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charset="us-ascii" Content-ID: <39B734EA806E8C4C8E24101B28C2DEC2@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 7acaee31-2e0e-4e73-9296-08d7856cf056 X-MS-Exchange-CrossTenant-originalarrivaltime: 20 Dec 2019 16:52:03.4470 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: iHx8w2Jmq+FdpkanrIazbUoUskVeOzAAFJ9eQBUpCM8pBFnzuCq8V6bSv29FbLYE X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR15MB3406 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-12-20_04:2019-12-17,2019-12-20 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 clxscore=1015 malwarescore=0 mlxscore=0 lowpriorityscore=0 mlxlogscore=497 phishscore=0 spamscore=0 bulkscore=0 adultscore=0 suspectscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1912200127 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Dec 19, 2019 at 11:22:17PM -0800, Martin Lau wrote: > [ ... ] >=20 > > > +/* __bpf_##_name (e.g. __bpf_tcp_congestion_ops) is the map's value > > > + * exposed to the userspace and its btf-type-id is stored > > > + * at the map->btf_vmlinux_value_type_id. > > > + * > > > + * The *_name##_dummy is to ensure the BTF type is emitted. > > > + */ > > > + > > > #define BPF_STRUCT_OPS_TYPE(_name) \ > > > -extern struct bpf_struct_ops bpf_##_name; > > > +extern struct bpf_struct_ops bpf_##_name; \ > > > + \ > > > +static struct __bpf_##_name { \ > > > + BPF_STRUCT_OPS_COMMON_VALUE; \ > > > + struct _name data ____cacheline_aligned_in_smp; \ > > > +} *_name##_dummy; > >=20 > > There are other ways to retain types in debug info without > > creating new variables. For example, you can use it in a cast > > like > > (void *)(struct __bpf_##_name *)v > hmm... What is v? Got it. "v" could be any dummy pointer in a function. I will use (void) instead of (void *) to avoid compiler warning. >=20 > > Not sure whether we could easily find a place for such casting or not. This can be done in bpf_struct_ops_init(). Thanks for the tips!