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Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1x8uHw-00000007NfL-0I3B; Tue, 22 Sep 2026 06:47:36 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 9CCD9300708; Tue, 22 Sep 2026 08:47:35 +0200 (CEST) Date: Tue, 22 Sep 2026 08:47:35 +0200 From: Peter Zijlstra To: "Mukesh Kumar Chaurasiya (IBM)" Cc: catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, maddy@linux.ibm.com, mpe@ellerman.id.au, npiggin@gmail.com, chleroy@kernel.org, ritesh.list@gmail.com, sshegde@linux.ibm.com, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, 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, nathan@kernel.org, ndesaulniers@google.com, morbo@google.com, justinstitt@google.com, jszhang@kernel.org, japo@linux.ibm.com, jpoimboe@kernel.org, seanjc@google.com, pmladek@suse.com, thuth@redhat.com, ynorov@nvidia.com, joelagnelf@nvidia.com, david@davidgow.net, fujita.tomonori@gmail.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, rust-for-linux@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [RFC] rust: kernel: Add KUnit tests for ARCH_WARN_ASM bug table emission Message-ID: <20260922064735.GS4121339@noisy.programming.kicks-ass.net> References: <20260922054959.955093-2-mkchauras@gmail.com> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260922054959.955093-2-mkchauras@gmail.com> On Tue, Sep 22, 2026 at 11:20:00AM +0530, Mukesh Kumar Chaurasiya (IBM) wrote: > Verify that the __bug_table entry emitted by ARCH_WARN_ASM has a correct > bug_addr displacement — i.e. the arch's trap label reference resolves to > the trap instruction — by calling find_bug() with the exact virtual address > of the trap, mirroring what the real trap handler does. > > To support all architectures, each arch that implements ARCH_WARN_ASM now > defines ARCH_WARN_ASM_TRAP_LABEL, a string constant naming the local label > at which the trap instruction is placed: > > x86 "1" (ud2 at label 1:) > powerpc "1" (twi at label 1:) > riscv "1" (ebreak at label 1:) > arm64 "14471" (brk placed at 14471: by __BUG_ENTRY_END) > s390 "0" (mc at label 0:) > > The label is used consistently: in ARCH_WARN_ASM itself, in the > bug_addr back-reference inside __BUG_ENTRY / _EMIT_BUG_ENTRY, > diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h > index 23ab05438269..6cca8880660e 100644 > --- a/arch/x86/include/asm/bug.h > +++ b/arch/x86/include/asm/bug.h > @@ -62,8 +62,9 @@ extern void __WARN_trap(struct bug_entry *bug, ...); > #define HAVE_ARCH_BUG_FORMAT_ARGS > #endif > > +#define ARCH_WARN_ASM_TRAP_LABEL "1" > #define __BUG_ENTRY(format, file, line, flags) \ > - "\t.long 1b - ." "\t# bug_entry::bug_addr\n" \ > + "\t.long " ARCH_WARN_ASM_TRAP_LABEL "b - ." "\t# bug_entry::bug_addr\n" \ > __BUG_ENTRY_FORMAT(format) \ > __BUG_ENTRY_VERBOSE(file, line) \ > "\t.word " flags "\t# bug_entry::flags\n" > @@ -101,7 +102,7 @@ do { \ > "99:\n" \ > "\t.string \"\"\n" \ > ".popsection\n" \ > - "1:\t " ASM_UD2 "\n" \ > + ARCH_WARN_ASM_TRAP_LABEL ":\t " ASM_UD2 "\n" \ > _BUG_FLAGS_ASM("99b", file, line, flags, size, "") > > #else Not really a fan of that. And I can't really tell what you're doing with it either. The kunit is in Rust and thus unreadable :-( I would rather you fix up is_valid_bugaddr(), some architectures seem to have an always true stub because of the callchains always being from the break instruction.