Kexec loading grub2

[Joey Korkames]

For a number of weird reasons, I would find the ability to kexec into grub2 
from a running linux system useful.

In looking at the current code out there, there seems to be two ways to make 
grub2 able to support this:

1)  Add a 32-bit load segment to boot/i386/pc/lnxboot.S as described by
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/x86/boot.txt
 (at the bottom)

 grub4dos (which is kexec'able) implements this in startup_32: @ 
http://svn.gna.org/viewcvs/grub4dos/trunk/stage2/dosstart.S?view=markup


2) Adjust the ELF images made by grub-mkimage (for coreboot) to be loaded by 
kexec-tools's ELF loader (or vice-versa).
 
 I figure this is the best route to go about adding kexec boot ability to grub2
 since the BIOS-services-less kexec environment may be similar to coreboot's 
environment.

 Currently, loading this image:

   grub-mkelfimage --directory=/usr/lib/grub/i386-coreboot 
--prefix="/boot/grub" --output=grub2.elf --memdisk=memdisk.cpio memdisk cpio

   #readelf -l grub2.elf 
   > 
   > Elf file type is EXEC (Executable file)
   > Entry point 0x8200
   > There are 3 program headers, starting at offset 52
   > 
   > Program Headers:
   >   Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
   >   LOAD           0x000094 0x00008200 0x00008200 0x06fd8 0x0e86c RWE 0x20
   >   GNU_STACK      0x00706c 0x00000000 0x00000000 0x00000 0x00000 RWE 0x4
   >   LOAD           0x00706c 0x00017000 0x00017000 0x73fb0 0x73fb0 RWE 0x4
   > 

   #file -k grub2.elf 
   > grub2.elf: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), statically linked, stripped
 
 like so:
 (using latest 
git://git.kernel.org/pub/scm/linux/kernel/git/horms/kexec-tools.git)
 # kexec --type multiboot-x86 --load grub2.elf
 
 issues this error:
 > Base address: 8200 is not page aligned
 
 The original kexec kernel patch maintainer had these things to say about that:
 https://lists.linux-foundation.org/pipermail/fastboot/2005-August/008743.html
 http://www.mail-archive.com/address@hidden/msg00249.html

 I noticed this line in the grub2 src:
  ./conf/i386-coreboot.rmk:36:kernel_elf_LDFLAGS = $(COMMON_LDFLAGS) 
-Wl,-N,-S,-Ttext,0x8200,-Bstatic
 but I'm sure there's gonna be more involved than just changing that to 0x8000.
 
 kexec_test is an example of a kexec-loadable elf:
  
(http://git.kernel.org/?p=linux/kernel/git/horms/kexec-tools.git;a=tree;f=kexec_test;hb=HEAD)
  #file -k kexec-tools.git/build/lib/kexec-tools/kexec_test
  > kexec_test: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), 
statically linked, not stripped

  #readelf -l /tmp/kexec-tools/build/lib/kexec-tools/kexec
  > 
  > Elf file type is EXEC (Executable file)
  > Entry point 0x109c4
  > There are 2 program headers, starting at offset 52
  > 
  > Program Headers:
  >   Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  >   LOAD           0x001000 0x00010000 0x00010000 0x00e40 0x00e40 R E 0x1000
  >   LOAD           0x002000 0x00011000 0x00011000 0x00000 0x0102c RW  0x1000
  > 
  >  Section to Segment mapping:
  >   Segment Sections...
  >    00     .text 
  >    01     .bss
  

I don't have the know-how currently to implement either route but I may be able 
to
learn with a little guidance. I'm asking about it here so as not to repeat any 
work-in-progress.

Thanks
-joey