Kernel-hardening archive on lore.kernel.org
 help / color / Atom feed
From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Jason Yan <yanaijie@huawei.com>,
	mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org,
	diana.craciun@nxp.com, benh@kernel.crashing.org,
	paulus@samba.org, npiggin@gmail.com, keescook@chromium.org,
	kernel-hardening@lists.openwall.com
Cc: linux-kernel@vger.kernel.org, wangkefeng.wang@huawei.com,
	yebin10@huawei.com, thunder.leizhen@huawei.com,
	jingxiangfeng@huawei.com, fanchengyang@huawei.com
Subject: Re: [RFC PATCH 10/10] powerpc/fsl_booke/kaslr: dump out kernel offset information on panic
Date: Mon, 29 Jul 2019 13:43:05 +0200
Message-ID: <d10db1e3-6bc4-eaa4-d68e-b7343e35b55f@c-s.fr> (raw)
In-Reply-To: <20190717080621.40424-11-yanaijie@huawei.com>



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 <yanaijie@huawei.com>
> Cc: Diana Craciun <diana.craciun@nxp.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Christophe Leroy <christophe.leroy@c-s.fr>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Kees Cook <keescook@chromium.org>
> ---
>   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 <asm-generic/memory_model.h>
>   #endif /* __ASSEMBLY__ */
>   #include <asm/slice.h>
> 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 ?

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
> 

  reply index

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-17  8:06 [RFC PATCH 00/10] implement KASLR for powerpc/fsl_booke/32 Jason Yan
2019-07-17  8:06 ` [RFC PATCH 01/10] powerpc: unify definition of M_IF_NEEDED Jason Yan
2019-07-29 10:59   ` Christophe Leroy
2019-07-17  8:06 ` [RFC PATCH 02/10] powerpc: move memstart_addr and kernstart_addr to init-common.c Jason Yan
2019-07-29 11:00   ` Christophe Leroy
2019-07-29 14:31   ` Christoph Hellwig
2019-07-30  0:47     ` Jason Yan
2019-07-17  8:06 ` [RFC PATCH 03/10] powerpc: introduce kimage_vaddr to store the kernel base Jason Yan
2019-07-29 11:00   ` Christophe Leroy
2019-07-29 14:32   ` Christoph Hellwig
2019-07-17  8:06 ` [RFC PATCH 04/10] powerpc/fsl_booke/32: introduce create_tlb_entry() helper Jason Yan
2019-07-29 11:05   ` Christophe Leroy
2019-07-29 13:26     ` Jason Yan
2019-07-17  8:06 ` [RFC PATCH 05/10] powerpc/fsl_booke/32: introduce reloc_kernel_entry() helper Jason Yan
2019-07-29 11:08   ` Christophe Leroy
2019-07-29 13:35     ` Jason Yan
2019-07-17  8:06 ` [RFC PATCH 06/10] powerpc/fsl_booke/32: implement KASLR infrastructure Jason Yan
2019-07-29 11:16   ` Christophe Leroy
2019-07-17  8:06 ` [RFC PATCH 07/10] powerpc/fsl_booke/32: randomize the kernel image offset Jason Yan
2019-07-29 11:33   ` Christophe Leroy
2019-07-29 13:53     ` Jason Yan
2019-07-17  8:06 ` [RFC PATCH 08/10] powerpc/fsl_booke/kaslr: clear the original kernel if randomized Jason Yan
2019-07-29 11:19   ` Christophe Leroy
2019-07-29 13:43     ` Jason Yan
2019-07-17  8:06 ` [RFC PATCH 09/10] powerpc/fsl_booke/kaslr: support nokaslr cmdline parameter Jason Yan
2019-07-29 11:38   ` Christophe Leroy
2019-07-29 14:04     ` Jason Yan
2019-07-17  8:06 ` [RFC PATCH 10/10] powerpc/fsl_booke/kaslr: dump out kernel offset information on panic Jason Yan
2019-07-29 11:43   ` Christophe Leroy [this message]
2019-07-29 14:08     ` Jason Yan
2019-07-25  7:16 ` [RFC PATCH 00/10] implement KASLR for powerpc/fsl_booke/32 Jason Yan
2019-07-25 19:58   ` Kees Cook
2019-07-26  7:20     ` Jason Yan
2019-07-26 16:15       ` Kees Cook
2019-07-26  7:04   ` Diana Madalina Craciun
2019-07-26  7:26     ` Jason Yan
2019-07-29 14:30 ` Diana Madalina Craciun

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=d10db1e3-6bc4-eaa4-d68e-b7343e35b55f@c-s.fr \
    --to=christophe.leroy@c-s.fr \
    --cc=benh@kernel.crashing.org \
    --cc=diana.craciun@nxp.com \
    --cc=fanchengyang@huawei.com \
    --cc=jingxiangfeng@huawei.com \
    --cc=keescook@chromium.org \
    --cc=kernel-hardening@lists.openwall.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=mpe@ellerman.id.au \
    --cc=npiggin@gmail.com \
    --cc=paulus@samba.org \
    --cc=thunder.leizhen@huawei.com \
    --cc=wangkefeng.wang@huawei.com \
    --cc=yanaijie@huawei.com \
    --cc=yebin10@huawei.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Kernel-hardening archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kernel-hardening/0 kernel-hardening/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kernel-hardening kernel-hardening/ https://lore.kernel.org/kernel-hardening \
		kernel-hardening@lists.openwall.com
	public-inbox-index kernel-hardening

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/com.openwall.lists.kernel-hardening


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git