From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH] Extract initrd free logic from arch-specific code. Date: Thu, 29 Mar 2018 18:32:47 +0100 Message-ID: <20180329173247.GF16141@n2100.armlinux.org.uk> References: <20180328152714.6103-1-shea@shealevy.com> <05620fee-e8b5-0668-77b8-da073dc78c40@landley.net> <20180328164813.GA3888@n2100.armlinux.org.uk> <20180328221401.GA14084@n2100.armlinux.org.uk> <20180329152749.GC16141@n2100.armlinux.org.uk> <20180329155827.GD16141@n2100.armlinux.org.uk> <86zi2qrfgl.wl-marc.zyngier@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=IrYpVinQA9O6CSUZMmK4bWyPPCwgeXRQFkoby113AMI=; b=q/Q2brfCDJyRff 3juI4Fe9iCM6RmxIOiRx0hhrgN9xE0aan705C/cw8hmKFeUg55FifL3suhQ6n/j34cv0BsAf3zSaa X1Dwbcr/eLMTEbdbuMkl1ij8Df3gGEJg1f5b6tbmjfFhl++XYRyAxv29ZMkgjFNxcV7LCczR4rZeh 3ei7czh/ar7ccbBjxfFYPanbnUrUWwTkg1Qika930kh0PioEHoLUmdxKRTn96eC5m2QT6faOPo82l zQ1pzydkTAY6qxOrkCgUrKOU1xpFMbA5ZSe+eIcMJgK4SF5FNZ5cti1CfdUGdG0tAun8Twwq8yS4g NPvll5Z7UU7wNiEabOqQ==; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2014; h=Sender:In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date; bh=KxVBphA9o9Afyy2W8Ch7czbfQG563m9670sM3VaTKFM=; b=ohTapLUofv5UJCDQSnyRhzkret1vmCa1vJoSECL6fIfN5PXYvAGfdsodjmUwDkaTfZEYe5Bz/hVMbTk2e78xOdflHrd/X5KJck6pZa5Cn+TerTq5w6tujc3srySIdINst2ZHc/83+YvXe+/YNKHlalPWJdLfTYWNZViI85KahSM=; Content-Disposition: inline In-Reply-To: <86zi2qrfgl.wl-marc.zyngier@arm.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+gla-linux-snps-arc=m.gmane.org@lists.infradead.org To: Marc Zyngier Cc: Linux MIPS Mailing List , Linux-sh list , Benjamin Herrenschmidt , Linus Walleij , Will Deacon , Paul Mackerras , Michael Ellerman , "James E.J. Bottomley" , Christoph Hellwig , Geert Uytterhoeven , Catalin Marinas , Matt Turner , Eugeniy Paltsev , "moderated list:H8/300 ARCHITECTURE" , Vladimir Murzin , adi-buildroot-devel@lists.sourceforge.net, Nicholas Piggin , Al Viro , Thomas Gleixner , Richard Henderson , Cris On Thu, Mar 29, 2018 at 05:53:14PM +0100, Marc Zyngier wrote: > On Thu, 29 Mar 2018 16:58:27 +0100, > Russell King - ARM Linux wrote: > > > > On Thu, Mar 29, 2018 at 05:43:47PM +0200, Geert Uytterhoeven wrote: > > > On Thu, Mar 29, 2018 at 5:27 PM, Russell King - ARM Linux > > > wrote: > > > > On Thu, Mar 29, 2018 at 09:37:52AM +1100, Oliver wrote: > > > >> On Thu, Mar 29, 2018 at 9:14 AM, Russell King - ARM Linux > > > >> wrote: > > > >> > On Wed, Mar 28, 2018 at 02:04:22PM -0500, Rob Landley wrote: > > > >> >> On 03/28/2018 11:48 AM, Russell King - ARM Linux wrote: > > > >> >> > On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote: > > > >> >> >> On 03/28/2018 10:26 AM, Shea Levy wrote: > > > >> >> >>> Now only those architectures that have custom initrd free requirements > > > >> >> >>> need to define free_initrd_mem. > > > >> >> >> ... > > > >> >> >>> --- a/arch/arc/mm/init.c > > > >> >> >>> +++ b/arch/arc/mm/init.c > > > >> >> >>> @@ -229,10 +229,3 @@ void __ref free_initmem(void) > > > >> >> >>> { > > > >> >> >>> free_initmem_default(-1); > > > >> >> >>> } > > > >> >> >>> - > > > >> >> >>> -#ifdef CONFIG_BLK_DEV_INITRD > > > >> >> >>> -void __init free_initrd_mem(unsigned long start, unsigned long end) > > > >> >> >>> -{ > > > >> >> >>> - free_reserved_area((void *)start, (void *)end, -1, "initrd"); > > > >> >> >>> -} > > > >> >> >>> -#endif > > > >> >> >>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > > > >> >> >>> index 3f972e83909b..19d1c5594e2d 100644 > > > >> >> >>> --- a/arch/arm/Kconfig > > > >> >> >>> +++ b/arch/arm/Kconfig > > > >> >> >>> @@ -47,6 +47,7 @@ config ARM > > > >> >> >>> select HARDIRQS_SW_RESEND > > > >> >> >>> select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT) > > > >> >> >>> select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6 > > > >> >> >>> + select HAVE_ARCH_FREE_INITRD_MEM > > > >> >> >>> select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU > > > >> >> >>> select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU > > > >> >> >>> select HAVE_ARCH_MMAP_RND_BITS if MMU > > > >> >> >> > > > >> >> >> Isn't this why weak symbols were invented? > > > >> >> > > > > >> >> > Weak symbols means that we end up with both the weakly-referenced code > > > >> >> > and the arch code in the kernel image. That's fine if the weak code > > > >> >> > is small. > > > >> >> > > > >> >> The kernel's been able to build with link time garbage collection since 2016: > > > >> >> > > > >> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b67067f1176d > > > >> >> > > > >> >> Wouldn't that remove the unused one? > > > >> > > > > >> > Probably, if anyone bothered to use that, which they don't. > > > >> > > > > >> > LD_DEAD_CODE_DATA_ELIMINATION is a symbol without a prompt, and from > > > >> > what I can see, nothing selects it. Therefore, the symbol is always > > > >> > disabled, and so the feature never gets used in mainline kernels. > > > >> > > > > >> > Brings up the obvious question - why is it there if it's completely > > > >> > unused? (Maybe to cause confusion, and allowing a justification > > > >> > for __weak ?) > > > >> > > > >> IIRC Nick had some patches to do the arch enablement for powerpc, but > > > >> I'm not sure what happened to them though. I suspect it just fell down > > > >> Nick's ever growing TODO list. > > > > > > > > I've given it a go on ARM, marking every linker-built table with KEEP() > > > > and comparing the System.map files. The resulting kernel is around > > > > 150k smaller, which seems good. > > > > > > > > However, it doesn't boot - and I don't know why. Booting the kernel > > > > under kvmtool in a VM using virtio-console, I can find no way to get > > > > any kernel messages out of it. Using lkvm debug, I can see that the > > > > PC is stuck inside die(), and that's the only information I have. > > > > It dies before bringing up the other CPUs, so it's a very early death. > > > > > > > > I don't think other console types are available under ARM64. > > > > > > earlycon? > > > > Through what - as I say above, I think the only thing that's present is > > virtio-console, and the virtio stack only get initialised much later in > > boot. > > > > Eg, there's the memory-based virtio driver which interfaces any virtio > > driver to a memory-based ring structures for communication with the host > > (drivers/virtio/virtio_mmio.c) which is initialised at module_init() > > time, and so isn't available for earlycon. > > > > I don't think merely changing the module_init() calls in the appropriate > > virtio bits will suffice - it's why I pointed out that it dies before > > SMP initialisation, which also means that it dies before we start > > running the initcalls for subsystems and drivers. > > > > I'm not aware of there being an emulated UART in the guest's address > > space, so serial based stuff doesn't work. > > "earlycon=uart,mmio,0x3f8" is what you're looking for: Does that also mean that we have a RTC at the standard PC IO addresses as well, but in mmio space? -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up According to speedtest.net: 8.21Mbps down 510kbps up