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

server OS

Date: Wed, 7 Sep 2016 14:17:10 +0800
From: Baoquan He <bhe@...hat.com>
To: AKASHI Takahiro <takahiro.akashi@...aro.org>,
        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 09/07/16 at 03:09pm, AKASHI Takahiro wrote:
> 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().

Yes, agree. Previously the reason I put KERNEL_IMAGE_SIZE in
crash_save_vmcoreinfo_init is kernel text randomization could be a
generic method for all ARCHes. Then it can be taken out from the #ifdef
scope. Now seeing it again, it's better to be put in
arch_crash_save_vmcoreinfo, at least for the time being.

Hi Thomas,

By the way, will you repost with the VMCOREINFO_NUMBER format? If not, I
can repost after I test all kexec/makedumpfile changes. 

Thanks
Baoquan

> 
> -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