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Mon, 27 Oct 2025 04:34:52 -0700 (PDT) Received: from fedora ([103.120.31.122]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-29498cf33f9sm78216485ad.22.2025.10.27.04.34.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Oct 2025 04:34:52 -0700 (PDT) From: Ankit Khushwaha To: linux-kselftest@vger.kernel.org, Shuah Khan Cc: Bala-Vignesh-Reddy , Andrew Morton , Wei Yang , linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, Ankit Khushwaha Subject: [PATCH] selftests/user_events: Avoid taking address of packed member in perf_test Date: Mon, 27 Oct 2025 17:04:39 +0530 Message-ID: <20251027113439.36059-1-ankitkhushwaha.linux@gmail.com> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-kernel-mentees@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Accessing 'reg.write_index' directly triggers a -Waddress-of-packed-member warning due to potential unaligned pointer access: perf_test.c:239:38: warning: taking address of packed member 'write_index' of class or structure 'user_reg' may result in an unaligned pointer value [-Waddress-of-packed-member] 239 | ASSERT_NE(-1, write(self->data_fd, ®.write_index, | ^~~~~~~~~~~~~~~ Use memcpy() instead to safely copy the value and avoid unaligned pointer access across architectures. Signed-off-by: Ankit Khushwaha --- tools/testing/selftests/user_events/perf_test.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/user_events/perf_test.c b/tools/testing/selftests/user_events/perf_test.c index 201459d8094d..e4385f4aa231 100644 --- a/tools/testing/selftests/user_events/perf_test.c +++ b/tools/testing/selftests/user_events/perf_test.c @@ -201,6 +201,7 @@ TEST_F(user, perf_empty_events) { struct perf_event_mmap_page *perf_page; int page_size = sysconf(_SC_PAGESIZE); int id, fd; + __u32 write_index; __u32 *val; reg.size = sizeof(reg); @@ -236,7 +237,8 @@ TEST_F(user, perf_empty_events) { ASSERT_EQ(1 << reg.enable_bit, self->check); /* Ensure write shows up at correct offset */ - ASSERT_NE(-1, write(self->data_fd, ®.write_index, + memcpy(&write_index, ®.write_index, sizeof(reg.write_index)); + ASSERT_NE(-1, write(self->data_fd, &write_index, sizeof(reg.write_index))); val = (void *)(((char *)perf_page) + perf_page->data_offset); ASSERT_EQ(PERF_RECORD_SAMPLE, *val); -- 2.51.0