BTF data can represent packed enums correctly without any special
handling from pahole side. Previously pahole's own `enum vscope` would
be omitted causing problems.
Original commit tried to generate correct struct bitfield member type if
the member is an enum. This was dated before kind_flag implementation.
Later, kind_flag support was added and now pahole always generates BTF
with kind_flag = 1 for structures with bitfield, where bitfield size is
encoded in btf_member, so this workaround is not needed any more.
Removing this "hack" makes handling it easier to handle packed enums
correctly.
Repro:
$ cat test/packed_enum.c
enum packed_enum {
VALUE1,
VALUE2,
VALUE3
} __attribute__((packed));
struct s {
int x;
enum packed_enum e;
int y;
};
int main()
{
struct s s;
return 0;
}
$ gcc -g -c test/packed_enum.c -o test/packed_enum.o
$ ~/local/pahole/build/pahole -JV test/packed_enum.o
File test/packed_enum.o:
[1] INT (anon) size=1 bit_offset=0 nr_bits=8 encoding=SIGNED
[2] STRUCT s kind_flag=0 size=12 vlen=3
x type_id=3 bits_offset=0
e type_id=1 bits_offset=32
y type_id=3 bits_offset=64
[3] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
$ ~/local/pahole/build/pahole -F dwarf test/packed_enum.o
struct s {
int x; /* 0 4 */
enum packed_enum e; /* 4 1 */
/* XXX 3 bytes hole, try to pack */
int y; /* 8 4 */
/* size: 12, cachelines: 1, members: 3 */
/* sum members: 9, holes: 1, sum holes: 3 */
/* last cacheline: 12 bytes */
};
$ ~/local/pahole/build/pahole -F btf test/packed_enum.o
struct s {
int x; /* 0 4 */
nameless base type! e; /* 4 1 */
/* XXX 3 bytes hole, try to pack */
int y; /* 8 4 */
/* size: 12, cachelines: 1, members: 3 */
/* sum members: 9, holes: 1, sum holes: 3 */
/* last cacheline: 12 bytes */
};
Notice how pahole's log doesn't have a mention of encoding 'packed_enum'
(anonymous integer is generated instead), which causes 'nameless base
type!' output above.
Fix this change:
$ ~/local/pahole/build/pahole -JV test/packed_enum.o
File test/packed_enum.o:
[1] ENUM packed_enum size=1 vlen=3
VALUE1 val=0
VALUE2 val=1
VALUE3 val=2
[2] STRUCT s kind_flag=0 size=12 vlen=3
x type_id=3 bits_offset=0
e type_id=1 bits_offset=32
y type_id=3 bits_offset=64
[3] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
$ ~/local/pahole/build/pahole -F btf test/packed_enum.o
struct s {
int x; /* 0 4 */
enum packed_enum e; /* 4 1 */
/* XXX 3 bytes hole, try to pack */
int y; /* 8 4 */
/* size: 12, cachelines: 1, members: 3 */
/* sum members: 9, holes: 1, sum holes: 3 */
/* last cacheline: 12 bytes */
};
$ PAHOLE=~/local/pahole/build/pahole ./btfdiff test/packed_enum.o
Also verified on pahole, kernel and glibc:
$ PAHOLE=~/local/pahole/build/pahole ./btfdiff ~/local/btf/pahole.debug
$ PAHOLE=~/local/pahole/build/pahole ./btfdiff ~/local/btf/libc-2.28.so.debug
$ PAHOLE=~/local/pahole/build/pahole ./btfdiff ~/local/btf/vmlinux4
Fixes: b18354f64cc2 ("btf: Generate correct struct bitfield member types")
Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
Acked-by: Yonghong Song <yhs@xxxxxx>
---
btf_encoder.c | 9 ---------
1 file changed, 9 deletions(-)
diff --git a/btf_encoder.c b/btf_encoder.c
index 9cf0831..d8dc368 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -116,15 +116,6 @@ static int32_t enumeration_type__encode(struct btf_elf *btfe, struct tag *tag)
struct enumerator *pos;
int32_t type_id;
- /* if enumerator bit_size is not 32, generate an int type instead. */
- if (etype->size != 32) {
- struct base_type bt = {};
-
- bt.bit_size = etype->size;
- bt.is_signed = true;
- return btf_elf__add_base_type(btfe, &bt);
- }
-
type_id = btf_elf__add_enum(btfe, etype->namespace.name, etype->size, etype->nr_members);
if (type_id < 0)
return type_id;
--
2.17.1
