Re: [PATCH] kexec: Export memory sections virtual addresses to vmcoreinfo

From: Baoquan He <bhe@redhat.com>
To: Dave Young <dyoung@redhat.com>
Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	keescook@chromium.org, ats-kumagai@wm.jp.nec.com,
	thgarnie@google.com, takahiro.akashi@linaro.org,
	mingo@redhat.com, ebiederm@xmission.com, hpa@zytor.com,
	tglx@linutronix.de, akpm@linux-foundation.org, tonli@redhat.com,
	anderson@redhat.com, panand@redhat.com
Subject: Re: [PATCH] kexec: Export memory sections virtual addresses to vmcoreinfo
Date: Tue, 1 Nov 2016 13:33:53 +0800	[thread overview]
Message-ID: <20161101053353.GC20838@x1> (raw)
In-Reply-To: <20161101051019.GB4625@dhcp-128-65.nay.redhat.com>

On 11/01/16 at 01:10pm, Dave Young wrote:
> On 10/06/16 at 04:46pm, Baoquan He wrote:
> > KASLR memory randomization can randomize the base of the physical memory
> > mapping (PAGE_OFFSET), vmalloc (VMALLOC_START) and vmemmap
> > (VMEMMAP_START). These need be exported to VMCOREINFO so that user space
> > utility, mainly makedumpfile can use them to identify the base of each
> > memory section. Here using VMCOREINFO_NUMBER we can reuse the existing
> > struct number_table in makedumpfile to import data easily.
> > 
> > Since they are related to x86_64 only, put them into
> > arch_crash_save_vmcoreinfo. And move the exportion of KERNEL_IMAGE_SIZE
> > together since it's also for x86_64 only.
> > 
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > ---
> >  arch/x86/kernel/machine_kexec_64.c | 4 ++++
> >  kernel/kexec_core.c                | 3 ---
> >  2 files changed, 4 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> > index 5a294e4..e150dd7 100644
> > --- a/arch/x86/kernel/machine_kexec_64.c
> > +++ b/arch/x86/kernel/machine_kexec_64.c
> > @@ -337,6 +337,10 @@ void arch_crash_save_vmcoreinfo(void)
> >  #endif
> >  	vmcoreinfo_append_str("KERNELOFFSET=%lx\n",
> >  			      kaslr_offset());
> > +	VMCOREINFO_NUMBER(KERNEL_IMAGE_SIZE);
> > +	VMCOREINFO_NUMBER(PAGE_OFFSET);
> > +	VMCOREINFO_NUMBER(VMALLOC_START);
> > +	VMCOREINFO_NUMBER(VMEMMAP_START);
> 
> Pratyush has posted makedumpfile patches below to avoid the VMCOREINFO:
> http://lists.infradead.org/pipermail/kexec/2016-October/017540.html
> 
> But we have this in mainline which also introduced the VMCOREINFO
> numbers, can you send a patch to revert them?

OK, will do.

However for find_vmemmap_x86_64() in makedumpfile, vmemmap_start is
still needed. I checked code, seems no better way to avoid. I am not
sure how many people are really using "-e" option to exclude unused
vmemmap pages.

Maybe just leave it as is, and fix it when people complain?

> commit 0549a3c02efb350776bc869685a361045efd3a29
> Author: Thomas Garnier <thgarnie@google.com>
> Date:   Tue Oct 11 13:55:08 2016 -0700
> 
>     kdump, vmcoreinfo: report memory sections virtual addresses
> [snip]]
> 
> >  }
> >  
> >  /* arch-dependent functionality related to kexec file-based syscall */
> > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> > index 5616755..8ad3a29e 100644
> > --- a/kernel/kexec_core.c
> > +++ b/kernel/kexec_core.c
> > @@ -1467,9 +1467,6 @@ static int __init crash_save_vmcoreinfo_init(void)
> >  #endif
> >  	VMCOREINFO_NUMBER(PG_head_mask);
> >  	VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE);
> > -#ifdef CONFIG_X86
> > -	VMCOREINFO_NUMBER(KERNEL_IMAGE_SIZE);
> > -#endif
> 
> Moving KERNEL_IMAGE_SIZE to x86 should be a standalone patch.
> I remember Dave Anderson said he use it in crash utility, cced him.
> 
> >  #ifdef CONFIG_HUGETLB_PAGE
> >  	VMCOREINFO_NUMBER(HUGETLB_PAGE_DTOR);
> >  #endif
> > -- 
> > 2.5.5
> > 
> > 
> > _______________________________________________
> > kexec mailing list
> > kexec@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
> 
> Thanks
> Dave