From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AA8644A1DEE; Thu, 10 Sep 2026 15:09:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789052946; cv=none; b=MSUdWglxrFcDStB3xn2KobjkGh4k1pLCEddseY3vpefzQqC1lGTvWBR/OSm6XHUsepzeQnjVSyip3e8xeN36NCsAh/t00pShUA+CxCrvvwlpkAMPscTs6PkMNkmE+JRjGCkV3Xpii8hK/qGMQ2M4YKTkJ2amF8mJ4dmOrmenb/s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789052946; c=relaxed/simple; bh=E+bCaqLa5JsCu/ya4ZosVIdin/DGLmTcw6GYXeHy71I=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=r+e+nluF600wU43dbWEn4/qWYIkkI9evyhyoeDV28yrjOfhFG4GQf6Fww5qldPXfqTqfxC3UHj3ZgOUjRDmeMp3/bT9XZL8lXjR1cGZ/SDjDyth4UZVghAuqc7LRlmdPSMJ3Lvv/BV15EQ/Sr2KL/gvu0uDlhZ8sRdQHvcRhQNc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Fw0TDgul; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Fw0TDgul" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9A17E1F000FF; Thu, 10 Sep 2026 15:08:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789052936; bh=mQXXn4qhJ4aChLx2QAED5a/xeQKG/2zmtNcuT7UoMHE=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Fw0TDgulMnT8zjUzucAUywAXhKdwFptF1XubEt8K4TOL0zMtDRw6xCMEnhSlhL6WV dt4zgR+488zDolV+m0gKYVeqJ2WNZ/aTuJvlmQOilF+7/2UffuW4IzPCo2ylc69wb8 V2FfTr+KbdcTZMqJi0jxVOVr6OHMFLWpzHRT0x8Pr0s1HE6rH85HvN1GTe9VPUW63k KdYwTdNWsrmT4iidxQk6++iVr+EWhDoi8IhC2kSD3vrN5fXKgS2RlL6AG9Glryw47s H4Eo6Aspwu4IYhQ7hF5gPFM88yD9bEnE3Tvcbg6bb1vKMtVf5B/E84Rkoq+BakHPr8 FrozPsKSM4smw== Message-ID: Date: Thu, 10 Sep 2026 17:08:48 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V3] 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, 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 References: <20260910100801.2159785-2-mkchauras@gmail.com> Content-Language: fr-FR From: "Christophe Leroy (CS GROUP)" In-Reply-To: <20260910100801.2159785-2-mkchauras@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Le 10/09/2026 à 12:08, 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 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 > ``` > > To add ARCH_WARN_ASM, _EMIT_BUG_ENTRY first needs to be refactored. > The old definition was a bare macro with no parameters, relying on > positional asm operand references (%0-%3), hardcoding the backward > reference to local label 1b, and including .org/.previous directives > inline. That made it impossible to compose as a plain string outside of > an asm operand context, and left an invisible contract that callers must > always emit their trap at label 1:. > > Refactor _EMIT_BUG_ENTRY to take explicit (label, file, line, flags) > string arguments via string concatenation. This removes the dependency > on asm operand numbering and makes the trap label an explicit argument, > so the caller's intent is visible at the call site and a future caller > using a different label cannot silently produce a wrong bug table entry. > > Move the .org and .previous directives out of _EMIT_BUG_ENTRY and into > each call site, so BUG_ENTRY() can still pass sizeof(struct bug_entry) > as an asm operand while ARCH_WARN_ASM can supply its own size string > 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: > V2 -> V3: > - Add label argument in _EMIT_BUG_ENTRY > V2: https://lore.kernel.org/all/20260910071252.1950488-2-mkchauras@gmail.com > > V1 -> V2: > - commit message now has error, fixes tag and closes tag > V1: https://lore.kernel.org/all/20260819084825.969116-1-mkchauras@gmail.com > > arch/powerpc/include/asm/bug.h | 36 +++++++++++++++++++--------------- > 1 file changed, 20 insertions(+), 16 deletions(-) > > diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h > index 0db48977c70c..df2183c35945 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 \ > - ".section __bug_table,\"aw\"\n" \ > - "2: .4byte 1b - .\n" \ > - " .4byte %0 - .\n" \ > - " .short %1, %2\n" \ > - ".org 2b+%3\n" \ > - ".previous\n" > +#define _EMIT_BUG_ENTRY(label, file, line, flags) \ > + ".section __bug_table,\"aw\"\n" \ > + "2: .4byte " label "b - .\n" \ Ah, you left the b here. The label is 1b which mean "the first 1: you find going backward". Could as well be "1f" instead meaning "the first 1: you find going forward". So I think you should use 1b or 1f as the label, not just 1. I would also try to use #label to stringigy the label in order to avoid having to put the arguments into quotes (untested), same for other ones. Cdlt Christophe > + " .4byte " file " - .\n" \ > + " .short " line ", " flags "\n" > #else > -#define _EMIT_BUG_ENTRY \ > - ".section __bug_table,\"aw\"\n" \ > - "2: .4byte 1b - .\n" \ > - " .short %2\n" \ > - ".org 2b+%3\n" \ > - ".previous\n" > +#define _EMIT_BUG_ENTRY(label, file, line, flags) \ > + ".section __bug_table,\"aw\"\n" \ > + "2: .4byte " label "b - .\n" \ > + " .short " flags "\n" > #endif > > #define BUG_ENTRY(cond_str, insn, flags, ...) \ > __asm__ __volatile__( \ > "1: " insn "\n" \ > - _EMIT_BUG_ENTRY \ > + _EMIT_BUG_ENTRY("1", "%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("1", 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