From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.linuxfoundation.org ([140.211.169.12]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1Y0enn-00035H-Gv for kexec@lists.infradead.org; Mon, 15 Dec 2014 23:11:44 +0000 Date: Mon, 15 Dec 2014 15:11:20 -0800 From: Andrew Morton Subject: Re: [PATCH v2] kdump, vmcoreinfo: report actual value of phys_base Message-Id: <20141215151120.b44112413e15a8c390d39147@linux-foundation.org> In-Reply-To: <20141113.113011.630216167285231824.d.hatayama@jp.fujitsu.com> References: <20141113.113011.630216167285231824.d.hatayama@jp.fujitsu.com> Mime-Version: 1.0 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: HATAYAMA Daisuke Cc: kumagai-atsushi@mxc.nes.nec.co.jp, kexec@lists.infradead.org, ebiederm@xmission.com, vgoyal@redhat.com, anderson@redhat.com (cc trimmed a bit) On Thu, 13 Nov 2014 11:30:11 +0900 (JST) HATAYAMA Daisuke wrote: > Currently, VMCOREINFO note information reports the virtual address of > phys_base that is assigned to symbol phys_base. But this doesn't make > sense because to refer to phys_base, it's necessary to get the value > of phys_base itself we are now about to refer to. Folks, could we please get a bit of reviewing, acking or nacking for this one? From: HATAYAMA Daisuke Subject: kdump, vmcoreinfo: report actual value of phys_base Currently, VMCOREINFO note information reports the virtual address of phys_base that is assigned to symbol phys_base. But this doesn't make sense because to refer to phys_base, it's necessary to get the value of phys_base itself we are now about to refer to. Userland tools related to kdump such as makedumpfile and crash utility so far have made some efforts to calculate phys_base on crash dump formats generated by mechanisms running outside Linux kernel, such as virtual machine hypervisor such as qemu dump, which ordinary users use via virsh dump, or ones implemented on vendor specific firmware. That is, find a kernel data whose virtual and physical addresses are available via its note information and calculate phys_base from it. However, such data structure is not the one prepared for phys_base purpose. There's no guarantee that other crash dump mechanisms include such information that can be used to calculate phys_base similarly. To get VMCOREINFO in vmcore, it's easy to use strings and grep commands like this; VMCOREINFO consists of simple string: $ strings vmcore-3.10.0-121.el7.x86_64 | grep -E ".*VMCOREINFO.*" -A 100 VMCOREINFO OSRELEASE=3.10.0-121.el7.x86_64 PAGESIZE=4096 ... This is also useful to get value of phys_base in kdump 2nd kernel contained in vmcore using the above-mentioned external crash dump mechanism; kdump 2nd kernel is an inherently relocated kernel. This commit doesn't remove VMCOREINFO_SYMBOL(phys_base) line because makedumpfile refers to it and if removing it, old versions makedumpfile doesn't work well. Signed-off-by: HATAYAMA Daisuke Cc: Eric W. Biederman Cc: Vivek Goyal Cc: Atsushi Kumagai Cc: Dave Anderson Signed-off-by: Andrew Morton --- arch/x86/kernel/machine_kexec_64.c | 1 + include/linux/kexec.h | 2 ++ 2 files changed, 3 insertions(+) diff -puN arch/x86/kernel/machine_kexec_64.c~kdump-vmcoreinfo-report-actual-value-of-phys_base arch/x86/kernel/machine_kexec_64.c --- a/arch/x86/kernel/machine_kexec_64.c~kdump-vmcoreinfo-report-actual-value-of-phys_base +++ a/arch/x86/kernel/machine_kexec_64.c @@ -334,6 +334,7 @@ void arch_crash_save_vmcoreinfo(void) #endif vmcoreinfo_append_str("KERNELOFFSET=%lx\n", (unsigned long)&_text - __START_KERNEL); + VMCOREINFO_PHYS_BASE(phys_base); } /* arch-dependent functionality related to kexec file-based syscall */ diff -puN include/linux/kexec.h~kdump-vmcoreinfo-report-actual-value-of-phys_base include/linux/kexec.h --- a/include/linux/kexec.h~kdump-vmcoreinfo-report-actual-value-of-phys_base +++ a/include/linux/kexec.h @@ -258,6 +258,8 @@ unsigned long paddr_vmcoreinfo_note(void vmcoreinfo_append_str("NUMBER(%s)=%ld\n", #name, (long)name) #define VMCOREINFO_CONFIG(name) \ vmcoreinfo_append_str("CONFIG_%s=y\n", #name) +#define VMCOREINFO_PHYS_BASE(value) \ + vmcoreinfo_append_str("PHYS_BASE=%lx\n", (unsigned long)value) extern struct kimage *kexec_image; extern struct kimage *kexec_crash_image; _ _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec