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Wed, 02 Jun 2021 11:15:21 +0100 Date: Wed, 2 Jun 2021 11:15:21 +0100 From: "Russell King (Oracle)" To: Mike Rapoport Cc: Mike Rapoport , linux-kernel@vger.kernel.org, Andrew Morton , Catalin Marinas , Christian Borntraeger , David Hildenbrand , Heiko Carstens , Thomas Bogendoerfer , Vasily Gorbik , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org Subject: Re: [RFC/RFT PATCH 2/5] memblock: introduce generic memblock_setup_resources() Message-ID: <20210602101521.GD30436@shell.armlinux.org.uk> References: <20210531122959.23499-1-rppt@kernel.org> <20210531122959.23499-3-rppt@kernel.org> <20210601135415.GZ30436@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Queue-Id: ADF378019369 Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=armlinux.org.uk header.s=pandora-2019 header.b=Bme3nUMc; spf=none (imf08.hostedemail.com: domain of linux@armlinux.org.uk has no SPF policy when checking 78.32.30.218) smtp.mailfrom=linux@armlinux.org.uk; dmarc=pass (policy=none) header.from=armlinux.org.uk X-Rspamd-Server: rspam04 X-Stat-Signature: w9f1higix5rkp95fqdm6a1f16314x9ur X-HE-Tag: 1622628919-688112 X-Bogosity: Ham, tests=bogofilter, spamicity=0.005578, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jun 02, 2021 at 11:33:10AM +0300, Mike Rapoport wrote: > On Tue, Jun 01, 2021 at 02:54:15PM +0100, Russell King (Oracle) wrote: > > On Mon, May 31, 2021 at 03:29:56PM +0300, Mike Rapoport wrote: > > > + code_resource.start = __pa_symbol(_text); > > > + code_resource.end = __pa_symbol(_etext)-1; > > > + rodata_resource.start = __pa_symbol(__start_rodata); > > > + rodata_resource.end = __pa_symbol(__end_rodata)-1; > > > + data_resource.start = __pa_symbol(_sdata); > > > + data_resource.end = __pa_symbol(_edata)-1; > > > + bss_resource.start = __pa_symbol(__bss_start); > > > + bss_resource.end = __pa_symbol(__bss_stop)-1; > > > > This falls short on 32-bit ARM. The old code was: > > > > - kernel_code.start = virt_to_phys(_text); > > - kernel_code.end = virt_to_phys(__init_begin - 1); > > - kernel_data.start = virt_to_phys(_sdata); > > - kernel_data.end = virt_to_phys(_end - 1); > > > > If I look at one of my kernels: > > > > c0008000 T _text > > c0b5b000 R __end_rodata > > ... exception and unwind tables live here ... > > c0c00000 T __init_begin > > c0e00000 D _sdata > > c0e68870 D _edata > > c0e68870 B __bss_start > > c0e995d4 B __bss_stop > > c0e995d4 B _end > > > > So the original covers _text..__init_begin-1 which includes the > > exception and unwind tables. Your version above omits these, which > > leaves them exposed. > > Right, this needs to be fixed. Is there any reason the exception and unwind > tables cannot be placed between _sdata and _edata? > > It seems to me that they were left outside for purely historical reasons. > Commit ee951c630c5c ("ARM: 7568/1: Sort exception table at compile time") > moved the exception tables out of .data section before _sdata existed. > Commit 14c4a533e099 ("ARM: 8583/1: mm: fix location of _etext") moved > _etext before the unwind tables and didn't bother to put them into data or > rodata areas. You can not assume that all sections will be between these symbols. This isn't specific to 32-bit ARM. If you look at x86's vmlinux.lds.in, you will see that BUG_TABLE and ORC_UNWIND_TABLE are after _edata, along with many other undiscarded sections before __bss_start. So it seems your assumptions in trying to clean this up are somewhat false. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!