From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=pass header.oldest-pass=0 smtp.remote-ip=52.101.52.31 ARC-Seal: i=2; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=pass; t=1793650093; b=PKlP1GVd0wt0j4Hu/FL/O3HdEiXt9JMMf0hOrqEoL9H7icX7LxY704Y3t/Szy94hv3su 9/I2jWkX663aDgJaLE/wSaoMozfnlqziFFBXXeo0wundcI6JuuU6ZJGku8E5yOyBU3PmL qzPteW/vxOK1cOtLbEV9IrNsEixoPAjllDynLt6Nyl+Pf3dxjrohdt8kF4WYHDVos1thK Zk2x1WS9veCivzj9NwmcNLhVSvV4BYDfJMSM9GtyaKDpOiAkq7xw0H4VfGZtDxQBBEBk2 MnEzv1LeSMJxyeFGurz6JAvqPRQ7hFDqy3qvnZNIZ3VjitPC2fpAGQS9G5vAD5TXCCQ== ARC-Message-Signature: i=2; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793650093; h=DMARC-Filter:DKIM-Signature:Received:Received:Message-ID:Date: User-Agent:To:Cc:References:Subject:Content-Language:From:Autocrypt: In-Reply-To:Content-Type:Content-Transfer-Encoding:X-ClientProxiedBy: MIME-Version:X-MS-PublicTrafficType:X-MS-TrafficTypeDiagnostic: X-MS-Office365-Filtering-Correlation-Id:X-MS-Exchange-SenderADCheck: X-MS-Exchange-AntiSpam-Relay:X-Microsoft-Antispam: X-Microsoft-Antispam-Message-Info:X-Forefront-Antispam-Report: X-MS-Exchange-AntiSpam-MessageData-ChunkCount: X-MS-Exchange-AntiSpam-MessageData-0:X-OriginatorOrg: X-MS-Exchange-CrossTenant-Network-Message-Id: X-MS-Exchange-CrossTenant-AuthSource:X-MS-Exchange-CrossTenant-AuthAs: X-MS-Exchange-CrossTenant-OriginalArrivalTime: X-MS-Exchange-CrossTenant-FromEntityHeader: X-MS-Exchange-CrossTenant-Id:X-MS-Exchange-CrossTenant-MailboxType: X-MS-Exchange-CrossTenant-UserPrincipalName: X-MS-Exchange-Transport-CrossTenantHeadersStamped; bh=YnepNDLCyaaJ8MbOETiX81vhFZHRWE19wPdxm/bUwog=; b=0wlH1sm076yw20Pg6AZ/zhXDnca4krhKj5XCOAzJPC6sNQ8YZzwygwBgm18OyZ7aJL+L GC+DZsX5iIaa59ZqLBjSaghqHce3fbGDqjDxc6Yk31ZgTpkjMLvArE2YErz3/qKOKGJk/ 1dipPaPMz+5FgNoXRbluYlNA0lC9kO1FWct3uC6xJJe/JFP9mxrxhu1PtogdCo5bb0Y44 Ou/7tgSvBCB0tEifizOZZspJwd7S5uxkG02JCy7wC1g/zME3dUH7lGsCWDutdwRHWP9Tk un6N+gjYna10BjOKEdV1mNEjOl86VG3+8WtB1F7PaUEzvgXl5cHmD1Sd1QE9PcxJwkg== ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=pass header.from=citrix.com; spf=pass smtp.mailfrom=citrix.com; dkim=pass header.d=citrix.com header.i=@citrix.com header.a=rsa-sha256 header.s=selector1 header.b=WSv19YEI; arc=pass header.oldest-pass=0 smtp.remote-ip=52.101.52.31 Received: from BL2PR02CU003.outbound.protection.outlook.com (mail-eastusazon11011031.outbound.protection.outlook.com [52.101.52.31]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (secp384r1) server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 93ECA606A326 for ; Mon, 2 Nov 2026 20:08:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 93ECA606A326 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=citrix.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=citrix.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=citrix.com header.i=@citrix.com header.a=rsa-sha256 header.s=selector1 header.b=WSv19YEI ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=OLb6P+oJ4Xq1sduAAUg9EOAF+QrKlWtg3xge4tzht8t7N2QESvaU4Y7HdQ+qS1ESEeyFQvPxgg+VK0qOKYRvBtNWeJXobegUD9xFO36o+rOEJYjPJX6ByAbTCMvBZPbQ4sQxD9rz0EnfOjTL3i/K0I0bxwl7RHRpijogQTLS4TMsvcPLdqcw07VERBRmt2K6OeBm6eyixprGKEccLimDR5rE3PogdASZ9azQyGixTUqsHe7h3AOd8HwmLSss/XkWVw/fid2YPuJITmZ9ASg99ZwCFlE/ldpa8keFJcQ2I+746qZT6uVDO4UkN8EY+p+yPYyps5t4XPjc6epHwvbLBA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=YnepNDLCyaaJ8MbOETiX81vhFZHRWE19wPdxm/bUwog=; b=BU6hOQE/d7jvNhdQFNp2Kp/cQnABUQVVNK1/Zw+ITD/1ElnY7+MLUtbR58SOhrAuxz2vEGp1CWr53I4zwrfAuzVLvStJFAy33K3IOGF2MQ5a1/yxdfSVvWYwecInLhCPYLptkfB10XnoA+xtUGc0e3IxnSHxbGHBiTbtfQDy42dNMrAGFHj/xi80f7q1e3FRHorEr1kPB/2Pt+Vi908JR6NZUqvV4R7fEebsdS+Re3+H21MEjtxqDR+hVKmMqdPNpQavi7c4fdquvekI3utXqHJc4ig76x+wOIHGVhlbSYRXPhBcJZ+756LhSoXKQ7CL76H9Fipmh3CgkJ8UMCd07w== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=YnepNDLCyaaJ8MbOETiX81vhFZHRWE19wPdxm/bUwog=; b=WSv19YEIxGg6iOZ71P13yhH+RxFnXReJU5vxRM4/cvlk4tel+nfloURMg9i+n+z8FO2I7Xy+k0uRbeVNeEussBJtJKmMnU6spuWxzYSo0/jPYYFCmCXhEESBzaQOMphjXiiClWVHIKpuLfzTaeS31cpiFqY3+9MbK5O+gspVfyM= Authentication-Results: mx.microsoft.com 1; dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=citrix.com; Received: from CH8PR03MB8275.namprd03.prod.outlook.com (2603:10b6:610:2b9::7) by CH1PR03MB8168.namprd03.prod.outlook.com (2603:10b6:610:2b0::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.569.12; Mon, 2 Nov 2026 20:06:08 +0000 Received: from CH8PR03MB8275.namprd03.prod.outlook.com ([fe80::a70d:dc32:bba8:ce37]) by CH8PR03MB8275.namprd03.prod.outlook.com ([fe80::a70d:dc32:bba8:ce37%4]) with mapi id 15.21.0569.011; Mon, 2 Nov 2026 20:06:07 +0000 Message-ID: <86f2f603-c1a7-4715-ad43-ac9c90f6a837@citrix.com> Date: Mon, 2 Nov 2026 20:06:02 +0000 User-Agent: Mozilla Thunderbird To: torvalds@linux-foundation.org Cc: Andrew Cooper , bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, jpoimboe@kernel.org, justinstitt@google.com, kernel-team@meta.com, leitao@debian.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, luto@kernel.org, mingo@redhat.com, morbo@google.com, nathan@kernel.org, ndesaulniers@google.com, pawan.kumar.gupta@linux.intel.com, peterz@infradead.org, tglx@kernel.org, x86@kernel.org References: Subject: Re: [PATCH RFC] x86/syscall: Dispatch via sys_call_table when Spectre v2 and BHI are off Content-Language: en-GB From: Andrew Cooper Autocrypt: addr=andrew.cooper3@citrix.com; keydata= xsFNBFLhNn8BEADVhE+Hb8i0GV6mihnnr/uiQQdPF8kUoFzCOPXkf7jQ5sLYeJa0cQi6Penp VtiFYznTairnVsN5J+ujSTIb+OlMSJUWV4opS7WVNnxHbFTPYZVQ3erv7NKc2iVizCRZ2Kxn srM1oPXWRic8BIAdYOKOloF2300SL/bIpeD+x7h3w9B/qez7nOin5NzkxgFoaUeIal12pXSR Q354FKFoy6Vh96gc4VRqte3jw8mPuJQpfws+Pb+swvSf/i1q1+1I4jsRQQh2m6OTADHIqg2E ofTYAEh7R5HfPx0EXoEDMdRjOeKn8+vvkAwhviWXTHlG3R1QkbE5M/oywnZ83udJmi+lxjJ5 YhQ5IzomvJ16H0Bq+TLyVLO/VRksp1VR9HxCzItLNCS8PdpYYz5TC204ViycobYU65WMpzWe LFAGn8jSS25XIpqv0Y9k87dLbctKKA14Ifw2kq5OIVu2FuX+3i446JOa2vpCI9GcjCzi3oHV e00bzYiHMIl0FICrNJU0Kjho8pdo0m2uxkn6SYEpogAy9pnatUlO+erL4LqFUO7GXSdBRbw5 gNt25XTLdSFuZtMxkY3tq8MFss5QnjhehCVPEpE6y9ZjI4XB8ad1G4oBHVGK5LMsvg22PfMJ ISWFSHoF/B5+lHkCKWkFxZ0gZn33ju5n6/FOdEx4B8cMJt+cWwARAQABzSlBbmRyZXcgQ29v cGVyIDxhbmRyZXcuY29vcGVyM0BjaXRyaXguY29tPsLBegQTAQgAJAIbAwULCQgHAwUVCgkI CwUWAgMBAAIeAQIXgAUCWKD95wIZAQAKCRBlw/kGpdefoHbdD/9AIoR3k6fKl+RFiFpyAhvO 59ttDFI7nIAnlYngev2XUR3acFElJATHSDO0ju+hqWqAb8kVijXLops0gOfqt3VPZq9cuHlh IMDquatGLzAadfFx2eQYIYT+FYuMoPZy/aTUazmJIDVxP7L383grjIkn+7tAv+qeDfE+txL4 SAm1UHNvmdfgL2/lcmL3xRh7sub3nJilM93RWX1Pe5LBSDXO45uzCGEdst6uSlzYR/MEr+5Z JQQ32JV64zwvf/aKaagSQSQMYNX9JFgfZ3TKWC1KJQbX5ssoX/5hNLqxMcZV3TN7kU8I3kjK mPec9+1nECOjjJSO/h4P0sBZyIUGfguwzhEeGf4sMCuSEM4xjCnwiBwftR17sr0spYcOpqET ZGcAmyYcNjy6CYadNCnfR40vhhWuCfNCBzWnUW0lFoo12wb0YnzoOLjvfD6OL3JjIUJNOmJy RCsJ5IA/Iz33RhSVRmROu+TztwuThClw63g7+hoyewv7BemKyuU6FTVhjjW+XUWmS/FzknSi dAG+insr0746cTPpSkGl3KAXeWDGJzve7/SBBfyznWCMGaf8E2P1oOdIZRxHgWj0zNr1+ooF /PzgLPiCI4OMUttTlEKChgbUTQ+5o0P080JojqfXwbPAyumbaYcQNiH1/xYbJdOFSiBv9rpt TQTBLzDKXok86M7BTQRS4TZ/ARAAkgqudHsp+hd82UVkvgnlqZjzz2vyrYfz7bkPtXaGb9H4 Rfo7mQsEQavEBdWWjbga6eMnDqtu+FC+qeTGYebToxEyp2lKDSoAsvt8w82tIlP/EbmRbDVn 7bhjBlfRcFjVYw8uVDPptT0TV47vpoCVkTwcyb6OltJrvg/QzV9f07DJswuda1JH3/qvYu0p vjPnYvCq4NsqY2XSdAJ02HrdYPFtNyPEntu1n1KK+gJrstjtw7KsZ4ygXYrsm/oCBiVW/OgU g/XIlGErkrxe4vQvJyVwg6YH653YTX5hLLUEL1NS4TCo47RP+wi6y+TnuAL36UtK/uFyEuPy wwrDVcC4cIFhYSfsO0BumEI65yu7a8aHbGfq2lW251UcoU48Z27ZUUZd2Dr6O/n8poQHbaTd 6bJJSjzGGHZVbRP9UQ3lkmkmc0+XCHmj5WhwNNYjgbbmML7y0fsJT5RgvefAIFfHBg7fTY/i kBEimoUsTEQz+N4hbKwo1hULfVxDJStE4sbPhjbsPCrlXf6W9CxSyQ0qmZ2bXsLQYRj2xqd1 bpA+1o1j2N4/au1R/uSiUFjewJdT/LX1EklKDcQwpk06Af/N7VZtSfEJeRV04unbsKVXWZAk uAJyDDKN99ziC0Wz5kcPyVD1HNf8bgaqGDzrv3TfYjwqayRFcMf7xJaL9xXedMcAEQEAAcLB XwQYAQgACQUCUuE2fwIbDAAKCRBlw/kGpdefoG4XEACD1Qf/er8EA7g23HMxYWd3FXHThrVQ HgiGdk5Yh632vjOm9L4sd/GCEACVQKjsu98e8o3ysitFlznEns5EAAXEbITrgKWXDDUWGYxd pnjj2u+GkVdsOAGk0kxczX6s+VRBhpbBI2PWnOsRJgU2n10PZ3mZD4Xu9kU2IXYmuW+e5KCA vTArRUdCrAtIa1k01sPipPPw6dfxx2e5asy21YOytzxuWFfJTGnVxZZSCyLUO83sh6OZhJkk b9rxL9wPmpN/t2IPaEKoAc0FTQZS36wAMOXkBh24PQ9gaLJvfPKpNzGD8XWR5HHF0NLIJhgg 4ZlEXQ2fVp3XrtocHqhu4UZR4koCijgB8sB7Tb0GCpwK+C4UePdFLfhKyRdSXuvY3AHJd4CP 4JzW0Bzq/WXY3XMOzUTYApGQpnUpdOmuQSfpV9MQO+/jo7r6yPbxT7CwRS5dcQPzUiuHLK9i nvjREdh84qycnx0/6dDroYhp0DFv4udxuAvt1h4wGwTPRQZerSm4xaYegEFusyhbZrI0U9tJ B8WrhBLXDiYlyJT6zOV2yZFuW47VrLsjYnHwn27hmxTC/7tvG3euCklmkn9Sl9IAKFu29RSo d5bD8kMSCYsTqtTfT6W4A3qHGvIDta3ptLYpIAOD2sY3GYq2nf3Bbzx81wZK14JdDDHUX2Rs 6+ahAA== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: LO4P123CA0368.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:18e::13) To CH8PR03MB8275.namprd03.prod.outlook.com (2603:10b6:610:2b9::7) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH8PR03MB8275:EE_|CH1PR03MB8168:EE_ X-MS-Office365-Filtering-Correlation-Id: 68827ac9-488a-49f2-a3ce-08df391cbb51 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|1800799024|366016|23010399003|10067099003|18002099003|22082099003|261102123227099003|56012099006|11063799006|261026121527099003|261021121427099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CH8PR03MB8275.namprd03.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(7416014)(376014)(1800799024)(366016)(23010399003)(10067099003)(18002099003)(22082099003)(261102123227099003)(56012099006)(11063799006)(261026121527099003)(261021121427099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?S1c2a2g2c3pTM0VFRzVlM0FYVDZqM2NNRTVrVG53blVNUnY5OWQzRWlpb1h4?= =?utf-8?B?UUovVjA2Q2FTVWNScmVHWGZ2ZHY3SCtUeWRQRmd4VmVNYzhIQm05dW9SN25J?= =?utf-8?B?OE1ya3NPc1FtWkJXR1pualNLazJodGIyNFp6OWJEOVZYbENQcDBLRGFXWEZE?= =?utf-8?B?Wi9zUlYwYzU2bVJBejNSRDlkUEFHQTByQTdyRVV5Wkk0bjJ5d3JXRXdqUkVt?= =?utf-8?B?NFRYVmdkeXVacDJRWU82V2NJVm5xYWFjWStTWHNoZWQ5enpNSTZ4aFF2N1BE?= =?utf-8?B?MlRGbm8yWGh4M3Z1NlVRaWRyYXMzaHRxSEFwbkhyOVlmcmJoZXhYbjQ5Z3di?= =?utf-8?B?WTllOXVPRkF0VjFRMDhZVHpSSCtyaDhtaThsSC9qenZBei85UC9HVkNNVjFW?= =?utf-8?B?WnlEeXZXSVpaZVpTM3hpRHFhMkpOYkM1ZWx2STV4V1Fhc3JSQjUvcGdONVZr?= =?utf-8?B?emVFYVhsRWpjRzFhYTRyRXFQSmkyVkljK1VxcTFQSk1ZMTYvd2l3cGdqTFRp?= =?utf-8?B?QUVZendpbEJtcTB5Zm1OeVZZS2pWL1hPR2RwTCs1UzFoUTFGaVNjN3NZWWpq?= =?utf-8?B?cnFOUzNYbXdwbFlNSDRBVXRsUkVrU3M5SHB0eGR5Qm1Qa0FNeEFsQm1wUU13?= =?utf-8?B?QkRLbG05L0I2Y3JnWHJwQmZtNy9McTF0M0ExbnFxYlJ1aUFsd3d4cXA1a3Zu?= =?utf-8?B?WUhIK1RzdjdZVEhPeWMyanNJaTNla2c1QWhMajR2eGFZbHc3bVk2MUVmeTlw?= =?utf-8?B?a3Q0Y1VnMGZaNHF5U1AwRmdtc3YwaDNEY0FVajVSUHZPNEc5M0w4Z2ZkT2I1?= =?utf-8?B?OHk3R1VpbTZ5aGNTY0dRdjZZaE5YNlhWaU5qRXR4VkJ4SlBPZXVFdDVXZ0pk?= =?utf-8?B?a2Jrbkl3blRJOUpDOWxNaWVJL1d1cmMyVnlVTHhGRWJjZUpsUWVPODBDRzNL?= =?utf-8?B?TmZQRHZMQ2QveTZha01zMUdMTUkxVGFsZzAySWhsOEZuUU5jVXpOTGtBdURk?= =?utf-8?B?bXJVZkZVaTNXS2hEdE15NTFkY2R5alhkaE5GRDNUQURBRjlvWDN3eG45eFBm?= =?utf-8?B?TDVUL2lTRTBFdHFsMXAzZkdGWCtrUWlvc0ZoMzJ1Z3hreGxpS20veFhSaFFN?= =?utf-8?B?c3U1dlV6dmFNbHVNY0RzWHdNWXVsMllXN3hkYnFYV2l1cThHZk9PcmVlcHZS?= =?utf-8?B?ZDVTcW5NVlIvelMrTmFGdENDUlFRT0Vtb1NmaVVERGNFSUJLcjk1VlVSRita?= =?utf-8?B?aEJrVExJc1E2dDBna2JaUEV5RFF3cngrK1U1czFNVVpQY09nUm1CYndXYVU0?= =?utf-8?B?dXFnSVg4QzJ6S1JpbktvaXJ3ci9XVi8xUUdtZVB2YzVPT3Vqam1sN2d1MGR0?= =?utf-8?B?QkZXU3lKeDdUVkFia3FwMW9PT1kybHZPZGN6cTR5OU5vbU5OTU1LeUpLMWJ5?= =?utf-8?B?TDNiRjFsMHM2QUE4RDk2MG5OSmhMSUV1ajRqbjFkYkcvMkE2MzhURTFGdWZJ?= =?utf-8?B?QTErTE9JRFUrdEFycG1MWHpNcTlHaitsdngwbmhCbEV0ZzJCaUhaNTgyZWN0?= =?utf-8?B?enBVL0ZKUGlWUm1sblBZem9pTCtvWFpqeXBNOStuOFBudVNicEI4WTZDSTU2?= =?utf-8?B?Wnl1OGpTZmxJZ3hBTVVjREIwcFZJd3FnNzNPaFFkMW50d0s5a1NHKzVlTW9z?= =?utf-8?B?Vk93YmdkckhzYW1uVnFVcFdwa2p3R2NDMkNmUVBsZlBrKytFQzlJUUU1UU9k?= =?utf-8?B?OXppTENMcHN5b2Q2aWI4ZCsvVkViaUhuZzlvZ3VLc1FzaVdaMjJaWExzMWFT?= =?utf-8?B?Q0kwYVNBdmVUeWFYUkx5SWFsOVUvbDJ6L0dNSkQzWUM2WkhDaXR0RVFUcFdN?= =?utf-8?B?b2NSeVJZZ3EvdzhFUHZmNjJjek9ncFhjWDJ6NHdOcGlDK2c2WU9EWDNXTjZY?= =?utf-8?B?NXRzWHJ5VCs0SG4zY0xaQXZKaVUvaThnL2R0U2JJYU90ZTZ0TGhPcHJQaFlG?= =?utf-8?B?N3RkMkxHeHgxWFRqZjVUSDhGeHV2bmFjS2xzRm9zMFhFMjRKUktkemo2cnAv?= =?utf-8?B?cmV2M0U1SytDY3dnMW03Wjc3QnZnb2dTdENzQ2dCRTdFakI4QWpuVFZEeEUx?= =?utf-8?B?Z2h5cGg4NE9GK0RPWnZTZG9iRUlRbWRSbUdISDBqMGp3SGNIWGU2TVl1T1Rn?= =?utf-8?B?VDI0OGxLYng1V1BkbVEzWjcySm9wM2w0dU9DT3d4dTAyVWN4R1p5QmJHNys0?= =?utf-8?B?YVhjRmtJUEZ5WS83ZFlURG5XbHVyb0VLMkRtSVRQWFlZaE5yNHJZWit2cVZk?= =?utf-8?B?VFZZZFdLVHR2bHAzZ1pnczB6WW1GTWd5M1d4cFh3amZIVXNyZVczQT09?= X-OriginatorOrg: citrix.com X-MS-Exchange-CrossTenant-Network-Message-Id: 68827ac9-488a-49f2-a3ce-08df391cbb51 X-MS-Exchange-CrossTenant-AuthSource: CH8PR03MB8275.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Nov 2026 20:06:07.6142 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 335836de-42ef-43a2-b145-348c2ee9ca5b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: BOnaL/lh3z8qWv5vSb2vWgWKYlNtg9S+2CTTfvjCIAVcKhinuc+a6VbeogjFHm9fbPn3r3m7XaUZ4UqaII0Niq9XsugdI6BSVv2LkGuGfqE= X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH1PR03MB8168 > I do wonder if we could do computed jumps. It would be lovely if we > could basically do something like > > # syscall number in %rax > leaq table(%rax,%rax,4),%rax > jmp *%rax > table: > jmp syscall0 > jmp syscall1 > jmp syscall2 > .... > > and avoid any indirect memory lookup or indirect branches (outside of > the one computed one). And no extra call/ret frame. You would need ENDBR64's too, when building for CET-IBT. > It's possible that the branch prediction hardware hates those kinds of > very dense jmp patterns, though. I don't know. This doesn't buy you anything, except a larger code footprint and more branch predictor pressure. The moment you've got any indirect branch reasonable from the syscall entrypoint, you're open to all the Spectre v2 attacks. That's fine if the user wants to go fast, but then just use a real jump table pointing to the real system calls.  This is a Not-Inveted-Here halfway house which is just extra bytes to decode and an extra jump to perform. ~Andrew