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From: Song Liu <songliubraving@fb.com>
To: Alexei Starovoitov <ast@kernel.org>
Cc: David Miller <davem@davemloft.net>,
	"daniel@iogearbox.net" <daniel@iogearbox.net>,
	"x86@kernel.org" <x86@kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH v3 bpf-next 15/18] bpf: Support attaching tracing BPF program to other BPF programs
Date: Fri, 8 Nov 2019 18:49:21 +0000
Message-ID: <34A3894D-C928-4332-BD82-9B7C1459A8D1@fb.com> (raw)
In-Reply-To: <20191108064039.2041889-16-ast@kernel.org>



> On Nov 7, 2019, at 10:40 PM, Alexei Starovoitov <ast@kernel.org> wrote:
> 
> Allow FENTRY/FEXIT BPF programs to attach to other BPF programs of any type
> including their subprograms. This feature allows snooping on input and output
> packets in XDP, TC programs including their return values. In order to do that
> the verifier needs to track types not only of vmlinux, but types of other BPF
> programs as well. The verifier also needs to translate uapi/linux/bpf.h types
> used by networking programs into kernel internal BTF types used by FENTRY/FEXIT
> BPF programs. In some cases LLVM optimizations can remove arguments from BPF
> subprograms without adjusting BTF info that LLVM backend knows. When BTF info
> disagrees with actual types that the verifiers sees the BPF trampoline has to
> fallback to conservative and treat all arguments as u64. The FENTRY/FEXIT
> program can still attach to such subprograms, but won't be able to recognize
> pointer types like 'struct sk_buff *' into won't be able to pass them to
					^^^^^ these few words are confusing
> bpf_skb_output() for dumping to user space.
> 
> The BPF_PROG_LOAD command is extended with attach_prog_fd field. When it's set
> to zero the attach_btf_id is one vmlinux BTF type ids. When attach_prog_fd
> points to previously loaded BPF program the attach_btf_id is BTF type id of
> main function or one of its subprograms.
> 
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> 

[...]

> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index cd9a9395c4b5..f385c4043594 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -9390,13 +9390,17 @@ static void print_verification_stats(struct bpf_verifier_env *env)
> static int check_attach_btf_id(struct bpf_verifier_env *env)
> {
> 	struct bpf_prog *prog = env->prog;
> +	struct bpf_prog *tgt_prog = prog->aux->linked_prog;
> 	u32 btf_id = prog->aux->attach_btf_id;
> 	const char prefix[] = "btf_trace_";
> 	struct bpf_trampoline *tr;
> 	const struct btf_type *t;
> +	int ret, subprog = -1, i;
> +	bool conservative = true;
> 	const char *tname;
> +	struct btf *btf;
> 	long addr;
> -	int ret;
> +	u64 key;
> 
> 	if (prog->type != BPF_PROG_TYPE_TRACING)
> 		return 0;
> @@ -9405,19 +9409,42 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
> 		verbose(env, "Tracing programs must provide btf_id\n");
> 		return -EINVAL;
> 	}
> -	t = btf_type_by_id(btf_vmlinux, btf_id);
> +	btf = bpf_prog_get_target_btf(prog);

btf could be NULL here, so we need to check it?


[...]

  reply index

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-08  6:40 [PATCH v3 bpf-next 00/18] Introduce BPF trampoline Alexei Starovoitov
2019-11-08  6:40 ` [PATCH v3 bpf-next 01/18] bpf: refactor x86 JIT into helpers Alexei Starovoitov
2019-11-08 19:27   ` Andrii Nakryiko
2019-11-08  6:40 ` [PATCH v3 bpf-next 02/18] bpf: Add bpf_arch_text_poke() helper Alexei Starovoitov
2019-11-08  6:56   ` Song Liu
2019-11-08  8:23   ` Björn Töpel
2019-11-08 14:09     ` Alexei Starovoitov
2019-11-08  9:11   ` Peter Zijlstra
2019-11-08  9:36     ` Peter Zijlstra
2019-11-08 13:41       ` Alexei Starovoitov
2019-11-08 19:32         ` Alexei Starovoitov
2019-11-08 21:36           ` Peter Zijlstra
2019-11-08 21:39             ` David Miller
2019-11-11  8:14               ` Peter Zijlstra
2019-11-11 10:21                 ` Daniel Borkmann
2019-11-11 16:10                 ` Jonathan Corbet
2019-11-08 23:05             ` Alexei Starovoitov
2019-11-10 10:54               ` Thomas Gleixner
2019-11-08  6:40 ` [PATCH v3 bpf-next 03/18] bpf: Introduce BPF trampoline Alexei Starovoitov
2019-11-08  7:04   ` Song Liu
2019-11-08  6:40 ` [PATCH v3 bpf-next 04/18] libbpf: Introduce btf__find_by_name_kind() Alexei Starovoitov
2019-11-08  7:05   ` Song Liu
2019-11-08 19:21   ` Andrii Nakryiko
2019-11-08  6:40 ` [PATCH v3 bpf-next 05/18] libbpf: Add support to attach to fentry/fexit tracing progs Alexei Starovoitov
2019-11-08  7:12   ` Song Liu
2019-11-08 19:44   ` Andrii Nakryiko
2019-11-08  6:40 ` [PATCH v3 bpf-next 06/18] selftest/bpf: Simple test for fentry/fexit Alexei Starovoitov
2019-11-08  6:40 ` [PATCH v3 bpf-next 07/18] bpf: Add kernel test functions for fentry testing Alexei Starovoitov
2019-11-08  6:40 ` [PATCH v3 bpf-next 08/18] selftests/bpf: Add test for BPF trampoline Alexei Starovoitov
2019-11-08  6:40 ` [PATCH v3 bpf-next 09/18] selftests/bpf: Add fexit tests " Alexei Starovoitov
2019-11-08  6:40 ` [PATCH v3 bpf-next 10/18] selftests/bpf: Add combined fentry/fexit test Alexei Starovoitov
2019-11-08  7:14   ` Song Liu
2019-11-08  6:40 ` [PATCH v3 bpf-next 11/18] selftests/bpf: Add stress test for maximum number of progs Alexei Starovoitov
2019-11-08  7:24   ` Song Liu
2019-11-08  6:40 ` [PATCH v3 bpf-next 12/18] bpf: Reserve space for BPF trampoline in BPF programs Alexei Starovoitov
2019-11-08  7:25   ` Song Liu
2019-11-08  6:40 ` [PATCH v3 bpf-next 13/18] bpf: Fix race in btf_resolve_helper_id() Alexei Starovoitov
2019-11-08  7:32   ` Song Liu
2019-11-08 19:58   ` Andrii Nakryiko
2019-11-08  6:40 ` [PATCH v3 bpf-next 14/18] bpf: Compare BTF types of functions arguments with actual types Alexei Starovoitov
2019-11-08 17:28   ` Song Liu
2019-11-08 17:32     ` Song Liu
2019-11-08 17:57       ` Alexei Starovoitov
2019-11-08 17:59         ` Song Liu
2019-11-08 23:46   ` Andrii Nakryiko
2019-11-08  6:40 ` [PATCH v3 bpf-next 15/18] bpf: Support attaching tracing BPF program to other BPF programs Alexei Starovoitov
2019-11-08 18:49   ` Song Liu [this message]
2019-11-08 18:59     ` Alexei Starovoitov
2019-11-08 20:17   ` Toke Høiland-Jørgensen
2019-11-08 21:14     ` Alexei Starovoitov
2019-11-08 21:32       ` Toke Høiland-Jørgensen
2019-11-10  7:17   ` Andrii Nakryiko
2019-11-11 23:04     ` Alexei Starovoitov
2019-11-12  4:38       ` Andrii Nakryiko
2019-11-12  4:47         ` Alexei Starovoitov
2019-11-08  6:40 ` [PATCH v3 bpf-next 16/18] libbpf: Add support for attaching BPF programs " Alexei Starovoitov
2019-11-08 18:57   ` Song Liu
2019-11-08 19:13     ` Alexei Starovoitov
2019-11-08 19:14       ` Song Liu
2019-11-10 16:56   ` Andrii Nakryiko
2019-11-08  6:40 ` [PATCH v3 bpf-next 17/18] selftests/bpf: Extend test_pkt_access test Alexei Starovoitov
2019-11-08 19:03   ` Song Liu
2019-11-10 16:58   ` Andrii Nakryiko
2019-11-08  6:40 ` [PATCH v3 bpf-next 18/18] selftests/bpf: Add a test for attaching BPF prog to another BPF prog and subprog Alexei Starovoitov
2019-11-08 19:13   ` Song Liu
2019-11-10 17:04   ` Andrii Nakryiko
2019-11-11 23:07     ` Alexei Starovoitov

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