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authorAndrii Nakryiko <andriin@fb.com>2019-03-10 17:44:09 -0700
committerAlexei Starovoitov <ast@kernel.org>2019-03-14 13:53:18 -0700
commit9768095ba97ce946838e8210f0b44f2fd36ec31d (patch)
tree991332fbd5ee7eacdf4beb46cda6c32110d8834e /tools
parentf48a920504e516bded420255946f8e1cb8a0944a (diff)
downloadlinux-9768095ba97ce946838e8210f0b44f2fd36ec31d.tar.bz2
btf: resolve enum fwds in btf_dedup
GCC and clang support enum forward declarations as an extension. Such forward-declared enums will be represented as normal BTF_KIND_ENUM types with vlen=0. This patch adds ability to resolve such enums to their corresponding fully defined enums. This helps to avoid duplicated BTF type graphs which only differ by some types referencing forward-declared enum vs full enum. One such example in kernel is enum irqchip_irq_state, defined in include/linux/interrupt.h and forward-declared in include/linux/irq.h. This causes entire struct task_struct and all referenced types to be duplicated in btf_dedup output. This patch eliminates such duplication cases. Signed-off-by: Andrii Nakryiko <andriin@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'tools')
-rw-r--r--tools/lib/bpf/btf.c51
1 files changed, 38 insertions, 13 deletions
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 1b8d8cdd3575..87e3020ac1bc 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1602,16 +1602,12 @@ static bool btf_equal_int(struct btf_type *t1, struct btf_type *t2)
/* Calculate type signature hash of ENUM. */
static __u32 btf_hash_enum(struct btf_type *t)
{
- struct btf_enum *member = (struct btf_enum *)(t + 1);
- __u32 vlen = BTF_INFO_VLEN(t->info);
- __u32 h = btf_hash_common(t);
- int i;
+ __u32 h;
- for (i = 0; i < vlen; i++) {
- h = hash_combine(h, member->name_off);
- h = hash_combine(h, member->val);
- member++;
- }
+ /* don't hash vlen and enum members 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;
}
@@ -1637,6 +1633,22 @@ static bool btf_equal_enum(struct btf_type *t1, struct btf_type *t2)
return true;
}
+static inline bool btf_is_enum_fwd(struct btf_type *t)
+{
+ return BTF_INFO_KIND(t->info) == BTF_KIND_ENUM &&
+ BTF_INFO_VLEN(t->info) == 0;
+}
+
+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;
+}
+
/*
* Calculate type signature hash of STRUCT/UNION, ignoring referenced type IDs,
* as referenced type IDs equivalence is established separately during type
@@ -1860,6 +1872,17 @@ static int btf_dedup_prim_type(struct btf_dedup *d, __u32 type_id)
new_id = cand_node->type_id;
break;
}
+ if (d->opts.dont_resolve_fwds)
+ continue;
+ if (btf_compat_enum(t, cand)) {
+ if (btf_is_enum_fwd(t)) {
+ /* resolve fwd to full enum */
+ new_id = cand_node->type_id;
+ break;
+ }
+ /* resolve canonical enum fwd to full enum */
+ d->map[cand_node->type_id] = type_id;
+ }
}
break;
@@ -2084,15 +2107,15 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
return fwd_kind == real_kind;
}
- if (cand_type->info != canon_type->info)
- return 0;
-
switch (cand_kind) {
case BTF_KIND_INT:
return btf_equal_int(cand_type, canon_type);
case BTF_KIND_ENUM:
- return btf_equal_enum(cand_type, canon_type);
+ if (d->opts.dont_resolve_fwds)
+ return btf_equal_enum(cand_type, canon_type);
+ else
+ return btf_compat_enum(cand_type, canon_type);
case BTF_KIND_FWD:
return btf_equal_common(cand_type, canon_type);
@@ -2103,6 +2126,8 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
case BTF_KIND_PTR:
case BTF_KIND_TYPEDEF:
case BTF_KIND_FUNC:
+ if (cand_type->info != canon_type->info)
+ return 0;
return btf_dedup_is_equiv(d, cand_type->type, canon_type->type);
case BTF_KIND_ARRAY: {