Alexei Starovoitov c997f28917 libbpf: Fix ld_imm64 copy logic for ksym in light skeleton.
[ Upstream commit a506d6ce1dd184051037dc9d26c3eb187c9fe625 ]

Unlike normal libbpf the light skeleton 'loader' program is doing
btf_find_by_name_kind() call at run-time to find ksym in the kernel and
populate its {btf_id, btf_obj_fd} pair in ld_imm64 insn. To avoid doing the
search multiple times for the same ksym it remembers the first patched ld_imm64
insn and copies {btf_id, btf_obj_fd} from it into subsequent ld_imm64 insn.
Fix a bug in copying logic, since it may incorrectly clear BPF_PSEUDO_BTF_ID flag.

Also replace always true if (btf_obj_fd >= 0) check with unconditional JMP_JA
to clarify the code.

Fixes: d995816b77 ("libbpf: Avoid reload of imm for weak, unresolved, repeating ksym")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230319203014.55866-1-alexei.starovoitov@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-05-11 23:03:18 +09:00
2022-09-28 09:02:20 +02:00
2023-05-01 08:26:28 +09:00

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