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+.. SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+
+==============
+BPF drgn tools
+==============
+
+drgn scripts is a convenient and easy to use mechanism to retrieve arbitrary
+kernel data structures. drgn is not relying on kernel UAPI to read the data.
+Instead it's reading directly from ``/proc/kcore`` or vmcore and pretty prints
+the data based on DWARF debug information from vmlinux.
+
+This document describes BPF related drgn tools.
+
+See `drgn/tools`_ for all tools available at the moment and `drgn/doc`_ for
+more details on drgn itself.
+
+bpf_inspect.py
+--------------
+
+Description
+===========
+
+`bpf_inspect.py`_ is a tool intended to inspect BPF programs and maps. It can
+iterate over all programs and maps in the system and print basic information
+about these objects, including id, type and name.
+
+The main use-case `bpf_inspect.py`_ covers is to show BPF programs of types
+``BPF_PROG_TYPE_EXT`` and ``BPF_PROG_TYPE_TRACING`` attached to other BPF
+programs via ``freplace``/``fentry``/``fexit`` mechanisms, since there is no
+user-space API to get this information.
+
+Getting started
+===============
+
+List BPF programs (full names are obtained from BTF)::
+
+ % sudo bpf_inspect.py prog
+ 27: BPF_PROG_TYPE_TRACEPOINT tracepoint__tcp__tcp_send_reset
+ 4632: BPF_PROG_TYPE_CGROUP_SOCK_ADDR tw_ipt_bind
+ 49464: BPF_PROG_TYPE_RAW_TRACEPOINT raw_tracepoint__sched_process_exit
+
+List BPF maps::
+
+ % sudo bpf_inspect.py map
+ 2577: BPF_MAP_TYPE_HASH tw_ipt_vips
+ 4050: BPF_MAP_TYPE_STACK_TRACE stack_traces
+ 4069: BPF_MAP_TYPE_PERCPU_ARRAY ned_dctcp_cntr
+
+Find BPF programs attached to BPF program ``test_pkt_access``::
+
+ % sudo bpf_inspect.py p | grep test_pkt_access
+ 650: BPF_PROG_TYPE_SCHED_CLS test_pkt_access
+ 654: BPF_PROG_TYPE_TRACING test_main linked:[650->25: BPF_TRAMP_FEXIT test_pkt_access->test_pkt_access()]
+ 655: BPF_PROG_TYPE_TRACING test_subprog1 linked:[650->29: BPF_TRAMP_FEXIT test_pkt_access->test_pkt_access_subprog1()]
+ 656: BPF_PROG_TYPE_TRACING test_subprog2 linked:[650->31: BPF_TRAMP_FEXIT test_pkt_access->test_pkt_access_subprog2()]
+ 657: BPF_PROG_TYPE_TRACING test_subprog3 linked:[650->21: BPF_TRAMP_FEXIT test_pkt_access->test_pkt_access_subprog3()]
+ 658: BPF_PROG_TYPE_EXT new_get_skb_len linked:[650->16: BPF_TRAMP_REPLACE test_pkt_access->get_skb_len()]
+ 659: BPF_PROG_TYPE_EXT new_get_skb_ifindex linked:[650->23: BPF_TRAMP_REPLACE test_pkt_access->get_skb_ifindex()]
+ 660: BPF_PROG_TYPE_EXT new_get_constant linked:[650->19: BPF_TRAMP_REPLACE test_pkt_access->get_constant()]
+
+It can be seen that there is a program ``test_pkt_access``, id 650 and there
+are multiple other tracing and ext programs attached to functions in
+``test_pkt_access``.
+
+For example the line::
+
+ 658: BPF_PROG_TYPE_EXT new_get_skb_len linked:[650->16: BPF_TRAMP_REPLACE test_pkt_access->get_skb_len()]
+
+, means that BPF program id 658, type ``BPF_PROG_TYPE_EXT``, name
+``new_get_skb_len`` replaces (``BPF_TRAMP_REPLACE``) function ``get_skb_len()``
+that has BTF id 16 in BPF program id 650, name ``test_pkt_access``.
+
+Getting help:
+
+.. code-block:: none
+
+ % sudo bpf_inspect.py
+ usage: bpf_inspect.py [-h] {prog,p,map,m} ...
+
+ drgn script to list BPF programs or maps and their properties
+ unavailable via kernel API.
+
+ See https://github.com/osandov/drgn/ for more details on drgn.
+
+ optional arguments:
+ -h, --help show this help message and exit
+
+ subcommands:
+ {prog,p,map,m}
+ prog (p) list BPF programs
+ map (m) list BPF maps
+
+Customization
+=============
+
+The script is intended to be customized by developers to print relevant
+information about BPF programs, maps and other objects.
+
+For example, to print ``struct bpf_prog_aux`` for BPF program id 53077:
+
+.. code-block:: none
+
+ % git diff
+ diff --git a/tools/bpf_inspect.py b/tools/bpf_inspect.py
+ index 650e228..aea2357 100755
+ --- a/tools/bpf_inspect.py
+ +++ b/tools/bpf_inspect.py
+ @@ -112,7 +112,9 @@ def list_bpf_progs(args):
+ if linked:
+ linked = f" linked:[{linked}]"
+
+ - print(f"{id_:>6}: {type_:32} {name:32} {linked}")
+ + if id_ == 53077:
+ + print(f"{id_:>6}: {type_:32} {name:32}")
+ + print(f"{bpf_prog.aux}")
+
+
+ def list_bpf_maps(args):
+
+It produces the output::
+
+ % sudo bpf_inspect.py p
+ 53077: BPF_PROG_TYPE_XDP tw_xdp_policer
+ *(struct bpf_prog_aux *)0xffff8893fad4b400 = {
+ .refcnt = (atomic64_t){
+ .counter = (long)58,
+ },
+ .used_map_cnt = (u32)1,
+ .max_ctx_offset = (u32)8,
+ .max_pkt_offset = (u32)15,
+ .max_tp_access = (u32)0,
+ .stack_depth = (u32)8,
+ .id = (u32)53077,
+ .func_cnt = (u32)0,
+ .func_idx = (u32)0,
+ .attach_btf_id = (u32)0,
+ .linked_prog = (struct bpf_prog *)0x0,
+ .verifier_zext = (bool)0,
+ .offload_requested = (bool)0,
+ .attach_btf_trace = (bool)0,
+ .func_proto_unreliable = (bool)0,
+ .trampoline_prog_type = (enum bpf_tramp_prog_type)BPF_TRAMP_FENTRY,
+ .trampoline = (struct bpf_trampoline *)0x0,
+ .tramp_hlist = (struct hlist_node){
+ .next = (struct hlist_node *)0x0,
+ .pprev = (struct hlist_node **)0x0,
+ },
+ .attach_func_proto = (const struct btf_type *)0x0,
+ .attach_func_name = (const char *)0x0,
+ .func = (struct bpf_prog **)0x0,
+ .jit_data = (void *)0x0,
+ .poke_tab = (struct bpf_jit_poke_descriptor *)0x0,
+ .size_poke_tab = (u32)0,
+ .ksym_tnode = (struct latch_tree_node){
+ .node = (struct rb_node [2]){
+ {
+ .__rb_parent_color = (unsigned long)18446612956263126665,
+ .rb_right = (struct rb_node *)0x0,
+ .rb_left = (struct rb_node *)0xffff88a0be3d0088,
+ },
+ {
+ .__rb_parent_color = (unsigned long)18446612956263126689,
+ .rb_right = (struct rb_node *)0x0,
+ .rb_left = (struct rb_node *)0xffff88a0be3d00a0,
+ },
+ },
+ },
+ .ksym_lnode = (struct list_head){
+ .next = (struct list_head *)0xffff88bf481830b8,
+ .prev = (struct list_head *)0xffff888309f536b8,
+ },
+ .ops = (const struct bpf_prog_ops *)xdp_prog_ops+0x0 = 0xffffffff820fa350,
+ .used_maps = (struct bpf_map **)0xffff889ff795de98,
+ .prog = (struct bpf_prog *)0xffffc9000cf2d000,
+ .user = (struct user_struct *)root_user+0x0 = 0xffffffff82444820,
+ .load_time = (u64)2408348759285319,
+ .cgroup_storage = (struct bpf_map *[2]){},
+ .name = (char [16])"tw_xdp_policer",
+ .security = (void *)0xffff889ff795d548,
+ .offload = (struct bpf_prog_offload *)0x0,
+ .btf = (struct btf *)0xffff8890ce6d0580,
+ .func_info = (struct bpf_func_info *)0xffff889ff795d240,
+ .func_info_aux = (struct bpf_func_info_aux *)0xffff889ff795de20,
+ .linfo = (struct bpf_line_info *)0xffff888a707afc00,
+ .jited_linfo = (void **)0xffff8893fad48600,
+ .func_info_cnt = (u32)1,
+ .nr_linfo = (u32)37,
+ .linfo_idx = (u32)0,
+ .num_exentries = (u32)0,
+ .extable = (struct exception_table_entry *)0xffffffffa032d950,
+ .stats = (struct bpf_prog_stats *)0x603fe3a1f6d0,
+ .work = (struct work_struct){
+ .data = (atomic_long_t){
+ .counter = (long)0,
+ },
+ .entry = (struct list_head){
+ .next = (struct list_head *)0x0,
+ .prev = (struct list_head *)0x0,
+ },
+ .func = (work_func_t)0x0,
+ },
+ .rcu = (struct callback_head){
+ .next = (struct callback_head *)0x0,
+ .func = (void (*)(struct callback_head *))0x0,
+ },
+ }
+
+
+.. Links
+.. _drgn/doc: https://drgn.readthedocs.io/en/latest/
+.. _drgn/tools: https://github.com/osandov/drgn/tree/master/tools
+.. _bpf_inspect.py:
+ https://github.com/osandov/drgn/blob/master/tools/bpf_inspect.py
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-29 09:03:12 +0000