From: Vivek Goyal <vgoyal@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Yinghai Lu <yinghai@kernel.org>,
Kexec Mailing List <kexec@lists.infradead.org>,
linux kernel mailing list <linux-kernel@vger.kernel.org>,
"Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: Kexec query about what makes sure control pages/page tables are not overwritten
Date: Mon, 11 Nov 2013 16:14:51 -0500 [thread overview]
Message-ID: <20131111211451.GF11547@redhat.com> (raw)
In-Reply-To: <15b29390-b535-4157-b7f2-8b1e03c919c1@email.android.com>
On Mon, Nov 11, 2013 at 12:57:12PM -0800, H. Peter Anvin wrote:
> It is pretty simple: the kernel exports how much text+data+bss+brk it needs, and the kernel cannot use memory outside that region until it is ready to control the address space itself.
Ok. So looks like that field is.
0260/4 2.10+ init_size Linear memory required during initialization
This helps. Thanks.
Vivek
>
> Vivek Goyal <vgoyal@redhat.com> wrote:
> >Hi,
> >
> >I am staring at control page allocation logic in case of kdump and
> >wondering what makes sure that these pages are not overwritten by
> >next kernel.
> >
> >I see that for 64bit entry, control pages have the page tables needed
> >for second kernel. In case of crash these pages from from crash kernel
> >reserved region. Page allocator is very simple and that is start from
> >lowest crash reserved range and move higher and allocate first
> >available
> >page which is not allocated to segments. What makes sure that these
> >pages
> >are not overwritten by second kernel.
> >
> >I guess it becomes a general bootloader question. How do we make sure
> >bootloader prepared page tables/gdt will not be overwritten by kernel
> >(till kernel sets up its own page tables and gdt) and how should we do
> >the
> >allocation and placement.
> >
> >Thanks
> >Vivek
>
> --
> Sent from my mobile phone. Please pardon brevity and lack of formatting.
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WARNING: multiple messages have this Message-ID (diff)
From: Vivek Goyal <vgoyal@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: linux kernel mailing list <linux-kernel@vger.kernel.org>,
Kexec Mailing List <kexec@lists.infradead.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Yinghai Lu <yinghai@kernel.org>
Subject: Re: Kexec query about what makes sure control pages/page tables are not overwritten
Date: Mon, 11 Nov 2013 16:14:51 -0500 [thread overview]
Message-ID: <20131111211451.GF11547@redhat.com> (raw)
In-Reply-To: <15b29390-b535-4157-b7f2-8b1e03c919c1@email.android.com>
On Mon, Nov 11, 2013 at 12:57:12PM -0800, H. Peter Anvin wrote:
> It is pretty simple: the kernel exports how much text+data+bss+brk it needs, and the kernel cannot use memory outside that region until it is ready to control the address space itself.
Ok. So looks like that field is.
0260/4 2.10+ init_size Linear memory required during initialization
This helps. Thanks.
Vivek
>
> Vivek Goyal <vgoyal@redhat.com> wrote:
> >Hi,
> >
> >I am staring at control page allocation logic in case of kdump and
> >wondering what makes sure that these pages are not overwritten by
> >next kernel.
> >
> >I see that for 64bit entry, control pages have the page tables needed
> >for second kernel. In case of crash these pages from from crash kernel
> >reserved region. Page allocator is very simple and that is start from
> >lowest crash reserved range and move higher and allocate first
> >available
> >page which is not allocated to segments. What makes sure that these
> >pages
> >are not overwritten by second kernel.
> >
> >I guess it becomes a general bootloader question. How do we make sure
> >bootloader prepared page tables/gdt will not be overwritten by kernel
> >(till kernel sets up its own page tables and gdt) and how should we do
> >the
> >allocation and placement.
> >
> >Thanks
> >Vivek
>
> --
> Sent from my mobile phone. Please pardon brevity and lack of formatting.
next prev parent reply other threads:[~2013-11-11 21:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-11 20:53 Kexec query about what makes sure control pages/page tables are not overwritten Vivek Goyal
2013-11-11 20:53 ` Vivek Goyal
2013-11-11 20:57 ` H. Peter Anvin
2013-11-11 20:57 ` H. Peter Anvin
2013-11-11 21:14 ` Vivek Goyal [this message]
2013-11-11 21:14 ` Vivek Goyal
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