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charset="us-ascii" Content-ID: MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SA1PR15MB5109.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 7b84a102-5883-4474-823e-08d96e5d94c8 X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Sep 2021 22:04:05.6200 (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: 1pg0dC2SHeaungLZuzaMr/TRLTX0AJ2WKzVm31SWZhEidzP5oKqlKIj+0UZMLpY1PvEnXzAvqU4qdhUM76Fpyg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR15MB5112 X-OriginatorOrg: fb.com X-Proofpoint-GUID: wKE8FY50zIHkWqGhJfuOrgC6oFeiUx-E X-Proofpoint-ORIG-GUID: wKE8FY50zIHkWqGhJfuOrgC6oFeiUx-E X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-09-02_04:2021-09-02,2021-09-02 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 mlxscore=0 bulkscore=0 impostorscore=0 clxscore=1015 priorityscore=1501 phishscore=0 malwarescore=0 adultscore=0 mlxlogscore=999 spamscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2108310000 definitions=main-2109020127 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Sep 2, 2021, at 1:56 PM, John Fastabend wrote: > > Song Liu wrote: >> Introduce bpf_get_branch_snapshot(), which allows tracing pogram to get >> branch trace from hardware (e.g. Intel LBR). To use the feature, the >> user need to create perf_event with proper branch_record filtering >> on each cpu, and then calls bpf_get_branch_snapshot in the bpf function. >> On Intel CPUs, VLBR event (raw event 0x1b00) can be use for this. >> >> Signed-off-by: Song Liu >> --- > > [...] > >> >> +BPF_CALL_3(bpf_get_branch_snapshot, void *, buf, u32, size, u64, flags) >> +{ >> +#ifndef CONFIG_X86 >> + return -ENOENT; >> +#else >> + static const u32 br_entry_size = sizeof(struct perf_branch_entry); >> + u32 entry_cnt = size / br_entry_size; >> + >> + if (unlikely(flags)) >> + return -EINVAL; >> + >> + if (!buf || (size % br_entry_size != 0)) >> + return -EINVAL; > > LGTM, but why fail if buffer is slightly larger than expected? I guess its a slightly > buggy program that would do this, but not actually harmful right? This check was added because bpf_read_branch_records() has a similar check. I guess it is OK either way. > > Acked-by: John Fastabend Thanks for the review!