From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D9BD43BB2E; Mon, 15 Jul 2024 17:32:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721064740; cv=none; b=C0SxWltFOJirgoCqZPWY2mu8nsP26FfnsxOOm/XRw8IhHscT0vBisJT2hlG3I1+LACTB/4CJ9amWJWur4BRn6W/80QbzjVChBPtOvGQE5ZXAmOr+X/QyJBhdeqSCWvrxnQfPPx7NhduqWBitwhf+i0dOxsgulLo4KVt38MfQQpY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721064740; c=relaxed/simple; bh=Ld9cDA3lpvsmdK2nYMlNTaSs7LqOmiT44dFooljuzFQ=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=ahzpVeljORVpOEKINGw8zUM13e5rOb2oHiAGCYTFMCi2L2EXaKeqEDy+2m0++AQtMT5EhkgpNkE3Ym3BckO2i3br7hdciUPw9RVhp1HiokcBk4JDbZ6HyQYvAelS0BUxDWv/jWL/0hQMZBy6vNsjno5ATDSUvEksVPMikG41AA8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SM1epBm8; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="SM1epBm8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 31650C32782; Mon, 15 Jul 2024 17:32:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1721064739; bh=Ld9cDA3lpvsmdK2nYMlNTaSs7LqOmiT44dFooljuzFQ=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=SM1epBm8MSPpexKCCvXL47i3FptPaZ7EwLUvGLmtJ6ozHQsxV0KGTr5X2ZTn9Kp2b khWr7AhKUiHuFvnypUfCmpcco40pRewuepBENg5u82267UBftGC2VAatmDrfdqqR2m 39CoC+mFoIg3KJPLnyrrXK5VIF95uAbE1osE1q/MH8I22Ib1FKfYsLgflrhH3xthit qdEn9j12mvVHR4Do9yYxhbdysWJdm7FUS9+Ii0/+PkQ3AAZuGo9Pb4TQPsqPxkFHzE UHI+kUA/m7NwpiwEjBfYzzZ3/oq729MLenpcuMKrI2XN4TYN6KxOs8r4T1x2OxkgOp fIDMVXPCI2LLA== From: Puranjay Mohan To: Alexei Starovoitov Cc: Daniel Borkmann , Manu Bretelle , KP Singh , Andrii Nakryiko , Eduard Zingerman , Mykola Lysenko , Alexei Starovoitov , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , "bpf@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Florent Revest Subject: Re: [PATCH bpf] selftests/bpf: DENYLIST.aarch64: Remove fexit_sleep In-Reply-To: References: <20240705145009.32340-1-puranjay@kernel.org> <224eeadb-fc5f-baeb-0808-a4f9916afa3c@iogearbox.net> <890d23f2-636e-12d1-31cc-eb6469f2a9ac@iogearbox.net> <978e127b-4967-950d-ccca-8575d1a885ae@iogearbox.net> Date: Mon, 15 Jul 2024 17:32:09 +0000 Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha512; protocol="application/pgp-signature" --=-=-= Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Alexei Starovoitov writes: > On Mon, Jul 15, 2024 at 9:32=E2=80=AFAM Puranjay Mohan wrote: >> >> >> Hi Daniel, Manu >> I was able to reproduce this issue on KVM and found the root cause for >> this hang! The other issue that we fixed is unrelated to this hang and >> doesn't occur on self hosted github runners as they use 48-bit VAs. >> >> The userspace test code has: >> >> #define STACK_SIZE (1024 * 1024) >> static char child_stack[STACK_SIZE]; >> >> cpid =3D clone(do_sleep, child_stack + STACK_SIZE, CLONE_FILES | SIG= CHLD, fexit_skel); >> >> arm64 requires the stack pointer to be 16 byte aligned otherwise >> SPAlignmentFault occurs, this appears as Bus error in the userspace. >> >> The stack provided to the clone system call is not guaranteed to be >> aligned properly in this selftest. >> >> The test hangs on the following line: >> while (READ_ONCE(fexit_skel->bss->fentry_cnt) !=3D 2); >> >> Because the child process is killed due to SPAlignmentFault, the >> fentry_cnt remains at 0! >> >> Reading the man page of clone system call, the correct way to allocate >> stack for this call is using mmap like this: >> >> stack =3D mmap(NULL, STACK_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | M= AP_ANONYMOUS | MAP_STACK, -1, 0); >> >> This fixes the issue, I will send a patch to use this and once again >> remove this test from DENYLIST and I hope this time it fixes it for good. > > Wow. Great find. Good to know. > prog_tests/ns_current_pid_tgid.c has the same issue probably. Yes, I checked that test as well using gdb and fortunately it gets a 16 byte aligned stack pointer, but this is just luck, so I will send a patch to fix that test as well. Thanks, Puranjay --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iIoEARYKADIWIQQ3wHGvVs/5bdl78BKwwPkjG3B2nQUCZpVdGhQccHVyYW5qYXlA a2VybmVsLm9yZwAKCRCwwPkjG3B2ncNtAP9ccbKwshl53VerOv2daBOQnK2BZ41e aLgFtIkQzm5jVQEAnvyxFRzuNIA60GgUagu+nAhYZ/Voo3z3sxJvjHAIwww= =Jnla -----END PGP SIGNATURE----- --=-=-=--