kexec: export the value of phys_base instead of symbol address

kexec: export the value of phys_base instead of symbol address

Currently in x86_64, the symbol address of phys_base is exported to
vmcoreinfo.  Dave Anderson complained this is really useless for his
Crash implementation.  Because in user-space utility Crash and
Makedumpfile which exported vmcore information is mainly used for, value
of phys_base is needed to covert virtual address of exported kernel
symbol to physical address.  Especially init_level4_pgt, if we want to
access and go over the page table to look up a PA corresponding to VA,
firstly we need calculate

  page_dir = SYMBOL(init_level4_pgt) - __START_KERNEL_map + phys_base;

Now in Crash and Makedumpfile, we have to analyze the vmcore elf program
header to get value of phys_base.  As Dave said, it would be preferable
if it were readily availabl in vmcoreinfo rather than depending upon the
PT_LOAD semantics.

Hence in this patch change to export the value of phys_base instead of
its virtual address.

And people also complained that KERNEL_IMAGE_SIZE exporting is x86_64
only, should be moved into arch dependent function
arch_crash_save_vmcoreinfo.  Do the moving in this patch.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Baoquan He <[email protected]>
Cc: Thomas Garnier <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H . Peter Anvin" <[email protected]>
Cc: Eric Biederman <[email protected]>
Cc: Xunlei Pang <[email protected]>
Cc: HATAYAMA Daisuke <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Eugene Surovegin <[email protected]>
Cc: Dave Young <[email protected]>
Cc: AKASHI Takahiro <[email protected]>
Cc: Atsushi Kumagai <[email protected]>
Cc: Dave Anderson <[email protected]>
Cc: Pratyush Anand <[email protected]>
Cc: Vivek Goyal <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>