From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.12] helo=sc8-sf-mx2.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1CSsj0-00028m-V2 for user-mode-linux-devel@lists.sourceforge.net; Fri, 12 Nov 2004 23:53:34 -0800 Received: from smtp002.mail.ukl.yahoo.com ([217.12.11.33]) by sc8-sf-mx2.sourceforge.net with smtp (Exim 4.41) id 1CSsiz-0001zI-MH for user-mode-linux-devel@lists.sourceforge.net; Fri, 12 Nov 2004 23:53:34 -0800 From: Blaisorblade Subject: Re: [uml-devel] [Patch 1/1] uml: fix uml-use-sysemu-for-tt.patch References: <4194C43D.6030107@fujitsu-siemens.com> In-Reply-To: <4194C43D.6030107@fujitsu-siemens.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200411130854.51896.blaisorblade_spam@yahoo.it> Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Sat, 13 Nov 2004 08:54:51 +0100 To: user-mode-linux-devel@lists.sourceforge.net Cc: Bodo Stroesser , Jeff Dike On Friday 12 November 2004 15:10, Bodo Stroesser wrote: > From: Bodo Stroesser > > The patch needs some small corrections: > 1) local_using_sysemu must be sampled *before* the next > ptrace(PTRACE_SYSEMU/SYSCALL) and must stay the same until do_syscall() > has been done. Currently it is sampled before do_syscall() and is used > after this for ptrace(PTRACE_SYSEMU/SYSCALL). Even if no problem is > visible to the UML user, a single syscall could be executed on the host > when switching on sysemu. The result of this then is overwritten by the > syscall execution in UML. > Since the first event the tracer has to handle is not a syscall, it's > enough to initialize local_using_sysemu to 0; Sorry, what happens if the first signal it gets is a SIGTRAP, and so local_using_sysemu is not yet set? If this is impossible, please add a comment in the code for this. However, it seems that it can get to the SIGTRAP case with tracing == 1. When beginning the procedure, it is 0, but it can be changed with the value from is_tracing(task). I've not checked if that is zeroed on process creation (i.e. by do_fork() calling copy_thread()), but just note that in the code. > 2) Even if the host never *does* a syscall in SYSEMU, we have to write the > syscall number with -1, to not have the host doing syscall restarting. > This would happen only with an invalid syscall number equal to one of > the -ERESTART values. > But to be perfect ... Yes, but shouldn't this be handled on the host? Restarting a syscall which has never been done does not seem something that SYSEMU should allow... I don't want anybody to need going through the code and checking that this is safe. -- Paolo Giarrusso, aka Blaisorblade Linux registered user n. 292729 ------------------------------------------------------- This SF.Net email is sponsored by: InterSystems CACHE FREE OODBMS DOWNLOAD - A multidimensional database that combines robust object and relational technologies, making it a perfect match for Java, C++,COM, XML, ODBC and JDBC. www.intersystems.com/match8 _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel