Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754300Ab3F0UYI (ORCPT ); Thu, 27 Jun 2013 16:24:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41483 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752933Ab3F0UYF (ORCPT ); Thu, 27 Jun 2013 16:24:05 -0400 Date: Thu, 27 Jun 2013 16:23:34 -0400 From: Vivek Goyal To: Michael Holzheu Cc: HATAYAMA Daisuke , Jan Willeke , Martin Schwidefsky , Heiko Carstens , linux-kernel@vger.kernel.org, kexec@lists.infradead.org Subject: Re: [PATCH v5 1/5] vmcore: Introduce ELF header in new memory feature Message-ID: <20130627202334.GL4899@redhat.com> References: <1370624161-2298-1-git-send-email-holzheu@linux.vnet.ibm.com> <1370624161-2298-2-git-send-email-holzheu@linux.vnet.ibm.com> <20130614185401.GL12023@redhat.com> <20130621161703.751b5f23@holzheu> <20130627193202.GK4899@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130627193202.GK4899@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3266 Lines: 86 On Thu, Jun 27, 2013 at 03:32:02PM -0400, Vivek Goyal wrote: > On Fri, Jun 21, 2013 at 04:17:03PM +0200, Michael Holzheu wrote: > > On Fri, 14 Jun 2013 14:54:02 -0400 > > Vivek Goyal wrote: > > > > > On Fri, Jun 07, 2013 at 06:55:57PM +0200, Michael Holzheu wrote: > > > > > > [..] > > > > @@ -935,10 +967,17 @@ static int __init vmcore_init(void) > > > > { > > > > int rc = 0; > > > > > > > > - /* If elfcorehdr= has been passed in cmdline, then capture the dump.*/ > > > > - if (!(is_vmcore_usable())) > > > > - return rc; > > > > + /* > > > > + * If elfcorehdr= has not been passed in cmdline, try to get the > > > > + * header from 2nd kernel, then capture the dump. > > > > + */ > > > > + if (!(is_vmcore_usable())) { > > > > + rc = elfcorehdr_alloc(); > > > > + if (rc) > > > > + return rc; > > > > + } > > > > > > Hi Michael, > > > > > > Patch description says that elfcorehdr_alloc() returns the addr and > > > size of elf headers. But that does not seem to be the case here. Has > > > it been modified in later patches. > > > > Sorry, that is a relict of one of my previous experiments where I tried > > to implement elfcorehdr_addr() similar to the way as you suggest it now. > > Because elfcorehdr_addr is a global variable, I decided to not pass > > it in the functions. But of course I can change that again if you prefer > > that. > > > > > Also will it be better if we call elfcorehdr_alloc() always and then > > > check for is_vmcore_usable(). > > > > > > Something like. > > > > > > elfcorehdr_addr = elfcorehdr_alloc() > > > if (elfcorehdr_addr < ) > > > return elfcorehdr_addr > > > > > > if (!(is_vmcore_usable())) > > > return error > > > > Ok, but then I think elfcorehdr_alloc() should also return > > the elfcorehdr_size. > > > > So what about the following patch: > > This patch looks good to me. There are little ugly pieces w.r.t not > setting elfcorehdr_addr null after calling free() as there are other > pieces depdendent on elfcorehdr_addr. I think sometime later we can > have a separate variable to track track whether this is kdump kernel > and remove dependency on elfcorehdr_addr being set. Hi Michael, Thinking more about it, I think let us cleanup with this little ugly bit too so that future changes become easy. Current convention is that elfcorehdr_addr and elfcorehdr_size are already set by arch code by the time vmcore.c starts reading it. Can't s390 allocate elf headers in early boot code and elfcorehdr_addr? Then we don't have to call elfcorehdr_alloc(). And once we are done with reading headers, we can call elfcorehdr_free() and s390 could free memory and set elfcorehdr_addr to ELFCORE_ADDR_ERR and elfcorehdr_size=0. That would signify that one can not try to read elf headers now and it must have been freed. is_kdump_kernel() will continue to work as elfcorehdr_addr is ELFCORE_ADDR_ERR. And that will mean that either elfcorehdr were not readable/usable to begin with or they have been freed now. Thanks Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/