[PATCH v4 00/24] vdso: Reject absolute relocations during build

[Thomas Weißschuh]

The compiler can emit absolute relocations in vDSO code,
which are invalid in vDSO code.
Detect them at compile-time.

libc elf.h is missing some of the relocation constants,
so make user of the kernels own UAPI headers instead.

Kbuild and Rust folks: This contains custom definitions of hostprog
bindgen and rust library commands.
These are currently only defined inside the subsystem directory.
Let me know if they should go into scripts/Makefile.host.

This will conflict with my SPARC64 generic vDSO patches [0].
If both end up being applied at the same time, please leave out commit 
'vdso/vdsocheck: Drop the transitional kconfig option' from this series.

[0] https://lore.kernel.org/lkml/20250724-vdso-sparc64-generic-2-v1-0-e376a3bd24d1@linutronix.de/

Signed-off-by: Thomas Weißschuh <thomas.weissschuh at linutronix.de>
---
Changes in v4:
- Replace the inline shell logic with a dedicated build-time tool
- Link to v3: https://lore.kernel.org/r/20250611-vdso-absolute-reloc-v3-0-47897d73784b@linutronix.de

Changes in v3:
- Drop already applied bugfix for arm64
- Disable LTO for the riscv vDSO, as it is incompatible
- Link to v2: https://lore.kernel.org/r/20250430-vdso-absolute-reloc-v2-0-5efcc3bc4b26@linutronix.de

Changes in v2:
- Link to openend (invalid) GCC bug containing more explanations
- Refine commit messages
- Don't fail on commit absolute relocations in debug info
- Link to v1: https://lore.kernel.org/r/20250429-vdso-absolute-reloc-v1-0-987a0afd10b5@linutronix.de

---
Thomas Weißschuh (24):
      elf, uapi: Add a header for relocation constants
      x86/elf, um/x86/elf: Move relocation constants to UAPI
      ARM: elf: Move relocation constants to UAPI
      arm64: elf: Move relocation constants to UAPI
      powerpc/elf: Move relocation constants to UAPI
      riscv: elf: Move relocation constants to UAPI
      LoongArch: Move relocation constants to UAPI
      s390/elf: Move relocation constants to UAPI
      MIPS: ELF: Move relocation constants to UAPI
      tools headers UAPI: Sync ELF headers with the kernel sources
      vdso: Add the vdsocheck tool
      x86/vdso: Enable the vdsocheck tool
      ARM: vdso: Enable the vdsocheck tool
      arm64: vdso: Enable the vdsocheck tool
      powerpc/elf: Add 32-bit REL16 relocation definitions
      powerpc/vdso: Enable the vdsocheck tool
      riscv: vdso: Deduplicate CFLAGS_REMOVE_* variables
      riscv: vdso: Disable LTO for the vDSO
      riscv: vdso: Enable the vdsocheck tool
      LoongArch: vDSO: Enable the vdsocheck tool
      s390/vdso: Enable the vdsocheck tool
      MIPS: ELF: Add more PC-relative relocation definitions
      MIPS: vdso: Enable the vdsocheck tool
      vdso/vdsocheck: Drop the transitional kconfig option

 arch/arm/include/asm/elf.h          |  24 --
 arch/arm/vdso/Makefile              |   4 +-
 arch/arm64/include/asm/elf.h        |  55 ----
 arch/arm64/kernel/vdso/Makefile     |   4 +-
 arch/loongarch/include/asm/elf.h    | 100 ------
 arch/loongarch/vdso/Makefile        |   4 +-
 arch/mips/include/asm/elf.h         |  53 ---
 arch/mips/vdso/Makefile             |   8 +-
 arch/powerpc/include/uapi/asm/elf.h | 201 ------------
 arch/powerpc/kernel/vdso/Makefile   |   4 +-
 arch/riscv/include/uapi/asm/elf.h   |  66 ----
 arch/riscv/kernel/vdso/Makefile     |  11 +-
 arch/s390/include/asm/elf.h         |  83 -----
 arch/s390/kernel/vdso32/Makefile    |   4 +-
 arch/s390/kernel/vdso64/Makefile    |   4 +-
 arch/x86/entry/vdso/Makefile        |   6 +-
 arch/x86/include/asm/elf.h          |  34 --
 arch/x86/um/asm/elf.h               |  33 --
 include/uapi/linux/elf-r.h          | 631 ++++++++++++++++++++++++++++++++++++
 include/uapi/linux/elf.h            |   1 +
 lib/vdso/Makefile                   |   2 +
 lib/vdso/Makefile.include           |  17 +
 lib/vdso/check/.gitignore           |   3 +
 lib/vdso/check/Makefile             |  28 ++
 lib/vdso/check/elf.rs               | 488 ++++++++++++++++++++++++++++
 lib/vdso/check/vdsocheck.rs         | 279 ++++++++++++++++
 tools/include/uapi/linux/elf-em.h   |  71 ++++
 tools/include/uapi/linux/elf-r.h    | 631 ++++++++++++++++++++++++++++++++++++
 tools/include/uapi/linux/elf.h      | 112 ++++++-
 29 files changed, 2277 insertions(+), 684 deletions(-)
---
base-commit: 5180c6526acc9f1cb58f8b11fba67583c22e0854
change-id: 20250428-vdso-absolute-reloc-a226293c1761

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh at linutronix.de>