Re: [PATCH dwarves] fprintf: Fix `*` not being printed for pointers with btf_type_tag

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On Fri, 2023-03-31 at 09:20 -0300, Arnaldo Carvalho de Melo wrote:
> Em Fri, Mar 31, 2023 at 09:14:39AM -0300, Arnaldo Carvalho de Melo escreveu:
> > > This part I didn't understand, do you see any possibility of a
> > > DW_TAG_LLVM_annotation pointing to another DW_TAG_LLVM_annotation?
> > 
> > I _think_ its a noop, so will test your patch as-is, thanks!
> 
> Tested, now we're left with normalizing base type names generated by
> clang and gcc, things like:
> 
> --- /tmp/gcc    2023-03-31 09:16:34.100006650 -0300
> +++ /tmp/clang  2023-03-31 09:16:26.211789489 -0300
> @@ -96,8 +96,8 @@
> 
>         /* XXX 4 bytes hole, try to pack */
> 
> -       long unsigned int          state;                /*   216     8 */
> -       long unsigned int          state2;               /*   224     8 */
> +       unsigned long              state;                /*   216     8 */
> +       unsigned long              state2;               /*   224     8 */
>         struct Qdisc *             next_sched;           /*   232     8 */
>         struct sk_buff_head        skb_bad_txq;          /*   240    24 */
> 
> @@ -112,7 +112,7 @@
>         /* XXX 40 bytes hole, try to pack */
> 
>         /* --- cacheline 6 boundary (384 bytes) --- */
> -       long int                   privdata[];           /*   384     0 */
> +       long                       privdata[];           /*   384     0 */
> 
>         /* size: 384, cachelines: 6, members: 28 */
>         /* sum members: 260, holes: 4, sum holes: 124 */
> @@ -145,19 +145,19 @@
>         /* XXX 4 bytes hole, try to pack */
> 
>         struct netdev_queue *      (*select_queue)(struct Qdisc *, struct tcmsg *); /*     8     8 */
> -       int                        (*graft)(struct Qdisc *, long unsigned int, struct Qdisc *, struct Qdisc * *, struct netlink_ext_ack *); /*    16     8 */
> +       int                        (*graft)(struct Qdisc *, unsigned long, struct Qdisc *, struct Qdisc * *, struct netlink_ext_ack *); /*    16     8 */
> -       struct Qdisc *             (*leaf)(struct Qdisc *, long unsigned int); /*    24     8 */
> +       struct Qdisc *             (*leaf)(struct Qdisc *, unsigned long); /*    24     8 */
> -       void                       (*qlen_notify)(struct Qdisc *, long unsigned int); /*    32     8 */
> +       void                       (*qlen_notify)(struct Qdisc *, unsigned long); /*    32     8 */
> -       long unsigned int          (*find)(struct Qdisc *, u32); /*    40     8 */
> +       unsigned long              (*find)(struct Qdisc *, u32); /*    40     8 */
> -       int                        (*change)(struct Qdisc *, u32, u32, struct nlattr * *, long unsigned int *, struct netlink_ext_ack *); /*    48     8 */
> +       int                        (*change)(struct Qdisc *, u32, u32, struct nlattr * *, unsigned long *, struct netlink_ext_ack *); /*    48     8 */
> -       int                        (*delete)(struct Qdisc *, long unsigned int, struct netlink_ext_ack *); /*    56     8 */
> +       int                        (*delete)(struct Qdisc *, unsigned long, struct netlink_ext_ack *); /*    56     8 */
>         /* --- cacheline 1 boundary (64 bytes) --- */
>         void                       (*walk)(struct Qdisc *, struct qdisc_walker *); /*    64     8 */
> -       struct tcf_block *         (*tcf_block)(struct Qdisc *, long unsigned int, struct netlink_ext_ack *); /*    72     8 */
> +       struct tcf_block *         (*tcf_block)(struct Qdisc *, unsigned long, struct netlink_ext_ack *); /*    72     8 */
> -       long unsigned int          (*bind_tcf)(struct Qdisc *, long unsigned int, u32); /*    80     8 */
> +       unsigned long              (*bind_tcf)(struct Qdisc *, unsigned long, u32); /*    80     8 */
> -       void                       (*unbind_tcf)(struct Qdisc *, long unsigned int); /*    88     8 */
> +       void                       (*unbind_tcf)(struct Qdisc *, unsigned long); /*    88     8 */
> -       int                        (*dump)(struct Qdisc *, long unsigned int, struct sk_buff *, struct tcmsg *); /*    96     8 */
> +       int                        (*dump)(struct Qdisc *, unsigned long, struct sk_buff *, struct tcmsg *); /*    96     8 */
> -       int                        (*dump_stats)(struct Qdisc *, long unsigned int, struct gnet_dump *); /*   104     8 */
> +       int                        (*dump_stats)(struct Qdisc *, unsigned long, struct gnet_dump *); /*   104     8 */
> 
>         /* size: 112, cachelines: 2, members: 14 */
>         /* sum members: 108, holes: 1, sum holes: 4 */
> @@ -227,21 +227,21 @@
> 
> This was affected somehow by these LLVM_annotation patches, I'll try to
> handle this later. 

Are you sure it is related to LLVM_annotation patches?
I tried (4d17096 "btf_encoder: Compare functions via prototypes not parameter names")
and see the same behavior.

Looking at the DWARF, itself gcc and clang use different names for these types:

gcc:
0x0000002b:   DW_TAG_base_type
                DW_AT_byte_size (0x08)
                DW_AT_encoding  (DW_ATE_unsigned)
                DW_AT_name      ("long unsigned int")

clang:
0x000000f7:   DW_TAG_base_type
                DW_AT_name      ("unsigned long")
                DW_AT_encoding  (DW_ATE_unsigned)
                DW_AT_byte_size (0x08)

And the base type names are copied to BTF as is. Looks like some
normalization is necessary either in dwarf_loader.c:base_type__new()
or in fprintf.

Thanks,
Eduard




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