[v2,5/5] rust: Add warn_on and warn_on_once

Commit Message

FUJITA Tomonori Dec. 18, 2024, 6:20 a.m. UTC

Add warn_on and warn_on_once macros. Wrapping the C's WARN_* and BUG_*
macros doesn't work so this uses the assembly code exported by the C
side via ARCH_WARN_ASM macro. Like the static branch code, this
generates the assembly code for rust dynamically by using the C
preprocessor.

file()! macro doesn't work for the Rust inline assembly in the same
way as __FILE__ for the C inline assembly. So the code to handle a
file name is different from the C assembly code (similar to the
arm64/loongarch assembly).

ASM_REACHABLE definition works in the same way to get objtool's
reachable asm code. The architectures which use objtool (x86 and
loongarch) needs it.

Signed-off-by: FUJITA Tomonori <[e-mail]>
---
 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 +
 6 files changed, 125 insertions(+)
 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

Patch

diff --git a/rust/Makefile b/rust/Makefile
index a40a3936126d..633b2c28605c 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -37,6 +37,9 @@  obj-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated.o
 obj-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated_kunit.o
 
 always-$(subst y,$(CONFIG_RUST),$(CONFIG_JUMP_LABEL)) += kernel/generated_arch_static_branch_asm.rs
+ifndef CONFIG_UML
+always-$(subst y,$(CONFIG_RUST),$(CONFIG_BUG)) += kernel/generated_arch_warn_asm.rs kernel/generated_arch_reachable_asm.rs
+endif
 
 # Avoids running `$(RUSTC)` for the sysroot when it may not be available.
 ifdef CONFIG_RUST
@@ -449,5 +452,10 @@  $(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/build_error.o \
 ifdef CONFIG_JUMP_LABEL
 $(obj)/kernel.o: $(obj)/kernel/generated_arch_static_branch_asm.rs
 endif
+ifndef CONFIG_UML
+ifdef CONFIG_BUG
+$(obj)/kernel.o: $(obj)/kernel/generated_arch_warn_asm.rs $(obj)/kernel/generated_arch_reachable_asm.rs
+endif
+endif
 
 endif # CONFIG_RUST
diff --git a/rust/kernel/.gitignore b/rust/kernel/.gitignore
index 6ba39a178f30..f1d7f4225332 100644
--- a/rust/kernel/.gitignore
+++ b/rust/kernel/.gitignore
@@ -1,3 +1,5 @@ 
 # SPDX-License-Identifier: GPL-2.0
 
 /generated_arch_static_branch_asm.rs
+/generated_arch_warn_asm.rs
+/generated_arch_reachable_asm.rs
\ No newline at end of file
diff --git a/rust/kernel/bug.rs b/rust/kernel/bug.rs
new file mode 100644
index 000000000000..7ffd9cb1ad75
--- /dev/null
+++ b/rust/kernel/bug.rs
@@ -0,0 +1,100 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2024 FUJITA Tomonori
+
+//! Support for BUG_* and WARN_* functionality.
+//!
+//! C header: [`include/asm-generic/bug.h`](srctree/include/asm-generic/bug.h)
+
+#[macro_export]
+#[doc(hidden)]
+#[cfg(all(CONFIG_BUG, not(CONFIG_UML)))]
+macro_rules! warn_flags {
+    ($flags:expr) => {
+        const FLAGS: u32 = $crate::bindings::BUGFLAG_WARNING | $flags;
+        // SAFETY: Just an FFI call.
+        #[cfg(CONFIG_DEBUG_BUGVERBOSE)]
+        unsafe {
+            $crate::asm!(concat!(
+                "/* {size} */",
+                ".pushsection .rodata.str1.1, \"aMS\",@progbits, 1\n",
+                "111:\t .string ", "\"", file!(), "\"\n",
+                ".popsection\n",
+                include!(concat!(env!("OBJTREE"), "/rust/kernel/generated_arch_warn_asm.rs")),
+                include!(concat!(env!("OBJTREE"), "/rust/kernel/generated_arch_reachable_asm.rs")));
+            line = const line!(),
+            flags = const FLAGS,
+            size = const ::core::mem::size_of::<$crate::bindings::bug_entry>(),
+            );
+        }
+        // SAFETY: Just an FFI call.
+        #[cfg(not(CONFIG_DEBUG_BUGVERBOSE))]
+        unsafe {
+            $crate::asm!(
+            concat!(
+                "/* {size} */",
+                include!(concat!(env!("OBJTREE"), "/rust/kernel/generated_arch_warn_asm.rs")),
+                include!(concat!(env!("OBJTREE"), "/rust/kernel/generated_arch_reachable_asm.rs")));
+            flags = const FLAGS,
+            size = const ::core::mem::size_of::<$crate::bindings::bug_entry>(),
+            );
+        }
+    }
+}
+
+#[macro_export]
+#[doc(hidden)]
+#[cfg(all(CONFIG_BUG, CONFIG_UML))]
+macro_rules! warn_flags {
+    ($flags:expr) => {
+        // SAFETY: Just an FFI call.
+        unsafe {
+            $crate::bindings::warn_slowpath_fmt(
+                $crate::c_str!(::core::file!()).as_ptr() as *const ::core::ffi::c_char,
+                line!() as i32,
+                $flags as u32,
+                ::core::ptr::null() as *const ::core::ffi::c_char,
+            );
+        }
+    };
+}
+
+#[macro_export]
+#[doc(hidden)]
+#[cfg(not(CONFIG_BUG))]
+macro_rules! warn_flags {
+    ($flags:expr) => {};
+}
+
+#[doc(hidden)]
+#[macro_export]
+macro_rules! bugflag_taint {
+    ($taint:expr) => {
+        $taint << 8
+    };
+}
+
+/// Report a warning only once.
+#[macro_export]
+macro_rules! warn_on_once {
+    ($cond:expr) => {
+        if $cond {
+            $crate::warn_flags!(
+                $crate::bindings::BUGFLAG_ONCE
+                    | $crate::bugflag_taint!($crate::bindings::TAINT_WARN)
+            );
+        }
+        $cond
+    };
+}
+
+/// Report a warning.
+#[macro_export]
+macro_rules! warn_on {
+    ($cond:expr) => {
+        if $cond {
+            $crate::warn_flags!($crate::bugflag_taint!($crate::bindings::TAINT_WARN));
+        }
+        $cond
+    };
+}
diff --git a/rust/kernel/generated_arch_reachable_asm.rs.S b/rust/kernel/generated_arch_reachable_asm.rs.S
new file mode 100644
index 000000000000..4e65525e4464
--- /dev/null
+++ b/rust/kernel/generated_arch_reachable_asm.rs.S
@@ -0,0 +1,7 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/objtool.h>
+
+// Cut here.
+
+::kernel::concat_literals!(ASM_REACHABLE)
diff --git a/rust/kernel/generated_arch_warn_asm.rs.S b/rust/kernel/generated_arch_warn_asm.rs.S
new file mode 100644
index 000000000000..8f239b431aa4
--- /dev/null
+++ b/rust/kernel/generated_arch_warn_asm.rs.S
@@ -0,0 +1,7 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/bug.h>
+
+// Cut here.
+
+::kernel::concat_literals!(ARCH_WARN_ASM("111b", "{line}",  "{flags}", "{size}"))
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index e1065a7551a3..913f3a5b2a98 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -32,6 +32,7 @@ 
 pub mod alloc;
 #[cfg(CONFIG_BLOCK)]
 pub mod block;
+pub mod bug;
 mod build_assert;
 pub mod cred;
 pub mod device;