From: Eduard Zingerman <eddyz87@gmail.com>
To: dwarves@vger.kernel.org, arnaldo.melo@gmail.com
Cc: bpf@vger.kernel.org, kernel-team@fb.com, ast@kernel.org,
daniel@iogearbox.net, andrii@kernel.org, yhs@fb.com,
Eduard Zingerman <eddyz87@gmail.com>
Subject: [PATCH dwarves] fprintf: Fix `*` not being printed for pointers with btf_type_tag
Date: Fri, 31 Mar 2023 00:27:00 +0300 [thread overview]
Message-ID: <20230330212700.697124-1-eddyz87@gmail.com> (raw)
Recent change to fprintf (see below) causes incorrect `type_fprintf()`
behavior for pointers annotated with btf_type_tag, for example:
$ cat tag-test.c
#define __t __attribute__((btf_type_tag("t1")))
struct foo {
int __t *a;
} 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 a; /* 0 8 */
...
};
Note that `*` is missing in the pahole output.
The issue is caused by `goto next_type` that jumps over the
`tag__name()` that is responsible for pointer printing.
As agreed in [1] `type__fprintf()` is modified to skip type tags for
now and would be modified to emit type tags later.
The change in `__tag__name()` is necessary to avoid the following behavior:
$ cat tag-test.c
#define __t __attribute__((btf_type_tag("t1")))
struct foo {
int __t *a;
int __t __t *b;
} 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 * a; /* 0 8 */
int * b; /* 8 8 */
...
};
Note the extra space before `*` for field `b`.
The issue was reported and tracked down to the root cause by
Arnaldo Carvalho de Melo.
Links:
[1] https://lore.kernel.org/dwarves/20230314230417.1507266-1-eddyz87@gmail.com/T/#md82b04f66867434524beec746138951f26a3977e
Fixes: e7fb771f2649 ("fprintf: Correct names for types with btf_type_tag attribute")
Reported-by: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Link: https://lore.kernel.org/dwarves/20230314230417.1507266-1-eddyz87@gmail.com/T/#mc630bcd474ddd64c70d237edd4e0590dc048d63d
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
dwarves_fprintf.c | 37 +++++++++++++++++++++++++++++--------
1 file changed, 29 insertions(+), 8 deletions(-)
diff --git a/dwarves_fprintf.c b/dwarves_fprintf.c
index 1e6147a..818db2d 100644
--- a/dwarves_fprintf.c
+++ b/dwarves_fprintf.c
@@ -572,7 +572,6 @@ static const char *__tag__name(const struct tag *tag, const struct cu *cu,
case DW_TAG_restrict_type:
case DW_TAG_atomic_type:
case DW_TAG_unspecified_type:
- case DW_TAG_LLVM_annotation:
type = cu__type(cu, tag->type);
if (type == NULL && tag->type != 0)
tag__id_not_found_snprintf(bf, len, tag->type);
@@ -618,6 +617,13 @@ static const char *__tag__name(const struct tag *tag, const struct cu *cu,
case DW_TAG_variable:
snprintf(bf, len, "%s", variable__name(tag__variable(tag)));
break;
+ case DW_TAG_LLVM_annotation:
+ type = cu__type(cu, tag->type);
+ if (type == NULL && tag->type != 0)
+ tag__id_not_found_snprintf(bf, len, tag->type);
+ else if (!tag__has_type_loop(tag, type, bf, len, NULL))
+ __tag__name(type, cu, bf, len, conf);
+ break;
default:
snprintf(bf, len, "%s%s", tag__prefix(cu, tag->tag, pconf),
type__name(tag__type(tag)) ?: "");
@@ -677,6 +683,22 @@ static size_t type__fprintf_stats(struct type *type, const struct cu *cu,
return printed;
}
+static type_id_t skip_llvm_annotations(const struct cu *cu, type_id_t id)
+{
+ struct tag *type;
+
+ for (;;) {
+ if (id == 0)
+ break;
+ type = cu__type(cu, id);
+ if (type == NULL || type->tag != DW_TAG_LLVM_annotation || type->type == id)
+ break;
+ id = type->type;
+ }
+
+ return id;
+}
+
static size_t union__fprintf(struct type *type, const struct cu *cu,
const struct conf_fprintf *conf, FILE *fp);
@@ -778,19 +800,17 @@ inner_struct:
next_type:
switch (type->tag) {
- case DW_TAG_pointer_type:
- if (type->type != 0) {
+ case DW_TAG_pointer_type: {
+ type_id_t ptype_id = skip_llvm_annotations(cu, type->type);
+
+ if (ptype_id != 0) {
int n;
- struct tag *ptype = cu__type(cu, type->type);
+ struct tag *ptype = cu__type(cu, ptype_id);
if (ptype == NULL)
goto out_type_not_found;
n = tag__has_type_loop(type, ptype, NULL, 0, fp);
if (n)
return printed + n;
- if (ptype->tag == DW_TAG_LLVM_annotation) {
- type = ptype;
- goto next_type;
- }
if (ptype->tag == DW_TAG_subroutine_type) {
printed += ftype__fprintf(tag__ftype(ptype),
cu, name, 0, 1,
@@ -811,6 +831,7 @@ next_type:
}
}
/* Fall Thru */
+ }
default:
print_default:
printed += fprintf(fp, "%-*s %s", tconf.type_spacing,
--
2.40.0
next reply other threads:[~2023-03-30 21:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-30 21:27 Eduard Zingerman [this message]
2023-03-31 12:13 ` [PATCH dwarves] fprintf: Fix `*` not being printed for pointers with btf_type_tag Arnaldo Carvalho de Melo
2023-03-31 12:14 ` Arnaldo Carvalho de Melo
2023-03-31 12:20 ` Arnaldo Carvalho de Melo
2023-03-31 14:12 ` Eduard Zingerman
2023-03-31 18:33 ` Arnaldo Carvalho de Melo
2023-03-31 13:35 ` Eduard Zingerman
2023-03-31 14:05 ` Arnaldo Carvalho de Melo
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