kernel BTF eBPF

TIPS之 Kernel 开启BTF

Kernel 开启BTF

Posted by 董江 on Sunday, October 8, 2023

Kernel 开启BTF 方式

背景

BTF（BPF Type Format）是一种元数据格式，对与BPF程序/map有关的调试信息进行编码。与BPF程序/map有关的元数据格式。BTF这个名字最初是用来描述数据类型的。后来，BTF被扩展到包括已定义的子程序的函数信息和源/行信息的行信息。

检查内核是否开启BTF调试

检查内核是否开启BTF调试:

$ cat /boot/config-`uname -r` | grep BTF
CONFIG_DEBUG_INFO_BTF=y

返回CONFIG_DEBUG_INFO_BTF=y 表示内核已经开启的BTF.

内核开启BTF 启用CONFIG_DEBUG_INFO_BTF=y内核选项即可。内核本身可以使用BTF功能，用于增强BPF验证程序自身的功能。

检查内核是否BTF vmlinux

$  pwd
/sys/kernel
$  ls btf
vmlinux

安装 bpf依赖包

安装依赖包：

$  yum install bpftool libbpf llvm-libs -y
Last metadata expiration check: 1 day, 0:30:54 ago on Sat 07 Oct 2023 02:32:23 PM CST.
Package bpftool-5.10.134-12.3.el8.bclinux.x86_64 is already installed.
Package libbpf-0.0.4-5.el8.x86_64 is already installed.
Package llvm-libs-9.0.1-5.module+el8.2.0+10180+9e405137.x86_64 is already installed.
Dependencies resolved.
Nothing to do.
Complete!

生成vmlinux.h文件:

$ bpftool btf dump file /sys/kernel/btf/vmlinux format c > /usr/local/include/vmlinux.h
$ ll /usr/local/include/vmlinux.h
-rw-r--r-- 1 root root 2033898 Oct  8 15:06 /usr/local/include/vmlinux.h

检查环境是否可用

$  bpftool prog show 
217501: tracepoint  name do_count  tag 164821634e7375ea  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 256B  jited 166B  memlock 4096B  map_ids 207631
        btf_id 139734
217504: kprobe  name do_count  tag 65e3ff56bff52e68  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 256B  jited 167B  memlock 4096B  map_ids 207632
        btf_id 139735
217508: kprobe  name do_count  tag 9d7cf2bf46590f5a  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 1640B  jited 1016B  memlock 4096B  map_ids 207636,207638,207635,207634
        btf_id 139736
217510: kprobe  name shrink_node_ent  tag a2782e80c654b953  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 112B  jited 85B  memlock 4096B  map_ids 207639
        btf_id 139737
217511: kprobe  name shrink_node_exi  tag af425d8de6a189fd  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 1240B  jited 666B  memlock 4096B  map_ids 207639,207640
        btf_id 139737
217513: raw_tracepoint  name block_rq_insert  tag b50a05896dc733b9  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 136B  jited 98B  memlock 4096B  map_ids 207643,207641
        btf_id 139738
217514: raw_tracepoint  name block_rq_issue  tag b50a05896dc733b9  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 136B  jited 98B  memlock 4096B  map_ids 207643,207641
        btf_id 139738
217515: raw_tracepoint  name block_rq_comple  tag 7293da2116c096ea  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 1568B  jited 870B  memlock 4096B  map_ids 207641,207642
        btf_id 139738
217517: kprobe  name kprobe__inet_cs  tag c5bb1723820097a7  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 112B  jited 85B  memlock 4096B  map_ids 207644
        btf_id 139739
217518: kprobe  name kprobe__inet_cs  tag 9b1903fee906166a  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 1288B  jited 736B  memlock 4096B  map_ids 207644,207645
        btf_id 139739
217520: kprobe  name trace_change  tag f5d2be95f6a869a3  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 184B  jited 118B  memlock 4096B  map_ids 207647,207646
        btf_id 139740
217522: kprobe  name do_init  tag f5d2be95f6a869a3  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 184B  jited 118B  memlock 4096B  map_ids 207647,207646
        btf_id 139740
217524: kprobe  name add_to_page_cac  tag ec7027a0bc58cb0c  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 320B  jited 198B  memlock 4096B  map_ids 207649
        btf_id 139741
217525: kprobe  name mark_page_acces  tag ec7027a0bc58cb0c  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 320B  jited 198B  memlock 4096B  map_ids 207649
        btf_id 139741
217526: kprobe  name folio_account_d  tag ec7027a0bc58cb0c  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 320B  jited 198B  memlock 4096B  map_ids 207649
        btf_id 139741
217527: kprobe  name mark_buffer_dir  tag ec7027a0bc58cb0c  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 320B  jited 198B  memlock 4096B  map_ids 207649
        btf_id 139741
217529: tracepoint  name do_count  tag 65e3ff56bff52e68  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 304B  jited 195B  memlock 4096B  map_ids 207650
        btf_id 139742
217531: perf_event  name on_cache_miss  tag d2fe31242294692d  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 272B  jited 172B  memlock 4096B  map_ids 207651
        btf_id 139743
217532: perf_event  name on_cache_refere  tag d2fe31242294692d  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 272B  jited 172B  memlock 4096B  map_ids 207652
        btf_id 139743
217534: raw_tracepoint  name do_count  tag 2bcaa1e785b61833  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 296B  jited 186B  memlock 4096B  map_ids 207653
        btf_id 139744
217536: kprobe  name kprobe__tcp_v4_  tag 415b2a1f2d0052ad  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 552B  jited 364B  memlock 4096B  map_ids 207654
        btf_id 139745
217537: kprobe  name kprobe__tcp_v6_  tag 415b2a1f2d0052ad  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 552B  jited 364B  memlock 4096B  map_ids 207654
        btf_id 139745
217539: kprobe  name tcp_try_rmem_sc  tag d25d2e6301497809  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 192B  jited 124B  memlock 4096B  map_ids 207656
        btf_id 139746
217540: kprobe  name tcp_try_rmem_sc  tag e9b4e55b2a20492e  gpl
        loaded_at 2023-07-28T12:03:14+0800  uid 0
        xlated 632B  jited 366B  memlock 4096B  map_ids 207656,207655
        btf_id 139746

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