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From: Andrew Morton <akpm@linux-foundation.org>
To: Ankit Khushwaha <ankitkhushwaha.linux@gmail.com>
Cc: linux-kselftest@vger.kernel.org, Shuah Khan <shuah@kernel.org>,
	Bala-Vignesh-Reddy <reddybalavignesh9979@gmail.com>,
	Wei Yang <richard.weiyang@gmail.com>,
	linux-kernel@vger.kernel.org,
	linux-kernel-mentees@lists.linuxfoundation.org,
	Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH] selftests/user_events: Avoid taking address of packed member in perf_test
Date: Tue, 28 Oct 2025 13:26:05 -0700	[thread overview]
Message-ID: <20251028132605.2926d3ef5eb6ea60d22ceffe@linux-foundation.org> (raw)
In-Reply-To: <aQD2Igc3svAF3klc@fedora>

On Tue, 28 Oct 2025 22:28:10 +0530 Ankit Khushwaha <ankitkhushwaha.linux@gmail.com> wrote:

> > > @@ -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, &reg.write_index,
> > > +	memcpy(&write_index, &reg.write_index, sizeof(reg.write_index));
> > > +	ASSERT_NE(-1, write(self->data_fd, &write_index,
> > >  	                    sizeof(reg.write_index)));
> > 
> > Simply casting &write_index to void* would fix this?
> 
> yes, this hides the type mismatch from the compiler. But i think
> casting to void * will not fix the alignment mismatch for packed struct.
> It works on x86, but might break on other platform.

It's the second argument to write(2)!  write(2) expects a const char *,
but void* will work.

  reply	other threads:[~2025-10-28 20:26 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-10-27 11:34 [PATCH] selftests/user_events: Avoid taking address of packed member in perf_test Ankit Khushwaha
2025-10-27 23:25 ` Andrew Morton
2025-10-28 16:58   ` Ankit Khushwaha
2025-10-28 20:26     ` Andrew Morton [this message]
2025-10-29 15:20       ` Ankit Khushwaha
2025-11-01  3:19         ` Andrew Morton

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