From: bot+bpf-ci@kernel.org
To: xukuohai@huaweicloud.com,bpf@vger.kernel.org,linux-kernel@vger.kernel.org
Cc: ast@kernel.org,daniel@iogearbox.net,andrii@kernel.org,eddyz87@gmail.com,memxor@gmail.com,emil@etsalapatis.com,yonghong.song@linux.dev,ast@kernel.org,andrii@kernel.org,daniel@iogearbox.net,martin.lau@kernel.org,eddyz87@gmail.com,yonghong.song@linux.dev,mason@kernel.org,ihor.solodrai@linux.dev
Subject: Re: [PATCH bpf-next 01/16] libbpf: Collect arena percpu data section
Date: Tue, 20 Oct 2026 14:17:06 +0000 (UTC) [thread overview]
Message-ID: <dfe1cca60761dd13e22962fea7221920539b98cdd2b0cbb949803e77e25c3632@mail.kernel.org> (raw)
In-Reply-To: <7b248b2be4834322ddaad8ee08d22d083877a932.1792503001.git.xukuohai@huawei.com>
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> libbpf: Collect arena percpu data section
TL;DR: Objects with .arena.percpu but no .maps section may get a misleading
libbpf error naming .addr_space.1 and "global __arena variables"; it's a
message-wording question, not a functional problem.
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 8fcb8cf39cc0..d79fc382319e 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
[ ... ]
> @@ -3201,7 +3212,7 @@ static int bpf_object__init_arena_data(struct bpf_object *obj)
>
> if (obj->arena_map_idx < 0) {
> /* bpf_object__init_user_btf_maps() didn't look: there is no .maps section */
> - if (obj->efile.arena_data) {
> + if (obj->efile.arena_data || obj->efile.arena_percpu_data) {
> pr_warn("elf: sec '%s': to use global __arena variables the ARENA map should be explicitly declared in SEC(\".maps\")\n",
> ARENA_SEC);
> return -ENOENT;
The condition now also fires on obj->efile.arena_percpu_data, but the warning
still names ARENA_SEC and talks about "global __arena variables". Is that the
intended message for the percpu case?
Consider an object with no SEC(".maps"), the ".arena.data" marker (the
data_in_arena case), some .data/.bss, a ".arena.percpu" section and no
".addr_space.1" section. bpf_object__init_user_btf_maps() returns 0 early
because btf_maps_shndx < 0, so its new ARENA_PERCPU_SEC message never runs.
bpf_object__init_arena_data() then reaches this block with arena_data == NULL
and arena_percpu_data != NULL, and prints:
elf: sec '.addr_space.1': to use global __arena variables the ARENA map
should be explicitly declared in SEC(".maps")
That points at a section the object does not have and at a kind of variable
the user did not declare. The real problem is the .arena.percpu variables.
The same patch adds a separate message for this case in
bpf_object__init_user_btf_maps():
pr_warn("elf: sec '%s': to use arena percpu variables the ARENA map should be explicitly declared in SEC(\".maps\")\n",
ARENA_PERCPU_SEC);
So the two paths report the same condition differently. Should the no-.maps
path in bpf_object__init_arena_data() choose its section name and wording
based on which of arena_data / arena_percpu_data is set?
The message is unchanged at the end of the series (08224ba2de19
"selftests/bpf: Add test for arena percpu bounds"), so no later commit
addresses this.
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/39434884362
next prev parent reply other threads:[~2026-10-20 14:17 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-20 13:22 [PATCH bpf-next 00/16] Add percpu variable support for bpf arena Xu Kuohai
2026-10-20 13:22 ` [PATCH bpf-next 01/16] libbpf: Collect arena percpu data section Xu Kuohai
2026-10-20 14:17 ` bot+bpf-ci [this message]
2026-10-20 13:22 ` [PATCH bpf-next 02/16] libbpf: Create arena percpu chunk from the arena percpu ELF section Xu Kuohai
2026-10-20 14:17 ` bot+bpf-ci
2026-10-20 13:22 ` [PATCH bpf-next 03/16] libbpf: Place the percpu chunks in the bpf arena Xu Kuohai
2026-10-20 13:22 ` [PATCH bpf-next 04/16] libbpf: Copy the percpu chunks into " Xu Kuohai
2026-10-20 14:17 ` bot+bpf-ci
2026-10-20 13:22 ` [PATCH bpf-next 05/16] libbpf: Add the arena percpu chunk attribute to map creation options Xu Kuohai
2026-10-20 14:17 ` bot+bpf-ci
2026-10-20 13:22 ` [PATCH bpf-next 06/16] libbpf: Relocate arena percpu access instructions Xu Kuohai
2026-10-20 14:29 ` bot+bpf-ci
2026-10-20 13:22 ` [PATCH bpf-next 07/16] libbpf: Add arena percpu feature probe Xu Kuohai
2026-10-20 14:17 ` bot+bpf-ci
2026-10-20 13:22 ` [PATCH bpf-next 08/16] bpf: Extend syscall to accept arena percpu information Xu Kuohai
2026-10-20 14:17 ` bot+bpf-ci
2026-10-20 13:22 ` [PATCH bpf-next 09/16] bpf: Teach verifier about arena percpu instructions Xu Kuohai
2026-10-20 14:29 ` bot+bpf-ci
2026-10-20 13:22 ` [PATCH bpf-next 10/16] bpf, x86: Add support for arena percpu Xu Kuohai
2026-10-20 13:22 ` [PATCH bpf-next 11/16] bpf, arm64: " Xu Kuohai
2026-10-20 14:17 ` bot+bpf-ci
2026-10-20 13:22 ` [PATCH bpf-next 12/16] libbpf: Introduce arena percpu helpers for user space Xu Kuohai
2026-10-20 14:17 ` bot+bpf-ci
2026-10-20 13:22 ` [PATCH bpf-next 13/16] bpftool: Emit the arena percpu datasec into skeleton Xu Kuohai
2026-10-20 13:22 ` [PATCH bpf-next 14/16] selftests/bpf: Add test for arena percpu-only object Xu Kuohai
2026-10-20 14:17 ` bot+bpf-ci
2026-10-20 13:23 ` [PATCH bpf-next 15/16] selftests/bpf: Add test for mixed arena percpu object Xu Kuohai
2026-10-20 13:23 ` [PATCH bpf-next 16/16] selftests/bpf: Add test for arena percpu bounds Xu Kuohai
2026-10-20 14:17 ` bot+bpf-ci
2026-10-20 14:47 ` [PATCH bpf-next 00/16] Add percpu variable support for bpf arena Alexei Starovoitov
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