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Wed, 29 Apr 2020 20:51:57 +0000 Subject: Re: [PATCH bpf-next v1 09/19] bpf: add PTR_TO_BTF_ID_OR_NULL support To: Andrii Nakryiko CC: Andrii Nakryiko , bpf , Martin KaFai Lau , Networking , Alexei Starovoitov , Daniel Borkmann , Kernel Team References: <20200427201235.2994549-1-yhs@fb.com> <20200427201245.2995342-1-yhs@fb.com> From: Yonghong Song Message-ID: <7624d62c-05f5-ccd0-1471-eb64d15ce991@fb.com> Date: Wed, 29 Apr 2020 13:51:54 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: CO2PR07CA0074.namprd07.prod.outlook.com (2603:10b6:100::42) To BYAPR15MB4088.namprd15.prod.outlook.com (2603:10b6:a02:c3::18) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from macbook-pro-52.local.dhcp.thefacebook.com (2620:10d:c090:400::5:99f7) by CO2PR07CA0074.namprd07.prod.outlook.com (2603:10b6:100::42) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2958.20 via Frontend Transport; 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>> struct bpf_map *map; >> }; >> >> The kernel guarantees that meta is not NULL, but >> map pointer maybe NULL. The NULL map indicates that all >> objects have been traversed, so bpf program can take >> proper action, e.g., do final aggregation and/or send >> final report to user space. >> >> Add btf_id_or_null_non0_off to prog->aux structure, to >> indicate that for tracing programs, if the context access >> offset is not 0, set to PTR_TO_BTF_ID_OR_NULL instead of >> PTR_TO_BTF_ID. This bit is set for tracing/iter program. >> >> Signed-off-by: Yonghong Song >> --- >> include/linux/bpf.h | 2 ++ >> kernel/bpf/btf.c | 5 ++++- >> kernel/bpf/verifier.c | 19 ++++++++++++++----- >> 3 files changed, 20 insertions(+), 6 deletions(-) >> > > [...] > >> >> static bool reg_may_point_to_spin_lock(const struct bpf_reg_state *reg) >> @@ -410,7 +411,8 @@ static bool reg_type_may_be_refcounted_or_null(enum bpf_reg_type type) >> return type == PTR_TO_SOCKET || >> type == PTR_TO_SOCKET_OR_NULL || >> type == PTR_TO_TCP_SOCK || >> - type == PTR_TO_TCP_SOCK_OR_NULL; >> + type == PTR_TO_TCP_SOCK_OR_NULL || >> + type == PTR_TO_BTF_ID_OR_NULL; > > BTF_ID is not considered to be refcounted for the purpose of verifier, > unless I'm missing something? You are correct. PTR_TO_BTF_ID is not there is a clear sign PTR_TO_BTF_ID_OR_NULL should not be there either. > >> } >> >> static bool arg_type_may_be_refcounted(enum bpf_arg_type type) >> @@ -462,6 +464,7 @@ static const char * const reg_type_str[] = { >> [PTR_TO_TP_BUFFER] = "tp_buffer", >> [PTR_TO_XDP_SOCK] = "xdp_sock", >> [PTR_TO_BTF_ID] = "ptr_", >> + [PTR_TO_BTF_ID_OR_NULL] = "ptr_or_null_", >> }; >> > > [...] >