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Date: Wed, 19 Nov 2014 16:49:02 +0000 From: Russell King - ARM Linux <linux@....linux.org.uk> To: Nicolas Pitre <nicolas.pitre@...aro.org> Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>, Konstantin Khlebnikov <koct9i@...il.com>, Arnd Bergmann <arnd@...db.de>, Andrey Ryabinin <a.ryabinin@...sung.com>, Konstantin Khlebnikov <k.khlebnikov@...sung.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org> Subject: Re: [PATCH RFC] ARM: option for loading modules into vmalloc area On Wed, Nov 19, 2014 at 11:37:47AM -0500, Nicolas Pitre wrote: > On Wed, 19 Nov 2014, Russell King - ARM Linux wrote: > > Which is not a good idea either, because the compiler needs to know how > > far away its own manually generated literal pool is from the instructions > > which reference it. The .ltorg statement can end up emitting any number > > of literals at that point, which makes it indeterminant how many words > > are contained within the asm() statement. > > > > Yes, it isn't desirable to waste an entire data cache line per indirect > > call like the original quote above, but I don't see a practical > > alternative. > > Modules could be built without far calls by default, and then the module > linker would only have to redirect those calls whose destination is too > far away to a dynamically created trampoline table. > > If I remember correctly you even posted some patches to that effect a > couple years ago. Maybe those could be salvaged? 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. -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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