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Message-ID: <0eee016f-2d37-4c80-98cf-fc134d3ad917@gmail.com>
Date: Fri, 21 Feb 2025 02:09:33 +0800
From: Tao Chen <chen.dylane@...il.com>
To: Eduard Zingerman <eddyz87@...il.com>, ast@...nel.org,
daniel@...earbox.net, andrii@...nel.org, haoluo@...gle.com,
jolsa@...nel.org, qmo@...nel.org
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND bpf-next v7 0/4] Add prog_kfunc feature probe
在 2025/2/19 06:51, Eduard Zingerman 写道:
> On Mon, 2025-02-17 at 13:21 +0800, Tao Chen wrote:
>> 在 2025/2/12 23:39, Tao Chen 写道:
>>> More and more kfunc functions are being added to the kernel.
>>> Different prog types have different restrictions when using kfunc.
>>> Therefore, prog_kfunc probe is added to check whether it is supported,
>>> and the use of this api will be added to bpftool later.
>>>
>>> Change list:
>>> - v6 -> v7:
>>> - wrap err with libbpf_err
>>> - comments fix
>>> - handle btf_fd < 0 as vmlinux
>>> - patchset Reviewed-by: Jiri Olsa <jolsa@...nel.org>
>>> - v6
>>> https://lore.kernel.org/bpf/20250211111859.6029-1-chen.dylane@gmail.com
>>>
>>> - v5 -> v6:
>>> - remove fd_array_cnt
>>> - test case clean code
>>> - v5
>>> https://lore.kernel.org/bpf/20250210055945.27192-1-chen.dylane@gmail.com
>>>
>>> - v4 -> v5:
>>> - use fd_array on stack
>>> - declare the scope of use of btf_fd
>>> - v4
>>> https://lore.kernel.org/bpf/20250206051557.27913-1-chen.dylane@gmail.com/
>>>
>>> - v3 -> v4:
>>> - add fd_array init for kfunc in mod btf
>>> - add test case for kfunc in mod btf
>>> - refactor common part as prog load type check for
>>> libbpf_probe_bpf_{helper,kfunc}
>>> - v3
>>> https://lore.kernel.org/bpf/20250124144411.13468-1-chen.dylane@gmail.com
>>>
>>> - v2 -> v3:
>>> - rename parameter off with btf_fd
>>> - extract the common part for libbpf_probe_bpf_{helper,kfunc}
>>> - v2
>>> https://lore.kernel.org/bpf/20250123170555.291896-1-chen.dylane@gmail.com
>>>
>>> - v1 -> v2:
>>> - check unsupported prog type like probe_bpf_helper
>>> - add off parameter for module btf
>>> - check verifier info when kfunc id invalid
>>> - v1
>>> https://lore.kernel.org/bpf/20250122171359.232791-1-chen.dylane@gmail.com
>>>
>>> Tao Chen (4):
>>> libbpf: Extract prog load type check from libbpf_probe_bpf_helper
>>> libbpf: Init fd_array when prog probe load
>>> libbpf: Add libbpf_probe_bpf_kfunc API
>>> selftests/bpf: Add libbpf_probe_bpf_kfunc API selftests
>>>
>>> tools/lib/bpf/libbpf.h | 19 ++-
>>> tools/lib/bpf/libbpf.map | 1 +
>>> tools/lib/bpf/libbpf_probes.c | 86 +++++++++++---
>>> .../selftests/bpf/prog_tests/libbpf_probes.c | 111 ++++++++++++++++++
>>> 4 files changed, 201 insertions(+), 16 deletions(-)
>>>
>>
>> Ping...
>>
>> Hi Andrii, Eduard,
>>
>> I've revised the previous suggestions. Please review it again. Thanks.
>>
>
> I tried the test enumerating all kfuncs in BTF and doing
> libbpf_probe_bpf_kfunc for BPF_PROG_TYPE_{KPROBE,XDP}.
> (Source code at the end of the email).
>
> The set of kfuncs returned for XDP looks correct.
> The set of kfuncs returned for KPROBE contains a few incorrect entries:
> - bpf_xdp_metadata_rx_hash
> - bpf_xdp_metadata_rx_timestamp
> - bpf_xdp_metadata_rx_vlan_tag
>
> This is because of a different string reported by verifier for these
> three functions.
>
> Ideally, I'd write some script looking for
> register_btf_kfunc_id_set(BPF_PROG_TYPE_***, kfunc_set)
> calls in the kernel source code and extracting the prog type /
> functions in the set, and comparing results of this script with
> output of the test below for all program types.
> But up to you if you'd like to do such rigorous verification or not.
>
> Otherwise patch-set looks good to me, for all patch-set:
>
> Reviewed-by: Eduard Zingerman <eddyz87@...il.com>
>
Hi Eduard,
I try to run your test case, but it seems btf_is_decl_tag always return
false, Are there any special restrictions for the tag feature of btf？
My compilation environment：
pahole --version
v1.29
clang --version
Ubuntu clang version 18.1.3 (1ubuntu1)
> --- 8< -----------------------------------------------------
>
> static const struct {
> const char *name;
> int code;
> } program_types[] = {
> #define _T(n) { #n, BPF_PROG_TYPE_ ## n }
> _T(KPROBE),
> _T(XDP),
> #undef _T
> };
>
> void test_libbpf_probe_kfuncs_many(void)
> {
> int i, kfunc_id, ret, id;
> const struct btf_type *t;
> struct btf *btf = NULL;
> const char *kfunc;
> const char *tag;
>
> btf = btf__parse("/sys/kernel/btf/vmlinux", NULL);
> if (!ASSERT_OK_PTR(btf, "btf_parse"))
> return;
>
> for (id = 0; id < btf__type_cnt(btf); ++id) {
> t = btf__type_by_id(btf, id);
> if (!btf_is_decl_tag(t))
> continue;
> tag = btf__name_by_offset(btf, t->name_off);
> if (strcmp(tag, "bpf_kfunc") != 0)
> continue;
> kfunc_id = t->type;
> t = btf__type_by_id(btf, kfunc_id);
> if (!btf_is_func(t))
> continue;
> kfunc = btf__name_by_offset(btf, t->name_off);
> printf("[%-6d] %-42s ", kfunc_id, kfunc);
> for (i = 0; i < ARRAY_SIZE(program_types); ++i) {
> ret = libbpf_probe_bpf_kfunc(program_types[i].code, kfunc_id, -1, NULL);
> if (ret < 0)
> printf("%-8d ", ret);
> else if (ret == 0)
> printf("%8s ", "");
> else
> printf("%8s ", program_types[i].name);
> }
> printf("\n");
> }
> btf__free(btf);
> }
>
> ----------------------------------------------------- >8 ---
>
--
Best Regards
Tao Chen
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