[PATCH V2] powerpc/bug: Add ARCH_WARN_ASM and refactor _EMIT_BUG_ENTRY for Rust support
From: Mukesh Kumar Chaurasiya (IBM) <hidden>
Date: 2026-09-10 07:13:33
The Rust kernel infrastructure generates inline asm for WARN() via ARCH_WARN_ASM(file, line, flags, size), expanding it through a C preprocessor pass (generated_arch_warn_asm.rs.S) to produce an arch-specific asm template string for use in Rust's core::arch macros. powerpc currently lacks ARCH_WARN_ASM and ARCH_WARN_REACHABLE, causing Rust builds to fail on powerpc with
error: no rules expected `ARCH_WARN_ASM`
--> /home/linkmauve/dev/linux/wii/rust/kernel/generated_arch_warn_asm.rs:1:28
|
1 | ::kernel::concat_literals!(ARCH_WARN_ASM("{file}", "{line}", "{flags}", "{size}"))
| ^^^^^^^^^^^^^ no rules expected this token in macro call
|
::: ../rust/kernel/lib.rs:279:1
|
279 | macro_rules! concat_literals {
| ---------------------------- when calling this macro
|
= note: while trying to match sequence start
error: no rules expected `ARCH_WARN_REACHABLE`
--> /home/linkmauve/dev/linux/wii/rust/kernel/generated_arch_reachable_asm.rs:1:28
|
1 | ::kernel::concat_literals!(ARCH_WARN_REACHABLE)
| ^^^^^^^^^^^^^^^^^^^ no rules expected this token in macro call
|
::: ../rust/kernel/lib.rs:279:1
|
279 | macro_rules! concat_literals {
| ---------------------------- when calling this macro
|
= note: while trying to match sequence start
error: aborting due to 2 previous errors
Refactor _EMIT_BUG_ENTRY to accept explicit (file, line, flags) string
arguments rather than relying on positional asm operand references
(%0, %1, %2, %3). This allows the macro to be composed as a plain
string concatenation, which is required for ARCH_WARN_ASM where no asm
operand context exists.
Move the .org and .previous directives out of _EMIT_BUG_ENTRY and into
the BUG_ENTRY() call site to preserve existing behaviour while enabling
ARCH_WARN_ASM to supply its own size operand independently.
Add ARCH_WARN_REACHABLE as an empty define, matching the arm64
convention, indicating that no additional reachability annotation is
needed after a WARN on powerpc.
This brings powerpc into line with x86, arm64, s390, and riscv, all of
which already define ARCH_WARN_ASM and ARCH_WARN_REACHABLE.
Reported-by: FUJITA Tomonori <redacted>
Closes: https://lore.kernel.org/all/anG67Q6Y59kDqh-c@desktop
Fixes: 73b741adb264 ("rust: Add PowerPC support")
Signed-off-by: Mukesh Kumar Chaurasiya (IBM) <redacted>
---
Changelog:
V1 -> V2:
- commit message now has error, fixes tag and closes tag
arch/powerpc/include/asm/bug.h | 28 ++++++++++++++++------------
1 file changed, 16 insertions(+), 12 deletions(-)
diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
index 0db48977c70c..8aba39e0cf26 100644
--- a/arch/powerpc/include/asm/bug.h
+++ b/arch/powerpc/include/asm/bug.h@@ -32,34 +32,38 @@ #endif /* verbose */ #else /* !__ASSEMBLER__ */ -/* _EMIT_BUG_ENTRY expects args %0,%1,%2,%3 to be FILE, LINE, flags and - sizeof(struct bug_entry), respectively */ #ifdef CONFIG_DEBUG_BUGVERBOSE -#define _EMIT_BUG_ENTRY \ +#define _EMIT_BUG_ENTRY(file, line, flags) \ ".section __bug_table,\"aw\"\n" \ "2: .4byte 1b - .\n" \ - " .4byte %0 - .\n" \ - " .short %1, %2\n" \ - ".org 2b+%3\n" \ - ".previous\n" + " .4byte " file " - .\n" \ + " .short " line ", " flags "\n" #else -#define _EMIT_BUG_ENTRY \ +#define _EMIT_BUG_ENTRY(file, line, flags) \ ".section __bug_table,\"aw\"\n" \ "2: .4byte 1b - .\n" \ - " .short %2\n" \ - ".org 2b+%3\n" \ - ".previous\n" + " .short " flags "\n" #endif #define BUG_ENTRY(cond_str, insn, flags, ...) \ __asm__ __volatile__( \ "1: " insn "\n" \ - _EMIT_BUG_ENTRY \ + _EMIT_BUG_ENTRY("%0", "%1", "%2") \ + ".org 2b+%3\n" \ + ".previous\n" \ : : "i" (WARN_CONDITION_STR(cond_str) __FILE__), "i" (__LINE__), \ "i" (flags), \ "i" (sizeof(struct bug_entry)), \ ##__VA_ARGS__) +#define ARCH_WARN_ASM(file, line, flags, size) \ + "1: twi 31, 0, 0\n" \ + _EMIT_BUG_ENTRY(file, line, flags) \ + ".org 2b+" size "\n" \ + ".previous\n" + +#define ARCH_WARN_REACHABLE + /* * BUG_ON() and WARN_ON() do their best to cooperate with compile-time * optimisations. However depending on the complexity of the condition
--
2.55.0