From: sdf@google.com
To: bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
martin.lau@linux.dev, song@kernel.org, yhs@fb.com,
john.fastabend@gmail.com, kpsingh@kernel.org, haoluo@google.com,
jolsa@kernel.org
Subject: Re: [PATCH bpf] bpf: make DEBUG_INFO_BTF_MODULES selectable independently
Date: Tue, 4 Oct 2022 17:33:30 -0700 [thread overview]
Message-ID: <YzzQ2mI/srLNazNO@google.com> (raw)
In-Reply-To: <20221004222725.2813510-1-sdf@google.com>
On 10/04, Stanislav Fomichev wrote:
> We're having an issue where we have a recent clang that seems
> to generate kind_flag for enums (aka, adding signed/unsigned).
> Trying to install a module on a kernel that doesn't have commit
> 6089fb325cf7 ("bpf: Add btf enum64 support") returns the following:
> [ 3.176954] BPF:Invalid btf_info kind_flag
> The enum that it complains about doesn't seem to have anything special
> except having a sign:
> [1721] ENUM 'perf_event_state' encoding=SIGNED size=4 vlen=6
> 'PERF_EVENT_STATE_DEAD' val=-4
> 'PERF_EVENT_STATE_EXIT' val=-3
> 'PERF_EVENT_STATE_ERROR' val=-2
> 'PERF_EVENT_STATE_OFF' val=-1
> 'PERF_EVENT_STATE_INACTIVE' val=0
> 'PERF_EVENT_STATE_ACTIVE' val=1
> We are not currently using CONFIG_DEBUG_INFO_BTF_MODULES and
> don't plan to use module BTF, so it's preferable to be able
> to explicits disable it in the kernel config. Unfortunately,
> because that kconfig option doesn't have a name, it's not
> possible to flip it independently from CONFIG_DEBUG_INFO_BTF.
> Let's add a name to make sure module BTF is user-controllable.
[..]
> (Not sure, but maybe the right fix is to also have a stable patch
> to relax that "Invalid btf_info kind_flag" check?)
Answering to myself, looks like we do need the following for
non-enum64-compatible older/stable kernels:
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 3cfba41a0829..928f4955090a 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3301,11 +3301,6 @@ static s32 btf_enum_check_meta(struct
btf_verifier_env *env,
return -EINVAL;
}
- if (btf_type_kflag(t)) {
- btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
- return -EINVAL;
- }
-
if (t->size > 8 || !is_power_of_2(t->size)) {
btf_verifier_log_type(env, t, "Unexpected size");
return -EINVAL;
Anything I'm missing? Feels like any pre-6089fb325cf7 ("bpf: Add btf
enum64 support") kernel will have an issue with a recent clang
that puts sign into kflag?
> Fixes: 5f9ae91f7c0d ("kbuild: Build kernel module BTFs if BTF is enabled
> and pahole supports it")
> Signed-off-by: Stanislav Fomichev <sdf@google.com>
> ---
> lib/Kconfig.debug | 1 +
> 1 file changed, 1 insertion(+)
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index c77fe36bb3d8..6336a697c9f5 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -326,6 +326,7 @@ config PAHOLE_HAS_SPLIT_BTF
> def_bool $(success, test `$(PAHOLE) --version | sed
> -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "119")
> config DEBUG_INFO_BTF_MODULES
> + bool "Generate BTF module typeinfo"
> def_bool y
> depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF
> help
> --
> 2.38.0.rc1.362.ged0d419d3c-goog
next prev parent reply other threads:[~2022-10-05 0:33 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-04 22:27 [PATCH bpf] bpf: make DEBUG_INFO_BTF_MODULES selectable independently Stanislav Fomichev
2022-10-05 0:33 ` sdf [this message]
2022-10-05 1:39 ` Alexei Starovoitov
2022-10-05 2:04 ` Stanislav Fomichev
2022-10-05 23:28 ` Andrii Nakryiko
2022-10-06 7:21 ` Jiri Olsa
2022-10-06 16:20 ` Stanislav Fomichev
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