[PATCH v4 0/3] riscv: vdso: Implement __vdso_futex_robust_try_unlock()

[Nam Cao <namcao@linutronix.de>]

This series adds new vdso futex entries, allowing user to address the
robust futex race condition regarding clearing the
robust_list_head::list_op_pending pointer.

Thomas wrote a summary of the problem:
https://lore.kernel.org/lkml/20260602084648.462672743@kernel.org/

The core infrastructure has been implemented along with x86 support. This
series adds RISC-V support.

The first 4 patches prepare compat vdso Makefile. The final patch is the
main show.

v4:
  - fix minor whitespace issue
  - stop touching -march in Makefile, instead use .option arch

v3:
  - add missing include guard
  - switch to if/else for compare-and-exchange vs load-reserved/store-conditional

v2:
  - address Sashiko's comments


Nam Cao (3):
  riscv: compat_vdso: switch to standard kbuild rule
  riscv: compat_vdso: Allow *.c source files
  riscv: vdso: Implement __vdso_futex_robust_try_unlock()

 arch/riscv/Kconfig                         |  1 +
 arch/riscv/include/asm/cpufeature-macros.h |  2 +
 arch/riscv/include/asm/futex_robust.h      | 16 ++++
 arch/riscv/include/asm/vdso/futex.h        | 14 ++++
 arch/riscv/kernel/compat_vdso/Makefile     | 16 ++--
 arch/riscv/kernel/compat_vdso/futex.c      |  3 +
 arch/riscv/kernel/vdso.c                   | 61 +++++++++++++++
 arch/riscv/kernel/vdso/Makefile            |  7 +-
 arch/riscv/kernel/vdso/futex.c             | 87 ++++++++++++++++++++++
 arch/riscv/kernel/vdso/vdso.lds.S          |  8 ++
 10 files changed, 206 insertions(+), 9 deletions(-)
 create mode 100644 arch/riscv/include/asm/futex_robust.h
 create mode 100644 arch/riscv/include/asm/vdso/futex.h
 create mode 100644 arch/riscv/kernel/compat_vdso/futex.c
 create mode 100644 arch/riscv/kernel/vdso/futex.c

-- 
2.47.3