Changes de-duplication logic for enums in the following way:
- update btf_hash_enum to ignore size and kind fields to get
ENUM and ENUM64 types in a same hash bucket;
- update btf_compat_enum to consider enum fwd to be compatible with
full enum64 (and vice versa);
This allows BTF de-duplication in the following case:
// CU #1
enum foo;
struct s {
enum foo *a;
} *x;
// CU #2
enum foo {
x = 0xfffffffff // big enough to force enum64
};
struct s {
enum foo *a;
} *y;
De-duplicated BTF prior to this commit:
[1] ENUM64 'foo' encoding=UNSIGNED size=8 vlen=1
'x' val=68719476735ULL
[2] INT 'long unsigned int' size=8 bits_offset=0 nr_bits=64
encoding=(none)
[3] STRUCT 's' size=8 vlen=1
'a' type_id=4 bits_offset=0
[4] PTR '(anon)' type_id=1
[5] PTR '(anon)' type_id=3
[6] STRUCT 's' size=8 vlen=1
'a' type_id=8 bits_offset=0
[7] ENUM 'foo' encoding=UNSIGNED size=4 vlen=0
[8] PTR '(anon)' type_id=7
[9] PTR '(anon)' type_id=6
De-duplicated BTF after this commit:
[1] ENUM64 'foo' encoding=UNSIGNED size=8 vlen=1
'x' val=68719476735ULL
[2] INT 'long unsigned int' size=8 bits_offset=0 nr_bits=64
encoding=(none)
[3] STRUCT 's' size=8 vlen=1
'a' type_id=4 bits_offset=0
[4] PTR '(anon)' type_id=1
[5] PTR '(anon)' type_id=3
Enum forward declarations in C do not provide information about
enumeration values range. Thus the `btf_type->size` field is
meaningless for forward enum declarations. In fact, GCC does not
encode size in DWARF for forward enum declarations
(but dwarves sets enumeration size to a default value of `sizeof(int) * 8`
when size is not specified see dwarf_loader.c:die__create_new_enumeration).
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221101235413.1824260-1-eddyz87@gmail.com
btf_dump_emit_struct_def attempts to print empty structures at a
single line, e.g. `struct empty {}`. However, it has to account for a
case when there are no regular but some padding fields in the struct.
In such case `vlen` would be zero, but size would be non-zero.
E.g. here is struct bpf_timer from vmlinux.h before this patch:
struct bpf_timer {
long: 64;
long: 64;};
And after this patch:
struct bpf_dynptr {
long: 64;
long: 64;
};
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221001104425.415768-1-eddyz87@gmail.com
Eduard Zingerman