 and is then divided-by/modulus-by then the
parsing aborts. Add a debug error message to better enable debugging
when this happens.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/expr.y | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y
index 54260094b947..21e82a1e11a2 100644
--- a/tools/perf/util/expr.y
+++ b/tools/perf/util/expr.y
@@ -103,8 +103,18 @@ expr:	  NUMBER
 	| 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; $$ = (long)$1 % (long)$3; }
+	| expr '/' expr		{ if ($3 == 0) {
+					pr_debug("division by zero\n");
+					YYABORT;
+				  }
+				  $$ = $1 / $3;
+	                        }
+	| expr '%' expr		{ if ((long)$3 == 0) {
+					pr_debug("division by zero\n");
+					YYABORT;
+				  }
+				  $$ = (long)$1 % (long)$3;
+	                        }
 	| '-' expr %prec NEG	{ $$ = -$2; }
 	| '(' if_expr ')'	{ $$ = $2; }
 	| MIN '(' expr ',' expr ')' { $$ = $3 < $5 ? $3 : $5; }
-- 
2.26.2.303.gf8c07b1a785-goog