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([fe80::d886:b658:e2eb:a906]) by SN6PR1501MB2064.namprd15.prod.outlook.com ([fe80::d886:b658:e2eb:a906%5]) with mapi id 15.20.4287.023; Thu, 1 Jul 2021 01:45:49 +0000 Subject: Re: [PATCH bpf-next 4/5] bpf: Add bpf_get_func_ip helper for kprobe programs To: Masami Hiramatsu CC: Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , , , Martin KaFai Lau , Song Liu , John Fastabend , KP Singh References: <20210629192945.1071862-1-jolsa@kernel.org> <20210629192945.1071862-5-jolsa@kernel.org> <9286ce63-5cba-e16a-a7db-886548a04a64@fb.com> <20210701085854.0f2aeafc0fce11f3ca9d52a8@kernel.org> From: Yonghong Song Message-ID: <9bf11f44-37cf-3d39-619d-87b9b611716e@fb.com> Date: Wed, 30 Jun 2021 18:45:46 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 In-Reply-To: <20210701085854.0f2aeafc0fce11f3ca9d52a8@kernel.org> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 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SN6PR1501MB2064.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Jul 2021 01:45:49.5333 (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: ILrB+grvZzPDv93lvsyUQqfPBTZjk/0uxQJhF7kwQwRJ2XP5ta4Tk1KYc99Fz6h6 X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR15MB4497 X-OriginatorOrg: fb.com X-Proofpoint-ORIG-GUID: 0zzWI0EG0BE3ZwUnXKDeh7Pp2rRxWAA6 X-Proofpoint-GUID: 0zzWI0EG0BE3ZwUnXKDeh7Pp2rRxWAA6 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-06-30_13:2021-06-30,2021-06-30 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 impostorscore=0 mlxscore=0 lowpriorityscore=0 malwarescore=0 bulkscore=0 clxscore=1015 priorityscore=1501 spamscore=0 mlxlogscore=999 suspectscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107010010 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 6/30/21 4:58 PM, Masami Hiramatsu wrote: > On Wed, 30 Jun 2021 10:47:01 -0700 > Yonghong Song wrote: > >> >> >> On 6/29/21 12:29 PM, Jiri Olsa wrote: >>> Adding bpf_get_func_ip helper for BPF_PROG_TYPE_KPROBE programs, >>> so it's now possible to call bpf_get_func_ip from both kprobe and >>> kretprobe programs. >>> >>> Taking the caller's address from 'struct kprobe::addr', which is >>> defined for both kprobe and kretprobe. >>> >>> Signed-off-by: Jiri Olsa >>> --- >>> include/uapi/linux/bpf.h | 2 +- >>> kernel/bpf/verifier.c | 2 ++ >>> kernel/trace/bpf_trace.c | 14 ++++++++++++++ >>> kernel/trace/trace_kprobe.c | 20 ++++++++++++++++++-- >>> kernel/trace/trace_probe.h | 5 +++++ >>> tools/include/uapi/linux/bpf.h | 2 +- >>> 6 files changed, 41 insertions(+), 4 deletions(-) >>> >>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h >>> index 83e87ffdbb6e..4894f99a1993 100644 >>> --- a/include/uapi/linux/bpf.h >>> +++ b/include/uapi/linux/bpf.h >>> @@ -4783,7 +4783,7 @@ union bpf_attr { >>> * >>> * u64 bpf_get_func_ip(void *ctx) >>> * Description >>> - * Get address of the traced function (for tracing programs). >>> + * Get address of the traced function (for tracing and kprobe programs). >>> * Return >>> * Address of the traced function. >>> */ >>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c >>> index 701ff7384fa7..b66e0a7104f8 100644 >>> --- a/kernel/bpf/verifier.c >>> +++ b/kernel/bpf/verifier.c >>> @@ -5979,6 +5979,8 @@ static bool has_get_func_ip(struct bpf_verifier_env *env) >>> return -ENOTSUPP; >>> } >>> return 0; >>> + } else if (type == BPF_PROG_TYPE_KPROBE) { >>> + return 0; >>> } >>> >>> verbose(env, "func %s#%d not supported for program type %d\n", >>> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c >>> index 9edd3b1a00ad..1a5bddce9abd 100644 >>> --- a/kernel/trace/bpf_trace.c >>> +++ b/kernel/trace/bpf_trace.c >>> @@ -961,6 +961,18 @@ static const struct bpf_func_proto bpf_get_func_ip_proto_tracing = { >>> .arg1_type = ARG_PTR_TO_CTX, >>> }; >>> >>> +BPF_CALL_1(bpf_get_func_ip_kprobe, struct pt_regs *, regs) >>> +{ >>> + return trace_current_kprobe_addr(); >>> +} >>> + >>> +static const struct bpf_func_proto bpf_get_func_ip_proto_kprobe = { >>> + .func = bpf_get_func_ip_kprobe, >>> + .gpl_only = true, >>> + .ret_type = RET_INTEGER, >>> + .arg1_type = ARG_PTR_TO_CTX, >>> +}; >>> + >>> const struct bpf_func_proto * >>> bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) >>> { >>> @@ -1092,6 +1104,8 @@ kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) >>> case BPF_FUNC_override_return: >>> return &bpf_override_return_proto; >>> #endif >>> + case BPF_FUNC_get_func_ip: >>> + return &bpf_get_func_ip_proto_kprobe; >>> default: >>> return bpf_tracing_func_proto(func_id, prog); >>> } >>> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c >>> index ea6178cb5e33..b07d5888db14 100644 >>> --- a/kernel/trace/trace_kprobe.c >>> +++ b/kernel/trace/trace_kprobe.c >>> @@ -1570,6 +1570,18 @@ static int kretprobe_event_define_fields(struct trace_event_call *event_call) >>> } >>> >>> #ifdef CONFIG_PERF_EVENTS >>> +/* Used by bpf get_func_ip helper */ >>> +DEFINE_PER_CPU(u64, current_kprobe_addr) = 0; >> >> Didn't check other architectures. But this should work >> for x86 where if nested kprobe happens, the second >> kprobe will not call kprobe handlers. > > No problem, other architecture also does not call nested kprobes handlers. > However, you don't need this because you can use kprobe_running() > in kprobe context. > > kp = kprobe_running(); > if (kp) > return kp->addr; > > BTW, I'm not sure why don't you use instruction_pointer(regs)? How about kretprobe? I guess kp->addr should still point to function address but instruction_pointer(regs) does not? > > Thank you, > >> >> This essentially is to provide an additional parameter to >> bpf program. Andrii is developing a mechanism to >> save arbitrary data in *current task_struct*, which >> might be used here to save current_kprobe_addr, we can >> save one per cpu variable. >> >>> + >>> +u64 trace_current_kprobe_addr(void) >>> +{ >>> + return *this_cpu_ptr(¤t_kprobe_addr); >>> +} >>> + >>> +static void trace_current_kprobe_set(struct trace_kprobe *tk) >>> +{ >>> + __this_cpu_write(current_kprobe_addr, (u64) tk->rp.kp.addr); >>> +} >>> >>> /* Kprobe profile handler */ >>> static int >>> @@ -1585,6 +1597,7 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs) >>> unsigned long orig_ip = instruction_pointer(regs); >>> int ret; >>> >>> + trace_current_kprobe_set(tk); >>> ret = trace_call_bpf(call, regs); >>> >>> /* >>> @@ -1631,8 +1644,11 @@ kretprobe_perf_func(struct trace_kprobe *tk, struct kretprobe_instance *ri, >>> int size, __size, dsize; >>> int rctx; >>> >>> - if (bpf_prog_array_valid(call) && !trace_call_bpf(call, regs)) >>> - return; >>> + if (bpf_prog_array_valid(call)) { >>> + trace_current_kprobe_set(tk); >>> + if (!trace_call_bpf(call, regs)) >>> + return; >>> + } >>> >>> head = this_cpu_ptr(call->perf_events); >>> if (hlist_empty(head)) >> [...] > >