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author | David S. Miller <davem@davemloft.net> | 2020-07-13 18:04:05 -0700 |
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committer | David S. Miller <davem@davemloft.net> | 2020-07-13 18:04:05 -0700 |
commit | 07dd1b7e68e4b83a1004b14dffd7e142c0bc79bd (patch) | |
tree | 06a5898494308d55fcecbb3dff647d93c01afe47 /Documentation | |
parent | bfe4c40333065639cf0f364b8ea9e93270781699 (diff) | |
parent | 8afb259a9840fa953efb9a7835356a083ac8ec74 (diff) |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next
Alexei Starovoitov says:
====================
pull-request: bpf-next 2020-07-13
The following pull-request contains BPF updates for your *net-next* tree.
We've added 36 non-merge commits during the last 7 day(s) which contain
a total of 62 files changed, 2242 insertions(+), 468 deletions(-).
The main changes are:
1) Avoid trace_printk warning banner by switching bpf_trace_printk to use
its own tracing event, from Alan.
2) Better libbpf support on older kernels, from Andrii.
3) Additional AF_XDP stats, from Ciara.
4) build time resolution of BTF IDs, from Jiri.
5) BPF_CGROUP_INET_SOCK_RELEASE hook, from Stanislav.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/bpf/btf.rst | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst index 4d565d202ce3..b5361b8621c9 100644 --- a/Documentation/bpf/btf.rst +++ b/Documentation/bpf/btf.rst @@ -691,6 +691,42 @@ kernel API, the ``insn_off`` is the instruction offset in the unit of ``struct bpf_insn``. For ELF API, the ``insn_off`` is the byte offset from the beginning of section (``btf_ext_info_sec->sec_name_off``). +4.2 .BTF_ids section +==================== + +The .BTF_ids section encodes BTF ID values that are used within the kernel. + +This section is created during the kernel compilation with the help of +macros defined in ``include/linux/btf_ids.h`` header file. Kernel code can +use them to create lists and sets (sorted lists) of BTF ID values. + +The ``BTF_ID_LIST`` and ``BTF_ID`` macros define unsorted list of BTF ID values, +with following syntax:: + + BTF_ID_LIST(list) + BTF_ID(type1, name1) + BTF_ID(type2, name2) + +resulting in following layout in .BTF_ids section:: + + __BTF_ID__type1__name1__1: + .zero 4 + __BTF_ID__type2__name2__2: + .zero 4 + +The ``u32 list[];`` variable is defined to access the list. + +The ``BTF_ID_UNUSED`` macro defines 4 zero bytes. It's used when we +want to define unused entry in BTF_ID_LIST, like:: + + BTF_ID_LIST(bpf_skb_output_btf_ids) + BTF_ID(struct, sk_buff) + BTF_ID_UNUSED + BTF_ID(struct, task_struct) + +All the BTF ID lists and sets are compiled in the .BTF_ids section and +resolved during the linking phase of kernel build by ``resolve_btfids`` tool. + 5. Using BTF ************ |