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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 21711C433EF for ; Fri, 1 Jul 2022 11:37:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=hNrvIePcKMl5YhSZWJG2hfHq8k4fdexDujRAuDr75bU=; b=ZddBs/Uxe9L4Si 17qCjeQpR3joM3DqQaUW6iQ6H86mbNT2kdqMmtBprgU1EiVvDv72fwS4iI51ZHEb6OP26Xlji0tkf UJKTuIVEHfksu2VV/NG/2y7Bpi1ccSK8PLovdf1T6QP4JhgouoY0W/KLSiw9901JCydpP0r1KsBUh 5YG13q4gPCZ2/NM2/plhc5QUrt3TvjGK3Fqw0EMSnKJQtL8IDmAoLrfTamWMuOmw59t4qv+iva2Mb C1K3mEi48v3zepvwMjKzTeMe+Q3miuU7lD/APOWougEv81sEu+7rYLagrfq4dXeV084lIXW3Tx/Lx qleSBoohdceYwVNjPWXw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1o7Ex0-004PkJ-CQ; Fri, 01 Jul 2022 11:36:42 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1o7Ewx-004PjY-8b for linux-arm-kernel@lists.infradead.org; Fri, 01 Jul 2022 11:36:40 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id BEDFE6257E; Fri, 1 Jul 2022 11:36:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D8F63C3411E; Fri, 1 Jul 2022 11:36:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1656675398; bh=ht0/icXtp2sEhQfzOe1RuBtF1QGRO0mLy1F9NHIwIJo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qyZWqqP3YjsMKExY+ED0ZanHiTPDFeMdcC/nLGmH+vSBWrYqBQh8SxDCTc5Q21gLf Lv5facBuIZ1jWgWiHzMjhxV4Occp1skkxdu6vo21XEI1H/F53M6Ye4LgopehyHWt49 htVQPCblbBFrPs9L7ob86ybN7B2z263YOm5+d3cq+yTRVCh0+rvTSDCHjwePEH5+wo XEndL5gBSwwkmwkIWxSXidRDERgwEVE4V96JMjZ6g0aIzNE1k2HqV4wEZsAVbitjak PC9dlRbm/nJ44eKV1THZwK+9YC2Sx7dSYUGjsd2DMCBAEuX9rSalrKbr+HGGdzg/1b A5IWpBj0QR6GA== Date: Fri, 1 Jul 2022 12:36:32 +0100 From: Will Deacon To: Francis Laniel 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. Message-ID: <20220701113631.GC28070@willie-the-truck> References: <20220608162447.666494-1-flaniel@linux.microsoft.com> <20220628135834.GA24116@willie-the-truck> <3439466.iIbC2pHGDl@pwmachine> <4722000.GXAFRqVoOG@pwmachine> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <4722000.GXAFRqVoOG@pwmachine> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220701_043639_422179_C8D45B80 X-CRM114-Status: GOOD ( 40.44 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jun 30, 2022 at 07:16:44PM +0200, Francis Laniel wrote: > Hi. > = > Le mardi 28 juin 2022, 21:26:32 CEST Francis Laniel a =E9crit : > > 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_exe= cve > > > > 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->sysca= llno > > > > to its previous value. > > > > = > > > > Signed-off-by: Francis Laniel > > > > --- > > > > = > > > > arch/arm64/include/asm/processor.h | 3 ++- > > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > = > > > > diff --git a/arch/arm64/include/asm/processor.h > > > > b/arch/arm64/include/asm/processor.h index 9e58749db21d..86eb0bfe3b= 38 > > > > 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); > > > > = > > > > static inline void start_thread_common(struct pt_regs *regs, unsig= ned > > > > long pc) { > > > > = > > > > + s32 previous_syscall =3D regs->syscallno; > > > > = > > > > memset(regs, 0, sizeof(*regs)); > > > > = > > > > - forget_syscall(regs); > > > > + regs->syscallno =3D previous_syscall; > > > = > > > I'm still unsure about this. Even if we preserve the syscall number h= ere, > > > won't all the arguments be reported as 0? > > = > > I am not really sure what you meant about arguments, can you please pre= cise > > between command line arguments (ls -al) and syscall arguments (argp, en= vp, > > etc.)? > > Indeed, if my understanding is correct syscall arguments are showed by > > 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 > > syscall_trace_exit() but set in invoke_syscall() after the syscall fini= shes > > [1, 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) > > = > > > 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 tested arm32 and it is not affected (even though I did not have = > CONFIG_BINFMT_ELF_FDPIC set). > Here is ftrace output for arm64 without this patch: > bash-316 [000] ..... 72.167342: sys_execve(filename: = > aaaaf9bbcd30, argv: aaaaf9bb54f0, envp: aaaaf9a7d9b0) > Here is the output for arm64 with this patch: > cat-313 [000] ..... 417.926073: sys_execve(filename: = > aaaaee7ce9f0, argv: aaaaee7833a0, envp: aaaaee6a69b0) > cat-313 [000] ..... 417.939619: sys_execve -> 0x0 > And here is output for arm32: > cat-254 [000] ..... 127.804128: sys_execve(filename: 5= bff18, = > argv: 53bb00, envp: 5543a8) > cat-254 [000] ..... 127.809142: sys_execve -> 0x0 > From the above, the arm32 output seems correct even though: > # CONFIG_BINFMT_ELF_FDPIC is not set > = > After some debugging, I realized that arm32 syscall_get_nr() uses abi_sys= call = > to get the syscall number and not a register (I guess abi_syscall was set= to = > value of R7 before) [1]. > So the fact that regs->uregs are memset'ed to 0 is not a problem. Thanks for confirming this, I'll go ahead and queue your patch and let's hope nothing breaks :) Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel