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Wed, 19 Aug 2026 11:50:52 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 744891F000E9; Wed, 19 Aug 2026 11:50:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787140252; bh=PzZQi/+zyv5tISCSrhzpaU2w5pSh1zq3AvPapYtU2N4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=LNVICCgHe+pAUQZvzTWDm972iLfklbfwbVcaoSdCB8MxiUZjCBG/6a4PRM1NczvzE vuq1+vZTyHmI/D/1ZxhbKkj6NYhS0QcLq/rxGhscQpHzRTnmcP8s2fSfZwyZG7rVuN IVuiabGroKi3jjXib5l7Zqej8ydmEfMBPYs69FrJiFNA80q/ia+BsZoCvmTa0vaYyi 24fTaD7hPfhY0KohdeIT2kkaYH+wxtWU3q/jn5opEGDVOAn6CpBqaHY19x8r65gFjx Wy9xtLM9ASCA5Y9U9x7dnUng6dWG08KvDHiZwiGTMl22dK720ddr6lSCBPsHyxBig1 CeqbwaNmUZxtw== Message-ID: <4c5b2ab5-83f8-4ee7-bb02-3046ed01fd84@kernel.org> Date: Wed, 19 Aug 2026 13:50:43 +0200 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] powerpc/bug: Add ARCH_WARN_ASM and refactor _EMIT_BUG_ENTRY for Rust support To: "Mukesh Kumar Chaurasiya (IBM)" , maddy@linux.ibm.com, mpe@ellerman.id.au, npiggin@gmail.com, 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, thuth@redhat.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, rust-for-linux@vger.kernel.org Cc: FUJITA Tomonori References: <20260819084825.969116-1-mkchauras@gmail.com> Content-Language: fr-FR From: "Christophe Leroy (CS GROUP)" In-Reply-To: <20260819084825.969116-1-mkchauras@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Le 19/08/2026 à 10:48, Mukesh Kumar Chaurasiya (IBM) a écrit : > 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. > > 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. > > Suggested-by: FUJITA Tomonori > Signed-off-by: Mukesh Kumar Chaurasiya (IBM) > --- > 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__ */ Sorry, I still don't understand. The only place the new macro is used is a .S file (namely rust/kernel/generated_arch_warn_asm.rs.S), and the change this patch implements is inside a #if !__ASSEMBLER__. What am I missing ? Christophe > -/* _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