[PATCH v2 0/5] rust: Add bug/warn abstractions

[PATCH v2 0/5] rust: Add bug/warn abstractions

[FUJITA Tomonori]

This patchset adds warn_on and warn_on_once macros with the bug/warn
abstraction.

Wrapping C's BUG/WARN macros does not work the same way on
architectures that support Rust (x86, RISC-V, ARM64, LoongArch). Rust
code needs to directly execute the same assembly code used on the C
side. To avoid duplicating the assembly code, this approach mirrors
what the static branch code does: it dynamically generates the
assembly code for Rust using the C preprocessor.

The 1st to 4th patches export the BUG/WARN assembly code for Rust on
each architecture, with no functional changes on the C side. The
changes for x86 and RISC-V are straightforward. However, the ARM64 and
LoongArch assembly code are designed differently; they are used by
both C inline assembly and assembly code. As a result, sharing this
code with Rust is complicated.

The last patch adds the bug abstraction with warn_on and warn_on_once
implementations.

This has been tested on x86, ARM64, and RISC-V (QEMU), with only a
compile test performed for LoongArch.

The assembly code can be used for both BUG and WARN, but currently
only supports warn_on and warn_on_once. I will work on the remaining
functionality after this abstraction is merged.

v2:
- remove target_arch cfg by using asm comment
- clean up the changes to loongarch asm
v1: https://lore.kernel.org/linux-arm-kernel/20241210001802.228725-1-fujita.tomonori@gmail.com/


FUJITA Tomonori (5):
  x86/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with
    Rust
  riscv/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with
    Rust
  arm64/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with
    Rust
  loongarch/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing
    with Rust
  rust: Add warn_on and warn_on_once

 arch/arm64/include/asm/asm-bug.h              |  31 +++++-
 arch/loongarch/include/asm/bug.h              |  31 +++++-
 arch/riscv/include/asm/bug.h                  |  35 +++---
 arch/x86/include/asm/bug.h                    |  51 +++++----
 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 +
 10 files changed, 224 insertions(+), 49 deletions(-)
 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


base-commit: 517743c4e303252cd8c1a1fb1bed28e7d94d4678
-- 
2.43.0


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[PATCH v2 1/5] x86/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with Rust

[FUJITA Tomonori]

Add new ARCH_WARN_ASM macro for BUG/WARN assembly code sharing with
Rust to avoid the duplication.

No functional changes.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 arch/x86/include/asm/bug.h | 51 ++++++++++++++++++--------------------
 1 file changed, 24 insertions(+), 27 deletions(-)

diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
index 806649c7f23d..71df68e2a731 100644
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -28,45 +28,42 @@
 #ifdef CONFIG_GENERIC_BUG
 
 #ifdef CONFIG_X86_32
-# define __BUG_REL(val)	".long " __stringify(val)
+# define __BUG_REL(val)	".long " val
 #else
-# define __BUG_REL(val)	".long " __stringify(val) " - ."
+# define __BUG_REL(val)	".long " val " - ."
 #endif
 
 #ifdef CONFIG_DEBUG_BUGVERBOSE
+#define __BUG_ENTRY(file, line, flags)					\
+	"2:\t" __BUG_REL("1b") "\t# bug_entry::bug_addr\n"		\
+	"\t" __BUG_REL(file)   "\t# bug_entry::file\n"			\
+	"\t.word " line        "\t# bug_entry::line\n"			\
+	"\t.word " flags       "\t# bug_entry::flags\n"
+#else
+#define __BUG_ENTRY(file, ine, flags)					\
+	"2:\t" __BUG_REL("1b") "\t# bug_entry::bug_addr\n"		\
+	"\t.word " flags       "\t# bug_entry::flags\n"
+#endif
+
+#define _BUG_FLAGS_ASM(ins, file, line, flags, size, extra)		\
+	"1:\t" ins "\n"							\
+	".pushsection __bug_table,\"aw\"\n"				\
+	__BUG_ENTRY(file, line, flags)					\
+	"\t.org 2b + " size "\n"					\
+	".popsection\n"							\
+	extra
 
 #define _BUG_FLAGS(ins, flags, extra)					\
 do {									\
-	asm_inline volatile("1:\t" ins "\n"				\
-		     ".pushsection __bug_table,\"aw\"\n"		\
-		     "2:\t" __BUG_REL(1b) "\t# bug_entry::bug_addr\n"	\
-		     "\t"  __BUG_REL(%c0) "\t# bug_entry::file\n"	\
-		     "\t.word %c1"        "\t# bug_entry::line\n"	\
-		     "\t.word %c2"        "\t# bug_entry::flags\n"	\
-		     "\t.org 2b+%c3\n"					\
-		     ".popsection\n"					\
-		     extra						\
+	asm_inline volatile(_BUG_FLAGS_ASM(ins, "%c0",			\
+					   "%c1", "%c2", "%c3", extra)	\
 		     : : "i" (__FILE__), "i" (__LINE__),		\
 			 "i" (flags),					\
 			 "i" (sizeof(struct bug_entry)));		\
 } while (0)
 
-#else /* !CONFIG_DEBUG_BUGVERBOSE */
-
-#define _BUG_FLAGS(ins, flags, extra)					\
-do {									\
-	asm_inline volatile("1:\t" ins "\n"				\
-		     ".pushsection __bug_table,\"aw\"\n"		\
-		     "2:\t" __BUG_REL(1b) "\t# bug_entry::bug_addr\n"	\
-		     "\t.word %c0"        "\t# bug_entry::flags\n"	\
-		     "\t.org 2b+%c1\n"					\
-		     ".popsection\n"					\
-		     extra						\
-		     : : "i" (flags),					\
-			 "i" (sizeof(struct bug_entry)));		\
-} while (0)
-
-#endif /* CONFIG_DEBUG_BUGVERBOSE */
+#define ARCH_WARN_ASM(file, line, flags, size)				\
+	_BUG_FLAGS_ASM(ASM_UD2, file, line, flags, size, "")
 
 #else
 
-- 
2.43.0


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Re: [PATCH v2 1/5] x86/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with Rust

[Peter Zijlstra]

On Wed, Dec 18, 2024 at 03:20:05PM +0900, FUJITA Tomonori wrote:
> Add new ARCH_WARN_ASM macro for BUG/WARN assembly code sharing with
> Rust to avoid the duplication.

This conflicts with some patches I've been sitting on, but nothing that
I can't resolve I think.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

> Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
> ---
>  arch/x86/include/asm/bug.h | 51 ++++++++++++++++++--------------------
>  1 file changed, 24 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
> index 806649c7f23d..71df68e2a731 100644
> --- a/arch/x86/include/asm/bug.h
> +++ b/arch/x86/include/asm/bug.h
> @@ -28,45 +28,42 @@
>  #ifdef CONFIG_GENERIC_BUG
>  
>  #ifdef CONFIG_X86_32
> -# define __BUG_REL(val)	".long " __stringify(val)
> +# define __BUG_REL(val)	".long " val
>  #else
> -# define __BUG_REL(val)	".long " __stringify(val) " - ."
> +# define __BUG_REL(val)	".long " val " - ."
>  #endif
>  
>  #ifdef CONFIG_DEBUG_BUGVERBOSE
> +#define __BUG_ENTRY(file, line, flags)					\
> +	"2:\t" __BUG_REL("1b") "\t# bug_entry::bug_addr\n"		\
> +	"\t" __BUG_REL(file)   "\t# bug_entry::file\n"			\
> +	"\t.word " line        "\t# bug_entry::line\n"			\
> +	"\t.word " flags       "\t# bug_entry::flags\n"
> +#else
> +#define __BUG_ENTRY(file, ine, flags)					\
> +	"2:\t" __BUG_REL("1b") "\t# bug_entry::bug_addr\n"		\
> +	"\t.word " flags       "\t# bug_entry::flags\n"
> +#endif
> +
> +#define _BUG_FLAGS_ASM(ins, file, line, flags, size, extra)		\
> +	"1:\t" ins "\n"							\
> +	".pushsection __bug_table,\"aw\"\n"				\
> +	__BUG_ENTRY(file, line, flags)					\
> +	"\t.org 2b + " size "\n"					\
> +	".popsection\n"							\
> +	extra
>  
>  #define _BUG_FLAGS(ins, flags, extra)					\
>  do {									\
> -	asm_inline volatile("1:\t" ins "\n"				\
> -		     ".pushsection __bug_table,\"aw\"\n"		\
> -		     "2:\t" __BUG_REL(1b) "\t# bug_entry::bug_addr\n"	\
> -		     "\t"  __BUG_REL(%c0) "\t# bug_entry::file\n"	\
> -		     "\t.word %c1"        "\t# bug_entry::line\n"	\
> -		     "\t.word %c2"        "\t# bug_entry::flags\n"	\
> -		     "\t.org 2b+%c3\n"					\
> -		     ".popsection\n"					\
> -		     extra						\
> +	asm_inline volatile(_BUG_FLAGS_ASM(ins, "%c0",			\
> +					   "%c1", "%c2", "%c3", extra)	\
>  		     : : "i" (__FILE__), "i" (__LINE__),		\
>  			 "i" (flags),					\
>  			 "i" (sizeof(struct bug_entry)));		\
>  } while (0)
>  
> -#else /* !CONFIG_DEBUG_BUGVERBOSE */
> -
> -#define _BUG_FLAGS(ins, flags, extra)					\
> -do {									\
> -	asm_inline volatile("1:\t" ins "\n"				\
> -		     ".pushsection __bug_table,\"aw\"\n"		\
> -		     "2:\t" __BUG_REL(1b) "\t# bug_entry::bug_addr\n"	\
> -		     "\t.word %c0"        "\t# bug_entry::flags\n"	\
> -		     "\t.org 2b+%c1\n"					\
> -		     ".popsection\n"					\
> -		     extra						\
> -		     : : "i" (flags),					\
> -			 "i" (sizeof(struct bug_entry)));		\
> -} while (0)
> -
> -#endif /* CONFIG_DEBUG_BUGVERBOSE */
> +#define ARCH_WARN_ASM(file, line, flags, size)				\
> +	_BUG_FLAGS_ASM(ASM_UD2, file, line, flags, size, "")
>  
>  #else
>  
> -- 
> 2.43.0
> 
> 

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[PATCH v2 2/5] riscv/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with Rust

[FUJITA Tomonori]

Add new ARCH_WARN_ASM macro for BUG/WARN assembly code sharing with
Rust to avoid the duplication.

No functional changes.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 arch/riscv/include/asm/bug.h | 35 ++++++++++++++++++++---------------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/arch/riscv/include/asm/bug.h b/arch/riscv/include/asm/bug.h
index 1aaea81fb141..ee6b9b787e46 100644
--- a/arch/riscv/include/asm/bug.h
+++ b/arch/riscv/include/asm/bug.h
@@ -31,40 +31,45 @@ typedef u32 bug_insn_t;
 
 #ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
 #define __BUG_ENTRY_ADDR	RISCV_INT " 1b - ."
-#define __BUG_ENTRY_FILE	RISCV_INT " %0 - ."
+#define __BUG_ENTRY_FILE(file)	RISCV_INT " " file " - ."
 #else
 #define __BUG_ENTRY_ADDR	RISCV_PTR " 1b"
-#define __BUG_ENTRY_FILE	RISCV_PTR " %0"
+#define __BUG_ENTRY_FILE(file)	RISCV_PTR " " file
 #endif
 
 #ifdef CONFIG_DEBUG_BUGVERBOSE
-#define __BUG_ENTRY			\
+#define __BUG_ENTRY(file, line, flags)	\
 	__BUG_ENTRY_ADDR "\n\t"		\
-	__BUG_ENTRY_FILE "\n\t"		\
-	RISCV_SHORT " %1\n\t"		\
-	RISCV_SHORT " %2"
+	__BUG_ENTRY_FILE(file) "\n\t"	\
+	RISCV_SHORT " " line "\n\t"	\
+	RISCV_SHORT " " flags
 #else
-#define __BUG_ENTRY			\
-	__BUG_ENTRY_ADDR "\n\t"		\
-	RISCV_SHORT " %2"
+#define __BUG_ENTRY(file, line, flags)		\
+	__BUG_ENTRY_ADDR "\n\t"			\
+	RISCV_SHORT " " flags
 #endif
 
 #ifdef CONFIG_GENERIC_BUG
-#define __BUG_FLAGS(flags)					\
-do {								\
-	__asm__ __volatile__ (					\
+
+#define ARCH_WARN_ASM(file, line, flags, size)			\
 		"1:\n\t"					\
 			"ebreak\n"				\
 			".pushsection __bug_table,\"aw\"\n\t"	\
 		"2:\n\t"					\
-			__BUG_ENTRY "\n\t"			\
-			".org 2b + %3\n\t"                      \
-			".popsection"				\
+		__BUG_ENTRY(file, line, flags) "\n\t"		\
+			".org 2b + " size "\n\t"                \
+			".popsection\n"				\
+
+#define __BUG_FLAGS(flags)					\
+do {								\
+	__asm__ __volatile__ (					\
+		ARCH_WARN_ASM("%0", "%1", "%2", "%3")		\
 		:						\
 		: "i" (__FILE__), "i" (__LINE__),		\
 		  "i" (flags),					\
 		  "i" (sizeof(struct bug_entry)));              \
 } while (0)
+
 #else /* CONFIG_GENERIC_BUG */
 #define __BUG_FLAGS(flags) do {					\
 	__asm__ __volatile__ ("ebreak\n");			\
-- 
2.43.0


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[PATCH v2 3/5] arm64/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with Rust

[FUJITA Tomonori]

Add new ARCH_WARN_ASM macro for BUG/WARN assembly code sharing with
Rust to avoid the duplication.

No functional changes.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 arch/arm64/include/asm/asm-bug.h | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/asm-bug.h b/arch/arm64/include/asm/asm-bug.h
index 6e73809f6492..822e9d51d3e9 100644
--- a/arch/arm64/include/asm/asm-bug.h
+++ b/arch/arm64/include/asm/asm-bug.h
@@ -21,16 +21,21 @@
 #endif
 
 #ifdef CONFIG_GENERIC_BUG
-
-#define __BUG_ENTRY(flags) 				\
+#define __BUG_ENTRY_START				\
 		.pushsection __bug_table,"aw";		\
 		.align 2;				\
 	14470:	.long 14471f - .;			\
-_BUGVERBOSE_LOCATION(__FILE__, __LINE__)		\
-		.short flags; 				\
+
+#define __BUG_ENTRY_END					\
 		.align 2;				\
 		.popsection;				\
 	14471:
+
+#define __BUG_ENTRY(flags)				\
+		__BUG_ENTRY_START			\
+_BUGVERBOSE_LOCATION(__FILE__, __LINE__)		\
+		.short flags;				\
+		__BUG_ENTRY_END
 #else
 #define __BUG_ENTRY(flags)
 #endif
@@ -41,4 +46,22 @@ _BUGVERBOSE_LOCATION(__FILE__, __LINE__)		\
 
 #define ASM_BUG()	ASM_BUG_FLAGS(0)
 
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+#define __BUG_LOCATION_STRING(file, line)		\
+		".long " file "- .;"			\
+		".short " line ";"
+#else
+#define __BUG_LOCATION_STRING(file, line)
+#endif
+
+#define __BUG_ENTRY_STRING(file, line, flags)		\
+		__stringify(__BUG_ENTRY_START)		\
+		__BUG_LOCATION_STRING(file, line)	\
+		".short " flags ";"			\
+		__stringify(__BUG_ENTRY_END)
+
+#define ARCH_WARN_ASM(file, line, flags, size)		\
+	__BUG_ENTRY_STRING(file, line, flags)		\
+	__stringify(brk BUG_BRK_IMM)
+
 #endif /* __ASM_ASM_BUG_H */
-- 
2.43.0


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[PATCH v2 4/5] loongarch/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with Rust

[FUJITA Tomonori]

Add new ARCH_WARN_ASM macro for BUG/WARN assembly code sharing with
Rust to avoid the duplication.

No functional changes.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 arch/loongarch/include/asm/bug.h | 31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/arch/loongarch/include/asm/bug.h b/arch/loongarch/include/asm/bug.h
index 08388876ade4..5cac2d3efd75 100644
--- a/arch/loongarch/include/asm/bug.h
+++ b/arch/loongarch/include/asm/bug.h
@@ -21,14 +21,21 @@
 #ifndef CONFIG_GENERIC_BUG
 #define __BUG_ENTRY(flags)
 #else
-#define __BUG_ENTRY(flags) 					\
+
+#define __BUG_ENTRY_START					\
 		.pushsection __bug_table, "aw";			\
 		.align 2;					\
 	10000:	.long 10001f - .;				\
-		_BUGVERBOSE_LOCATION(__FILE__, __LINE__)	\
-		.short flags; 					\
+
+#define __BUG_ENTRY_END						\
 		.popsection;					\
 	10001:
+
+#define __BUG_ENTRY(flags)					\
+		__BUG_ENTRY_START			\
+		_BUGVERBOSE_LOCATION(__FILE__, __LINE__)	\
+		.short flags;					\
+		__BUG_ENTRY_END
 #endif
 
 #define ASM_BUG_FLAGS(flags)					\
@@ -55,6 +62,24 @@ do {								\
 	unreachable();						\
 } while (0)
 
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+#define __BUG_LOCATION_STRING(file, line)			\
+		".long " file "- .;"				\
+		".short " line ";"
+#else
+#define __BUG_LOCATION_STRING(file, line)
+#endif
+
+#define __BUG_ENTRY_STRING(file, line, flags)			\
+		__stringify(__BUG_ENTRY_START)			\
+		__BUG_LOCATION_STRING(file, line)		\
+		".short " flags ";"				\
+		__stringify(__BUG_ENTRY_END)
+
+#define ARCH_WARN_ASM(file, line, flags, size)			\
+	__BUG_ENTRY_STRING(file, line, flags)			\
+	__stringify(break BRK_BUG) ";"
+
 #define HAVE_ARCH_BUG
 
 #include <asm-generic/bug.h>
-- 
2.43.0


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

[FUJITA Tomonori]

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 <fujita.tomonori@gmail.com>
---
 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

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;
-- 
2.43.0


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