Re: kexec -p loads

From: Vivek Goyal <vgoyal@redhat.com>
To: Bernhard Walle <bwalle@suse.de>
Cc: Kexec Mailing List <kexec@lists.infradead.org>,
	Cliff Wickman <cpw@sgi.com>
Subject: Re: kexec -p loads
Date: Wed, 27 Aug 2008 11:36:22 -0400	[thread overview]
Message-ID: <20080827153622.GD3694@redhat.com> (raw)
In-Reply-To: <20080827173035.71358a1f@halley.suse.de>

On Wed, Aug 27, 2008 at 05:30:35PM +0200, Bernhard Walle wrote:
> * Vivek Goyal [2008-08-27 11:28]:
> > > > 
> > > > > I have this debugging output from my kexec:
> > > > > 
> > > > > cpw: elf_x86_64_load returning entry:0x1550
> > > > > cpw: after call to file_type[i].load: nr_segments:6 entry:0x1550
> > > > > kexec_load: entry = 0x1550 flags = 1
> > > > > nr_segments = 6
> > > > > segment[0].buf   = 0x5237a0
> > > > > segment[0].bufsz = 7100
> > > > > segment[0].mem   = 0x1000
> > > > > segment[0].memsz = 9000
> > > > > 
> > > > > segment[1].buf   = 0x52aaf0
> > > > > segment[1].bufsz = 1000
> > > > > segment[1].mem   = 0xa000
> > > > > segment[1].memsz = 1000
> > > > > 
> > > > 
> > > > I think above two segments are not being loaded at right place. Looks like
> > > > kexec-tools decided to load first one at physical address 0x1000 and other at
> > > > physical address 0xa000. For crash kernel this is not right. It should
> > > > come out of reserved memory area and that's why you are encountering the
> > > > error.
> > > 
> > > Relocatability in ELF image never worked on x86_64 because of GDB but
> > > (so the binary was marked as ET_EXEC instead of ET_DYN).
> > > 
> > > You have to use bzImage for kdump in any case.
> > 
> > True that vmlinux is not relocatable. But one can always compile the
> > vmlinux for a fixed physical address (Address in reserved region) and then
> > use it?  In this case his vmlinux seems to have been compiled for physical
> > address 16MB. Which should be usable if there is a reserved memory region
> > at 16MB.
> 
> Of course, that's true. I just thought when Cliff uses the same kernel
> for "kexec -l" and "kexec -p", then it's the "normal" kernel. But I
> didn't calculate the numbers.
> 
> 

Its litle tricky. I think one can always do both "kexec -l" and "kexec -p"
on a vmlinux which has been built for kdump (for reserved region).

But one can not do "kexec -p" on normal kernel vmlinux.

So I am assuming that Cliff is running into first case. But he can tell
us more. 

Cliff, is it same vmlinux which you use for first kernel or a different
vmlinux compiled for dump capture.

Thanks
Vivek

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