Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756187AbaKSR7P (ORCPT ); Wed, 19 Nov 2014 12:59:15 -0500 Received: from mail-la0-f54.google.com ([209.85.215.54]:34282 "EHLO mail-la0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755343AbaKSR7N (ORCPT ); Wed, 19 Nov 2014 12:59:13 -0500 MIME-Version: 1.0 In-Reply-To: References: <20141118173413.GB4042@n2100.arm.linux.org.uk> <546B8C64.3010904@samsung.com> <2041617.Kxhx5O4MMr@wuerfel> <20141119160747.GH4042@n2100.arm.linux.org.uk> <20141119164902.GK4042@n2100.arm.linux.org.uk> <20141119165948.GM4042@n2100.arm.linux.org.uk> Date: Wed, 19 Nov 2014 18:59:12 +0100 Message-ID: Subject: Re: [PATCH RFC] ARM: option for loading modules into vmalloc area From: Ard Biesheuvel To: Nicolas Pitre Cc: Russell King - ARM Linux , Konstantin Khlebnikov , Arnd Bergmann , Andrey Ryabinin , Konstantin Khlebnikov , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19 November 2014 18:12, Nicolas Pitre wrote: > On Wed, 19 Nov 2014, Russell King - ARM Linux wrote: > >> On Wed, Nov 19, 2014 at 11:57:15AM -0500, Nicolas Pitre wrote: >> > On Wed, 19 Nov 2014, Russell King - ARM Linux wrote: >> > > I don't think I ever did, because its pretty much impossible to do as I >> > > explained in a follow up to this thread. >> > > >> > > We _used_ to do this with the userspace insmod methods, but since we got >> > > this kernel-side linker, it's been pretty much impossible to do without >> > > rewriting the module code. That's not going to happen on account of one >> > > quirky architecture which Linus doesn't particularly like. >> > >> > Still... We could try adding a hook in the generic module linker code >> > for a pre-relocation pass. Maybe only ARM would use it, but if the need >> > to load big modules is real then I imagine Linus could be amenable to a >> > compromise. >> >> So, how big a table would you allocate for the trampolines, based upon >> not knowing anything about the module being loaded? 4K? 8K? 64K? > > The idea of a pre-relocation pass is to determine that. That could be > something similar to calling apply_relocate() twice: once to determine > the number of trampoline entries, and a second time to perform the > actual relocation. > Well, the veneers shouldn't take more than 3 words each, right? ldr ip, [pc] bx ip .long symbol and you would need at most one veneer per unique external symbol referenced by one or more R_ARM_CALL relocations. Is there no way to just add that to the static mem footprint as padding, and let the loader populate it as needed at module relocation time? -- Ard. -- 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/