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charset="us-ascii" Content-ID: <91682D9EE4230A49B4EAE26E33436353@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: a6603b85-731d-4609-6b07-08d77e8c952c X-MS-Exchange-CrossTenant-originalarrivaltime: 11 Dec 2019 22:50:56.4209 (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: iKEcOupmQqVWCG4J9QUriBIHn9Bhk/NyF1ZvsdyIa9NQzPAmOBc/EtrLOQGeA3bB X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR15MB2543 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-12-11_07:2019-12-11,2019-12-11 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 bulkscore=0 priorityscore=1501 clxscore=1015 impostorscore=0 malwarescore=0 spamscore=0 mlxscore=0 suspectscore=0 phishscore=0 lowpriorityscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1912110179 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Dec 09, 2019 at 05:14:34PM -0800, Andrii Nakryiko wrote: > Add `bpftool gen skeleton` command, which takes in compiled BPF .o object= file > and dumps a BPF skeleton struct and related code to work with that skelet= on. > Skeleton itself is tailored to a specific structure of provided BPF objec= t > file, containing accessors (just plain struct fields) for every map and > program, as well as dedicated space for bpf_links. If BPF program is usin= g > global variables, corresponding structure definitions of compatible memor= y > layout are emitted as well, making it possible to initialize and subseque= ntly > read/update global variables values using simple and clear C syntax for > accessing fields. This skeleton majorly improves usability of > opening/loading/attaching of BPF object, as well as interacting with it > throughout the lifetime of loaded BPF object. >=20 > Generated skeleton struct has the following structure: >=20 > struct { > /* used by libbpf's skeleton API */ > struct bpf_object_skeleton *skeleton; > /* bpf_object for libbpf APIs */ > struct bpf_object *obj; > struct { > /* for every defined map in BPF object: */ > struct bpf_map *; > } maps; > struct { > /* for every program in BPF object: */ > struct bpf_program *; > } progs; > struct { > /* for every program in BPF object: */ > struct bpf_link *; > } links; > /* for every present global data section: */ > struct __ { > /* memory layout of corresponding data section, > * with every defined variable represented as a struct field > * with exactly the same type, but without const/volatile > * modifiers, e.g.: > */ > int *my_var_1; > ... > } *; > }; >=20 > This provides great usability improvements: > - no need to look up maps and programs by name, instead just > my_obj->maps.my_map or my_obj->progs.my_prog would give necessary > bpf_map/bpf_program pointers, which user can pass to existing libbpf AP= Is; > - pre-defined places for bpf_links, which will be automatically populated= for > program types that libbpf knows how to attach automatically (currently > tracepoints, kprobe/kretprobe, raw tracepoint and tracing programs). On > tearing down skeleton, all active bpf_links will be destroyed (meaning = BPF > programs will be detached, if they are attached). For cases in which li= bbpf > doesn't know how to auto-attach BPF program, user can manually create l= ink > after loading skeleton and they will be auto-detached on skeleton > destruction: >=20 > my_obj->links.my_fancy_prog =3D bpf_program__attach_cgroup_whatever( > my_obj->progs.my_fancy_prog, =20 > - it's extremely easy and convenient to work with global data from usersp= ace > now. Both for read-only and read/write variables, it's possible to > pre-initialize them before skeleton is loaded: >=20 > skel =3D my_obj__open(raw_embed_data); > my_obj->rodata->my_var =3D 123; This will be very useful. I can think of one immediate use on this for my current TCP work. > my_obj__load(skel); /* 123 will be initialization value for my_var */ >=20