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| author |   Yonghong Song <yhs@fb.com> | 2021-05-22 09:23:41 -0700 |
|---|---|---|
| committer |   Andrii Nakryiko <andrii@kernel.org> | 2021-05-24 21:03:05 -0700 |
| commit | 9f0c317f6aa12b160103ee3946d79276c14b95e2 (patch) | |
| tree | 4074f1348ce4cf03fdb699bab22de0da96a17f65 /tools/lib/bpf/linker.c | |
| parent | Merge branch 'Add lookup_and_delete_elem support to BPF hash map types' (diff) | |
| download | linux-dev-9f0c317f6aa12b160103ee3946d79276c14b95e2.tar.xz linux-dev-9f0c317f6aa12b160103ee3946d79276c14b95e2.zip | |
libbpf: Add support for new llvm bpf relocations
LLVM patch https://reviews.llvm.org/D102712
narrowed the scope of existing R_BPF_64_64
and R_BPF_64_32 relocations, and added three
new relocations, R_BPF_64_ABS64, R_BPF_64_ABS32
and R_BPF_64_NODYLD32. The main motivation is
to make relocations linker friendly.
This change, unfortunately, breaks libbpf build,
and we will see errors like below:
libbpf: ELF relo #0 in section #6 has unexpected type 2 in
/home/yhs/work/bpf-next/tools/testing/selftests/bpf/bpf_tcp_nogpl.o
Error: failed to link
'/home/yhs/work/bpf-next/tools/testing/selftests/bpf/bpf_tcp_nogpl.o':
Unknown error -22 (-22)
The new relocation R_BPF_64_ABS64 is generated
and libbpf linker sanity check doesn't understand it.
Relocation section '.rel.struct_ops' at offset 0x1410 contains 1 entries:
Offset Info Type Symbol's Value Symbol's Name
0000000000000018 0000000700000002 R_BPF_64_ABS64 0000000000000000 nogpltcp_init
Look at the selftests/bpf/bpf_tcp_nogpl.c,
void BPF_STRUCT_OPS(nogpltcp_init, struct sock *sk)
{
}
SEC(".struct_ops")
struct tcp_congestion_ops bpf_nogpltcp = {
.init = (void *)nogpltcp_init,
.name = "bpf_nogpltcp",
};
The new llvm relocation scheme categorizes 'nogpltcp_init' reference
as R_BPF_64_ABS64 instead of R_BPF_64_64 which is used to specify
ld_imm64 relocation in the new scheme.
Let us fix the linker sanity checking by including
R_BPF_64_ABS64 and R_BPF_64_ABS32. There is no need to
check R_BPF_64_NODYLD32 which is used for .BTF and .BTF.ext.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210522162341.3687617-1-yhs@fb.com
Diffstat (limited to 'tools/lib/bpf/linker.c')
| -rw-r--r-- | tools/lib/bpf/linker.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c index b594a88620ce..1dca41a24f75 100644 --- a/tools/lib/bpf/linker.c +++ b/tools/lib/bpf/linker.c @@ -892,7 +892,8 @@ static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *se size_t sym_idx = ELF64_R_SYM(relo->r_info); size_t sym_type = ELF64_R_TYPE(relo->r_info); - if (sym_type != R_BPF_64_64 && sym_type != R_BPF_64_32) { + if (sym_type != R_BPF_64_64 && sym_type != R_BPF_64_32 && + sym_type != R_BPF_64_ABS64 && sym_type != R_BPF_64_ABS32) { pr_warn("ELF relo #%d in section #%zu has unexpected type %zu in %s\n", i, sec->sec_idx, sym_type, obj->filename); return -EINVAL; |