[PATCH v1] rust: bug: skip arch-specific asm in `testlib` builds

From: FUJITA Tomonori <[email protected]>

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 <[email protected]>
Closes: https://lore.kernel.org/all/CANiq72n4=fz=JNKY0Jdm8BnLa=RmHB2B7s0bO47YTJ7hygqBZg@mail.gmail.com/
Signed-off-by: FUJITA Tomonori <[email protected]>
---
 rust/kernel/bug.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/bug.rs b/rust/kernel/bug.rs
index ed943960f851..8e4c21e393c9 100644
--- a/rust/kernel/bug.rs
+++ b/rust/kernel/bug.rs
@@ -8,6 +8,7 @@
 
 #[macro_export]
 #[doc(hidden)]
+#[cfg(not(testlib))]
 #[cfg(all(CONFIG_BUG, not(CONFIG_UML), not(CONFIG_LOONGARCH), not(CONFIG_ARM)))]
 #[cfg(CONFIG_DEBUG_BUGVERBOSE)]
 macro_rules! warn_flags {
@@ -47,6 +48,7 @@ macro_rules! warn_flags {
 
 #[macro_export]
 #[doc(hidden)]
+#[cfg(not(testlib))]
 #[cfg(all(CONFIG_BUG, not(CONFIG_UML), not(CONFIG_LOONGARCH), not(CONFIG_ARM)))]
 #[cfg(not(CONFIG_DEBUG_BUGVERBOSE))]
 macro_rules! warn_flags {
@@ -73,6 +75,7 @@ macro_rules! warn_flags {
 
 #[macro_export]
 #[doc(hidden)]
+#[cfg(not(testlib))]
 #[cfg(all(CONFIG_BUG, CONFIG_UML))]
 macro_rules! warn_flags {
     ($file:expr, $flags:expr) => {
@@ -91,6 +94,7 @@ macro_rules! warn_flags {
 
 #[macro_export]
 #[doc(hidden)]
+#[cfg(not(testlib))]
 #[cfg(all(CONFIG_BUG, any(CONFIG_LOONGARCH, CONFIG_ARM)))]
 macro_rules! warn_flags {
     ($file:expr, $flags:expr) => {
@@ -101,7 +105,7 @@ macro_rules! warn_flags {
 
 #[macro_export]
 #[doc(hidden)]
-#[cfg(not(CONFIG_BUG))]
+#[cfg(any(testlib, not(CONFIG_BUG)))]
 macro_rules! warn_flags {
     ($file:expr, $flags:expr) => {};
 }

base-commit: 075b74841bd0065a3bda3440873c747938e69b68
-- 
2.43.0