Callers that go through `kernel::prelude` have `CStrExt` in scope, but
code inside the `kernel` crate imports explicitly and may not. Using
`warn_on!` from such a module fails to build on UML, which is the only
configuration where `warn_flags!` needs a C string pointer rather than an
inline asm bug entry:
error[E0599]: no method named `as_char_ptr` found for reference `&ffi::CStr` in the current scope
--> linux/rust/kernel/bug.rs:83:49
|
83 | $crate::c_str!(::core::file!()).as_char_ptr(),
| ^^^^^^^^^^^
|
::: linux/rust/kernel/time.rs:427:9
|
427 | warn_on!(self.nanos < 0);
| ------------------------ in this macro invocation
|
= help: items from traits can only be used if the trait is in scope
= note: this error originates in the macro `$crate::warn_flags` which comes from the expansion of the macro `warn_on` (in Nightly builds, run with -Z mac)
help: trait `CStrExt` which provides `as_char_ptr` is implemented but not in scope; perhaps you want to import it
--> linux/rust/kernel/time.rs:27:1
|
27 + use crate::str::CStrExt;
Call the method through its fully qualified path, which resolves
without any import at the expansion site.
Cc: stable@vger.kernel.org
Fixes: dff64b0727 ("rust: Add warn_on macro")
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Link: https://patch.msgid.link/20260807112427.1039056-1-tomo@flapping.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
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: dff64b0727 ("rust: Add warn_on macro")
Link: https://patch.msgid.link/20260808022608.1125174-1-tomo@flapping.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Fix the following dead_code warning on some configurations in an
atomic development branch:
warning: constant `WARN_ON_FLAGS` is never used
--> linux/rust/kernel/bug.rs:126:19
|
126 | const WARN_ON_FLAGS: u32 = $crate:🐛:bugflag_taint($crate::bindings::TAINT_WARN);
| ^^^^^^^^^^^^^
|
::: linux/rust/kernel/sync/srcu.rs:106:12
|
106 | if crate::warn_on!(
| ____________-
107 | | // SAFETY: By the type invariants, `self` contains a valid and pinned `struct srcu_struct`
108 | | // and `srcu_readers_active()` only checks the active reader count.
109 | | unsafe { bindings::srcu_readers_active(ptr) }
110 | | ) {
| |_________- in this macro invocation
|
= note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default
= note: this warning originates in the macro `crate::warn_on` (in Nightly builds, run with -Z macro-backtrace for more info)
The warn_on! macro always defines a WARN_ON_FLAGS constant and hands it
to warn_flags!. On configurations where warn_flags! does not reference
its flags argument (the LOONGARCH/ARM variant, which only calls
WARN_ON(), and the !CONFIG_BUG no-op variant), the constant is left
unused and triggers a dead_code warning.
warn_flags! is the macro that accepts (and here discards) the flags
argument, so make it responsible for the argument it drops.
Also rename `_COND_STR` to `COND_STR` and consume `$file` for consistency.
Fixes: dff64b0727 ("rust: Add warn_on macro")
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260801024841.786664-1-tomo@flapping.org
[ Added newlines. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Make warn_on() support DEBUG_BUGVERBOSE_DETAILED option, which was
introduced by the commit aec58b4851 ("bugs/core: Extend
__WARN_FLAGS() with the 'cond_str' parameter").
When the option is enabled, WARN splats now show the evaluated
warn_on() condition alongside the file path, e.g.:
------------[ cut here ]------------
WARNING: [val == 1] linux/samples/rust/rust_minimal.rs:27 at _RNvXCsk7t4azzUqHP_12rust_minimalNtB2_11RustMinimalNtCs8pcx3n4
Modules linked in: rust_minimal(+)
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260108013350.2880613-1-fujita.tomonori@gmail.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Add warn_on macro, uses the BUG/WARN feature (lib/bug.c) via assembly
for x86_64/arm64/riscv.
The current Rust code simply wraps BUG() macro but doesn't provide the
proper debug information. The BUG/WARN feature can only be used from
assembly.
This uses the assembly code exported by the C side via ARCH_WARN_ASM
macro. To avoid duplicating the assembly code, this approach follows
the same strategy as the static branch code: it generates the assembly
code for Rust using the C preprocessor at compile time.
Similarly, ARCH_WARN_REACHABLE is also used at compile time to
generate the assembly code; objtool's reachable annotation code. It's
used for only architectures that use objtool.
For now, Loongarch and arm just use a wrapper for WARN macro.
UML doesn't use the assembly BUG/WARN feature; just wrapping generic
BUG/WARN functions implemented in C works.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20250502094537.231725-5-fujita.tomonori@gmail.com
[ Avoid evaluating the condition twice (a good idea in general,
but it also matches the C side). Simplify with `as_char_ptr()`
to avoid a cast. Cast to `ffi` integer types for
`warn_slowpath_fmt`. Avoid cast for `null()`. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
