From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4CE4C433EF for ; Mon, 6 Sep 2021 15:22:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AC3DA60F13 for ; Mon, 6 Sep 2021 15:22:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229531AbhIFPXy (ORCPT ); Mon, 6 Sep 2021 11:23:54 -0400 Received: from foss.arm.com ([217.140.110.172]:56682 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233929AbhIFPXy (ORCPT ); Mon, 6 Sep 2021 11:23:54 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1CA3A31B; Mon, 6 Sep 2021 08:22:49 -0700 (PDT) Received: from e121896.arm.com (unknown [10.57.47.83]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id B7C3E3F766; Mon, 6 Sep 2021 08:22:47 -0700 (PDT) From: James Clark To: acme@kernel.org, linux-perf-users@vger.kernel.org Cc: James Clark , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , linux-kernel@vger.kernel.org Subject: [PATCH] perf tests: Fix flaky test 'Object code reading' Date: Mon, 6 Sep 2021 16:22:38 +0100 Message-Id: <20210906152238.3415467-1-james.clark@arm.com> X-Mailer: git-send-email 2.28.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org This test occasionally fails on aarch64 when a sample is taken in free@plt and it fails with "Bytes read differ from those read by objdump". This is because that symbol is near a section boundary in the elf file. Despite the -z option to always output zeros, objdump uses bfd_map_over_sections() to iterate through the elf file so it doesn't see outside of the sections where these zeros are and can't print them. For example this boundary proceeds free@plt in libc with a gap of 48 bytes between .plt and .text: objdump -d -z --start-address=0x23cc8 --stop-address=0x23d08 libc-2.30.so libc-2.30.so: file format elf64-littleaarch64 Disassembly of section .plt: 0000000000023cc8 <*ABS*+0x7fd00@plt+0x8>: 23cc8: 91018210 add x16, x16, #0x60 23ccc: d61f0220 br x17 Disassembly of section .text: 0000000000023d00 : 23d00: a9bf7bfd stp x29, x30, [sp, #-16]! 23d04: 910003fd mov x29, sp Taking a sample in free@plt is very rare because it is so small, but the test can be forced to fail almost every time on any platform by linking the test with a shared library that has a single empty function and calling it in a loop. The fix is to zero the buffers so that when there is a jump in the addresses output by objdump, zeros are already filled in between. Signed-off-by: James Clark --- tools/perf/tests/code-reading.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c index 9866cddebf23..9b4a765e4b73 100644 --- a/tools/perf/tests/code-reading.c +++ b/tools/perf/tests/code-reading.c @@ -229,8 +229,8 @@ static int read_object_code(u64 addr, size_t len, u8 cpumode, struct thread *thread, struct state *state) { struct addr_location al; - unsigned char buf1[BUFSZ]; - unsigned char buf2[BUFSZ]; + unsigned char buf1[BUFSZ] = {0}; + unsigned char buf2[BUFSZ] = {0}; size_t ret_len; u64 objdump_addr; const char *objdump_name; -- 2.28.0