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Thu, 10 Sep 2026 00:13:14 -0700 (PDT) Received: from li-1a3e774c-28e4-11b2-a85c-acc9f2883e29.bl1-in.ibm.com ([129.41.58.4]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2db14ae8af3sm82366995ad.80.2026.09.10.00.13.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Sep 2026 00:13:14 -0700 (PDT) From: "Mukesh Kumar Chaurasiya (IBM)" To: maddy@linux.ibm.com, mpe@ellerman.id.au, npiggin@gmail.com, chleroy@kernel.org, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, ojeda@kernel.org, boqun@kernel.org, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, aliceryhl@google.com, tmgross@umich.edu, dakr@kernel.org, daniel.almeida@collabora.com, tamird@kernel.org, acourbot@nvidia.com, work@onurozkan.dev, mkchauras@gmail.com, linkmauve@linkmauve.fr, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, rust-for-linux@vger.kernel.org Cc: FUJITA Tomonori Subject: [PATCH V2] powerpc/bug: Add ARCH_WARN_ASM and refactor _EMIT_BUG_ENTRY for Rust support Date: Thu, 10 Sep 2026 12:42:53 +0530 Message-ID: <20260910071252.1950488-2-mkchauras@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 Closes: https://lore.kernel.org/all/anG67Q6Y59kDqh-c@desktop Fixes: 73b741adb264 ("rust: Add PowerPC support") Signed-off-by: Mukesh Kumar Chaurasiya (IBM) --- 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