This patchset adds warn_on and warn_on_once macros with the bug/warn
abstraction.

Wrapping C's BUG/WARN macros does not work well for x86, RISC-V,
ARM64, and LoongArch. Rust code needs to directly execute the same
assembly code used on the C side. To avoid duplicating the assembly
code, this approach mirrors what the static branch code does: it
generates the assembly code for Rust using the C preprocessor at
compile time.

The 1st to 4th patches export the BUG/WARN assembly code for Rust on
each architecture, with no functional changes on the C side. The
changes for x86 and RISC-V are straightforward. However, the ARM64 and
LoongArch assembly code are designed differently; they are used by
both C inline assembly and assembly code. As a result, sharing this
code with Rust is complicated.

The last patch adds the bug abstraction with warn_on and warn_on_once
implementations.

This has been tested on x86, ARM64, and RISC-V (QEMU), with only a
compile test performed for LoongArch.

The assembly code can be used for both BUG and WARN, but currently
only supports warn_on and warn_on_once. I will work on the remaining
functionality after this abstraction is merged.

v3:
- rebased on rust-next
- use ANNOTATE_REACHABLE macro (replaced ASM_REACHABLE)
- added Acked-by tag to the x86 change
v2: https://lore.kernel.org/linux-arm-kernel/20241218062009.2402650-1-fujita.tomonori@gmail.com/ (local)
- remove target_arch cfg by using asm comment
- clean up the changes to loongarch asm
v1: https://lore.kernel.org/linux-arm-kernel/20241210001802.228725-1-fujita.tomonori@gmail.com/ (local)

FUJITA Tomonori (5):
  x86/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with
    Rust
  riscv/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with
    Rust
  arm64/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with
    Rust
  loongarch/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing
    with Rust
  rust: Add warn_on and warn_on_once

 arch/arm64/include/asm/asm-bug.h              |  33 +++++-
 arch/loongarch/include/asm/bug.h              |  35 +++++-
 arch/riscv/include/asm/bug.h                  |  37 ++++---
 arch/x86/include/asm/bug.h                    |  56 +++++-----
 rust/Makefile                                 |   8 ++
 rust/kernel/.gitignore                        |   2 +
 rust/kernel/bug.rs                            | 100 ++++++++++++++++++
 rust/kernel/generated_arch_reachable_asm.rs.S |   7 ++
 rust/kernel/generated_arch_warn_asm.rs.S      |   7 ++
 rust/kernel/lib.rs                            |   1 +
 10 files changed, 235 insertions(+), 51 deletions(-)
 create mode 100644 rust/kernel/bug.rs
 create mode 100644 rust/kernel/generated_arch_reachable_asm.rs.S
 create mode 100644 rust/kernel/generated_arch_warn_asm.rs.S


base-commit: beeb78d46249cab8b2b8359a2ce8fa5376b5ad2d
-- 
2.43.0