* [PATCH bpf-next] libbpf: add support for new llvm bpf relocations
@ 2021-05-22 16:23 Yonghong Song
2021-05-24 17:26 ` Andrii Nakryiko
0 siblings, 1 reply; 3+ messages in thread
From: Yonghong Song @ 2021-05-22 16:23 UTC (permalink / raw)
To: bpf; +Cc: Alexei Starovoitov, Andrii Nakryiko, Daniel Borkmann, kernel-team
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>
---
tools/lib/bpf/libbpf_internal.h | 6 ++++++
tools/lib/bpf/linker.c | 3 ++-
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 55d9b4dca64f..e2db08573bf0 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -28,6 +28,12 @@
#ifndef R_BPF_64_64
#define R_BPF_64_64 1
#endif
+#ifndef R_BPF_64_ABS64
+#define R_BPF_64_ABS64 2
+#endif
+#ifndef R_BPF_64_ABS32
+#define R_BPF_64_ABS32 3
+#endif
#ifndef R_BPF_64_32
#define R_BPF_64_32 10
#endif
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;
--
2.30.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH bpf-next] libbpf: add support for new llvm bpf relocations
2021-05-22 16:23 [PATCH bpf-next] libbpf: add support for new llvm bpf relocations Yonghong Song
@ 2021-05-24 17:26 ` Andrii Nakryiko
2021-05-24 19:09 ` John Fastabend
0 siblings, 1 reply; 3+ messages in thread
From: Andrii Nakryiko @ 2021-05-24 17:26 UTC (permalink / raw)
To: Yonghong Song
Cc: bpf, Alexei Starovoitov, Andrii Nakryiko, Daniel Borkmann, Kernel Team
On Sat, May 22, 2021 at 9:23 AM Yonghong Song <yhs@fb.com> wrote:
>
> 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>
> ---
LGTM. Is there a chance that those relocations will get renamed or
expanded before LLVM diff lands? Or it's safe to apply now and LLVM
side won't change much?
> tools/lib/bpf/libbpf_internal.h | 6 ++++++
> tools/lib/bpf/linker.c | 3 ++-
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
> index 55d9b4dca64f..e2db08573bf0 100644
> --- a/tools/lib/bpf/libbpf_internal.h
> +++ b/tools/lib/bpf/libbpf_internal.h
> @@ -28,6 +28,12 @@
> #ifndef R_BPF_64_64
> #define R_BPF_64_64 1
> #endif
> +#ifndef R_BPF_64_ABS64
> +#define R_BPF_64_ABS64 2
> +#endif
> +#ifndef R_BPF_64_ABS32
> +#define R_BPF_64_ABS32 3
> +#endif
> #ifndef R_BPF_64_32
> #define R_BPF_64_32 10
> #endif
> 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;
> --
> 2.30.2
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH bpf-next] libbpf: add support for new llvm bpf relocations
2021-05-24 17:26 ` Andrii Nakryiko
@ 2021-05-24 19:09 ` John Fastabend
0 siblings, 0 replies; 3+ messages in thread
From: John Fastabend @ 2021-05-24 19:09 UTC (permalink / raw)
To: Andrii Nakryiko, Yonghong Song
Cc: bpf, Alexei Starovoitov, Andrii Nakryiko, Daniel Borkmann, Kernel Team
Andrii Nakryiko wrote:
> On Sat, May 22, 2021 at 9:23 AM Yonghong Song <yhs@fb.com> wrote:
> >
> > 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>
> > ---
Acked-by: John Fastabend <john.fastabend@gmail.com>
>
> LGTM. Is there a chance that those relocations will get renamed or
> expanded before LLVM diff lands? Or it's safe to apply now and LLVM
> side won't change much?
>
> > tools/lib/bpf/libbpf_internal.h | 6 ++++++
> > tools/lib/bpf/linker.c | 3 ++-
> > 2 files changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
> > index 55d9b4dca64f..e2db08573bf0 100644
> > --- a/tools/lib/bpf/libbpf_internal.h
> > +++ b/tools/lib/bpf/libbpf_internal.h
> > @@ -28,6 +28,12 @@
> > #ifndef R_BPF_64_64
> > #define R_BPF_64_64 1
> > #endif
> > +#ifndef R_BPF_64_ABS64
> > +#define R_BPF_64_ABS64 2
> > +#endif
> > +#ifndef R_BPF_64_ABS32
> > +#define R_BPF_64_ABS32 3
> > +#endif
> > #ifndef R_BPF_64_32
> > #define R_BPF_64_32 10
> > #endif
> > 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;
> > --
> > 2.30.2
> >
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-05-24 19:09 UTC | newest]
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2021-05-22 16:23 [PATCH bpf-next] libbpf: add support for new llvm bpf relocations Yonghong Song
2021-05-24 17:26 ` Andrii Nakryiko
2021-05-24 19:09 ` John Fastabend
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