+ selftests-user_events-fix-type-cast-for-write_index-packed-member-in-perf_test.patch added to mm-hotfixes-unstable branch

+ selftests-user_events-fix-type-cast-for-write_index-packed-member-in-perf_test.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: selftests/user_events: fix type cast for write_index packed member in perf_test
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     selftests-user_events-fix-type-cast-for-write_index-packed-member-in-perf_test.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-user_events-fix-type-cast-for-write_index-packed-member-in-perf_test.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Ankit Khushwaha <ankitkhushwaha.linux@gmail.com>
Subject: selftests/user_events: fix type cast for write_index packed member in perf_test
Date: Thu, 6 Nov 2025 15:25:32 +0530

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, &reg.write_index,
      |                                             ^~~~~~~~~~~~~~~

Since write(2) works with any alignment. Casting '&reg.write_index'
explicitly to 'void *' to suppress this warning.

Link: https://lkml.kernel.org/r/20251106095532.15185-1-ankitkhushwaha.linux@gmail.com
Fixes: 42187bdc3ca4 ("selftests/user_events: Add perf self-test for empty arguments events")
Signed-off-by: Ankit Khushwaha <ankitkhushwaha.linux@gmail.com>
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: sunliming <sunliming@kylinos.cn>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/user_events/perf_test.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/testing/selftests/user_events/perf_test.c~selftests-user_events-fix-type-cast-for-write_index-packed-member-in-perf_test
+++ a/tools/testing/selftests/user_events/perf_test.c
@@ -236,7 +236,7 @@ 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, &reg.write_index,
+	ASSERT_NE(-1, write(self->data_fd, (void *)&reg.write_index,
 					sizeof(reg.write_index)));
 	val = (void *)(((char *)perf_page) + perf_page->data_offset);
 	ASSERT_EQ(PERF_RECORD_SAMPLE, *val);
_

Patches currently in -mm which might be from ankitkhushwaha.linux@gmail.com are

selftests-user_events-fix-type-cast-for-write_index-packed-member-in-perf_test.patch