rust: bug: skip arch-specific asm in `testlib` builds

Running `make rusttest` with `ARCH=` set to an architecture other than
the host's fails, e.g. `ARCH=arm64` on an x86_64 host:

error: invalid instruction mnemonic 'brk'
  --> rust/kernel/bug.rs:63:17
   |
63 | /                 concat!(
64 | |                     "/* {size} */",
65 | |                     include!(concat!(env!("OBJTREE"), "/rust/kernel/generated_arch_warn_asm.rs")),
66 | |                     include!(concat!(env!("OBJTREE"), "/rust/kernel/generated_arch_reachable_asm.rs")));
   | |_______________________________________________________________________________________________________^
   |
note: instantiated into assembly here
  --> <inline asm>:1:115
   |
 1 |     /* 8 */.pushsection __bug_table,"aw"; .align 2; 14470: .long 14471f - .;.short 2305;.align 2; .popsection; 14471:brk 0x800
   |                                                                                                                      ^^^

The reason is that `rusttest` builds the `kernel` crate as a host
library: it passes the `CONFIG_*` cfgs of the configured architecture,
but not `--target`, so code generation happens for the
host. `warn_flags!` then selects the arch-specific inline asm arm
based on `CONFIG_*`, and the host assembler rejects it.

This does not happen with the current `master` because `warn_on!` has
no user inside the `kernel` crate itself yet, but it will as soon as
one is added.

Reported-by: Miguel Ojeda <ojeda@kernel.org>
Closes: https://lore.kernel.org/all/CANiq72n4=fz=JNKY0Jdm8BnLa=RmHB2B7s0bO47YTJ7hygqBZg@mail.gmail.com/
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Cc: stable@vger.kernel.org
Fixes: dff64b072708 ("rust: Add warn_on macro")
Link: https://patch.msgid.link/20260808022608.1125174-1-tomo@flapping.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

0 files changed, 0 insertions, 0 deletions