From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-qk0-f172.google.com ([209.85.220.172]) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1bFyr8-0003XV-IR for kexec@lists.infradead.org; Thu, 23 Jun 2016 07:15:19 +0000 Received: by mail-qk0-f172.google.com with SMTP id a186so96323665qkf.0 for ; Thu, 23 Jun 2016 00:14:57 -0700 (PDT) Date: Thu, 23 Jun 2016 12:44:12 +0530 From: Pratyush Anand Subject: Re: [PATCH v19 10/13] arm64: kdump: add VMCOREINFO's for user-space coredump tools Message-ID: <20160623071412.GA16398@dhcppc9> References: <6e96110e85e7b1167043d789e85f9c916fdf281a.1466120418.git.geoff@infradead.org> <20160620053222.GB14309@dhcppc9> <20160622055940.GY20774@linaro.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20160622055940.GY20774@linaro.org> 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: AKASHI Takahiro , Geoff Levand , Catalin Marinas , Will Deacon , Mark Rutland , marc.zyngier@arm.com, kexec@lists.infradead.org, James Morse , linux-arm-kernel@lists.infradead.org, Atsushi Kumagai Hi Takahiro, Thanks for your reply. On 22/06/2016:02:59:41 PM, AKASHI Takahiro wrote: > On Mon, Jun 20, 2016 at 11:02:22AM +0530, Pratyush Anand wrote: > > +Atsushi > > > > Hi Takahiro, > > > > On 16/06/2016:11:48:28 PM, Geoff Levand wrote: > > > From: AKASHI Takahiro > > > > > > For the current crash utility, we need to know, at least, > > > - kimage_voffset > > > - PHYS_OFFSET > > > to handle the contents of core dump file (/proc/vmcore) correctly due to > > > the introduction of KASLR (CONFIG_RANDOMIZE_BASE) in v4.6. > > > This patch puts them as VMCOREINFO's into the file. > > > > > > - VA_BITS > > > is also added for makedumpfile command. > > > > Thanks for adding them. They are quite helpful for makedumpfile as well. > > > > > More VMCOREINFO's may be added later. > > > > Yes, we will need to pass VMCOREINFO_SYMBOL(_text) and VMCOREINFO_SYMBOL(_end) > > in order to work with makedumpfile. > > I know that adding those symbols is the easiest way, but > theoretically, if we know the physical address of "swapper_pg_dir", But, we know only it's virtual address. > instead of its virtual address, we can access all the memory pointed to > by any kernel virtual address. > How do you rationalize that we need to know "_text" and "_end"? Well, we need some mechanism so that we can decide if an address can be translated using linear mapping of virt_to_phys(). Alternatively, probably we can do like this: -- Translate all address between "SYMBOL(swapper_pg_dir)" and "SYMBOL(swapper_pg_dir) + SWAPPER_DIR_SIZE" using virt_to_phys() and now we can read values from dumpfile using that physical address. This way we can get PGD/PMD/PUD values. -- PTE values may lie out side this range, however that address should still be linearly translatable. We can use virt_to_phys() macro from them as well. In summary, we can translate address of PGD/PMD/PUD/PTE using virt_to_phys() and rest all can be translated using page table entries. ~Pratyush _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec