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@xxxxxxxxx>
---
tools/lib/bpf/btf.c | 75 +++++++++++++++------------------------------
1 file changed, 25 insertions(+), 50 deletions(-)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 675a0df5c840..6efc11a35afe 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -3404,23 +3404,17 @@ static long btf_hash_enum(struct btf_type *t)
{
long h;
- /* don't hash vlen and enum members to support enum fwd resolving */
+ /* don't hash vlen, enum members and size to support enum fwd resolving */
h = hash_combine(0, t->name_off);
- h = hash_combine(h, t->info & ~0xffff);
- h = hash_combine(h, t->size);
return h;
}
-/* Check structural equality of two ENUMs. */
-static bool btf_equal_enum(struct btf_type *t1, struct btf_type *t2)
+static bool btf_equal_enum_members(struct btf_type *t1, struct btf_type *t2)
{
const struct btf_enum *m1, *m2;
__u16 vlen;
int i;
- if (!btf_equal_common(t1, t2))
- return false;
-
vlen = btf_vlen(t1);
m1 = btf_enum(t1);
m2 = btf_enum(t2);
@@ -3433,15 +3427,12 @@ static bool btf_equal_enum(struct btf_type *t1, struct btf_type *t2)
return true;
}
-static bool btf_equal_enum64(struct btf_type *t1, struct btf_type *t2)
+static bool btf_equal_enum64_members(struct btf_type *t1, struct btf_type *t2)
{
const struct btf_enum64 *m1, *m2;
__u16 vlen;
int i;
- if (!btf_equal_common(t1, t2))
- return false;
-
vlen = btf_vlen(t1);
m1 = btf_enum64(t1);
m2 = btf_enum64(t2);
@@ -3455,6 +3446,19 @@ static bool btf_equal_enum64(struct btf_type *t1, struct btf_type *t2)
return true;
}
+/* Check structural equality of two ENUMs. */
+static bool btf_equal_enum(struct btf_type *t1, struct btf_type *t2)
+{
+ if (!btf_equal_common(t1, t2))
+ return false;
+
+ /* t1 & t2 kinds are identical because of btf_equal_common */
+ if (btf_kind(t1) == BTF_KIND_ENUM)
+ return btf_equal_enum_members(t1, t2);
+ else
+ return btf_equal_enum64_members(t1, t2);
+}
+
static inline bool btf_is_enum_fwd(struct btf_type *t)
{
return btf_is_any_enum(t) && btf_vlen(t) == 0;
@@ -3464,21 +3468,14 @@ static bool btf_compat_enum(struct btf_type *t1, struct btf_type *t2)
{
if (!btf_is_enum_fwd(t1) && !btf_is_enum_fwd(t2))
return btf_equal_enum(t1, t2);
- /* ignore vlen when comparing */
- return t1->name_off == t2->name_off &&
- (t1->info & ~0xffff) == (t2->info & ~0xffff) &&
- t1->size == t2->size;
-}
-
-static bool btf_compat_enum64(struct btf_type *t1, struct btf_type *t2)
-{
- if (!btf_is_enum_fwd(t1) && !btf_is_enum_fwd(t2))
- return btf_equal_enum64(t1, t2);
-
- /* ignore vlen when comparing */
+ /* At this point either t1 or t2 or both are forward declarations, thus:
+ * - skip comparing vlen because it is zero for forward declarations;
+ * - skip comparing size to allow enum forward declarations
+ * to be compatible with enum64 full declarations;
+ * - skip comparing kind for the same reason.
+ */
return t1->name_off == t2->name_off &&
- (t1->info & ~0xffff) == (t2->info & ~0xffff) &&
- t1->size == t2->size;
+ btf_is_any_enum(t1) && btf_is_any_enum(t2);
}
/*
@@ -3763,6 +3760,7 @@ static int btf_dedup_prim_type(struct btf_dedup *d, __u32 type_id)
break;
case BTF_KIND_ENUM:
+ case BTF_KIND_ENUM64:
h = btf_hash_enum(t);
for_each_dedup_cand(d, hash_entry, h) {
cand_id = (__u32)(long)hash_entry->value;
@@ -3783,27 +3781,6 @@ static int btf_dedup_prim_type(struct btf_dedup *d, __u32 type_id)
}
break;
- case BTF_KIND_ENUM64:
- h = btf_hash_enum(t);
- for_each_dedup_cand(d, hash_entry, h) {
- cand_id = (__u32)(long)hash_entry->value;
- cand = btf_type_by_id(d->btf, cand_id);
- if (btf_equal_enum64(t, cand)) {
- new_id = cand_id;
- break;
- }
- if (btf_compat_enum64(t, cand)) {
- if (btf_is_enum_fwd(t)) {
- /* resolve fwd to full enum */
- new_id = cand_id;
- break;
- }
- /* resolve canonical enum fwd to full enum */
- d->map[cand_id] = type_id;
- }
- }
- break;
-
case BTF_KIND_FWD:
case BTF_KIND_FLOAT:
h = btf_hash_common(t);
@@ -4099,10 +4076,8 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
return btf_equal_int_tag(cand_type, canon_type);
case BTF_KIND_ENUM:
- return btf_compat_enum(cand_type, canon_type);
-
case BTF_KIND_ENUM64:
- return btf_compat_enum64(cand_type, canon_type);
+ return btf_compat_enum(cand_type, canon_type);
case BTF_KIND_FWD:
case BTF_KIND_FLOAT:
--
2.34.1
