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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 807DAC43334 for ; Tue, 28 Jun 2022 19:30:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232240AbiF1Taj (ORCPT ); Tue, 28 Jun 2022 15:30:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39770 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230044AbiF1TaF (ORCPT ); Tue, 28 Jun 2022 15:30:05 -0400 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id A9B8A2CC8F; Tue, 28 Jun 2022 12:26:37 -0700 (PDT) Received: from pwmachine.localnet (lfbn-lyo-1-1062-211.w86-248.abo.wanadoo.fr [86.248.131.211]) by linux.microsoft.com (Postfix) with ESMTPSA id 28D8620CDF22; Tue, 28 Jun 2022 12:26:35 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 28D8620CDF22 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1656444397; bh=yr6ynDdw6pyVh9Iwg4x+jvCjxckbKOv/2p2g1OJXeOk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mduRND+hdKqkoVwX7rwN2WOfSSmhv5moEqFiXNXdSoyWo8lF1IcJzK1POPG9dc71u hcOxNdCTFYo+kw2fDyx1WE3cXbj585ZTHmUK0vNTkkbW4ypZwnGgBHwP3coyHuMO0y mxSyI6BDmOlJM5RsyUO0sm4gNpKKdVXnW3+CPANQ= From: Francis Laniel To: Will Deacon Cc: linux-trace-devel@vger.kernel.org, James Morse , Daniel Kiss , Catalin Marinas , Mark Brown , Peter Collingbourne , Kees Cook , Mark Rutland , Christophe Leroy , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/1] arm64: Do not forget syscall when starting a new thread. Date: Tue, 28 Jun 2022 21:26:32 +0200 Message-ID: <3439466.iIbC2pHGDl@pwmachine> Organization: Microsoft In-Reply-To: <20220628135834.GA24116@willie-the-truck> References: <20220608162447.666494-1-flaniel@linux.microsoft.com> <20220608162447.666494-2-flaniel@linux.microsoft.com> <20220628135834.GA24116@willie-the-truck> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org Hi. Le mardi 28 juin 2022, 15:58:35 CEST Will Deacon a =E9crit : > On Wed, Jun 08, 2022 at 05:24:46PM +0100, Francis Laniel wrote: > > This patch enables exeve*() to be traced with syscalls:sys_exit_execve > > tracepoint. > > Previous to it, by calling forget_syscall(), this tracepoint would not > > print its information as syscall is -1. > > So, this patch removes call to forget_syscall() and set regs->syscallno > > to its previous value. > >=20 > > Signed-off-by: Francis Laniel > > --- > >=20 > > arch/arm64/include/asm/processor.h | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > >=20 > > diff --git a/arch/arm64/include/asm/processor.h > > b/arch/arm64/include/asm/processor.h index 9e58749db21d..86eb0bfe3b38 > > 100644 > > --- a/arch/arm64/include/asm/processor.h > > +++ b/arch/arm64/include/asm/processor.h > > @@ -272,8 +272,9 @@ void tls_preserve_current_state(void); > >=20 > > static inline void start_thread_common(struct pt_regs *regs, unsigned > > long pc) { > >=20 > > + s32 previous_syscall =3D regs->syscallno; > >=20 > > memset(regs, 0, sizeof(*regs)); > >=20 > > - forget_syscall(regs); > > + regs->syscallno =3D previous_syscall; >=20 > I'm still unsure about this. Even if we preserve the syscall number here, > won't all the arguments be reported as 0? I am not really sure what you meant about arguments, can you please precise= =20 between command line arguments (ls -al) and syscall arguments (argp, envp,= =20 etc.)? Indeed, if my understanding is correct syscall arguments are showed by=20 sys_enter_* while sys_exit_* only reports the syscall return code. Regarding the return code I think the value is correct as it is used in=20 syscall_trace_exit() but set in invoke_syscall() after the syscall finishes= [1,=20 2]. The comparison of arm64 and amd64 output also shows no difference: # amd64 ls 435739 [002] 24689.292479: syscalls:sys_exit_execve: 0x0 7fc43732e100 _start+0x0 (/usr/lib/x86_64-linux-gnu/ld-2.31.so) # arm64 ls 266 [000] 34.708444: syscalls:sys_exit_execve: 0x0 1140 [unknown] (/usr/lib/aarch64-linux-gnu/ld-2.31.so) =20 > I also looked quickly at the 32-bit arch/arm/ code and it looks like the > same behaviour exists there (module CONFIG_BINFMT_ELF_FDPIC). I can try to fix it for this architecture too. Can you please point me the part of the code which shows the same behavior? =20 > Will Best regards. =2D-- [1] https://elixir.bootlin.com/linux/v5.18/source/arch/arm64/kernel/ ptrace.c#L1868 [2] https://elixir.bootlin.com/linux/v5.18/source/arch/arm64/kernel/ syscall.c#L57