linux-kernel - Re: incorrect layout of globals from head

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Date:	Fri, 6 Jul 2012 17:54:57 +0200
From:	Daniel Kiper <dkiper@...-space.pl>
To:	Olaf Hering <olaf@...fle.de>
Cc:	Daniel Kiper <dkiper@...-space.pl>, kexec@...ts.infradead.org,
	xen-devel@...ts.xensource.com, linux-kernel@...r.kernel.org
Subject: Re: incorrect layout of globals from head_64.S during kexec boot

On Fri, Jul 06, 2012 at 02:07:50PM +0200, Olaf Hering wrote:
> On Fri, Jul 06, Daniel Kiper wrote:
>
> > Copy is done a few times durnig kexec/kdump but the most important
> > in this case, I think, is in relocate_kernel() function (look for
> > rep movsl or rep movsq and code around it). But I am a bit surprised
> > that kernel is decompressing itself. I always thought that it is done
> > during kexec/kdump load phase but maybe I am wrong. Could you send

I am wrong.

> > me more info about your Linux Kernel version, kexec-tools version
> > and exact commands which you are using to load/exececute kernel?
>
> Its kexec-tools and kernel mainline, but it happens also with older
> versions of both. kexec works fine with the forward ported version of
> xenlinux.
>
> kexec -l bzImage --ramdisk=/boot/initrd-3.5.0-rc5-bug694863+ '--command-line=root=/dev/disk/by-label/sles11sp1_full
> sysrq=yes
> panic=9
> oops=panic
> console=ttyS0,115200
> log_buf_len=16M
> ignore_loglevel
> initcall_debug
> debug earlyprintk=serial,ttyS0,115200' -t bzImage --console-serial --serial=ttyS0 --serial-baud=115200 --debug
> kexec -e

Nothing special. But try also ELF loader.

> As Jan pointed out, the copying is done in
> arch/x86/boot/compressed/misc.c. But adding some debug to inspect
> *output in parse_elf() shows that the second entry in program headers is
> already shifted by 44 bytes in my testing, the others are shifted by the
> same amount.
>
> Program Headers:
>   Type           Offset   VirtAddr           PhysAddr           FileSiz  MemSiz   Flg Align
>   LOAD           0x200000 0xffffffff81000000 0x0000000001000000 0xa3b000 0xa3b000 R E 0x200000
>   LOAD           0xe00000 0xffffffff81c00000 0x0000000001c00000 0x05b0e8 0x05b0e8 RW  0x200000
>   LOAD           0x1000000 0x0000000000000000 0x0000000001c5c000 0x012c40 0x012c40 RW  0x200000
>   LOAD           0x106f000 0xffffffff81c6f000 0x0000000001c6f000 0x087000 0x702000 RWE 0x200000
>   NOTE           0x82d5bc 0xffffffff8162d5bc 0x000000000162d5bc 0x00017c 0x00017c     0x4
>
> That makes me wonder wether kexec-tools is the culprit.

Is it relocatable kernel? If not please try use not relocatable one.
Then kernel will be always in the same place.

Daniel
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