From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8747E48C415; Tue, 5 May 2026 16:17:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=63.228.1.57 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777997849; cv=none; b=KixyFhWcTZoUAYylLZo/pRTiuOjsuJwBkCEx5rvfOkWX2Sh/OcpiaIRQgWzxfBreqLuimU0tHQlUrGejqxPt9X8TYo4NzpDZrhATjA3n/U52eu1ZcxP768Ww3AcgEtuqxV1v+yCe6l0dmlybMIEEFt70CH1Q7g3nFr031wVDke0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777997849; c=relaxed/simple; bh=ImitdmfyrLnPZx2shpCjqp5BsRTgtqtIPUUqMSOCi2k=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=sLP/spc/ENXFVfRKCrdwhu2KLVLRw0RgJGm3qnnKTCNwyeSUp5KU63puAGfCF/cEmF7aRyXJUh8v5jQE30gDPAnNtnf9MSYxT3zgvYCqeczxLAYweC3VXxbVhQYbBuULgcaEnKX6NLMj59X7gBwz/Ob7UrJS4SgYCuc/6Y3mA0w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org; spf=pass smtp.mailfrom=kernel.crashing.org; arc=none smtp.client-ip=63.228.1.57 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kernel.crashing.org Received: from gate.crashing.org (localhost [127.0.0.1]) by gate.crashing.org (8.18.1/8.18.1/Debian-2) with ESMTP id 645Fv4oO164706; Tue, 5 May 2026 10:57:04 -0500 Received: (from segher@localhost) by gate.crashing.org (8.18.1/8.18.1/Submit) id 645Fuwtk164700; Tue, 5 May 2026 10:56:58 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Tue, 5 May 2026 10:56:58 -0500 From: Segher Boessenkool To: Peter Zijlstra Cc: Sathvika Vasireddy , nathan@kernel.org, nsc@kernel.org, maddy@linux.ibm.com, mpe@ellerman.id.au, npiggin@gmail.com, chleroy@kernel.org, jpoimboe@kernel.org, ojeda@kernel.org, masahiroy@kernel.org, lossin@kernel.org, tamird@kernel.org, thomas.weissschuh@linutronix.de, rostedt@goodmis.org, ihor.solodrai@linux.dev, thuth@redhat.com, pmladek@suse.com, aliceryhl@google.com, elver@google.com, kees@kernel.org, legion@kernel.org, ardb@kernel.org, yuxuan.zuo@outlook.com, alexghiti@rivosinc.com, alexandre.chartre@oracle.com, bp@alien8.de, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v1 1/6] objtool/powerpc: Add build-time fixup of alternate feature branch targets Message-ID: References: <20260505084628.17940-1-sv@linux.ibm.com> <20260505084628.17940-2-sv@linux.ibm.com> <20260505144539.GX3126523@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260505144539.GX3126523@noisy.programming.kicks-ass.net> Hi! On Tue, May 05, 2026 at 04:45:39PM +0200, Peter Zijlstra wrote: > On Tue, May 05, 2026 at 02:16:23PM +0530, Sathvika Vasireddy wrote: > > switch (opcode) { > > + case 16: > > Like case 18 below, this wants a comment describing which instruction > this is; bclr ? Yes. It is 19/16, b[c]lr (primary opcode 19, secondary opcode 16). Where is it described what INSN_RETURN actually means for objtool? Not in the header file :-( For PowerPC, all three of b[c]lr[l], b[c]ctr[l], and b[c]tar[l] are indirect jumps, to an address in a register. They do absolutely nothing typically done in a function epilog, like "return" insns in some other archs do. But the BH field ("branch hint") in the instruction helps predict the control flow involving the insn as something in a call and return pattern :-) Segher