btf: Support BTF_KIND_ENUM64
BTF_KIND_ENUM64 is supported with latest libbpf, which supports 64-bit
enum values. Latest libbpf also supports signedness for enum values. Add
enum64 support in dwarf-to-btf conversion.
The following is an example of new encoding which covers signed/unsigned
enum64/enum variations.
$ cat t.c
enum { /* signed, enum64 */
A = -1,
B = 0xffffffff,
} g1;
enum { /* unsigned, enum64 */
C = 1,
D = 0xfffffffff,
} g2;
enum { /* signed, enum */
E = -1,
F = 0xfffffff,
} g3;
enum { /* unsigned, enum */
G = 1,
H = 0xfffffff,
} g4;
$ clang -g -c t.c
$ pahole -JV t.o
btf_encoder__new: 't.o' doesn't have '.data..percpu' section
Found 0 per-CPU variables!
File t.o:
[1] ENUM64 (anon) size=8
A val=-1
B val=4294967295
[2] INT long size=8 nr_bits=64 encoding=SIGNED
[3] ENUM64 (anon) size=8
C val=1
D val=68719476735
[4] INT unsigned long size=8 nr_bits=64 encoding=(none)
[5] ENUM (anon) size=4
E val=-1
F val=268435455
[6] INT int size=4 nr_bits=32 encoding=SIGNED
[7] ENUM (anon) size=4
G val=1
H val=268435455
[8] INT unsigned int size=4 nr_bits=32 encoding=(none)
With the flag to skip enum64 encoding,
$ pahole -JV t.o --skip_encoding_btf_enum64
btf_encoder__new: 't.o' doesn't have '.data..percpu' section
Found 0 per-CPU variables!
File t.o:
[1] ENUM (anon) size=8
A val=4294967295
B val=4294967295
[2] INT long size=8 nr_bits=64 encoding=SIGNED
[3] ENUM (anon) size=8
C val=1
D val=4294967295
[4] INT unsigned long size=8 nr_bits=64 encoding=(none)
[5] ENUM (anon) size=4
E val=4294967295
F val=268435455
[6] INT int size=4 nr_bits=32 encoding=SIGNED
[7] ENUM (anon) size=4
G val=1
H val=268435455
[8] INT unsigned int size=4 nr_bits=32 encoding=(none)
In the above BTF encoding without enum64, all enum types with the same
type size as the corresponding enum64. All these enum types have
unsigned type (kflag = 0) which is required before kernel enum64
support.
Committer notes:
Add entry about --skip_encoding_btf_enum64 in the man page.
Committer testing:
$ clang -g -c enum64.c
Before this patch:
$ pahole -JV enum64.o
btf_encoder__new: 'enum64.o' doesn't have '.data..percpu' section
Found 0 per-CPU variables!
File enum64.o:
[1] ENUM (anon) size=8
A val=-1
B val=-1
[2] INT long size=8 nr_bits=64 encoding=SIGNED
[3] ENUM (anon) size=8
C val=1
D val=-1
[4] INT unsigned long size=8 nr_bits=64 encoding=(none)
[5] ENUM (anon) size=4
E val=-1
F val=268435455
[6] INT int size=4 nr_bits=32 encoding=SIGNED
[7] ENUM (anon) size=4
G val=1
H val=268435455
[8] INT unsigned int size=4 nr_bits=32 encoding=(none)
$
After:
$ pahole -JV enum64.o
btf_encoder__new: 'enum64.o' doesn't have '.data..percpu' section
Found 0 per-CPU variables!
File enum64.o:
[1] ENUM64 (anon) size=8
A val=-1
B val=4294967295
[2] INT long size=8 nr_bits=64 encoding=SIGNED
[3] ENUM64 (anon) size=8
C val=1
D val=68719476735
[4] INT unsigned long size=8 nr_bits=64 encoding=(none)
[5] ENUM (anon) size=4
E val=-1
F val=268435455
[6] INT int size=4 nr_bits=32 encoding=SIGNED
[7] ENUM (anon) size=4
G val=1
H val=268435455
[8] INT unsigned int size=4 nr_bits=32 encoding=(none)
$
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: bpf@vger.kernel.org
Cc: dwarves@vger.kernel.org
Cc: kernel-team@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
7 files changed
