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

From: Vivek Goyal
Date: Mon Aug 14 2006 - 15:41:21 EST

On Mon, Aug 14, 2006 at 12:32:32PM -0700, H. Peter Anvin wrote:
> 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?

Sorry did not understand the question. Few more lines will help.

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