[PATCH bpf-next v3 05/13] tools: libbpf: expose the prog type guessing from section name logic

[Jakub Kicinski]

libbpf can guess program type based on ELF section names.  As libbpf
becomes more popular its association between section name strings and
types becomes more of a standard.  Allow libbpf users to use the same
logic for matching strings to types, e.g. when the string originates
from command line.

Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.com>
Reviewed-by: Quentin Monnet <quentin.mon...@netronome.com>
---
v3 (Andrey):
 - use -EINVAL error code;
 - rename helper to libbpf_prog_type_by_name().
---
 tools/lib/bpf/libbpf.c | 43 ++++++++++++++++++++++++------------------
 tools/lib/bpf/libbpf.h |  3 +++
 2 files changed, 28 insertions(+), 18 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 38ed3e92e393..42f31eff5f3f 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2081,23 +2081,31 @@ static const struct {
 #undef BPF_S_PROG_SEC
 #undef BPF_SA_PROG_SEC
 
-static int bpf_program__identify_section(struct bpf_program *prog)
+int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
+                            enum bpf_attach_type *expected_attach_type)
 {
        int i;
 
-       if (!prog->section_name)
-               goto err;
-
-       for (i = 0; i < ARRAY_SIZE(section_names); i++)
-               if (strncmp(prog->section_name, section_names[i].sec,
-                           section_names[i].len) == 0)
-                       return i;
+       if (!name)
+               return -EINVAL;
 
-err:
-       pr_warning("failed to guess program type based on section name %s\n",
-                  prog->section_name);
+       for (i = 0; i < ARRAY_SIZE(section_names); i++) {
+               if (strncmp(name, section_names[i].sec, section_names[i].len))
+                       continue;
+               *prog_type = section_names[i].prog_type;
+               *expected_attach_type = section_names[i].expected_attach_type;
+               return 0;
+       }
+       return -EINVAL;
+}
 
-       return -1;
+static int
+bpf_program__identify_section(struct bpf_program *prog,
+                             enum bpf_prog_type *prog_type,
+                             enum bpf_attach_type *expected_attach_type)
+{
+       return libbpf_prog_type_by_name(prog->section_name, prog_type,
+                                       expected_attach_type);
 }
 
 int bpf_map__fd(struct bpf_map *map)
@@ -2230,7 +2238,6 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr 
*attr,
        enum bpf_prog_type prog_type;
        struct bpf_object *obj;
        struct bpf_map *map;
-       int section_idx;
        int err;
 
        if (!attr)
@@ -2252,14 +2259,14 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr 
*attr,
                prog->prog_ifindex = attr->ifindex;
                expected_attach_type = attr->expected_attach_type;
                if (prog_type == BPF_PROG_TYPE_UNSPEC) {
-                       section_idx = bpf_program__identify_section(prog);
-                       if (section_idx < 0) {
+                       err = bpf_program__identify_section(prog, &prog_type,
+                                                           
&expected_attach_type);
+                       if (err < 0) {
+                               pr_warning("failed to guess program type based 
on section name %s\n",
+                                          prog->section_name);
                                bpf_object__close(obj);
                                return -EINVAL;
                        }
-                       prog_type = section_names[section_idx].prog_type;
-                       expected_attach_type =
-                               section_names[section_idx].expected_attach_type;
                }
 
                bpf_program__set_type(prog, prog_type);
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 564f4be9bae0..d1ce5c828e2e 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -92,6 +92,9 @@ int bpf_object__set_priv(struct bpf_object *obj, void *priv,
                         bpf_object_clear_priv_t clear_priv);
 void *bpf_object__priv(struct bpf_object *prog);
 
+int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
+                            enum bpf_attach_type *expected_attach_type);
+
 /* Accessors of bpf_program */
 struct bpf_program;
 struct bpf_program *bpf_program__next(struct bpf_program *prog,
-- 
2.17.1