Re: [Fastboot] [CFT] ELF Relocatable x86 and x86_64 bzImages

["H. Peter Anvin" <hpa@zytor.com>]

Vivek Goyal wrote:
> On Mon, Aug 14, 2006 at 10:04:29AM -0700, H. Peter Anvin wrote:
> > Vivek Goyal wrote:
> > > On Thu, Aug 10, 2006 at 02:09:58PM -0600, Eric W. Biederman wrote:
> > > > > I just reserved memory at non 2MB aligned location 65MB@15MB so that
> > > > > kernel is loaded at 16MB and other smaller segments below the compressed
> > > > > image, then I can successfully booted into the kdump kernel.
> > > > :)
> > > >
> > > > > So basically kexec on panic path seems to be clean except stomping issue.
> > > > > May be bzImage program header should reflect right "MemSize" which
> > > > > takes into account extra memory space calculations.
> > > > Yes.  That sounds like the right thing to do.  
> > > >
> > > > I remember trying to compute a good memsize when I created the bzImage
> > > > header but it is completely possible I missed some part of the
> > > > calculation or assumed that the kernels .bss section would always be
> > > > larger than what I needed for decompression.
> > Could someone please describe the intended semantics of this MemSize 
> > header, *and* its intended usage?
>
> Now and ELF header(attached to bzImage) is being used to describe
> the kernel executable. One program header of PT_LOAD type is being
> created. The "p_filesz" field of program header is basically 
> describing the vmlinux file size and "p_memsz" is giving how
> much memory will be consumed by kernel image at load time.
>
> Ideally "p_memsz" should be "p_memsz" summation of all the program
> headers of vmlinux file but I guess in this case we are stretching the
> ELF specification a little bit and also taking into the account the
> additional memory which will be used by decompressor and decompression
> logic by the time execution is transferred to the actual kernel.

What about once the kernel is booted?

	-hpa
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