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[23.128.96.18]) by mx.google.com with ESMTP id u21si15755751eds.43.2021.08.30.14.43.16; Mon, 30 Aug 2021 14:43:41 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@fb.com header.s=facebook header.b=WXh5IbId; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=fb.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238698AbhH3VmO (ORCPT + 99 others); Mon, 30 Aug 2021 17:42:14 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:41814 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238606AbhH3VmN (ORCPT ); Mon, 30 Aug 2021 17:42:13 -0400 Received: from pps.filterd (m0148460.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 17ULe5oM016355 for ; Mon, 30 Aug 2021 14:41:18 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=IlPZLgL4AQdy5d0I3ncGnp6ikd94kA8YfEuE30PUQOI=; b=WXh5IbIdlqHLt8gXN6cwB8rMDUhbx+j9DyqgI+yuDiiNihGBeFRXeKnl4K56fOIsVbQq L172qLRuzD//6W7nDWtXXBS4t8BtwMO22pEH06ACFDQZaQy/jU3qUOFpDXKvGJ8QmuRD Q5x2nSVP9DfWljeX4T1zQ74z1aSyasQOqSA= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 3aryp93ckv-6 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 30 Aug 2021 14:41:18 -0700 Received: from intmgw001.05.ash7.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::d) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.14; Mon, 30 Aug 2021 14:41:16 -0700 Received: by devbig006.ftw2.facebook.com (Postfix, from userid 4523) id 10B8EF146816; Mon, 30 Aug 2021 14:41:14 -0700 (PDT) From: Song Liu To: , CC: , , , , , Song Liu Subject: [PATCH v3 bpf-next 2/3] bpf: introduce helper bpf_get_branch_snapshot Date: Mon, 30 Aug 2021 14:41:05 -0700 Message-ID: <20210830214106.4142056-3-songliubraving@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210830214106.4142056-1-songliubraving@fb.com> References: <20210830214106.4142056-1-songliubraving@fb.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe Content-Type: text/plain X-FB-Source: Intern X-Proofpoint-GUID: 1n6SDcMjl2aF_2GfsNUM8KDO8TRmtA3v X-Proofpoint-ORIG-GUID: 1n6SDcMjl2aF_2GfsNUM8KDO8TRmtA3v X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-08-30_06:2021-08-30,2021-08-30 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 impostorscore=0 lowpriorityscore=0 mlxlogscore=999 clxscore=1015 spamscore=0 priorityscore=1501 mlxscore=0 phishscore=0 adultscore=0 malwarescore=0 suspectscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108300136 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- include/linux/bpf.h | 2 ++ include/linux/filter.h | 3 ++- include/uapi/linux/bpf.h | 16 +++++++++++++ kernel/bpf/trampoline.c | 13 ++++++++++ kernel/bpf/verifier.c | 12 ++++++++++ kernel/trace/bpf_trace.c | 43 ++++++++++++++++++++++++++++++++++ tools/include/uapi/linux/bpf.h | 16 +++++++++++++ 7 files changed, 104 insertions(+), 1 deletion(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index f4c16f19f83e3..1868434dc519a 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -2220,4 +2220,6 @@ int bpf_bprintf_prepare(char *fmt, u32 fmt_size, co= nst u64 *raw_args, u32 **bin_buf, u32 num_args); void bpf_bprintf_cleanup(void); =20 +DECLARE_PER_CPU(struct perf_branch_snapshot, bpf_perf_branch_snapshot); + #endif /* _LINUX_BPF_H */ diff --git a/include/linux/filter.h b/include/linux/filter.h index 7d248941ecea3..75aa541c8a134 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -575,7 +575,8 @@ struct bpf_prog { has_callchain_buf:1, /* callchain buffer allocated? */ enforce_expected_attach_type:1, /* Enforce expected_attach_type chec= king at attach time */ call_get_stack:1, /* Do we call bpf_get_stack() or bpf_get_stackid()= */ - call_get_func_ip:1; /* Do we call get_func_ip() */ + call_get_func_ip:1, /* Do we call get_func_ip() */ + call_get_branch:1; /* Do we call get_branch_snapshot() */ enum bpf_prog_type type; /* Type of BPF program */ enum bpf_attach_type expected_attach_type; /* For some prog types */ u32 len; /* Number of filter blocks */ diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 791f31dd0abee..1fd4e85d123da 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -4877,6 +4877,21 @@ union bpf_attr { * Get the struct pt_regs associated with **task**. * Return * A pointer to struct pt_regs. + * + * long bpf_get_branch_snapshot(void *entries, u32 size) + * Description + * Get branch trace from hardware engines like Intel LBR. The + * branch trace is taken soon after the trigger point of the + * BPF program, so it may contain some entries after the + * trigger point. The user need to filter these entries + * accordingly. + * + * The data is stored as struct perf_branch_entry into output + * buffer *entries*. *size* is the size of *entries* in bytes. + * + * Return + * > 0, number of valid output entries. + * **-EOPNOTSUPP**, the hardware/kernel does not support this function */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5055,6 +5070,7 @@ union bpf_attr { FN(get_func_ip), \ FN(get_attach_cookie), \ FN(task_pt_regs), \ + FN(get_branch_snapshot), \ /* */ =20 /* integer value in 'imm' field of BPF_CALL instruction selects which he= lper diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index fe1e857324e66..137293fcceed7 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -10,6 +10,7 @@ #include #include #include +#include =20 /* dummy _ops. The verifier will operate on target program's ops. */ const struct bpf_verifier_ops bpf_extension_verifier_ops =3D { @@ -564,6 +565,18 @@ static void notrace inc_misses_counter(struct bpf_pr= og *prog) u64 notrace __bpf_prog_enter(struct bpf_prog *prog) __acquires(RCU) { +#ifdef CONFIG_PERF_EVENTS + /* Calling migrate_disable costs two entries in the LBR. To save + * some entries, we call perf_snapshot_branch_stack before + * migrate_disable to save some entries. This is OK because we + * care about the branch trace before entering the BPF program. + * If migrate happens exactly here, there isn't much we can do to + * preserve the data. + */ + if (prog->call_get_branch) + static_call(perf_snapshot_branch_stack)( + this_cpu_ptr(&bpf_perf_branch_snapshot)); +#endif rcu_read_lock(); migrate_disable(); if (unlikely(__this_cpu_inc_return(*(prog->active)) !=3D 1)) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 206c221453cfa..72e8b49da0bf9 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6446,6 +6446,18 @@ static int check_helper_call(struct bpf_verifier_e= nv *env, struct bpf_insn *insn env->prog->call_get_func_ip =3D true; } =20 + if (func_id =3D=3D BPF_FUNC_get_branch_snapshot) { + if (env->prog->aux->sleepable) { + verbose(env, "sleepable progs cannot call get_branch_snapshot\n"); + return -ENOTSUPP; + } + if (!IS_ENABLED(CONFIG_PERF_EVENTS)) { + verbose(env, "func %s#%d not supported without CONFIG_PERF_EVENTS\n", + func_id_name(func_id), func_id); + return -ENOTSUPP; + } + env->prog->call_get_branch =3D true; + } if (changes_data) clear_all_pkt_pointers(env); return 0; diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 8e2eb950aa829..a01f26b7877e6 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1017,6 +1017,33 @@ static const struct bpf_func_proto bpf_get_attach_= cookie_proto_pe =3D { .arg1_type =3D ARG_PTR_TO_CTX, }; =20 +BPF_CALL_2(bpf_get_branch_snapshot, void *, buf, u32, size) +{ +#ifdef CONFIG_PERF_EVENTS + u32 max_size; + + if (this_cpu_ptr(&bpf_perf_branch_snapshot)->nr =3D=3D 0) + return -EOPNOTSUPP; + + max_size =3D this_cpu_ptr(&bpf_perf_branch_snapshot)->nr * + sizeof(struct perf_branch_entry); + memcpy(buf, this_cpu_ptr(&bpf_perf_branch_snapshot)->entries, + min_t(u32, size, max_size)); + + return this_cpu_ptr(&bpf_perf_branch_snapshot)->nr; +#else + return -EOPNOTSUPP; +#endif +} + +static const struct bpf_func_proto bpf_get_branch_snapshot_proto =3D { + .func =3D bpf_get_branch_snapshot, + .gpl_only =3D true, + .ret_type =3D RET_INTEGER, + .arg1_type =3D ARG_PTR_TO_UNINIT_MEM, + .arg2_type =3D ARG_CONST_SIZE_OR_ZERO, +}; + static const struct bpf_func_proto * bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *= prog) { @@ -1132,6 +1159,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, co= nst struct bpf_prog *prog) return &bpf_snprintf_proto; case BPF_FUNC_get_func_ip: return &bpf_get_func_ip_proto_tracing; + case BPF_FUNC_get_branch_snapshot: + return &bpf_get_branch_snapshot_proto; default: return bpf_base_func_proto(func_id); } @@ -1863,9 +1892,23 @@ void bpf_put_raw_tracepoint(struct bpf_raw_event_m= ap *btp) preempt_enable(); } =20 +DEFINE_PER_CPU(struct perf_branch_snapshot, bpf_perf_branch_snapshot); + static __always_inline void __bpf_trace_run(struct bpf_prog *prog, u64 *args) { +#ifdef CONFIG_PERF_EVENTS + /* Calling migrate_disable costs two entries in the LBR. To save + * some entries, we call perf_snapshot_branch_stack before + * migrate_disable to save some entries. This is OK because we + * care about the branch trace before entering the BPF program. + * If migrate happens exactly here, there isn't much we can do to + * preserve the data. + */ + if (prog->call_get_branch) + static_call(perf_snapshot_branch_stack)( + this_cpu_ptr(&bpf_perf_branch_snapshot)); +#endif cant_sleep(); rcu_read_lock(); (void) bpf_prog_run(prog, args); diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bp= f.h index 791f31dd0abee..1fd4e85d123da 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -4877,6 +4877,21 @@ union bpf_attr { * Get the struct pt_regs associated with **task**. * Return * A pointer to struct pt_regs. + * + * long bpf_get_branch_snapshot(void *entries, u32 size) + * Description + * Get branch trace from hardware engines like Intel LBR. The + * branch trace is taken soon after the trigger point of the + * BPF program, so it may contain some entries after the + * trigger point. The user need to filter these entries + * accordingly. + * + * The data is stored as struct perf_branch_entry into output + * buffer *entries*. *size* is the size of *entries* in bytes. + * + * Return + * > 0, number of valid output entries. + * **-EOPNOTSUPP**, the hardware/kernel does not support this function */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5055,6 +5070,7 @@ union bpf_attr { FN(get_func_ip), \ FN(get_attach_cookie), \ FN(task_pt_regs), \ + FN(get_branch_snapshot), \ /* */ =20 /* integer value in 'imm' field of BPF_CALL instruction selects which he= lper --=20 2.30.2