Em Fri, Oct 09, 2020 at 12:26:07PM -0700, Andrii Nakryiko escreveu:
> Differentiate between struct and union forwards. For BTF_KIND_FWD this is
> determined by kflag. So teach btf_loader to use that bit to decide whether
> forward is for union or struct.
So, before this patch 'btfdiff vmlinux' comes clean, i.e. pretty
printing from DWARF matches pretty printing from BTF, after it:
[acme@five pahole]$ btfdiff vmlinux | wc -l
1500
[acme@five pahole]$
One of the differences:
@@ -117457,7 +117457,7 @@ struct wireless_dev {
/* XXX last struct has 1 byte of padding */
- struct cfg80211_cqm_config * cqm_config; /* 952 8 */
+ union cfg80211_cqm_config * cqm_config; /* 952 8 */
/* --- cacheline 15 boundary (960 bytes) --- */
struct list_head pmsr_list; /* 960 16 */
spinlock_t pmsr_lock; /* 976 4 */
[acme@five pahole]$
Looking at the source code:
struct wireless_dev {
...
struct cfg80211_cqm_config *cqm_config;
...
}
Also:
struct nfnl_ct_hook {
- struct nf_conn * (*get_ct)(const struct sk_buff *, enum ip_conntrack_info *); /* 0 8 */
- size_t (*build_size)(const struct nf_conn *); /* 8 8 */
- int (*build)(struct sk_buff *, struct nf_conn *, enum ip_conntrack_info, u_int16_t, u_int16_t); /* 16 8 */
- int (*parse)(const struct nlattr *, struct nf_conn *); /* 24 8 */
- int (*attach_expect)(const struct nlattr *, struct nf_conn *, u32, u32); /* 32 8 */
- void (*seq_adjust)(struct sk_buff *, struct nf_conn *, enum ip_conntrack_info, s32); /* 40 8 */
+ union nf_conn * (*get_ct)(const struct sk_buff *, enum ip_conntrack_info *); /* 0 8 */
+ size_t (*build_size)(const union nf_conn *); /* 8 8 */
+ int (*build)(struct sk_buff *, union nf_conn *, enum ip_conntrack_info, u_int16_t, u_int16_t); /* 16 8 */
+ int (*parse)(const struct nlattr *, union nf_conn *); /* 24 8 */
+ int (*attach_expect)(const struct nlattr *, union nf_conn *, u32, u32); /* 32 8 */
+ void (*seq_adjust)(struct sk_buff *, union nf_conn *, enum ip_conntrack_info, s32); /* 40 8 */1
Looking at the source code:
struct nfnl_ct_hook {
struct nf_conn *(*get_ct)(const struct sk_buff *skb,
enum ip_conntrack_info *ctinfo);
size_t (*build_size)(const struct nf_conn *ct);
int (*build)(struct sk_buff *skb, struct nf_conn *ct,
enum ip_conntrack_info ctinfo,
u_int16_t ct_attr, u_int16_t ct_info_attr);
int (*parse)(const struct nlattr *attr, struct nf_conn *ct);
int (*attach_expect)(const struct nlattr *attr, struct nf_conn *ct,
u32 portid, u32 report);
void (*seq_adjust)(struct sk_buff *skb, struct nf_conn *ct,
enum ip_conntrack_info ctinfo, s32 off);
};
- Arnaldo
> Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> ---
> N.B. This patch is based on top of tmp.libbtf_encoder branch.
>
> Also seems like non-forward declared union has a slightly different
> representation from struct (class). Not sure why it is so, but this change
> doesn't seem to break anything.
> ---
>
> btf_loader.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/btf_loader.c b/btf_loader.c
> index 9b5da3a4997a..0cb23967fec3 100644
> --- a/btf_loader.c
> +++ b/btf_loader.c
> @@ -134,12 +134,13 @@ static struct type *type__new(uint16_t tag, strings_t name, size_t size)
> return type;
> }
>
> -static struct class *class__new(strings_t name, size_t size)
> +static struct class *class__new(strings_t name, size_t size, bool is_union)
> {
> struct class *class = tag__alloc(sizeof(*class));
> + uint32_t tag = is_union ? DW_TAG_union_type : DW_TAG_structure_type;
>
> if (class != NULL) {
> - type__init(&class->type, DW_TAG_structure_type, name, size);
> + type__init(&class->type, tag, name, size);
> INIT_LIST_HEAD(&class->vtable);
> }
>
> @@ -228,7 +229,7 @@ static int create_members(struct btf_elf *btfe, const struct btf_type *tp,
>
> static int create_new_class(struct btf_elf *btfe, const struct btf_type *tp, uint32_t id)
> {
> - struct class *class = class__new(tp->name_off, tp->size);
> + struct class *class = class__new(tp->name_off, tp->size, false);
> int member_size = create_members(btfe, tp, &class->type);
>
> if (member_size < 0)
> @@ -313,7 +314,7 @@ static int create_new_subroutine_type(struct btf_elf *btfe, const struct btf_typ
>
> static int create_new_forward_decl(struct btf_elf *btfe, const struct btf_type *tp, uint32_t id)
> {
> - struct class *fwd = class__new(tp->name_off, 0);
> + struct class *fwd = class__new(tp->name_off, 0, btf_kind(tp));
>
> if (fwd == NULL)
> return -ENOMEM;
> --
> 2.24.1
>
--
- Arnaldo
