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libbpf: fix log level propagation for light skeleton loaders

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bpftool's -d option is documented to enable bpf_trace_printk() messages
from the generated syscall loader when used with -L as specified in
commit d510296d33 ("bpftool: Use syscall/loader program in "prog load"
and "gen skeleton" command.")

However commit b59e4ce8bc ("bpftool: Switch bpf_object__load_xattr()
to bpf_object__load()") changed bpftool to use bpf_object__load() which
call the internal bpf_object_load with extra_log_level to 0 instead of
bpf_object__load_xattr with the user request log_level.

All the plumbing was still there to generate the bpf_trace_printk()
instructions from the generator but was now unreachable because
bpf_gen__init() was called with extra_log_level to 0, leaving
gen->log_level at 0.

This uses the obj->log_level field introduced in commit e0e3ea888c
("libbpf: Allow passing user log setting through bpf_object_open_opts")
set from reading verifier_logs in do_skeleton(). This preserves both
object-level and explicit load-time logging settings.

Fixes: b59e4ce8bc ("bpftool: Switch bpf_object__load_xattr() to bpf_object__load()")
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Mahe Tardy <mahe.tardy@gmail.com>
Link: https://lore.kernel.org/r/20260907170536.9996-1-mahe.tardy@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Mahe Tardy 2026-09-07 17:05:36 +00:00 committed by Alexei Starovoitov
parent a41c69c6ea
commit e18e82ba9e
1 changed files with 2 additions and 1 deletions
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3
tools/lib/bpf/libbpf.c
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@ -9139,7 +9139,8 @@ static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const ch
* permit cross-endian creation of "light skeleton".
*/
if (obj->gen_loader) {
bpf_gen__init(obj->gen_loader, extra_log_level, obj->nr_programs, obj->nr_maps);
bpf_gen__init(obj->gen_loader, obj->log_level | extra_log_level,
obj->nr_programs, obj->nr_maps);
} else if (!is_native_endianness(obj)) {
pr_warn("object '%s': loading non-native endianness is unsupported\n", obj->name);
return libbpf_err(-LIBBPF_ERRNO__ENDIAN);