[RFC 0/5] Reuse 32 bit C code more safely

[Frediano Ziglio <frediano.ziglio@xxxxxxxxx>]

This RFC series attempt to:
- use more C code, that is replace some assembly code with C;
- avoid some code duplication between C and assembly;
- prevent some issues having relocations in C code.

The idea is extending the current C to binary code conversion
done for 32 bit C code called from head.S making sure relocations
are safe and allowing external symbols usage from C code.

Note that, as an addition, scripts generating code check for no
data to allow code and data separation.

More details of the implementation are in commit message 2/5,
which is the largest patch.
Patch 1/5 is to prepare code and avoid data.
Patch 3/5 is an example of code reuse between 32 and 64 bit.
Patch 4/5 is also another example of code reuse but is more hacky and
dirty due to not being possible include use some headers.

Code boot successfully using:
- BIOS boot;
- EFI boot with Grub2 and ELF file;
- direct EFI boot without Grub.

Suggestions/opinions are welcome.

Code is currently based on "staging" branch, currently commit
6471badeeec92db1cb8155066551f7509cd82efd.

Frediano Ziglio (5):
  Avoid usage of global in reloc.c
  x86/boot: create a C bundle for 32 bit boot code and use it
  Reuse code to relocate trampoline
  Remove duplication preparing pages
  setup mapping for trampoline in setup_pagesXX

 .gitignore                                    |   3 +-
 xen/arch/x86/boot/Makefile                    |  30 ++-
 .../x86/boot/{build32.lds => build32.lds.S}   |  60 +++++-
 xen/arch/x86/boot/cmdline.c                   |   7 -
 xen/arch/x86/boot/head.S                      |  89 +--------
 xen/arch/x86/boot/reloc-trampoline.c          |  28 +++
 xen/arch/x86/boot/reloc-trampoline64.c        |   1 +
 xen/arch/x86/boot/reloc.c                     |  69 ++++---
 xen/arch/x86/boot/setup-pages.c               | 116 ++++++++++++
 xen/arch/x86/boot/setup-pages64.c             |   1 +
 xen/arch/x86/boot/x86_64.S                    |   2 +-
 xen/arch/x86/efi/efi-boot.h                   |  67 +------
 xen/arch/x86/include/asm/page.h               |   3 +-
 xen/tools/make_output                         | 177 ++++++++++++++++++
 14 files changed, 446 insertions(+), 207 deletions(-)
 rename xen/arch/x86/boot/{build32.lds => build32.lds.S} (52%)
 create mode 100644 xen/arch/x86/boot/reloc-trampoline.c
 create mode 120000 xen/arch/x86/boot/reloc-trampoline64.c
 create mode 100644 xen/arch/x86/boot/setup-pages.c
 create mode 120000 xen/arch/x86/boot/setup-pages64.c
 create mode 100755 xen/tools/make_output

-- 
2.46.0