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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?SPy2ac4unVNdNJFai1zWIx7NaNPpXBua0Xy/jw0rrJnhTlQCg93Vpm9kWv/9?= =?us-ascii?Q?VRAHzlC96cy7wwyamJQe16gwe+9Ei7xe58dWqDcFnAkGF4Cy6DDbgGV8t2Mu?= =?us-ascii?Q?XcJ6+69HC7mA/QJsIregV6DqmAvoFAqDpbxIBvi9C0peUvb3sqGnmmTwLFNR?= =?us-ascii?Q?xQNyn0oI8HZtuXJhmP1COx/nqOYCEof9wr0EPzaDW0wYLcEuOmtwpL3bSMJh?= =?us-ascii?Q?7q4Wl1xEXLxnjNQBrtOWIO4nEDKEWpBghpBBSNmTV6smskw/IRhE8a51Uifb?= =?us-ascii?Q?5K4sdq1fZxgLvvXh/7/Ei/CIiYc6npMr2P7OMQ3lNiX1sydbSVlExgbztCYN?= =?us-ascii?Q?2shuJaa6TesPnHhDWIcVLsLRp6iRoPOdV4PJJ727dEJq4szUCjCVk3qmCsz2?= =?us-ascii?Q?lV3/DB8gAraQ601OKc16hZy+87mOCIg64TszB9asaMwP0m6Gj5++yEACigdL?= =?us-ascii?Q?UelAVNWZFzcxyVLz0t6REh3IdD/AND2Igz5PR7P9qLUUvhSoKbmN2bp4nHxY?= =?us-ascii?Q?PFX4rI6mE1/mS8XTY/ZxFFS3N5M/DxiSJ26z80EtGtKwnkcOEDp9bhJq0td2?= =?us-ascii?Q?f0Rw2Wz0VHygjbp2Xj1kWGEl4XaXcXHwdxQNmrkL2e8T7FokpA+clj/0EvVr?= =?us-ascii?Q?5b0P8Psvr0LM9Uah7RBhALWSGeVXmaej3F4QHjKfX++hQzjb2lpcWbtWELXL?= =?us-ascii?Q?sCB5a2dmuURRSrZac7bfBs8aaNTdn+uuRJlpzMIwi7XBiHWrB+4uIVehx76g?= =?us-ascii?Q?fQdcXKJDfloWkZdmxPRFfLeLjEErse9Iqy/Jd0ulSCo4+dWR3PvEqkGsLNK/?= =?us-ascii?Q?jDAilCyFWL49oii/ptg0sRxpBonV9dR3F1QUAmMZGR2WeI7BM764ykSMFeJH?= =?us-ascii?Q?cvl/uf39taT7egfYDRTvDvCqQrSX82grgP6xqOc5ikTq1iEq4Ii8PFkatx0x?= =?us-ascii?Q?Aourgy79AyVHlS2fkQKaLzNVOMOS3kQEtBv6Cl/8vGfhN4IcVfUKAfjzzlOk?= =?us-ascii?Q?2E2gKi+7YSTQObIcEraFqPUwCiwQ5x7sM+DsvGtPoewJtW9YdTnyKQTsjUto?= =?us-ascii?Q?cbiZ74c+ynUzyszvnMogoGQL576EJIqcOOTgXIM6lmmCzjeZJ5JTBtyOIDjb?= =?us-ascii?Q?wwt9V/FciYwfJjmGG8ZjELZpkmEZ5BWjwXAwCzAd5Zxyc16GThKzVihYmajJ?= =?us-ascii?Q?KPMY6esrHvgJnUkQWfGx/r7DODW4Py1h9MoiXWNE+PwrgxDIEUy2840IOe83?= =?us-ascii?Q?ftlsVRbgttMLjTpLWb158G1mRU5TlOgBE6aBI8mtrIgOC/3kTLy1dqhrM8yi?= =?us-ascii?Q?lyohuxj3xtKMfJOZGWkf/ke1V7oOs/lckVnTY6tCTWldnlHQsSGkrNJhc0YE?= =?us-ascii?Q?vY8df2TCiQMWFEf7RUg65Y0oixE5lge0VTDYvrTXsxhD+05UqW4l0ZL30EZD?= =?us-ascii?Q?hhjRvNoKL9m+mPFWFxZmOGw+xWcEJscVg+Shwyg2tKoEm9whEUXzpL6BbC/+?= =?us-ascii?Q?KLsmF73VBOtXeEJYLQpwUZZKpXoVd1TCIGEsz2DimnkchNmLlsqcXPdcOKox?= =?us-ascii?Q?ENcCcEi6BCFnVSKzKV3VtBWCxJvEnIHo+hWQfxxQmuQ1pjRgCsCcKZOkbAK1?= =?us-ascii?Q?+/5egpnbYZZEne1QEFczAs4=3D?= X-OriginatorOrg: suse.com X-MS-Exchange-CrossTenant-Network-Message-Id: 93231251-9611-4346-7825-08d9b31f0d3b X-MS-Exchange-CrossTenant-AuthSource: VI1PR04MB5600.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Nov 2021 10:00:19.9673 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: f7a17af6-1c5c-4a36-aa8b-f5be247aa4ba X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: DcaGtsdK890K7QpxqfeqDcOXierzHPtJEpuv+JN09EkQ8U3rE63AQFsOom9geHMdriqHcvI3wOgXc3uuMu+GqQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR04MB7040 On 29.11.2021 10:38, Jan Beulich wrote: > On 26.11.2021 15:28, Andrew Cooper wrote: >> On 26/11/2021 14:21, Jan Beulich wrote: >>> On 26.11.2021 13:33, Andrew Cooper wrote: >>>> --- a/xen/include/xen/hypercall.h >>>> +++ b/xen/include/xen/hypercall.h >>>> @@ -18,12 +18,12 @@ >>>> #include >>>> #include >>>> =20 >>>> -extern long >>>> +extern long cf_check >>>> do_sched_op( >>>> int cmd, >>>> XEN_GUEST_HANDLE_PARAM(void) arg); >>> What purpose does the attribute serve on a declaration? On the surface >>> I would consider it meaningful only on definitions, like e.g. __init. >> >> Because GCC treats cf_check (and nocf_check) as part of the function >> type.=C2=A0 Simply getting it wrong will yield a "definition doesn't mat= ch >> prototype" error. >> >> Furthermore, it needs to be visible across translation units so one TU >> can spot (and complain at) creating a function pointer to a non-local >> non-endbr'd function. >=20 > Hmm, it might well be that way, but that's not what the doc (for 11.2) > says. While suggesting things are along the lines of what you say for > "nocf_check", for "cf_check" it really only talks about code generation: > "The cf_check attribute on a function is used to inform the compiler > that ENDBR instruction should be placed at the function entry when > =E2=80=98-fcf-protection=3Dbranch=E2=80=99 is enabled." And even for "noc= f_check" it talks > about extra compile time checks only when the attribute is applied to a > function pointer variable/field, not when applied to a function. The two attributes looks to indeed be as different as the doc suggests, after some experimenting. But I now understand that's what patch 56 is about. Jan