From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793675449; b=CCb0XhMXlfSXVQ7ZV+h2L4iHD7deeZc50mkThE/mH3zi4hHgw/V5nXMJHGszfW0COcNh HMm0I+XeT2P49fLkivwQYdjp2ZCH1fOt/L3XD5ZRv4BUHN6FrdaeBb0mJitDnOqcNWFhd W8VSW57w0Mo4hEoIule32+cQIZ43CnVtdq8hIBUv/6/7Nq/qpwpee99f+5XkACx0DmSbM NxW6+ydLM+lKyQv80Ux/fS3V5PBpOeeezrJiyWnG4k7Glzn6qc7AnzkgtEWb+Lg+xBbzW t92rHCCJKHfrgJFsdDNZ6tR3gPyM4MMW/N54HhNjmlDmdO2rDI1FbcG9+nB/ZQuR2Tw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793675449; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=B0Hc41BPLGJ8fuQziO5PWovZ32of8vYvTPjbIKQKEVw=; b=QCNM1DxXI6YL+7FbxWC/CAWWm2u+xG0QsQDNrHjh1HtNXlCs+aMKycDk8kMzp/xrLzQY 8FbE5lckBK1YvriStYvRASIV1zBtaEwYay09Mky5q8xThBMtPfTPnEsPoO8FjPlRnhBHO D6hax8ljUtm/1DZoV7+l+viWPvqW310rdwZXrUy18AqLSduQFX/oFiQZdjzx8K4YB8/Ux X1u17z1yljtVAQJLLFOqhAcQeKOK4GwK7rllb1sXTl3vmSaJ5UWhlnmMMNDchT1UsPxLA RaELvCNjNaVXlZk04Rley8bgkm+xP4hFxta2QwWVdooVctfLAO5zkQfpFt4afNlmxqA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=IsJr+KLW; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E3043606A324 for ; Tue, 3 Nov 2026 03:10:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=IsJr+KLW Received: by smtp.kernel.org (Postfix) with ESMTPSA id 62C721F000C1; Tue, 3 Nov 2026 03:10:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793675448; bh=B0Hc41BPLGJ8fuQziO5PWovZ32of8vYvTPjbIKQKEVw=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=IsJr+KLWEO3FXMvlUINvPgDj20mu2Vepp08PBpd9gyONRnLHRfmXVJvUcP6r1LZAi uvKzEI+ZYmROFYEFtQvFCxkAj3R5i6+OjYmcVZQD+n87v6egHlV01OnSX6eaUU+7F4 vEB1Y8YNBXzkjZKvRudkoM0WgsiLt0XaKVPlX4saMQX5Puwlka6IxLOvGkK9kc16oR 3lpF4M4VOaK/hBox+a3RUX+foGN8KcdL1lPsUMH+Q8Rsoy4z4ogQMffRR5KlOWdM5L No1mKr0iReNOUExcns68BJPE3OSThmSfgyoMv+SLiwWt7rMZQ6EEtlDu20z5HJc17N 4Ir5Q8puAvB2A== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v4 4/7] alpha/perf: do not report user registers from the entry code Reply-To: sashiko-reviews@lists.linux.dev To: "Matt Turner" Cc: linux-perf-users@vger.kernel.org In-Reply-To: <20261102-alpha-profileme-v4-4-61e00f5e1da8@gmail.com> References: <20261102-alpha-profileme-v4-0-61e00f5e1da8@gmail.com> <20261102-alpha-profileme-v4-4-61e00f5e1da8@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 03 Nov 2026 03:10:47 +0000 X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list > perf_get_regs_user() returns task_pt_regs() whenever a sample of a user > task lands in the kernel. But exception entry runs with interrupts > enabled, so the sample can land before the entry code has saved the user > registers. Only the part PALcode pushed is valid then. An interrupt > taken on the first instruction of entUna, say, pushes its own frame on > top of PALcode's, which overlaps the rest of the user frame, so r7 and r8 > read as the interrupt's r23 and r24. >=20 > Report no user registers while the interrupted PC is in the entry code. > Such a sample also gets no user stack dump. The range is all of the entry > code from entInt to the end of the save in entSys, so it also drops the > registers of samples that land after they were saved there. >=20 > An interrupt that nests on one taken in the entry code still reads the > incomplete frame, as its own PC has left the entry code. >=20 > Fixes: 9280e99d87dd ("alpha: add HAVE_PERF_REGS and HAVE_PERF_USER_STACK_= DUMP support") > Assisted-by: Claude:claude-opus-5-5 > Signed-off-by: Matt Turner Sashiko has reviewed this patch and found no issues. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261102-alpha-prof= ileme-v4-0-61e00f5e1da8@gmail.com?part=3D4