Fastboot] kexec and kdump on i386 and x86_64:kexec-tools-testing results

[magnus.damm at gmail.com (Magnus Damm)]

On 11/17/06, Dave Anderson <anderson at redhat.com> wrote:
>  Magnus Damm wrote:
> Hi Dave,
>
> On 11/16/06, Dave Anderson <anderson at redhat.com> wrote:
> >
> > Vivek Goyal <vgoyal at in.ibm.com> wrote:
> >  - I think this patch will break compatibility with gdb as we are not
> > mapping
> >   kernel in virtual address space. All the physical chunks are being
> mapped
> >   to linearly mapped region in virtual address space and none is being
> > mapped
> >   to kernel text virtual address region.
> >
> > Vivek,
> >
> > Wouldn't it also break the algorithm used by the crash utility
> > to determine the kernel's physical base address?
> >
> > Recall that we decided to search for the PT_LOAD segment
> > starting at  __START_KERNEL_map, and then calculate the
> > physical base address like so:
> >
> >   phys_base = phdr->p_paddr - (phdr->p_vaddr & ~(__START_KERNEL_map));
>
> But older versions the kexec-tools doesn't add the kernel PT_LOAD
> segment on x86_64, and on i386 that does not happen at all. Does that
> mean that crash needs a new version of kexec-tools to work properly?
> Maybe I'm misunderstanding...
>
>
>  The calculation above is only for relocatable x86_64 kernels;
> what I failed to mention is that it only takes affect if the
> "phys_base" entry point exists, which only exists in relocatable
> x86_64 kernels.  In all other x86_64 kernels, the default physical
> address base value of zero is used.
>
> The p_vaddr field of the PT_LOAD segments is only used by the crash
> utility in two circumstances:
>
> 1. to determine the physical base address for relocatable x86_64
>    kdump vmcores, and
> 2. to determine the physical base address for all ia64 kdump vmcores,
>    which have a singular region 5 PT_LOAD segment mapping the kernel's
>    text/static data (in addition to region 7 segments for the rest
>    of physical memory).

How does ia64 support differ from x86_64? Would having a separate
PT_LOAD segment
for the kernel work for both ia64 and x86_64? Together with the ram
segments of course.

Thanks!

/ magnus