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Date: Mon, 30 Nov 2020 23:26:19 -0800
From: Yonghong Song <yhs@...com>
To: Andrii Nakryiko <andrii@...nel.org>, <bpf@...r.kernel.org>,
<netdev@...r.kernel.org>, <ast@...com>, <daniel@...earbox.net>
CC: <kernel-team@...com>
Subject: Re: [PATCH v2 bpf-next 0/8] Support BTF-powered BPF tracing programs
for kernel modules
On 11/30/20 7:55 PM, Andrii Nakryiko wrote:
> Building on top of two previous patch sets ([0] and not yet landed [1]), this
> patch sets extends kernel and libbpf with support for attaching BTF-powered
> raw tracepoint (tp_btf) and tracing (fentry/fexit/fmod_ret/lsm) BPF programs
> to BPF hooks defined in kernel modules.
>
> Kernel UAPI for BPF_PROG_LOAD is extended with extra parameter
> (attach_btf_obj_id) which allows to specify kernel module BTF in which the BTF
> type is identifed by attach_btf_id.
>
> From end user perspective there are no extra actions that need to happen.
> Libbpf will continue searching across all kernel module BTFs, if desired
> attach BTF type is not found in vmlinux. That way it doesn't matter if BPF
> hook that user is trying to attach to is built-in into vmlinux image or is
> loaded in kernel module.
>
> Currently pahole doesn't generate BTF_KIND_FUNC info for ftrace-able static
> functions in kernel modules, so expose traced function in bpf_sidecar.ko. Once
bpf_sidecar.ko => bpf_testmod.ko
> pahole is enhanced, we can go back to static function.
>
> [0] https://patchwork.kernel.org/project/netdevbpf/list/?series=380759&state=*
> [1] https://patchwork.kernel.org/project/netdevbpf/list/?series=393677&state=*
>
> v1->v2:
> - avoid increasing bpf_reg_state by reordering fields (Alexei);
> - preserve btf_data_size in struct module;
> - rebase on top of v3 of patch [1].
>
> Andrii Nakryiko (8):
> bpf: keep module's btf_data_size intact after load
> bpf: remove hard-coded btf_vmlinux assumption from BPF verifier
> bpf: allow to specify kernel module BTFs when attaching BPF programs
> libbpf: factor out low-level BPF program loading helper
> libbpf: support attachment of BPF tracing programs to kernel modules
> selftests/bpf: add tp_btf CO-RE reloc test for modules
> selftests/bpf: make bpf_testmod's traceable function global
> selftests/bpf: add fentry/fexit/fmod_ret selftest for kernel module
>
> include/linux/bpf.h | 13 +-
> include/linux/bpf_verifier.h | 28 +++-
> include/linux/btf.h | 7 +-
> include/uapi/linux/bpf.h | 1 +
> kernel/bpf/btf.c | 90 +++++++----
> kernel/bpf/syscall.c | 44 +++++-
> kernel/bpf/verifier.c | 77 ++++++----
> kernel/module.c | 1 -
> net/ipv4/bpf_tcp_ca.c | 3 +-
> tools/include/uapi/linux/bpf.h | 1 +
> tools/lib/bpf/bpf.c | 101 ++++++++----
> tools/lib/bpf/libbpf.c | 145 +++++++++++++-----
> tools/lib/bpf/libbpf_internal.h | 30 ++++
> .../selftests/bpf/bpf_testmod/bpf_testmod.c | 3 +-
> .../selftests/bpf/prog_tests/core_reloc.c | 3 +-
> .../selftests/bpf/prog_tests/module_attach.c | 53 +++++++
> .../bpf/progs/test_core_reloc_module.c | 32 +++-
> .../selftests/bpf/progs/test_module_attach.c | 66 ++++++++
> 18 files changed, 546 insertions(+), 152 deletions(-)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/module_attach.c
> create mode 100644 tools/testing/selftests/bpf/progs/test_module_attach.c
>
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