From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yonghong Song Subject: Re: [PATCH net-next 1/2] bpf/tracing: allow user space to query prog array on the same tp Date: Thu, 30 Nov 2017 11:12:50 -0800 Message-ID: <0a11c37f-ea13-593d-ef5d-d1aa843d6a84@fb.com> References: <20171129072036.467246-1-yhs@fb.com> <20171129072036.467246-2-yhs@fb.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Cc: To: Daniel Borkmann , , , , , Return-path: Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:34248 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751096AbdK3TUk (ORCPT ); Thu, 30 Nov 2017 14:20:40 -0500 In-Reply-To: Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 11/30/17 9:27 AM, Daniel Borkmann wrote: > On 11/29/2017 08:20 AM, Yonghong Song wrote: >> Commit e87c6bc3852b ("bpf: permit multiple bpf attachments >> for a single perf event") added support to attach multiple >> bpf programs to a single perf event. >> Commit 2541517c32be ("tracing, perf: Implement BPF programs >> attached to kprobes") utilized the existing perf ioctl >> interface and added the command PERF_EVENT_IOC_SET_BPF >> to attach a bpf program to a tracepoint. >> >> This patch adds a new ioctl >> command, given a perf event fd, to query the bpf program array >> attached to the same perf tracepoint event. >> >> The new uapi ioctl command: >> PERF_EVENT_IOC_QUERY_BPF >> >> The new uapi/linux/perf_event.h structure: >> struct perf_event_query_bpf { >> __u64 prog_ids; >> __u32 prog_cnt; >> }; >> >> The usage: >> struct perf_event_query_bpf query; >> query.prog_ids = (__u64)usr_prog_ids_buf; >> query.prog_cnt = usr_prog_ids_buf_len; >> err = ioctl(pmu_efd, PERF_EVENT_IOC_QUERY_BPF, &query); >> >> Signed-off-by: Yonghong Song >> --- >> include/linux/bpf.h | 4 ++++ >> include/uapi/linux/perf_event.h | 6 ++++++ >> kernel/bpf/core.c | 24 ++++++++++++++++++++++++ >> kernel/events/core.c | 3 +++ >> kernel/trace/bpf_trace.c | 23 +++++++++++++++++++++++ >> 5 files changed, 60 insertions(+) >> >> diff --git a/include/linux/bpf.h b/include/linux/bpf.h >> index e55e425..f812ac5 100644 >> --- a/include/linux/bpf.h >> +++ b/include/linux/bpf.h >> @@ -254,6 +254,7 @@ typedef unsigned long (*bpf_ctx_copy_t)(void *dst, const void *src, >> >> u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size, >> void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy); >> +int bpf_event_query_prog_array(struct perf_event *event, void __user *info); >> >> int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr, >> union bpf_attr __user *uattr); >> @@ -285,6 +286,9 @@ int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs, >> >> void bpf_prog_array_delete_safe(struct bpf_prog_array __rcu *progs, >> struct bpf_prog *old_prog); >> +int bpf_prog_array_copy_info(struct bpf_prog_array __rcu *array, >> + __u32 __user *prog_ids, u32 request_cnt, >> + __u32 __user *prog_cnt); >> int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array, >> struct bpf_prog *exclude_prog, >> struct bpf_prog *include_prog, >> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h >> index b9a4953..fee0b43 100644 >> --- a/include/uapi/linux/perf_event.h >> +++ b/include/uapi/linux/perf_event.h >> @@ -418,6 +418,11 @@ struct perf_event_attr { >> __u16 __reserved_2; /* align to __u64 */ >> }; >> >> +struct perf_event_query_bpf { >> + __u64 prog_ids; >> + __u32 prog_cnt; >> +}; >> + >> #define perf_flags(attr) (*(&(attr)->read_format + 1)) >> >> /* >> @@ -433,6 +438,7 @@ struct perf_event_attr { >> #define PERF_EVENT_IOC_ID _IOR('$', 7, __u64 *) >> #define PERF_EVENT_IOC_SET_BPF _IOW('$', 8, __u32) >> #define PERF_EVENT_IOC_PAUSE_OUTPUT _IOW('$', 9, __u32) >> +#define PERF_EVENT_IOC_QUERY_BPF _IOWR('$', 10, struct perf_event_query_bpf *) >> >> enum perf_event_ioc_flags { >> PERF_IOC_FLAG_GROUP = 1U << 0, >> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c >> index b9f8686..40e3b8d 100644 >> --- a/kernel/bpf/core.c >> +++ b/kernel/bpf/core.c >> @@ -1461,6 +1461,8 @@ int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs, >> rcu_read_lock(); >> prog = rcu_dereference(progs)->progs; >> for (; *prog; prog++) { >> + if (*prog == &dummy_bpf_prog.prog) >> + continue; >> id = (*prog)->aux->id; >> if (copy_to_user(prog_ids + i, &id, sizeof(id))) { >> rcu_read_unlock(); >> @@ -1544,6 +1546,28 @@ int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array, >> return 0; >> } >> >> +int bpf_prog_array_copy_info(struct bpf_prog_array __rcu *array, >> + __u32 __user *prog_ids, u32 request_cnt, >> + __u32 __user *prog_cnt) >> +{ >> + struct bpf_prog **prog; >> + u32 cnt = 0; >> + >> + if (array) { >> + for (prog = array->progs; *prog; prog++) >> + if (*prog != &dummy_bpf_prog.prog) >> + cnt++; >> + } >> + >> + if (copy_to_user(prog_cnt, &cnt, sizeof(cnt))) >> + return -EFAULT; >> + >> + if (cnt == 0) >> + return 0; > > One minor thing I still noticed in bpf_prog_array_copy_info() was > that potentially we could return 0 as well if request_cnt was 0 if > users only want to query if progs are present (resp. how many attached) > but don't care which ones. > > Otherwise, in bpf_prog_array_copy_to_user() it tries to copy as much > prog ids as present if request_cnt == 0. Can we handle this in user > space e.g. by having an exposed max upper limit where user space can > define the prog id array with? For cgroup program array, in kernel/bpf/cgroup.c, we have if (copy_to_user(&uattr->query.prog_cnt, &cnt, sizeof(cnt))) return -EFAULT; if (attr->query.prog_cnt == 0 || !prog_ids || !cnt) /* return early if user requested only program count + flags */ return 0; If user requested prog_cnt is 0, or user provided prog_ids pointer is NULL, or the number of actual programs is 0, we will just return fine. I guess I can use the same logic here. Thanks for spotting this issue! Will add additional tests as well for this and send v2. > >> + return bpf_prog_array_copy_to_user(array, prog_ids, request_cnt); >> +} >> + >> static void bpf_prog_free_deferred(struct work_struct *work) >> { >> struct bpf_prog_aux *aux; >> diff --git a/kernel/events/core.c b/kernel/events/core.c >> index 9404c63..93aec2c 100644 >> --- a/kernel/events/core.c >> +++ b/kernel/events/core.c >> @@ -4723,6 +4723,9 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon >> rcu_read_unlock(); >> return 0; >> } >> + >> + case PERF_EVENT_IOC_QUERY_BPF: >> + return bpf_event_query_prog_array(event, (void __user *)arg); >> default: >> return -ENOTTY; >> } >> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c >> index 27d1f4f..7fb7f74 100644 >> --- a/kernel/trace/bpf_trace.c >> +++ b/kernel/trace/bpf_trace.c >> @@ -812,3 +812,26 @@ void perf_event_detach_bpf_prog(struct perf_event *event) >> unlock: >> mutex_unlock(&bpf_event_mutex); >> } >> + >> +int bpf_event_query_prog_array(struct perf_event *event, void __user *info) >> +{ >> + struct perf_event_query_bpf __user *uquery = info; >> + struct perf_event_query_bpf query = {}; >> + int ret; >> + >> + if (!capable(CAP_SYS_ADMIN)) >> + return -EPERM; >> + if (event->attr.type != PERF_TYPE_TRACEPOINT) >> + return -EINVAL; >> + if (copy_from_user(&query, uquery, sizeof(query))) >> + return -EFAULT; >> + >> + mutex_lock(&bpf_event_mutex); >> + ret = bpf_prog_array_copy_info(event->tp_event->prog_array, >> + u64_to_user_ptr(query.prog_ids), >> + query.prog_cnt, >> + &uquery->prog_cnt); >> + mutex_unlock(&bpf_event_mutex); >> + >> + return ret; >> +} >> >