From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from out02.mta.xmission.com ([166.70.13.232]) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1c2gEd-0007Im-D7 for kexec@lists.infradead.org; Fri, 04 Nov 2016 15:16:52 +0000 From: ebiederm@xmission.com (Eric W. Biederman) References: <3476672.cGrsQmUQKg@morokweng> <20161104073840.GD4314@x1> Date: Fri, 04 Nov 2016 10:13:39 -0500 In-Reply-To: <20161104073840.GD4314@x1> (Baoquan He's message of "Fri, 4 Nov 2016 15:38:40 +0800") Message-ID: <871syrcm70.fsf@xmission.com> MIME-Version: 1.0 Subject: Re: [RFC] kexec_file: Add support for purgatory built as PIE List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Baoquan He Cc: Dave Young , kexec@lists.infradead.org, Michael Ellerman , Thiago Jung Bauermann , linuxppc-dev@lists.ozlabs.org, Vivek Goyal Baoquan He writes: > On 11/02/16 at 04:00am, Thiago Jung Bauermann wrote: >> Hello, >> >> The kexec_file code currently builds the purgatory as a partially linked object >> (using ld -r). Is there a particular reason to use that instead of a position >> independent executable (PIE)? > > It's taken as "-r", relocatable in user space kexec-tools too originally. > I think Vivek just keeps it the same when moving into kernel. At least on x86 using just -r removed the need for a GOT and all of the other nasty dynamic relocatable bits, that are not needed when the you don't want to share your text bits with the page cache. I can see reaons for refactoring code but I expect PIE expecutables need a GOT and all of that pain in the neck stuff that can just be avoided by building the code to run at an absolute address. So far I have not seen ELF relocations that are difficult to process. Eric _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out02.mta.xmission.com (out02.mta.xmission.com [166.70.13.232]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3t9QQf3JhwzDt1M for ; Sat, 5 Nov 2016 02:16:10 +1100 (AEDT) From: ebiederm@xmission.com (Eric W. Biederman) To: Baoquan He Cc: Thiago Jung Bauermann , kexec@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, Michael Ellerman , Dave Young , Vivek Goyal References: <3476672.cGrsQmUQKg@morokweng> <20161104073840.GD4314@x1> Date: Fri, 04 Nov 2016 10:13:39 -0500 In-Reply-To: <20161104073840.GD4314@x1> (Baoquan He's message of "Fri, 4 Nov 2016 15:38:40 +0800") Message-ID: <871syrcm70.fsf@xmission.com> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [RFC] kexec_file: Add support for purgatory built as PIE List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Baoquan He writes: > On 11/02/16 at 04:00am, Thiago Jung Bauermann wrote: >> Hello, >> >> The kexec_file code currently builds the purgatory as a partially linked object >> (using ld -r). Is there a particular reason to use that instead of a position >> independent executable (PIE)? > > It's taken as "-r", relocatable in user space kexec-tools too originally. > I think Vivek just keeps it the same when moving into kernel. At least on x86 using just -r removed the need for a GOT and all of the other nasty dynamic relocatable bits, that are not needed when the you don't want to share your text bits with the page cache. I can see reaons for refactoring code but I expect PIE expecutables need a GOT and all of that pain in the neck stuff that can just be avoided by building the code to run at an absolute address. So far I have not seen ELF relocations that are difficult to process. Eric