On Tue, 2023-03-28 at 18:17 -0300, Arnaldo Carvalho de Melo wrote: > Em Tue, Mar 28, 2023 at 06:30:05PM +0300, Eduard Zingerman escreveu: > > On Tue, 2023-03-28 at 12:26 -0300, Arnaldo Carvalho de Melo wrote: > > [...] > > > Sure, but look: > > > > > > > > - struct qdisc_size_table * stab; /* 32 8 */ > > > > > + struct qdisc_size_table stab; /* 32 8 */ > > > > > > Its the DW_TAG_pointer_type that is getting lost somehow: > > > > > > <1><b0af32>: Abbrev Number: 81 (DW_TAG_structure_type) > > > <b0af33> DW_AT_name : (indirect string, offset: 0xe825): Qdisc > > > <b0af37> DW_AT_byte_size : 384 > > > <b0af39> DW_AT_decl_file : 223 > > > <b0af3a> DW_AT_decl_line : 72 > > > > > > <SNIP> > > > > > > <2><b0af77>: Abbrev Number: 65 (DW_TAG_member) > > > <b0af78> DW_AT_name : (indirect string, offset: 0x4745ff): stab > > > <b0af7c> DW_AT_type : <0xb0b76b> > > > <b0af80> DW_AT_decl_file : 223 > > > <b0af81> DW_AT_decl_line : 99 > > > <b0af82> DW_AT_data_member_location: 32 > > > > > > <SNIP> > > > > > > <1><b0b76b>: Abbrev Number: 61 (DW_TAG_pointer_type) > > > <b0b76c> DW_AT_type : <0xb0b77a> > > > <2><b0b770>: Abbrev Number: 62 (User TAG value: 0x6000) > > > <b0b771> DW_AT_name : (indirect string, offset: 0x378): btf_type_tag > > > <b0b775> DW_AT_const_value : (indirect string, offset: 0x6e93): rcu > > > <2><b0b779>: Abbrev Number: 0 > > > <1><b0b77a>: Abbrev Number: 69 (DW_TAG_structure_type) > > > <b0b77b> DW_AT_name : (indirect string, offset: 0x6e5ed): qdisc_size_table > > > <b0b77f> DW_AT_byte_size : 64 > > > <b0b780> DW_AT_decl_file : 223 > > > <b0b781> DW_AT_decl_line : 56 > > > > > > > > > So it's all there in the DWARF info: > > > > > > b0af77 has type 0xb0b76b which is a DW_TAG_pointer_type that has type > > > 0xb0b77a, that is DW_TAG_structure_type. > > > > > > Now lets see how this was encoded into BTF: > > > > > > [4725] STRUCT 'Qdisc' size=384 vlen=28 > > > <SNIP> > > > 'stab' type_id=4790 bits_offset=256 > > > <SNIP> > > > [4790] PTR '(anon)' type_id=4789 > > > <SNIP> > > > [4789] TYPE_TAG 'rcu' type_id=4791 > > > <SNIP> > > > [4791] STRUCT 'qdisc_size_table' size=64 vlen=5 > > > 'rcu' type_id=320 bits_offset=0 > > > 'list' type_id=87 bits_offset=128 > > > 'szopts' type_id=4792 bits_offset=256 > > > 'refcnt' type_id=16 bits_offset=448 > > > 'data' type_id=4659 bits_offset=480 > > > > > > So it all seems ok, we should keep all the info and teach fprintf to > > > handle TYPE_TAG. > > > > > > Which you tried, but somehow the '*' link is missing. > > > > Yep, thanks a lot for the analysis, I will take a look. > > Hopefully will send v2 tomorrow. > > So, with the patch below it gets equivalent, but some more tweaking is > needed to make the output completely match (spaces, "long usigned" -> > "unsigned long", which seems to be all equivalent): > > --- /tmp/gcc 2023-03-28 18:13:42.022385428 -0300 > +++ /tmp/clang 2023-03-28 18:13:45.854486885 -0300 > @@ -73,15 +73,15 @@ > unsigned int flags; /* 16 4 */ > u32 limit; /* 20 4 */ > const struct Qdisc_ops * ops; /* 24 8 */ > - struct qdisc_size_table * stab; /* 32 8 */ > + struct qdisc_size_table * stab; /* 32 8 */ > struct hlist_node hash; /* 40 16 */ > u32 handle; /* 56 4 */ > u32 parent; /* 60 4 */ > /* --- cacheline 1 boundary (64 bytes) --- */ > struct netdev_queue * dev_queue; /* 64 8 */ > - struct net_rate_estimator * rate_est; /* 72 8 */ > - struct gnet_stats_basic_sync * cpu_bstats; /* 80 8 */ > - struct gnet_stats_queue * cpu_qstats; /* 88 8 */ > + struct net_rate_estimator * rate_est; /* 72 8 */ > + struct gnet_stats_basic_sync * cpu_bstats; /* 80 8 */ > + struct gnet_stats_queue * cpu_qstats; /* 88 8 */ > int pad; /* 96 4 */ > refcount_t refcnt; /* 100 4 */ > > @@ -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 */ > > diff --git a/dwarves_fprintf.c b/dwarves_fprintf.c > index 1e6147a82056c188..1ecc24321bf8f975 100644 > --- a/dwarves_fprintf.c > +++ b/dwarves_fprintf.c > @@ -788,8 +788,15 @@ next_type: > if (n) > return printed + n; > if (ptype->tag == DW_TAG_LLVM_annotation) { > - type = ptype; > - goto next_type; > + // FIXME: Just skip this for now, we need to print this annotation > + // to match the original source code. > + > + if (ptype->type == 0) { > + printed += fprintf(fp, "%-*s %s", tconf.type_spacing, "void *", name); > + break; > + } > + > + ptype = cu__type(cu, ptype->type); > } > if (ptype->tag == DW_TAG_subroutine_type) { > printed += ftype__fprintf(tag__ftype(ptype), This explains why '*' was missing, but unfortunately it breaks apart when there are multiple type tags, e.g.: $ cat tag-test.c #define __t __attribute__((btf_type_tag("t1"))) struct foo { int (__t __t *a)(void); } g; $ clang -g -c tag-test.c -o tag-test.o && pahole -J tag-test.o && pahole --sort -F dwarf tag-test.o struct foo { int ()(void) * a; /* 0 8 */ /* size: 8, cachelines: 1, members: 1 */ /* last cacheline: 8 bytes */ }; $ clang -g -c tag-test.c -o tag-test.o && pahole -J tag-test.o && pahole --sort -F btf tag-test.o struct foo { int ()(void) * a; /* 0 8 */ /* size: 8, cachelines: 1, members: 1 */ /* last cacheline: 8 bytes */ }; What I don't understand is why pointer's type is LLVM_annotation. Probably, the cleanest solution would be to make DWARF and BTF loaders work in a similar way and attach LLVM_annotation as `annots` field of the `struct btf_type_tag_ptr_type`. Thus, avoiding 'LLVM_annotation's in the middle of type chains. I'll work on this.