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@xxxxxxxxxx>
---
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
