nolibc: Add static-pie support

For more background see:
https://lore.kernel.org/lkml/20260116122812.2421621-1-dan...

Basically I am trying to run normal ELF binaries created with
nolibc on nommu (m68k, 68000). To make this work without an external
linker nolibc needs code to do the relocation.

The following is my attempt at doing this by hacking just enough
together that static-pie binaries work on a few archs.
The ones that work have a patch in this series.

Answers to questions you might have:
Q: Don't we need to handle more relocation types?
A: Maybe, everything exception sparc only had R_x_RELATIVE in
   the nolibc test binary. sparc emits R_SPARC_NONE as well.

Q: Don't we need to make some sections writable for this to
   work.
A: Maybe, I tried to get most of the supported archs working.
   The only one that had relocations on a non-writable section
   was arm64 and I think I can fix it so it doesn't need that.

Q: Why can't you just pass -static-pie to gcc?
A: Only x86 seemed to actually produce static PIE binaries doing
   that. Everything else produced normal static ones. Maybe this
   is a compiler version thing?

There are probably things I'm missing, things I have done totally
wrong. Please feel free to grill me.

Daniel Palmer (9):
  elf: Add relocation types used by nolibc
  tools/nolibc: crt: Split _start_c() into stack-only and normal part
  tools/nolibc: Add basic ELF self-relocation support for static PIE
  tools/nolibc: m68k: Add relocation support
  tools/nolibc: x86: Add relocation support for x86_64
  tools/nolibc: riscv: Add relocation support
  tools/nolibc: arm: Add relocation support
  selftests/nolibc: Add option for building with -static-pie
  fs/binfmt_elf_fdpic: Reflect that PIE binaries also work in KConfig
    help

 fs/Kconfig.binfmt                             |  10 +
 include/uapi/linux/elf-r.h                    |  27 ++
 include/uapi/linux/elf.h                      |   1 +
 tools/include/nolibc/Makefile                 |   1 +
 tools/include/nolibc/arch-arm.h               |  17 ++
 tools/include/nolibc/arch-m68k.h              |  20 +-
 tools/include/nolibc/arch-riscv.h             |  18 ++
 tools/include/nolibc/arch-x86.h               |  35 +++
 tools/include/nolibc/crt.h                    |  62 +++--
 tools/include/nolibc/reloc.h                  | 240 ++++++++++++++++++
 tools/testing/selftests/nolibc/Makefile       |   2 +-
 .../testing/selftests/nolibc/Makefile.nolibc  |   8 +-
 tools/testing/selftests/nolibc/run-tests.sh   |  10 +-
 13 files changed, 423 insertions(+), 28 deletions(-)
 create mode 100644 include/uapi/linux/elf-r.h
 create mode 100644 tools/include/nolibc/reloc.h

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2.51.0