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[209.85.219.178]) by smtp.gmail.com with ESMTPSA id x132sm2207095ywx.27.2018.11.27.16.39.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 27 Nov 2018 16:39:52 -0800 (PST) Received: by mail-yb1-f178.google.com with SMTP id f6-v6so8476015ybg.12 for ; Tue, 27 Nov 2018 16:39:52 -0800 (PST) X-Received: by 2002:a25:a445:: with SMTP id f63-v6mr34342804ybi.171.1543365591765; Tue, 27 Nov 2018 16:39:51 -0800 (PST) MIME-Version: 1.0 Received: by 2002:a25:b906:0:0:0:0:0 with HTTP; Tue, 27 Nov 2018 16:39:50 -0800 (PST) In-Reply-To: <20181127232916.GG1824@MiWiFi-R3L-srv> References: <1542318469-13699-1-git-send-email-bhsharma@redhat.com> <20181121113944.GD27797@zn.tnic> <20181127232916.GG1824@MiWiFi-R3L-srv> From: Kees Cook Date: Tue, 27 Nov 2018 16:39:50 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2] x86_64, vmcoreinfo: Append 'page_offset_base' to vmcoreinfo To: Baoquan He Cc: Borislav Petkov , Kazuhito Hagio , Bhupesh Sharma , X86 ML , Kexec Mailing List , LKML , Omar Sandoval , Dave Anderson , James Morse , Thomas Gleixner , Bhupesh SHARMA , Ingo Molnar , linux-arm-kernel Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 27, 2018 at 3:29 PM, Baoquan He wrote: > On 11/27/18 at 02:16pm, Kees Cook wrote: >> Why is KERNELOFFSET= not sufficient? >> >> See commit b6085a865762 ("x86, kaslr: export offset in VMCOREINFO ELF notes") >> >> + vmcoreinfo_append_str("KERNELOFFSET=%lx\n", >> + (unsigned long)&_text - __START_KERNEL); > > KERNELOFFSET is virtual address delta after kernel text KASLR, namely > the offset from the original default kernel text virtual address, > 0xffffffff88000000. > > While after memory region KASLR in kernel_randomize_memory(), the > starting address of the direct mapping of physical memory, PAGE_OFFSET, > is changed too. We need get it to analyze memory in makedumpfile/crash. > Currently we deduce it from elf program segment of kcore: > Program Headers: > Type Offset VirtAddr PhysAddr > FileSiz MemSiz Flags Align > ...... > > LOAD 0x00000a62c0004000 0xffff8a62c0001000 0x0000000000001000 > 0x000000000009c000 0x000000000009c000 RWE 1000 > > page_offset = 0xffff8a62c0001000 - 0x0000000000001000; > Since we put the direct mapping segments at the bottom part of kcore, we > can always get page_offset right. > > Thanks > Baoquan > >> >> -Kees >> >> >> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c >> >> index 4c8acdfdc5a7..6161d77c5bfb 100644 >> >> --- a/arch/x86/kernel/machine_kexec_64.c >> >> +++ b/arch/x86/kernel/machine_kexec_64.c >> >> @@ -356,6 +356,9 @@ void arch_crash_save_vmcoreinfo(void) >> >> VMCOREINFO_SYMBOL(init_top_pgt); >> >> vmcoreinfo_append_str("NUMBER(pgtable_l5_enabled)=%d\n", >> >> pgtable_l5_enabled()); >> >> +#ifdef CONFIG_RANDOMIZE_BASE Okay, gotcha. In that case, shouldn't this be CONFIG_RANDOMIZE_MEMORY? -Kees >> >> + VMCOREINFO_NUMBER(page_offset_base); >> >> +#endif >> >> >> >> #ifdef CONFIG_NUMA >> >> VMCOREINFO_SYMBOL(node_data); >> >> -- >> Kees Cook >> >> _______________________________________________ >> kexec mailing list >> kexec@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/kexec -- Kees Cook