From: Alexei Starovoitov <ast@fb.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Alexei Starovoitov <ast@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>,
Daniel Borkmann <daniel@iogearbox.net>,
"x86@kernel.org" <x86@kernel.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH bpf-next 08/10] bpf: check types of arguments passed into helpers
Date: Wed, 9 Oct 2019 19:58:14 +0000 [thread overview]
Message-ID: <e92c76b7-0cbf-750b-1252-78e1a773a379@fb.com> (raw)
In-Reply-To: <CAEf4BzYpPMM=RZ=_kQqin1Aqj=RDx6T8YBJp=-sxgYq54bWhSw@mail.gmail.com>
On 10/9/19 11:01 AM, Andrii Nakryiko wrote:
> On Fri, Oct 4, 2019 at 10:04 PM Alexei Starovoitov <ast@kernel.org> wrote:
>>
>> Introduce new helper that reuses existing skb perf_event output
>> implementation, but can be called from raw_tracepoint programs
>> that receive 'struct sk_buff *' as tracepoint argument or
>> can walk other kernel data structures to skb pointer.
>>
>> In order to do that teach verifier to resolve true C types
>> of bpf helpers into in-kernel BTF ids.
>> The type of kernel pointer passed by raw tracepoint into bpf
>> program will be tracked by the verifier all the way until
>> it's passed into helper function.
>> For example:
>> kfree_skb() kernel function calls trace_kfree_skb(skb, loc);
>> bpf programs receives that skb pointer and may eventually
>> pass it into bpf_skb_output() bpf helper which in-kernel is
>> implemented via bpf_skb_event_output() kernel function.
>> Its first argument in the kernel is 'struct sk_buff *'.
>> The verifier makes sure that types match all the way.
>>
>> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
>> ---
>
> no real concerns, few questions and nits below. Looks great otherwise!
>
>> include/linux/bpf.h | 3 +
>> include/uapi/linux/bpf.h | 3 +-
>> kernel/bpf/btf.c | 73 +++++++++++++++++++++++
>> kernel/bpf/verifier.c | 29 +++++++++
>> kernel/trace/bpf_trace.c | 4 ++
>> net/core/filter.c | 15 ++++-
>> tools/include/uapi/linux/bpf.h | 3 +-
>> tools/testing/selftests/bpf/bpf_helpers.h | 4 ++
>> 8 files changed, 131 insertions(+), 3 deletions(-)
>>
>
> [...]
>
>> + args = (const struct btf_param *)(t + 1);
>> + if (arg >= btf_type_vlen(t)) {
>> + bpf_verifier_log_write(env,
>> + "bpf helper '%s' doesn't have %d-th argument\n",
>> + fnname, arg);
>> + return -EINVAL;
>> + }
>> +
>> + t = btf_type_by_id(btf_vmlinux, args[arg].type);
>> + if (!btf_type_is_ptr(t) || !t->type) {
>> + /* anything but the pointer to struct is a helper config bug */
>> + bpf_verifier_log_write(env,
>> + "ARG_PTR_TO_BTF is misconfigured\n");
>> +
>> + return -EFAULT;
>> + }
>> + btf_id = t->type;
>> +
>> + t = btf_type_by_id(btf_vmlinux, t->type);
>> + if (!btf_type_is_struct(t)) {
>
> resolve mods/typedefs?
fixed
>> + verbose(env, "Helper has type %s got %s in R%d\n",
>> + btf_name_by_offset(btf_vmlinux,
>> + btf_type_by_id(btf_vmlinux,
>> + meta->btf_id)->name_off),
>> + btf_name_by_offset(btf_vmlinux,
>> + btf_type_by_id(btf_vmlinux,
>> + reg->btf_id)->name_off),
>
> This is rather verbose, but popular, construct, maybe extract into a
> helper func and cut on code boilerplate? I think you had similar usage
> in few places in previous patches.
makes sense.
>> + if (fn->arg1_type == ARG_PTR_TO_BTF_ID) {
>> + if (!fn->btf_id[0])
>> + fn->btf_id[0] = btf_resolve_helper_id(env, fn->func, 0);
>> + meta.btf_id = fn->btf_id[0];
>> + }
>
> Is this this baby-stepping thing that we do it only for arg1? Any
> complications from doing a loop over all 5 params?
fixed
next prev parent reply other threads:[~2019-10-09 19:59 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-05 5:03 [PATCH bpf-next 00/10] bpf: revolutionize bpf tracing Alexei Starovoitov
2019-10-05 5:03 ` [PATCH bpf-next 01/10] bpf: add typecast to raw_tracepoints to help BTF generation Alexei Starovoitov
2019-10-05 18:40 ` Andrii Nakryiko
2019-10-06 3:58 ` John Fastabend
2019-10-05 5:03 ` [PATCH bpf-next 02/10] bpf: add typecast to bpf helpers " Alexei Starovoitov
2019-10-05 18:41 ` Andrii Nakryiko
2019-10-06 4:00 ` John Fastabend
2019-10-05 5:03 ` [PATCH bpf-next 03/10] bpf: process in-kernel BTF Alexei Starovoitov
2019-10-06 6:36 ` Andrii Nakryiko
2019-10-06 23:49 ` Alexei Starovoitov
2019-10-07 0:20 ` Andrii Nakryiko
2019-10-09 20:51 ` Martin Lau
2019-10-10 3:43 ` Alexei Starovoitov
2019-10-05 5:03 ` [PATCH bpf-next 04/10] libbpf: auto-detect btf_id of raw_tracepoint Alexei Starovoitov
2019-10-07 23:41 ` Andrii Nakryiko
2019-10-09 2:26 ` Alexei Starovoitov
2019-10-05 5:03 ` [PATCH bpf-next 05/10] bpf: implement accurate raw_tp context access via BTF Alexei Starovoitov
2019-10-07 16:32 ` Alan Maguire
2019-10-09 3:59 ` Alexei Starovoitov
2019-10-08 0:35 ` Andrii Nakryiko
2019-10-09 3:30 ` Alexei Starovoitov
2019-10-09 4:01 ` Andrii Nakryiko
2019-10-09 5:10 ` Andrii Nakryiko
2019-10-10 3:54 ` Alexei Starovoitov
2019-10-05 5:03 ` [PATCH bpf-next 06/10] bpf: add support for BTF pointers to interpreter Alexei Starovoitov
2019-10-08 3:08 ` Andrii Nakryiko
2019-10-05 5:03 ` [PATCH bpf-next 07/10] bpf: add support for BTF pointers to x86 JIT Alexei Starovoitov
2019-10-05 6:03 ` Eric Dumazet
2019-10-09 17:38 ` Andrii Nakryiko
2019-10-09 17:46 ` Alexei Starovoitov
2019-10-05 5:03 ` [PATCH bpf-next 08/10] bpf: check types of arguments passed into helpers Alexei Starovoitov
2019-10-09 18:01 ` Andrii Nakryiko
2019-10-09 19:58 ` Alexei Starovoitov [this message]
2019-10-05 5:03 ` [PATCH bpf-next 09/10] bpf: disallow bpf_probe_read[_str] helpers Alexei Starovoitov
2019-10-09 5:29 ` Andrii Nakryiko
2019-10-09 19:38 ` Alexei Starovoitov
2019-10-05 5:03 ` [PATCH bpf-next 10/10] selftests/bpf: add kfree_skb raw_tp test Alexei Starovoitov
2019-10-09 5:36 ` Andrii Nakryiko
2019-10-09 17:37 ` Alexei Starovoitov
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