Re: [RFC] rust: kernel: Add KUnit tests for ARCH_WARN_ASM bug table emission

On Tue, Sep 22, 2026 at 11:20:00AM +0530, Mukesh Kumar Chaurasiya (IBM) wrote:

Verify that the __bug_table entry emitted by ARCH_WARN_ASM has a correct
bug_addr displacement — i.e. the arch's trap label reference resolves to
the trap instruction — by calling find_bug() with the exact virtual address
of the trap, mirroring what the real trap handler does.

To support all architectures, each arch that implements ARCH_WARN_ASM now
defines ARCH_WARN_ASM_TRAP_LABEL, a string constant naming the local label
at which the trap instruction is placed:

  x86       "1"     (ud2 at label 1:)
  powerpc   "1"     (twi at label 1:)
  riscv     "1"     (ebreak at label 1:)
  arm64     "14471" (brk placed at 14471: by __BUG_ENTRY_END)
  s390      "0"     (mc at label 0:)

I'm not a fan of exposing such a low-level implementation detail out of
the architecture code, and I don't think we should expose this.

What exactly are you trying to verify here, and why? Has there been
some _specific_ issue on powerpc that caused you to look at this?

Mark.