kernel-hardening - Re: [PATCH v1] kdump, vmcoreinfo: report memory sections virtual addresses

server OS

Message-ID: <20160907060954.GF16712@linaro.org>
Date: Wed, 7 Sep 2016 15:09:57 +0900
From: AKASHI Takahiro <takahiro.akashi@...aro.org>
To: Baoquan He <bhe@...hat.com>
Cc: Thomas Garnier <thgarnie@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
	Eric Biederman <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Xunlei Pang <xlpang@...hat.com>,
	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>, keescook@...omium.org,
	kernel-hardening@...ts.openwall.com, surovegin@...gle.com,
	x86@...nel.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] kdump, vmcoreinfo: report memory sections virtual
 addresses

On Mon, Aug 29, 2016 at 06:11:37PM +0800, Baoquan He wrote:
> Hi Thomas,
> 
> I used below code and it works. Since using VMCOREINFO_NUMBER can reuse
> the existing struct number_table to import the data. It makes change
> easier. But the place could be next to KERNEL_IMAGE_SIZE, or as your
> patch did, both is fine.

I think we'd better avoid adding arch-specific code in generic code
if possible, especially in this case, since there is a dedicated interface,
arch_crash_save_vmcoreinfo().

-Takahiro AKASHI

> ---
>  kernel/kexec_core.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 5616755..81bde86 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -1469,6 +1469,9 @@ static int __init crash_save_vmcoreinfo_init(void)
>  	VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE);
>  #ifdef CONFIG_X86
>  	VMCOREINFO_NUMBER(KERNEL_IMAGE_SIZE);
> +	VMCOREINFO_NUMBER(PAGE_OFFSET);
> +	VMCOREINFO_NUMBER(VMALLOC_START);
> +	VMCOREINFO_NUMBER(VMEMMAP_START);
>  #endif
>  #ifdef CONFIG_HUGETLB_PAGE
>  	VMCOREINFO_NUMBER(HUGETLB_PAGE_DTOR);
> -- 
> 2.5.5
> 
> On 08/18/16 at 07:47am, Thomas Garnier wrote:
> > KASLR memory randomization can randomize the base of the physical memory
> > mapping (PAGE_OFFSET), vmalloc (VMALLOC_START) and vmemmap
> > (VMEMMAP_START). Adding these variables on VMCOREINFO so tools can
> > easily identify the base of each memory section.
> > 
> > Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
> > ---
> > Based on next-20160817
> > ---
> >  arch/x86/kernel/machine_kexec_64.c | 3 +++
> >  include/linux/kexec.h              | 6 ++++++
> >  2 files changed, 9 insertions(+)
> > 
> > diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> > index fc3389f..b1f15a2 100644
> > --- a/arch/x86/kernel/machine_kexec_64.c
> > +++ b/arch/x86/kernel/machine_kexec_64.c
> > @@ -338,6 +338,9 @@ void arch_crash_save_vmcoreinfo(void)
> >  	vmcoreinfo_append_str("KERNELOFFSET=%lx\n",
> >  			      kaslr_offset());
> >  	VMCOREINFO_PHYS_BASE(phys_base);
> > +	VMCOREINFO_PAGE_OFFSET(PAGE_OFFSET);
> > +	VMCOREINFO_VMALLOC_START(VMALLOC_START);
> > +	VMCOREINFO_VMEMMAP_START(VMEMMAP_START);
> >  }
> >  
> >  /* arch-dependent functionality related to kexec file-based syscall */
> > diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> > index d3ae429..cd3874c 100644
> > --- a/include/linux/kexec.h
> > +++ b/include/linux/kexec.h
> > @@ -261,6 +261,12 @@ phys_addr_t paddr_vmcoreinfo_note(void);
> >  	vmcoreinfo_append_str("CONFIG_%s=y\n", #name)
> >  #define VMCOREINFO_PHYS_BASE(value) \
> >  	vmcoreinfo_append_str("PHYS_BASE=%lx\n", (unsigned long)value)
> > +#define VMCOREINFO_PAGE_OFFSET(value) \
> > +	vmcoreinfo_append_str("PAGE_OFFSET=%lx\n", (unsigned long)value)
> > +#define VMCOREINFO_VMALLOC_START(value) \
> > +	vmcoreinfo_append_str("VMALLOC_START=%lx\n", (unsigned long)value)
> > +#define VMCOREINFO_VMEMMAP_START(value) \
> > +	vmcoreinfo_append_str("VMEMMAP_START=%lx\n", (unsigned long)value)
> >  
> >  extern struct kimage *kexec_image;
> >  extern struct kimage *kexec_crash_image;
> > -- 
> > 2.8.0.rc3.226.g39d4020
> > 
> > 
> > _______________________________________________
> > kexec mailing list
> > kexec@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec