From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AC5C8C7618B for ; Mon, 29 Jul 2019 14:09:00 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 16128216C8 for ; Mon, 29 Jul 2019 14:08:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 16128216C8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-16615-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 11714 invoked by uid 550); 29 Jul 2019 14:08:54 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 11678 invoked from network); 29 Jul 2019 14:08:53 -0000 Subject: Re: [RFC PATCH 10/10] powerpc/fsl_booke/kaslr: dump out kernel offset information on panic To: Christophe Leroy , , , , , , , , CC: , , , , , References: <20190717080621.40424-1-yanaijie@huawei.com> <20190717080621.40424-11-yanaijie@huawei.com> From: Jason Yan Message-ID: <599f9ff9-9799-b57e-4c88-cf9c60b94a46@huawei.com> Date: Mon, 29 Jul 2019 22:08:30 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.177.96.203] X-CFilter-Loop: Reflected On 2019/7/29 19:43, Christophe Leroy wrote: > > > Le 17/07/2019 à 10:06, Jason Yan a écrit : >> When kaslr is enabled, the kernel offset is different for every boot. >> This brings some difficult to debug the kernel. Dump out the kernel >> offset when panic so that we can easily debug the kernel. >> >> Signed-off-by: Jason Yan >> Cc: Diana Craciun >> Cc: Michael Ellerman >> Cc: Christophe Leroy >> Cc: Benjamin Herrenschmidt >> Cc: Paul Mackerras >> Cc: Nicholas Piggin >> Cc: Kees Cook >> --- >>   arch/powerpc/include/asm/page.h     |  5 +++++ >>   arch/powerpc/kernel/machine_kexec.c |  1 + >>   arch/powerpc/kernel/setup-common.c  | 23 +++++++++++++++++++++++ >>   3 files changed, 29 insertions(+) >> >> diff --git a/arch/powerpc/include/asm/page.h >> b/arch/powerpc/include/asm/page.h >> index 60a68d3a54b1..cd3ac530e58d 100644 >> --- a/arch/powerpc/include/asm/page.h >> +++ b/arch/powerpc/include/asm/page.h >> @@ -317,6 +317,11 @@ struct vm_area_struct; >>   extern unsigned long kimage_vaddr; >> +static inline unsigned long kaslr_offset(void) >> +{ >> +    return kimage_vaddr - KERNELBASE; >> +} >> + >>   #include >>   #endif /* __ASSEMBLY__ */ >>   #include >> diff --git a/arch/powerpc/kernel/machine_kexec.c >> b/arch/powerpc/kernel/machine_kexec.c >> index c4ed328a7b96..078fe3d76feb 100644 >> --- a/arch/powerpc/kernel/machine_kexec.c >> +++ b/arch/powerpc/kernel/machine_kexec.c >> @@ -86,6 +86,7 @@ void arch_crash_save_vmcoreinfo(void) >>       VMCOREINFO_STRUCT_SIZE(mmu_psize_def); >>       VMCOREINFO_OFFSET(mmu_psize_def, shift); >>   #endif >> +    vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset()); >>   } >>   /* >> diff --git a/arch/powerpc/kernel/setup-common.c >> b/arch/powerpc/kernel/setup-common.c >> index 1f8db666468d..49e540c0adeb 100644 >> --- a/arch/powerpc/kernel/setup-common.c >> +++ b/arch/powerpc/kernel/setup-common.c >> @@ -715,12 +715,35 @@ static struct notifier_block ppc_panic_block = { >>       .priority = INT_MIN /* may not return; must be done last */ >>   }; >> +/* >> + * Dump out kernel offset information on panic. >> + */ >> +static int dump_kernel_offset(struct notifier_block *self, unsigned >> long v, >> +                  void *p) >> +{ >> +    const unsigned long offset = kaslr_offset(); >> + >> +    if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && offset > 0) >> +        pr_emerg("Kernel Offset: 0x%lx from 0x%lx\n", >> +             offset, KERNELBASE); >> +    else >> +        pr_emerg("Kernel Offset: disabled\n"); > > Do we really need that else branch ? > > Why not just make the below atomic_notifier_chain_register() > conditionnal to IS_ENABLED(CONFIG_RANDOMIZE_BASE) && offset > 0 > and not print anything otherwise ? > I'm trying to keep the same fashion as x86/arm64 do. But I agree with you that it's simpler to not print anything else if not randomized. > Christophe > >> + >> +    return 0; >> +} >> + >> +static struct notifier_block kernel_offset_notifier = { >> +    .notifier_call = dump_kernel_offset >> +}; >> + >>   void __init setup_panic(void) >>   { >>       /* PPC64 always does a hard irq disable in its panic handler */ >>       if (!IS_ENABLED(CONFIG_PPC64) && !ppc_md.panic) >>           return; >>       atomic_notifier_chain_register(&panic_notifier_list, >> &ppc_panic_block); >> +    atomic_notifier_chain_register(&panic_notifier_list, >> +                       &kernel_offset_notifier); >>   } >>   #ifdef CONFIG_CHECK_CACHE_COHERENCY >> > > . >