netdev - Re: [PATCH bpf v2] bpf: fix configuration-dependent BTF function references

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Message-ID: <CAADnVQJQpVziHzrPCCpGE5=8uzw2OkxP8gqe1FkJ6_XVVyVbNw@mail.gmail.com>
Date: Thu, 19 Dec 2024 08:05:42 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Thomas Weißschuh <linux@...ssschuh.net>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Jesper Dangaard Brouer <hawk@...nel.org>, bpf <bpf@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf v2] bpf: fix configuration-dependent BTF function references

On Wed, Dec 18, 2024 at 11:24 PM Thomas Weißschuh <linux@...ssschuh.net> wrote:
>
> These BTF functions are not available unconditionally,
> only reference them when they are available.
>
> Avoid the following build warnings:
>
>   BTF     .tmp_vmlinux1.btf.o
> btf_encoder__tag_kfunc: failed to find kfunc 'bpf_send_signal_task' in BTF
> btf_encoder__tag_kfuncs: failed to tag kfunc 'bpf_send_signal_task'
>   NM      .tmp_vmlinux1.syms
>   KSYMS   .tmp_vmlinux1.kallsyms.S
>   AS      .tmp_vmlinux1.kallsyms.o
>   LD      .tmp_vmlinux2
>   NM      .tmp_vmlinux2.syms
>   KSYMS   .tmp_vmlinux2.kallsyms.S
>   AS      .tmp_vmlinux2.kallsyms.o
>   LD      vmlinux
>   BTFIDS  vmlinux
> WARN: resolve_btfids: unresolved symbol prog_test_ref_kfunc
> WARN: resolve_btfids: unresolved symbol bpf_crypto_ctx
> WARN: resolve_btfids: unresolved symbol bpf_send_signal_task
> WARN: resolve_btfids: unresolved symbol bpf_modify_return_test_tp
> WARN: resolve_btfids: unresolved symbol bpf_dynptr_from_xdp
> WARN: resolve_btfids: unresolved symbol bpf_dynptr_from_skb
>
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> ---
> Changes in v2:
> - Properly use BTF_ID_UNUSED in special_kfunc_list()
> - Link to v1: https://lore.kernel.org/r/20241213-bpf-cond-ids-v1-1-881849997219@weissschuh.net
> ---
>  kernel/bpf/helpers.c  |  4 ++++
>  kernel/bpf/verifier.c | 11 +++++++++++
>  2 files changed, 15 insertions(+)
>
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 751c150f9e1cd7f56e6a2b68a7ebb4ae89a30d2d..5edf5436a7804816b7dcf1bbef2624d71a985f20 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -3089,7 +3089,9 @@ BTF_ID_FLAGS(func, bpf_task_get_cgroup1, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
>  BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL)
>  BTF_ID_FLAGS(func, bpf_task_from_vpid, KF_ACQUIRE | KF_RET_NULL)
>  BTF_ID_FLAGS(func, bpf_throw)
> +#ifdef CONFIG_BPF_EVENTS
>  BTF_ID_FLAGS(func, bpf_send_signal_task, KF_TRUSTED_ARGS)
> +#endif
>  BTF_KFUNCS_END(generic_btf_ids)
>
>  static const struct btf_kfunc_id_set generic_kfunc_set = {
> @@ -3135,7 +3137,9 @@ BTF_ID_FLAGS(func, bpf_dynptr_is_null)
>  BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)
>  BTF_ID_FLAGS(func, bpf_dynptr_size)
>  BTF_ID_FLAGS(func, bpf_dynptr_clone)
> +#ifdef CONFIG_NET
>  BTF_ID_FLAGS(func, bpf_modify_return_test_tp)
> +#endif
>  BTF_ID_FLAGS(func, bpf_wq_init)
>  BTF_ID_FLAGS(func, bpf_wq_set_callback_impl)
>  BTF_ID_FLAGS(func, bpf_wq_start)
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 77f56674aaa99a0b88ced5100ba57409e255fd29..2704fa4477ee2504897c82f0416aa7d61fb086ed 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -5507,7 +5507,9 @@ static bool in_rcu_cs(struct bpf_verifier_env *env)
>
>  /* Once GCC supports btf_type_tag the following mechanism will be replaced with tag check */
>  BTF_SET_START(rcu_protected_types)
> +#ifdef CONFIG_NET
>  BTF_ID(struct, prog_test_ref_kfunc)
> +#endif
>  #ifdef CONFIG_CGROUPS
>  BTF_ID(struct, cgroup)
>  #endif
> @@ -5515,7 +5517,9 @@ BTF_ID(struct, cgroup)
>  BTF_ID(struct, bpf_cpumask)
>  #endif
>  BTF_ID(struct, task_struct)
> +#ifdef CONFIG_CRYPTO
>  BTF_ID(struct, bpf_crypto_ctx)
> +#endif
>  BTF_SET_END(rcu_protected_types)
>
>  static bool rcu_protected_object(const struct btf *btf, u32 btf_id)
> @@ -11486,8 +11490,10 @@ BTF_ID(func, bpf_rdonly_cast)
>  BTF_ID(func, bpf_rbtree_remove)
>  BTF_ID(func, bpf_rbtree_add_impl)
>  BTF_ID(func, bpf_rbtree_first)
> +#ifdef CONFIG_NET
>  BTF_ID(func, bpf_dynptr_from_skb)
>  BTF_ID(func, bpf_dynptr_from_xdp)
> +#endif
>  BTF_ID(func, bpf_dynptr_slice)
>  BTF_ID(func, bpf_dynptr_slice_rdwr)
>  BTF_ID(func, bpf_dynptr_clone)
> @@ -11515,8 +11521,13 @@ BTF_ID(func, bpf_rcu_read_unlock)
>  BTF_ID(func, bpf_rbtree_remove)
>  BTF_ID(func, bpf_rbtree_add_impl)
>  BTF_ID(func, bpf_rbtree_first)
> +#ifdef CONFIG_NET
>  BTF_ID(func, bpf_dynptr_from_skb)
>  BTF_ID(func, bpf_dynptr_from_xdp)
> +#else
> +BTF_ID_UNUSED
> +BTF_ID_UNUSED
> +#endif

The previous patch was already applied and it's too late
to revert.
Pls send an incremental fix with:
Fixes: 00a5acdbf398 ("bpf: Fix configuration-dependent BTF function references")

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