| Message ID | 20221110144320.1075367-2-eddyz87@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | libbpf: btf_decl_tag attribute for btf dump in C format | expand |
On Thu, Nov 10, 2022 at 6:43 AM Eduard Zingerman <eddyz87@gmail.com> wrote: > > Clang's `__attribute__((btf_decl_tag("...")))` is represented in BTF > as a record of kind BTF_KIND_DECL_TAG with `type` field pointing to > the type annotated with this attribute. This commit adds > reconstitution of such attributes for BTF dump in C format. > > BTF doc says that BTF_KIND_DECL_TAGs should follow a target type but > this is not enforced and tests don't honor this restriction. > This commit uses hashmap to map types to the list of decl tags. > The hashmap is filled incrementally by the function > `btf_dump_assign_decl_tags` called from `btf_dump__dump_type` and > `btf_dump__dump_type_data`. > > It is assumed that total number of types annotated with decl tags is > relatively small, thus some space is saved by using hashmap instead of > adding a new field to `struct btf_dump_type_aux_state`. > > It is assumed that list of decl tags associated with a single type is > small. Thus the list is represented by an array which grows linearly. > > To accommodate older Clang versions decl tags are dumped using the > following macro: > > #if __has_attribute(btf_decl_tag) > #define __btf_decl_tag(x) __attribute__((btf_decl_tag(x))) > #else > #define __btf_decl_tag(x) > #endif > > The macro definition is emitted upon first call to `btf_dump__dump_type`. > > Clang allows to attach btf_decl_tag attributes to the following kinds > of items: > - struct/union supported > - struct/union field supported > - typedef supported > - global variables supported > - function prototype parameters supported > - function not applicable > - function parameter not applicable > - local variables not applicable > > Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> > --- > tools/lib/bpf/btf_dump.c | 181 +++++++++++++++++++++++++++++++++++++-- > 1 file changed, 173 insertions(+), 8 deletions(-) > [...] > +/* > + * Scans all BTF objects looking for BTF_KIND_DECL_TAG entries. > + * The id's of the entries are stored in the `btf_dump.decl_tags` table, > + * grouped by a target type. > + */ > +static int btf_dump_assign_decl_tags(struct btf_dump *d) > +{ > + __u32 id, new_cnt, type_cnt = btf__type_cnt(d->btf); > + struct decl_tag_array *old_tags, *new_tags; > + const struct btf_type *t; > + size_t new_sz; > + int err; > + > + for (id = d->next_decl_tag_scan_id; id < type_cnt; id++) { > + t = btf__type_by_id(d->btf, id); > + if (!btf_is_decl_tag(t)) > + continue; > + > + old_tags = NULL; > + hashmap__find(d->decl_tags, t->type, &old_tags); > + /* Assume small number of decl tags per id, increase array size by 1 */ > + new_cnt = old_tags ? old_tags->cnt + 1 : 1; > + if (new_cnt == UINT_MAX) > + return -ERANGE; this can't happen, BTF IDs don't go up to UINT_MAX even, let's drop unnecessary check > + new_sz = sizeof(struct decl_tag_array) + new_cnt * sizeof(old_tags->tag_ids[0]); > + new_tags = realloc(old_tags, new_sz); > + if (!new_tags) > + return -ENOMEM; > + > + new_tags->tag_ids[new_cnt - 1] = id; > + new_tags->cnt = new_cnt; > + > + /* No need to update the map if realloc have not changed the pointer */ > + if (old_tags == new_tags) > + continue; this is a nice and simple optimization, I like it > + > + err = hashmap__set(d->decl_tags, t->type, new_tags, NULL, NULL); > + if (!err) > + continue; > + /* > + * If old_tags != NULL there is a record that holds it in the map, thus > + * the hashmap__set() call should not fail as it does not have to > + * allocate. If it does fail for some bizarre reason it's a bug and double > + * free is imminent because of the previous realloc call. > + */ > + if (old_tags) > + pr_warn("hashmap__set() failed to update value for existing entry\n"); > + free(new_tags); > + return err; but this is an overkill, it should not fail and btf_dump is not the place to log bugs in hashmap, please do just (void)hashmap__set(...); > + } > + > + d->next_decl_tag_scan_id = type_cnt; > + > + return 0; > +} > + [...] > static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id) > @@ -1438,9 +1593,12 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, > } > case BTF_KIND_FUNC_PROTO: { > const struct btf_param *p = btf_params(t); > + struct decl_tag_array *decl_tags = NULL; > __u16 vlen = btf_vlen(t); > int i; > > + hashmap__find(d->decl_tags, id, &decl_tags); > + > /* > * GCC emits extra volatile qualifier for > * __attribute__((noreturn)) function pointers. Clang should there be btf_dump_emit_decl_tags(d, decl_tags, -1) somewhere here to emit tags of FUNC_PROTO itself? > @@ -1481,6 +1639,7 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, > > name = btf_name_of(d, p->name_off); > btf_dump_emit_type_decl(d, p->type, name, lvl); > + btf_dump_emit_decl_tags(d, decl_tags, i); > } > > btf_dump_printf(d, ")"); > @@ -1896,6 +2055,7 @@ static int btf_dump_var_data(struct btf_dump *d, > const void *data) > { > enum btf_func_linkage linkage = btf_var(v)->linkage; > + struct decl_tag_array *decl_tags = NULL; > const struct btf_type *t; > const char *l; > __u32 type_id; > @@ -1920,7 +2080,10 @@ static int btf_dump_var_data(struct btf_dump *d, > type_id = v->type; > t = btf__type_by_id(d->btf, type_id); > btf_dump_emit_type_cast(d, type_id, false); > - btf_dump_printf(d, " %s = ", btf_name_of(d, v->name_off)); > + btf_dump_printf(d, " %s", btf_name_of(d, v->name_off)); > + hashmap__find(d->decl_tags, id, &decl_tags); > + btf_dump_emit_decl_tags(d, decl_tags, -1); > + btf_dump_printf(d, " = "); > return btf_dump_dump_type_data(d, NULL, t, type_id, data, 0, 0); > } > > @@ -2421,6 +2584,8 @@ int btf_dump__dump_type_data(struct btf_dump *d, __u32 id, > d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false); > d->typed_dump->emit_zeroes = OPTS_GET(opts, emit_zeroes, false); > > + btf_dump_assign_decl_tags(d); > + I'm actually not sure we want those tags on binary data dump. Generally data dump is not type definition dump, so this seems unnecessary, it will just distract from data itself. Let's drop it for now? If there would be a need we can add it easily later. > ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0); > > d->typed_dump = NULL; > -- > 2.34.1 >
On Fri, 2022-11-11 at 10:58 -0800, Andrii Nakryiko wrote: > On Thu, Nov 10, 2022 at 6:43 AM Eduard Zingerman <eddyz87@gmail.com> wrote: > > > [...] > > > static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id) > > @@ -1438,9 +1593,12 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, > > } > > case BTF_KIND_FUNC_PROTO: { > > const struct btf_param *p = btf_params(t); > > + struct decl_tag_array *decl_tags = NULL; > > __u16 vlen = btf_vlen(t); > > int i; > > > > + hashmap__find(d->decl_tags, id, &decl_tags); > > + > > /* > > * GCC emits extra volatile qualifier for > > * __attribute__((noreturn)) function pointers. Clang > > should there be btf_dump_emit_decl_tags(d, decl_tags, -1) somewhere > here to emit tags of FUNC_PROTO itself? Actually, I have not found a way to attach decl tag to a FUNC_PROTO itself: typedef void (*fn)(void) __decl_tag("..."); // here tag is attached to typedef struct foo { void (*fn)(void) __decl_tag("..."); // here tag is attached to a foo.fn field } void foo(void (*fn)(void) __decl_tag("...")); // here tag is attached to FUNC foo // parameter but should probably // be attached to // FUNC_PROTO parameter instead. Also, I think that Yonghong had reservations about decl tags attached to FUNC_PROTO parameters. Yonghong, could you please comment? > > > @@ -1481,6 +1639,7 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, > > > > name = btf_name_of(d, p->name_off); > > btf_dump_emit_type_decl(d, p->type, name, lvl); > > + btf_dump_emit_decl_tags(d, decl_tags, i); > > } > > > > btf_dump_printf(d, ")"); > > @@ -1896,6 +2055,7 @@ static int btf_dump_var_data(struct btf_dump *d, > > const void *data) > > { > > enum btf_func_linkage linkage = btf_var(v)->linkage; > > + struct decl_tag_array *decl_tags = NULL; > > const struct btf_type *t; > > const char *l; > > __u32 type_id; > > @@ -1920,7 +2080,10 @@ static int btf_dump_var_data(struct btf_dump *d, > > type_id = v->type; > > t = btf__type_by_id(d->btf, type_id); > > btf_dump_emit_type_cast(d, type_id, false); > > - btf_dump_printf(d, " %s = ", btf_name_of(d, v->name_off)); > > + btf_dump_printf(d, " %s", btf_name_of(d, v->name_off)); > > + hashmap__find(d->decl_tags, id, &decl_tags); > > + btf_dump_emit_decl_tags(d, decl_tags, -1); > > + btf_dump_printf(d, " = "); > > return btf_dump_dump_type_data(d, NULL, t, type_id, data, 0, 0); > > } > > > > @@ -2421,6 +2584,8 @@ int btf_dump__dump_type_data(struct btf_dump *d, __u32 id, > > d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false); > > d->typed_dump->emit_zeroes = OPTS_GET(opts, emit_zeroes, false); > > > > + btf_dump_assign_decl_tags(d); > > + > > I'm actually not sure we want those tags on binary data dump. > Generally data dump is not type definition dump, so this seems > unnecessary, it will just distract from data itself. Let's drop it for > now? If there would be a need we can add it easily later. Well, this is the only place where VARs are processed, removing this code would make the second patch in a series useless. But I like my second patch in a series :) should I just drop it? I can extract it as a separate series and simplify some of the existing data dump tests. > > > ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0); > > > > d->typed_dump = NULL; > > -- > > 2.34.1 > >
On Fri, Nov 11, 2022 at 1:30 PM Eduard Zingerman <eddyz87@gmail.com> wrote: > > On Fri, 2022-11-11 at 10:58 -0800, Andrii Nakryiko wrote: > > On Thu, Nov 10, 2022 at 6:43 AM Eduard Zingerman <eddyz87@gmail.com> wrote: > > > > > > [...] > > > > > static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id) > > > @@ -1438,9 +1593,12 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, > > > } > > > case BTF_KIND_FUNC_PROTO: { > > > const struct btf_param *p = btf_params(t); > > > + struct decl_tag_array *decl_tags = NULL; > > > __u16 vlen = btf_vlen(t); > > > int i; > > > > > > + hashmap__find(d->decl_tags, id, &decl_tags); > > > + > > > /* > > > * GCC emits extra volatile qualifier for > > > * __attribute__((noreturn)) function pointers. Clang > > > > should there be btf_dump_emit_decl_tags(d, decl_tags, -1) somewhere > > here to emit tags of FUNC_PROTO itself? > > Actually, I have not found a way to attach decl tag to a FUNC_PROTO itself: I'll need to check with Yonghong, but I think what happens right now with decl_tag being attached to FUNC instead of its underlying FUNC_PROTO might be a bug (or maybe it's by design, but certainly is quite confusing as FUNC itself doesn't have arguments, so component_idx != -1 is a bit weird). But regardless if Clang allows you to express it in C code today or not, if we support decl_tags on func proto args, for completeness let's support it also on func_proto itself (comp_idx == -1). You can build BTF manually for test, just like you do it for func_proto args, right? > > typedef void (*fn)(void) __decl_tag("..."); // here tag is attached to typedef > struct foo { > void (*fn)(void) __decl_tag("..."); // here tag is attached to a foo.fn field > } > void foo(void (*fn)(void) __decl_tag("...")); // here tag is attached to FUNC foo > // parameter but should probably > // be attached to > // FUNC_PROTO parameter instead. > > Also, I think that Yonghong had reservations about decl tags attached to > FUNC_PROTO parameters. > Yonghong, could you please comment? yep, curious to hear as well > > > > > > @@ -1481,6 +1639,7 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, > > > > > > name = btf_name_of(d, p->name_off); > > > btf_dump_emit_type_decl(d, p->type, name, lvl); > > > + btf_dump_emit_decl_tags(d, decl_tags, i); > > > } > > > > > > btf_dump_printf(d, ")"); > > > @@ -1896,6 +2055,7 @@ static int btf_dump_var_data(struct btf_dump *d, > > > const void *data) > > > { > > > enum btf_func_linkage linkage = btf_var(v)->linkage; > > > + struct decl_tag_array *decl_tags = NULL; > > > const struct btf_type *t; > > > const char *l; > > > __u32 type_id; > > > @@ -1920,7 +2080,10 @@ static int btf_dump_var_data(struct btf_dump *d, > > > type_id = v->type; > > > t = btf__type_by_id(d->btf, type_id); > > > btf_dump_emit_type_cast(d, type_id, false); > > > - btf_dump_printf(d, " %s = ", btf_name_of(d, v->name_off)); > > > + btf_dump_printf(d, " %s", btf_name_of(d, v->name_off)); > > > + hashmap__find(d->decl_tags, id, &decl_tags); > > > + btf_dump_emit_decl_tags(d, decl_tags, -1); > > > + btf_dump_printf(d, " = "); > > > return btf_dump_dump_type_data(d, NULL, t, type_id, data, 0, 0); > > > } > > > > > > @@ -2421,6 +2584,8 @@ int btf_dump__dump_type_data(struct btf_dump *d, __u32 id, > > > d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false); > > > d->typed_dump->emit_zeroes = OPTS_GET(opts, emit_zeroes, false); > > > > > > + btf_dump_assign_decl_tags(d); > > > + > > > > I'm actually not sure we want those tags on binary data dump. > > Generally data dump is not type definition dump, so this seems > > unnecessary, it will just distract from data itself. Let's drop it for > > now? If there would be a need we can add it easily later. > > Well, this is the only place where VARs are processed, removing this code > would make the second patch in a series useless. > But I like my second patch in a series :) should I just drop it? > I can extract it as a separate series and simplify some of the existing > data dump tests. yep, data dump tests can be completely orthogonal, send them separately if you are attached to that code ;) but for decl_tags on dump_type_data() I'd rather be conservative for now, unless in practice those decl_tags will turn out to be needed > > > > > > ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0); > > > > > > d->typed_dump = NULL; > > > -- > > > 2.34.1 > > > >
On 11/11/22 1:30 PM, Eduard Zingerman wrote: > On Fri, 2022-11-11 at 10:58 -0800, Andrii Nakryiko wrote: >> On Thu, Nov 10, 2022 at 6:43 AM Eduard Zingerman <eddyz87@gmail.com> wrote: >> >> >> [...] >> >>> static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id) >>> @@ -1438,9 +1593,12 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, >>> } >>> case BTF_KIND_FUNC_PROTO: { >>> const struct btf_param *p = btf_params(t); >>> + struct decl_tag_array *decl_tags = NULL; >>> __u16 vlen = btf_vlen(t); >>> int i; >>> >>> + hashmap__find(d->decl_tags, id, &decl_tags); >>> + >>> /* >>> * GCC emits extra volatile qualifier for >>> * __attribute__((noreturn)) function pointers. Clang >> >> should there be btf_dump_emit_decl_tags(d, decl_tags, -1) somewhere >> here to emit tags of FUNC_PROTO itself? > > Actually, I have not found a way to attach decl tag to a FUNC_PROTO itself: > > typedef void (*fn)(void) __decl_tag("..."); // here tag is attached to typedef > struct foo { > void (*fn)(void) __decl_tag("..."); // here tag is attached to a foo.fn field > } > void foo(void (*fn)(void) __decl_tag("...")); // here tag is attached to FUNC foo > // parameter but should probably > // be attached to > // FUNC_PROTO parameter instead. > > Also, I think that Yonghong had reservations about decl tags attached to > FUNC_PROTO parameters. > Yonghong, could you please comment? Currently, btf decl tag is not supported to attach FUNC_PROTO parameters. We could add support in clang, do we have an actual use case for this? if there is a use case, we can add support for it. > >> >>> @@ -1481,6 +1639,7 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, >>> >>> name = btf_name_of(d, p->name_off); >>> btf_dump_emit_type_decl(d, p->type, name, lvl); >>> + btf_dump_emit_decl_tags(d, decl_tags, i); >>> } >>> >>> btf_dump_printf(d, ")"); >>> @@ -1896,6 +2055,7 @@ static int btf_dump_var_data(struct btf_dump *d, >>> const void *data) >>> { >>> enum btf_func_linkage linkage = btf_var(v)->linkage; >>> + struct decl_tag_array *decl_tags = NULL; >>> const struct btf_type *t; >>> const char *l; >>> __u32 type_id; >>> @@ -1920,7 +2080,10 @@ static int btf_dump_var_data(struct btf_dump *d, >>> type_id = v->type; >>> t = btf__type_by_id(d->btf, type_id); >>> btf_dump_emit_type_cast(d, type_id, false); >>> - btf_dump_printf(d, " %s = ", btf_name_of(d, v->name_off)); >>> + btf_dump_printf(d, " %s", btf_name_of(d, v->name_off)); >>> + hashmap__find(d->decl_tags, id, &decl_tags); >>> + btf_dump_emit_decl_tags(d, decl_tags, -1); >>> + btf_dump_printf(d, " = "); >>> return btf_dump_dump_type_data(d, NULL, t, type_id, data, 0, 0); >>> } >>> >>> @@ -2421,6 +2584,8 @@ int btf_dump__dump_type_data(struct btf_dump *d, __u32 id, >>> d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false); >>> d->typed_dump->emit_zeroes = OPTS_GET(opts, emit_zeroes, false); >>> >>> + btf_dump_assign_decl_tags(d); >>> + >> >> I'm actually not sure we want those tags on binary data dump. >> Generally data dump is not type definition dump, so this seems >> unnecessary, it will just distract from data itself. Let's drop it for >> now? If there would be a need we can add it easily later. > > Well, this is the only place where VARs are processed, removing this code > would make the second patch in a series useless. > But I like my second patch in a series :) should I just drop it? > I can extract it as a separate series and simplify some of the existing > data dump tests. > >> >>> ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0); >>> >>> d->typed_dump = NULL; >>> -- >>> 2.34.1 >>> >
On 11/15/22 12:45 PM, Yonghong Song wrote: > > > On 11/11/22 1:30 PM, Eduard Zingerman wrote: >> On Fri, 2022-11-11 at 10:58 -0800, Andrii Nakryiko wrote: >>> On Thu, Nov 10, 2022 at 6:43 AM Eduard Zingerman <eddyz87@gmail.com> >>> wrote: >>> >>> >>> [...] >>> >>>> static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id) >>>> @@ -1438,9 +1593,12 @@ static void btf_dump_emit_type_chain(struct >>>> btf_dump *d, >>>> } >>>> case BTF_KIND_FUNC_PROTO: { >>>> const struct btf_param *p = btf_params(t); >>>> + struct decl_tag_array *decl_tags = NULL; >>>> __u16 vlen = btf_vlen(t); >>>> int i; >>>> >>>> + hashmap__find(d->decl_tags, id, &decl_tags); >>>> + >>>> /* >>>> * GCC emits extra volatile qualifier for >>>> * __attribute__((noreturn)) function >>>> pointers. Clang >>> >>> should there be btf_dump_emit_decl_tags(d, decl_tags, -1) somewhere >>> here to emit tags of FUNC_PROTO itself? >> >> Actually, I have not found a way to attach decl tag to a FUNC_PROTO >> itself: >> >> typedef void (*fn)(void) __decl_tag("..."); // here tag is attached >> to typedef >> struct foo { >> void (*fn)(void) __decl_tag("..."); // here tag is attached to a >> foo.fn field >> } >> void foo(void (*fn)(void) __decl_tag("...")); // here tag is >> attached to FUNC foo >> // parameter but >> should probably >> // be attached to >> // FUNC_PROTO >> parameter instead. >> >> Also, I think that Yonghong had reservations about decl tags attached to >> FUNC_PROTO parameters. >> Yonghong, could you please comment? > > Currently, btf decl tag is not supported to attach FUNC_PROTO > parameters. We could add support in clang, do we have an actual use case > for this? if there is a use case, we can add support for it. > >> >>> >>>> @@ -1481,6 +1639,7 @@ static void btf_dump_emit_type_chain(struct >>>> btf_dump *d, >>>> >>>> name = btf_name_of(d, p->name_off); >>>> btf_dump_emit_type_decl(d, p->type, >>>> name, lvl); >>>> + btf_dump_emit_decl_tags(d, >>>> decl_tags, i); >>>> } >>>> >>>> btf_dump_printf(d, ")"); >>>> @@ -1896,6 +2055,7 @@ static int btf_dump_var_data(struct btf_dump *d, >>>> const void *data) >>>> { >>>> enum btf_func_linkage linkage = btf_var(v)->linkage; >>>> + struct decl_tag_array *decl_tags = NULL; >>>> const struct btf_type *t; >>>> const char *l; >>>> __u32 type_id; >>>> @@ -1920,7 +2080,10 @@ static int btf_dump_var_data(struct btf_dump *d, >>>> type_id = v->type; >>>> t = btf__type_by_id(d->btf, type_id); >>>> btf_dump_emit_type_cast(d, type_id, false); >>>> - btf_dump_printf(d, " %s = ", btf_name_of(d, v->name_off)); >>>> + btf_dump_printf(d, " %s", btf_name_of(d, v->name_off)); >>>> + hashmap__find(d->decl_tags, id, &decl_tags); >>>> + btf_dump_emit_decl_tags(d, decl_tags, -1); >>>> + btf_dump_printf(d, " = "); >>>> return btf_dump_dump_type_data(d, NULL, t, type_id, data, >>>> 0, 0); >>>> } >>>> >>>> @@ -2421,6 +2584,8 @@ int btf_dump__dump_type_data(struct btf_dump >>>> *d, __u32 id, >>>> d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false); >>>> d->typed_dump->emit_zeroes = OPTS_GET(opts, emit_zeroes, >>>> false); >>>> >>>> + btf_dump_assign_decl_tags(d); >>>> + >>> >>> I'm actually not sure we want those tags on binary data dump. >>> Generally data dump is not type definition dump, so this seems >>> unnecessary, it will just distract from data itself. Let's drop it for >>> now? If there would be a need we can add it easily later. >> >> Well, this is the only place where VARs are processed, removing this code >> would make the second patch in a series useless. >> But I like my second patch in a series :) should I just drop it? >> I can extract it as a separate series and simplify some of the existing >> data dump tests. BTW, current use case of decl tag in the kernel is from Kumar's link list patch set: https://lore.kernel.org/bpf/20221114191547.1694267-23-memxor@gmail.com/ +#define __contains(name, node) __attribute__((btf_decl_tag("contains:" #name ":" #node))) to tag the struct member bpf_list_head as below: struct foo { struct bpf_list_node node; int data; }; struct map_value { struct bpf_list_head head __contains(foo, node); }; https://lore.kernel.org/bpf/20221114191547.1694267-5-memxor@gmail.com/ >> >>> >>>> ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0); >>>> >>>> d->typed_dump = NULL; >>>> -- >>>> 2.34.1 >>>> >>
On Mon, 2022-11-14 at 11:56 -0800, Andrii Nakryiko wrote: > On Fri, Nov 11, 2022 at 1:30 PM Eduard Zingerman <eddyz87@gmail.com> wrote: > > > > On Fri, 2022-11-11 at 10:58 -0800, Andrii Nakryiko wrote: > > > On Thu, Nov 10, 2022 at 6:43 AM Eduard Zingerman <eddyz87@gmail.com> wrote: > > > > > > > > > [...] > > > > > > > static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id) > > > > @@ -1438,9 +1593,12 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, > > > > } > > > > case BTF_KIND_FUNC_PROTO: { > > > > const struct btf_param *p = btf_params(t); > > > > + struct decl_tag_array *decl_tags = NULL; > > > > __u16 vlen = btf_vlen(t); > > > > int i; > > > > > > > > + hashmap__find(d->decl_tags, id, &decl_tags); > > > > + > > > > /* > > > > * GCC emits extra volatile qualifier for > > > > * __attribute__((noreturn)) function pointers. Clang > > > > > > should there be btf_dump_emit_decl_tags(d, decl_tags, -1) somewhere > > > here to emit tags of FUNC_PROTO itself? > > > > Actually, I have not found a way to attach decl tag to a FUNC_PROTO itself: > > I'll need to check with Yonghong, but I think what happens right now > with decl_tag being attached to FUNC instead of its underlying > FUNC_PROTO might be a bug (or maybe it's by design, but certainly is > quite confusing as FUNC itself doesn't have arguments, so > component_idx != -1 is a bit weird). > > But regardless if Clang allows you to express it in C code today or > not, if we support decl_tags on func proto args, for completeness > let's support it also on func_proto itself (comp_idx == -1). You can > build BTF manually for test, just like you do it for func_proto args, > right? I can construct the BTF manually, but I need a place in C where __decl_tag would be printed for such proto and currently there is no such place. As Yonghong suggests in a sibling comment there are currently no use-cases for decl tags on functions, function protos or function proto parameters. I suggest to drop these places from the current patch and get back to it when the need arises. > > > > typedef void (*fn)(void) __decl_tag("..."); // here tag is attached to typedef > > struct foo { > > void (*fn)(void) __decl_tag("..."); // here tag is attached to a foo.fn field > > } > > void foo(void (*fn)(void) __decl_tag("...")); // here tag is attached to FUNC foo > > // parameter but should probably > > // be attached to > > // FUNC_PROTO parameter instead. > > > > Also, I think that Yonghong had reservations about decl tags attached to > > FUNC_PROTO parameters. > > Yonghong, could you please comment? > > yep, curious to hear as well > > > > > > > > > > > @@ -1481,6 +1639,7 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, > > > > > > > > name = btf_name_of(d, p->name_off); > > > > btf_dump_emit_type_decl(d, p->type, name, lvl); > > > > + btf_dump_emit_decl_tags(d, decl_tags, i); > > > > } > > > > > > > > btf_dump_printf(d, ")"); > > > > @@ -1896,6 +2055,7 @@ static int btf_dump_var_data(struct btf_dump *d, > > > > const void *data) > > > > { > > > > enum btf_func_linkage linkage = btf_var(v)->linkage; > > > > + struct decl_tag_array *decl_tags = NULL; > > > > const struct btf_type *t; > > > > const char *l; > > > > __u32 type_id; > > > > @@ -1920,7 +2080,10 @@ static int btf_dump_var_data(struct btf_dump *d, > > > > type_id = v->type; > > > > t = btf__type_by_id(d->btf, type_id); > > > > btf_dump_emit_type_cast(d, type_id, false); > > > > - btf_dump_printf(d, " %s = ", btf_name_of(d, v->name_off)); > > > > + btf_dump_printf(d, " %s", btf_name_of(d, v->name_off)); > > > > + hashmap__find(d->decl_tags, id, &decl_tags); > > > > + btf_dump_emit_decl_tags(d, decl_tags, -1); > > > > + btf_dump_printf(d, " = "); > > > > return btf_dump_dump_type_data(d, NULL, t, type_id, data, 0, 0); > > > > } > > > > > > > > @@ -2421,6 +2584,8 @@ int btf_dump__dump_type_data(struct btf_dump *d, __u32 id, > > > > d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false); > > > > d->typed_dump->emit_zeroes = OPTS_GET(opts, emit_zeroes, false); > > > > > > > > + btf_dump_assign_decl_tags(d); > > > > + > > > > > > I'm actually not sure we want those tags on binary data dump. > > > Generally data dump is not type definition dump, so this seems > > > unnecessary, it will just distract from data itself. Let's drop it for > > > now? If there would be a need we can add it easily later. > > > > Well, this is the only place where VARs are processed, removing this code > > would make the second patch in a series useless. > > But I like my second patch in a series :) should I just drop it? > > I can extract it as a separate series and simplify some of the existing > > data dump tests. > > yep, data dump tests can be completely orthogonal, send them > separately if you are attached to that code ;) > > but for decl_tags on dump_type_data() I'd rather be conservative for > now, unless in practice those decl_tags will turn out to be needed > > > > > > > > > > > ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0); > > > > > > > > d->typed_dump = NULL; > > > > -- > > > > 2.34.1 > > > > > >
On Tue, Nov 15, 2022 at 5:51 PM Eduard Zingerman <eddyz87@gmail.com> wrote: > > On Mon, 2022-11-14 at 11:56 -0800, Andrii Nakryiko wrote: > > On Fri, Nov 11, 2022 at 1:30 PM Eduard Zingerman <eddyz87@gmail.com> wrote: > > > > > > On Fri, 2022-11-11 at 10:58 -0800, Andrii Nakryiko wrote: > > > > On Thu, Nov 10, 2022 at 6:43 AM Eduard Zingerman <eddyz87@gmail.com> wrote: > > > > > > > > > > > > [...] > > > > > > > > > static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id) > > > > > @@ -1438,9 +1593,12 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, > > > > > } > > > > > case BTF_KIND_FUNC_PROTO: { > > > > > const struct btf_param *p = btf_params(t); > > > > > + struct decl_tag_array *decl_tags = NULL; > > > > > __u16 vlen = btf_vlen(t); > > > > > int i; > > > > > > > > > > + hashmap__find(d->decl_tags, id, &decl_tags); > > > > > + > > > > > /* > > > > > * GCC emits extra volatile qualifier for > > > > > * __attribute__((noreturn)) function pointers. Clang > > > > > > > > should there be btf_dump_emit_decl_tags(d, decl_tags, -1) somewhere > > > > here to emit tags of FUNC_PROTO itself? > > > > > > Actually, I have not found a way to attach decl tag to a FUNC_PROTO itself: > > > > I'll need to check with Yonghong, but I think what happens right now > > with decl_tag being attached to FUNC instead of its underlying > > FUNC_PROTO might be a bug (or maybe it's by design, but certainly is > > quite confusing as FUNC itself doesn't have arguments, so > > component_idx != -1 is a bit weird). > > > > But regardless if Clang allows you to express it in C code today or > > not, if we support decl_tags on func proto args, for completeness > > let's support it also on func_proto itself (comp_idx == -1). You can > > build BTF manually for test, just like you do it for func_proto args, > > right? > > I can construct the BTF manually, but I need a place in C where > __decl_tag would be printed for such proto and currently there is no > such place. after func prototype definition: $ cat t.c #include <stdio.h> typedef int (* ff)(void *arg) __attribute__((nonnull(1))); static int blah(void *x) { return (int)(long)x; } int main() { int (*f1)(void *arg) __attribute__((nonnull(1))) = blah; ff f2 = blah; blah(NULL); f1(NULL); f2(NULL); printf("%lx %lx\n", (long)f1, (long)f2); return 0; } $ cc -g t.c -Wnonnull && ./a.out t.c: In function ‘main’: t.c:13:9: warning: argument 1 null where non-null expected [-Wnonnull] 13 | f1(NULL); | ^~ t.c:14:9: warning: argument 1 null where non-null expected [-Wnonnull] 14 | f2(NULL); | ^~ 401126 401126 Note that blah(NULL) doesn't generate a warning, which means nonnull attributes are applied only to func_proto. > > As Yonghong suggests in a sibling comment there are currently no > use-cases for decl tags on functions, function protos or function > proto parameters. I suggest to drop these places from the current > patch and get back to it when the need arises. decl_tags for functions and function protos are natural extensions of decl_tags for fields/structs/variables, so let's do the proper support for all conceivable use cases instead of doing this in a few months again. There is not ambiguity here. And btw, we do have decl_tags for FUNCs right now, and that seems wrong, because FUNC itself doesn't have arguments, it only points to FUNC_PROTO. So it seems like decl_tags should be moved to FUNC_PROTO instead anyways? > > > > > > > typedef void (*fn)(void) __decl_tag("..."); // here tag is attached to typedef > > > struct foo { > > > void (*fn)(void) __decl_tag("..."); // here tag is attached to a foo.fn field > > > } > > > void foo(void (*fn)(void) __decl_tag("...")); // here tag is attached to FUNC foo > > > // parameter but should probably > > > // be attached to > > > // FUNC_PROTO parameter instead. > > > > > > Also, I think that Yonghong had reservations about decl tags attached to > > > FUNC_PROTO parameters. > > > Yonghong, could you please comment? > > > > yep, curious to hear as well > > > > > > > > > > > > > > > > @@ -1481,6 +1639,7 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, > > > > > > > > > > name = btf_name_of(d, p->name_off); > > > > > btf_dump_emit_type_decl(d, p->type, name, lvl); > > > > > + btf_dump_emit_decl_tags(d, decl_tags, i); > > > > > } > > > > > > > > > > btf_dump_printf(d, ")"); > > > > > @@ -1896,6 +2055,7 @@ static int btf_dump_var_data(struct btf_dump *d, > > > > > const void *data) > > > > > { > > > > > enum btf_func_linkage linkage = btf_var(v)->linkage; > > > > > + struct decl_tag_array *decl_tags = NULL; > > > > > const struct btf_type *t; > > > > > const char *l; > > > > > __u32 type_id; > > > > > @@ -1920,7 +2080,10 @@ static int btf_dump_var_data(struct btf_dump *d, > > > > > type_id = v->type; > > > > > t = btf__type_by_id(d->btf, type_id); > > > > > btf_dump_emit_type_cast(d, type_id, false); > > > > > - btf_dump_printf(d, " %s = ", btf_name_of(d, v->name_off)); > > > > > + btf_dump_printf(d, " %s", btf_name_of(d, v->name_off)); > > > > > + hashmap__find(d->decl_tags, id, &decl_tags); > > > > > + btf_dump_emit_decl_tags(d, decl_tags, -1); > > > > > + btf_dump_printf(d, " = "); > > > > > return btf_dump_dump_type_data(d, NULL, t, type_id, data, 0, 0); > > > > > } > > > > > > > > > > @@ -2421,6 +2584,8 @@ int btf_dump__dump_type_data(struct btf_dump *d, __u32 id, > > > > > d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false); > > > > > d->typed_dump->emit_zeroes = OPTS_GET(opts, emit_zeroes, false); > > > > > > > > > > + btf_dump_assign_decl_tags(d); > > > > > + > > > > > > > > I'm actually not sure we want those tags on binary data dump. > > > > Generally data dump is not type definition dump, so this seems > > > > unnecessary, it will just distract from data itself. Let's drop it for > > > > now? If there would be a need we can add it easily later. > > > > > > Well, this is the only place where VARs are processed, removing this code > > > would make the second patch in a series useless. > > > But I like my second patch in a series :) should I just drop it? > > > I can extract it as a separate series and simplify some of the existing > > > data dump tests. > > > > yep, data dump tests can be completely orthogonal, send them > > separately if you are attached to that code ;) > > > > but for decl_tags on dump_type_data() I'd rather be conservative for > > now, unless in practice those decl_tags will turn out to be needed > > > > > > > > > > > > > > > > ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0); > > > > > > > > > > d->typed_dump = NULL; > > > > > -- > > > > > 2.34.1 > > > > > > > > >
diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c index 12f7039e0ab2..1cbc0da43cb4 100644 --- a/tools/lib/bpf/btf_dump.c +++ b/tools/lib/bpf/btf_dump.c @@ -75,6 +75,14 @@ struct btf_dump_data { bool is_array_char; }; +/* + * An array of ids of BTF_DECL_TAG objects associated with a specific type. + */ +struct decl_tag_array { + __u32 cnt; + __u32 tag_ids[0]; +}; + struct btf_dump { const struct btf *btf; btf_dump_printf_fn_t printf_fn; @@ -111,6 +119,18 @@ struct btf_dump { * name occurrences */ struct hashmap *ident_names; + /* + * maps type id to decl_tag_array, assume that relatively small + * fraction of types has btf_decl_tag's attached + */ + struct hashmap *decl_tags; + /* indicates whether '#define __btf_decl_tag ...' was printed */ + bool btf_decl_tag_is_defined; + /* + * next id to be scanned for decl tags presence, needed to update + * decl_tags map when dump_type calls are interleaved with BTF updates. + */ + __u32 next_decl_tag_scan_id; /* * data for typed display; allocated if needed. */ @@ -127,6 +147,16 @@ static bool str_equal_fn(long a, long b, void *ctx) return strcmp((void *)a, (void *)b) == 0; } +static size_t identity_hash_fn(long key, void *ctx) +{ + return (size_t)key; +} + +static bool identity_equal_fn(long k1, long k2, void *ctx) +{ + return k1 == k2; +} + static const char *btf_name_of(const struct btf_dump *d, __u32 name_off) { return btf__name_by_offset(d->btf, name_off); @@ -143,6 +173,7 @@ static void btf_dump_printf(const struct btf_dump *d, const char *fmt, ...) static int btf_dump_mark_referenced(struct btf_dump *d); static int btf_dump_resize(struct btf_dump *d); +static int btf_dump_assign_decl_tags(struct btf_dump *d); struct btf_dump *btf_dump__new(const struct btf *btf, btf_dump_printf_fn_t printf_fn, @@ -170,15 +201,19 @@ struct btf_dump *btf_dump__new(const struct btf *btf, d->type_names = hashmap__new(str_hash_fn, str_equal_fn, NULL); if (IS_ERR(d->type_names)) { err = PTR_ERR(d->type_names); - d->type_names = NULL; goto err; } d->ident_names = hashmap__new(str_hash_fn, str_equal_fn, NULL); if (IS_ERR(d->ident_names)) { err = PTR_ERR(d->ident_names); - d->ident_names = NULL; goto err; } + d->decl_tags = hashmap__new(identity_hash_fn, identity_equal_fn, NULL); + if (IS_ERR(d->decl_tags)) { + err = PTR_ERR(d->decl_tags); + goto err; + } + d->next_decl_tag_scan_id = 1; err = btf_dump_resize(d); if (err) @@ -219,13 +254,20 @@ static int btf_dump_resize(struct btf_dump *d) return 0; } -static void btf_dump_free_names(struct hashmap *map) +static void btf_dump_free_strs_map(struct hashmap *map, bool free_keys, bool free_values) { size_t bkt; struct hashmap_entry *cur; - hashmap__for_each_entry(map, cur, bkt) - free((void *)cur->pkey); + if (IS_ERR_OR_NULL(map)) + return; + + hashmap__for_each_entry(map, cur, bkt) { + if (free_keys) + free((void *)cur->pkey); + if (free_values) + free(cur->pvalue); + } hashmap__free(map); } @@ -248,14 +290,16 @@ void btf_dump__free(struct btf_dump *d) free(d->cached_names); free(d->emit_queue); free(d->decl_stack); - btf_dump_free_names(d->type_names); - btf_dump_free_names(d->ident_names); + btf_dump_free_strs_map(d->type_names, true, false); + btf_dump_free_strs_map(d->ident_names, true, false); + btf_dump_free_strs_map(d->decl_tags, false, true); free(d); } static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr); static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id); +static void btf_dump_ensure_btf_decl_tag_macro(struct btf_dump *d); /* * Dump BTF type in a compilable C syntax, including all the necessary @@ -284,6 +328,9 @@ int btf_dump__dump_type(struct btf_dump *d, __u32 id) if (err) return libbpf_err(err); + btf_dump_ensure_btf_decl_tag_macro(d); + btf_dump_assign_decl_tags(d); + d->emit_queue_cnt = 0; err = btf_dump_order_type(d, id, false); if (err < 0) @@ -373,6 +420,62 @@ static int btf_dump_mark_referenced(struct btf_dump *d) return 0; } +/* + * Scans all BTF objects looking for BTF_KIND_DECL_TAG entries. + * The id's of the entries are stored in the `btf_dump.decl_tags` table, + * grouped by a target type. + */ +static int btf_dump_assign_decl_tags(struct btf_dump *d) +{ + __u32 id, new_cnt, type_cnt = btf__type_cnt(d->btf); + struct decl_tag_array *old_tags, *new_tags; + const struct btf_type *t; + size_t new_sz; + int err; + + for (id = d->next_decl_tag_scan_id; id < type_cnt; id++) { + t = btf__type_by_id(d->btf, id); + if (!btf_is_decl_tag(t)) + continue; + + old_tags = NULL; + hashmap__find(d->decl_tags, t->type, &old_tags); + /* Assume small number of decl tags per id, increase array size by 1 */ + new_cnt = old_tags ? old_tags->cnt + 1 : 1; + if (new_cnt == UINT_MAX) + return -ERANGE; + new_sz = sizeof(struct decl_tag_array) + new_cnt * sizeof(old_tags->tag_ids[0]); + new_tags = realloc(old_tags, new_sz); + if (!new_tags) + return -ENOMEM; + + new_tags->tag_ids[new_cnt - 1] = id; + new_tags->cnt = new_cnt; + + /* No need to update the map if realloc have not changed the pointer */ + if (old_tags == new_tags) + continue; + + err = hashmap__set(d->decl_tags, t->type, new_tags, NULL, NULL); + if (!err) + continue; + /* + * If old_tags != NULL there is a record that holds it in the map, thus + * the hashmap__set() call should not fail as it does not have to + * allocate. If it does fail for some bizarre reason it's a bug and double + * free is imminent because of the previous realloc call. + */ + if (old_tags) + pr_warn("hashmap__set() failed to update value for existing entry\n"); + free(new_tags); + return err; + } + + d->next_decl_tag_scan_id = type_cnt; + + return 0; +} + static int btf_dump_add_emit_queue_id(struct btf_dump *d, __u32 id) { __u32 *new_queue; @@ -899,6 +1002,51 @@ static void btf_dump_emit_bit_padding(const struct btf_dump *d, } } +/* + * Define __btf_decl_tag to be either __attribute__ or noop. + */ +static void btf_dump_ensure_btf_decl_tag_macro(struct btf_dump *d) +{ + if (d->btf_decl_tag_is_defined || !hashmap__size(d->decl_tags)) + return; + + d->btf_decl_tag_is_defined = true; + btf_dump_printf(d, "#if __has_attribute(btf_decl_tag)\n"); + btf_dump_printf(d, "#define __btf_decl_tag(x) __attribute__((btf_decl_tag(x)))\n"); + btf_dump_printf(d, "#else\n"); + btf_dump_printf(d, "#define __btf_decl_tag(x)\n"); + btf_dump_printf(d, "#endif\n\n"); +} + +/* + * Emits a list of __btf_decl_tag(...) attributes attached to some type. + * Decl tags attached to a type and to it's fields reside in a same + * list, thus use component_idx to filter out relevant tags: + * - component_idx == -1 designates the type itself; + * - component_idx >= 0 designates specific field. + */ +static void btf_dump_emit_decl_tags(struct btf_dump *d, + struct decl_tag_array *decl_tags, + int component_idx) +{ + struct btf_type *t; + const char *text; + struct btf_decl_tag *tag; + __u32 i; + + if (!decl_tags) + return; + + for (i = 0; i < decl_tags->cnt; ++i) { + t = btf_type_by_id(d->btf, decl_tags->tag_ids[i]); + tag = btf_decl_tag(t); + if (tag->component_idx != component_idx) + continue; + text = btf__name_by_offset(d->btf, t->name_off); + btf_dump_printf(d, " __btf_decl_tag(\"%s\")", text); + } +} + static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id, const struct btf_type *t) { @@ -914,11 +1062,13 @@ static void btf_dump_emit_struct_def(struct btf_dump *d, int lvl) { const struct btf_member *m = btf_members(t); + struct decl_tag_array *decl_tags = NULL; bool is_struct = btf_is_struct(t); int align, i, packed, off = 0; __u16 vlen = btf_vlen(t); packed = is_struct ? btf_is_struct_packed(d->btf, id, t) : 0; + hashmap__find(d->decl_tags, id, &decl_tags); btf_dump_printf(d, "%s%s%s {", is_struct ? "struct" : "union", @@ -945,6 +1095,7 @@ static void btf_dump_emit_struct_def(struct btf_dump *d, m_sz = max((__s64)0, btf__resolve_size(d->btf, m->type)); off = m_off + m_sz * 8; } + btf_dump_emit_decl_tags(d, decl_tags, i); btf_dump_printf(d, ";"); } @@ -964,6 +1115,7 @@ static void btf_dump_emit_struct_def(struct btf_dump *d, btf_dump_printf(d, "%s}", pfx(lvl)); if (packed) btf_dump_printf(d, " __attribute__((packed))"); + btf_dump_emit_decl_tags(d, decl_tags, -1); } static const char *missing_base_types[][2] = { @@ -1090,6 +1242,7 @@ static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id, const struct btf_type *t, int lvl) { const char *name = btf_dump_ident_name(d, id); + struct decl_tag_array *decl_tags = NULL; /* * Old GCC versions are emitting invalid typedef for __gnuc_va_list @@ -1104,6 +1257,8 @@ static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id, btf_dump_printf(d, "typedef "); btf_dump_emit_type_decl(d, t->type, name, lvl); + hashmap__find(d->decl_tags, id, &decl_tags); + btf_dump_emit_decl_tags(d, decl_tags, -1); } static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id) @@ -1438,9 +1593,12 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, } case BTF_KIND_FUNC_PROTO: { const struct btf_param *p = btf_params(t); + struct decl_tag_array *decl_tags = NULL; __u16 vlen = btf_vlen(t); int i; + hashmap__find(d->decl_tags, id, &decl_tags); + /* * GCC emits extra volatile qualifier for * __attribute__((noreturn)) function pointers. Clang @@ -1481,6 +1639,7 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, name = btf_name_of(d, p->name_off); btf_dump_emit_type_decl(d, p->type, name, lvl); + btf_dump_emit_decl_tags(d, decl_tags, i); } btf_dump_printf(d, ")"); @@ -1896,6 +2055,7 @@ static int btf_dump_var_data(struct btf_dump *d, const void *data) { enum btf_func_linkage linkage = btf_var(v)->linkage; + struct decl_tag_array *decl_tags = NULL; const struct btf_type *t; const char *l; __u32 type_id; @@ -1920,7 +2080,10 @@ static int btf_dump_var_data(struct btf_dump *d, type_id = v->type; t = btf__type_by_id(d->btf, type_id); btf_dump_emit_type_cast(d, type_id, false); - btf_dump_printf(d, " %s = ", btf_name_of(d, v->name_off)); + btf_dump_printf(d, " %s", btf_name_of(d, v->name_off)); + hashmap__find(d->decl_tags, id, &decl_tags); + btf_dump_emit_decl_tags(d, decl_tags, -1); + btf_dump_printf(d, " = "); return btf_dump_dump_type_data(d, NULL, t, type_id, data, 0, 0); } @@ -2421,6 +2584,8 @@ int btf_dump__dump_type_data(struct btf_dump *d, __u32 id, d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false); d->typed_dump->emit_zeroes = OPTS_GET(opts, emit_zeroes, false); + btf_dump_assign_decl_tags(d); + ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0); d->typed_dump = NULL;
Clang's `__attribute__((btf_decl_tag("...")))` is represented in BTF as a record of kind BTF_KIND_DECL_TAG with `type` field pointing to the type annotated with this attribute. This commit adds reconstitution of such attributes for BTF dump in C format. BTF doc says that BTF_KIND_DECL_TAGs should follow a target type but this is not enforced and tests don't honor this restriction. This commit uses hashmap to map types to the list of decl tags. The hashmap is filled incrementally by the function `btf_dump_assign_decl_tags` called from `btf_dump__dump_type` and `btf_dump__dump_type_data`. It is assumed that total number of types annotated with decl tags is relatively small, thus some space is saved by using hashmap instead of adding a new field to `struct btf_dump_type_aux_state`. It is assumed that list of decl tags associated with a single type is small. Thus the list is represented by an array which grows linearly. To accommodate older Clang versions decl tags are dumped using the following macro: #if __has_attribute(btf_decl_tag) #define __btf_decl_tag(x) __attribute__((btf_decl_tag(x))) #else #define __btf_decl_tag(x) #endif The macro definition is emitted upon first call to `btf_dump__dump_type`. Clang allows to attach btf_decl_tag attributes to the following kinds of items: - struct/union supported - struct/union field supported - typedef supported - global variables supported - function prototype parameters supported - function not applicable - function parameter not applicable - local variables not applicable Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> --- tools/lib/bpf/btf_dump.c | 181 +++++++++++++++++++++++++++++++++++++-- 1 file changed, 173 insertions(+), 8 deletions(-)