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bpf: btf: export btf types and name by offset from lib 

This patch introduces btf__resolve_type() function and exports two
existing functions from libbpf. btf__resolve_type follows modifier
types like const and typedef until it hits a type which actually takes
up memory, and then returns it. This function follows similar pattern
to btf__resolve_size but instead of computing size, it just returns
the type.

These  functions will be used in the followig patch which parses
information inside array of `struct btf_type *`. btf_name_by_offset is
used for printing variable names.

Signed-off-by: Okash Khawaja <osk@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Okash Khawaja 2018-07-13 21:57:02 -07:00 committed by Daniel Borkmann
parent db42a21a1e
commit 92b57121ca
2 changed files with 48 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
tools/lib/bpf/btf.c
View File

@ -17,6 +17,11 @@
#define BTF_MAX_NR_TYPES 65535
#define IS_MODIFIER(k) (((k) == BTF_KIND_TYPEDEF) || \
((k) == BTF_KIND_VOLATILE) || \
((k) == BTF_KIND_CONST) || \
((k) == BTF_KIND_RESTRICT))
static struct btf_type btf_void;
struct btf {
@ -33,14 +38,6 @@ struct btf {
int fd;
};
static const char *btf_name_by_offset(const struct btf *btf, uint32_t offset)
{
if (offset < btf->hdr->str_len)
return &btf->strings[offset];
else
return NULL;
}
static int btf_add_type(struct btf *btf, struct btf_type *t)
{
if (btf->types_size - btf->nr_types < 2) {
@ -190,15 +187,6 @@ static int btf_parse_type_sec(struct btf *btf, btf_print_fn_t err_log)
return 0;
}
static const struct btf_type *btf_type_by_id(const struct btf *btf,
uint32_t type_id)
{
if (type_id > btf->nr_types)
return NULL;
return btf->types[type_id];
}
static bool btf_type_is_void(const struct btf_type *t)
{
return t == &btf_void || BTF_INFO_KIND(t->info) == BTF_KIND_FWD;
@ -234,7 +222,7 @@ int64_t btf__resolve_size(const struct btf *btf, uint32_t type_id)
int64_t size = -1;
int i;
t = btf_type_by_id(btf, type_id);
t = btf__type_by_id(btf, type_id);
for (i = 0; i < MAX_RESOLVE_DEPTH && !btf_type_is_void_or_null(t);
i++) {
size = btf_type_size(t);
@ -259,7 +247,7 @@ int64_t btf__resolve_size(const struct btf *btf, uint32_t type_id)
return -EINVAL;
}
t = btf_type_by_id(btf, type_id);
t = btf__type_by_id(btf, type_id);
}
if (size < 0)
@ -271,6 +259,26 @@ int64_t btf__resolve_size(const struct btf *btf, uint32_t type_id)
return nelems * size;
}
int btf__resolve_type(const struct btf *btf, __u32 type_id)
{
const struct btf_type *t;
int depth = 0;
t = btf__type_by_id(btf, type_id);
while (depth < MAX_RESOLVE_DEPTH &&
!btf_type_is_void_or_null(t) &&
IS_MODIFIER(BTF_INFO_KIND(t->info))) {
type_id = t->type;
t = btf__type_by_id(btf, type_id);
depth++;
}
if (depth == MAX_RESOLVE_DEPTH || btf_type_is_void_or_null(t))
return -EINVAL;
return type_id;
}
int32_t btf__find_by_name(const struct btf *btf, const char *type_name)
{
uint32_t i;
@ -280,7 +288,7 @@ int32_t btf__find_by_name(const struct btf *btf, const char *type_name)
for (i = 1; i <= btf->nr_types; i++) {
const struct btf_type *t = btf->types[i];
const char *name = btf_name_by_offset(btf, t->name_off);
const char *name = btf__name_by_offset(btf, t->name_off);
if (name && !strcmp(type_name, name))
return i;
@ -371,3 +379,20 @@ int btf__fd(const struct btf *btf)
{
return btf->fd;
}
const char *btf__name_by_offset(const struct btf *btf, __u32 offset)
{
if (offset < btf->hdr->str_len)
return &btf->strings[offset];
else
return NULL;
}
const struct btf_type *btf__type_by_id(const struct btf *btf,
__u32 type_id)
{
if (type_id > btf->nr_types)
return NULL;
return btf->types[type_id];
}

3
tools/lib/bpf/btf.h
View File

@ -17,6 +17,9 @@ void btf__free(struct btf *btf);
struct btf *btf__new(uint8_t *data, uint32_t size, btf_print_fn_t err_log);
int32_t btf__find_by_name(const struct btf *btf, const char *type_name);
int64_t btf__resolve_size(const struct btf *btf, uint32_t type_id);
int btf__resolve_type(const struct btf *btf, __u32 type_id);
int btf__fd(const struct btf *btf);
const char *btf__name_by_offset(const struct btf *btf, __u32 offset);
const struct btf_type *btf__type_by_id(const struct btf *btf, __u32 type_id);
#endif