kernel: Update changelog for elf-checkpoint file

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>

kernel/binfmt-elf-for-cr-5

@@ -5,9 +5,18 @@ Elf file format, which includes
 
  - new Elf file type ET_CKPT
  - three additional program header types PT_CKPT_VMA, PT_CKPT_CORE
-   and PT_CKPT_PAGES. PT_CKPT_VMA holds 'vma_entry' structure,
-   PT_CKPT_CORE -- 'core_entry' structure and PT_CKPT_PAGES --
-   a set of all pages which are to be read into process memory.
+   and PT_CKPT_PAGES.
+
+     PT_CKPT_VMA -- holds 'vma_entry' structure, which describes the
+     memory area kernel should map. It also might contain file descriptor
+     number so kernel will be mapping file povided. Usually such file get
+     opened by user-space helper which prepares 'vma_entry' structure
+     for kernel.
+
+     PT_CKPT_CORE -- 'core_entry' structure (registers, tls, etc)
+
+     PT_CKPT_PAGES -- a set of all pages which are to be read into
+     process memory.
 
 v2: (from Andrew Vagin)
  - load fs_base and gs_base via do_arch_prctl