bpftool: Set errno on skeleton failures and propagate errors

Follow libbpf's error handling conventions and pass through errors and errno
properly. Skeleton code always returned NULL on errors (not ERR_PTR(err)), so
there are no backwards compatibility concerns. But now we also set errno
properly, so it's possible to distinguish different reasons for failure, if
necessary.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210525035935.1461796-6-andrii@kernel.org

diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index 13b0aa7..1d71ff8 100644 (file)
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -713,6 +713,7 @@ static int do_skeleton(int argc, char **argv)
                #ifndef %2$s                                                \n\
                #define %2$s                                                \n\
                                                                            \n\
+               #include <errno.h>                                          \n\
                #include <stdlib.h>                                         \n\
                #include <bpf/libbpf.h>                                     \n\
                                                                            \n\
@@ -793,18 +794,23 @@ static int do_skeleton(int argc, char **argv)
                %1$s__open_opts(const struct bpf_object_open_opts *opts)    \n\
                {                                                           \n\
                        struct %1$s *obj;                                   \n\
+                       int err;                                            \n\
                                                                            \n\
                        obj = (struct %1$s *)calloc(1, sizeof(*obj));       \n\
-                       if (!obj)                                           \n\
+                       if (!obj) {                                         \n\
+                               errno = ENOMEM;                             \n\
                                return NULL;                                \n\
-                       if (%1$s__create_skeleton(obj))                     \n\
-                               goto err;                                   \n\
-                       if (bpf_object__open_skeleton(obj->skeleton, opts)) \n\
-                               goto err;                                   \n\
+                       }                                                   \n\
+                                                                           \n\
+                       err = %1$s__create_skeleton(obj);                   \n\
+                       err = err ?: bpf_object__open_skeleton(obj->skeleton, opts);\n\
+                       if (err)                                            \n\
+                               goto err_out;                               \n\
                                                                            \n\
                        return obj;                                         \n\
-               err:                                                        \n\
+               err_out:                                                    \n\
                        %1$s__destroy(obj);                                 \n\
+                       errno = -err;                                       \n\
                        return NULL;                                        \n\
                }                                                           \n\
                                                                            \n\
@@ -824,12 +830,15 @@ static int do_skeleton(int argc, char **argv)
                %1$s__open_and_load(void)                                   \n\
                {                                                           \n\
                        struct %1$s *obj;                                   \n\
+                       int err;                                            \n\
                                                                            \n\
                        obj = %1$s__open();                                 \n\
                        if (!obj)                                           \n\
                                return NULL;                                \n\
-                       if (%1$s__load(obj)) {                              \n\
+                       err = %1$s__load(obj);                              \n\
+                       if (err) {                                          \n\
                                %1$s__destroy(obj);                         \n\
+                               errno = -err;                               \n\
                                return NULL;                                \n\
                        }                                                   \n\
                        return obj;                                         \n\
@@ -860,7 +869,7 @@ static int do_skeleton(int argc, char **argv)
                                                                            \n\
                        s = (struct bpf_object_skeleton *)calloc(1, sizeof(*s));\n\
                        if (!s)                                             \n\
-                               return -1;                                  \n\
+                               goto err;                                   \n\
                        obj->skeleton = s;                                  \n\
                                                                            \n\
                        s->sz = sizeof(*s);                                 \n\
@@ -949,7 +958,7 @@ static int do_skeleton(int argc, char **argv)
                        return 0;                                           \n\
                err:                                                        \n\
                        bpf_object__destroy_skeleton(s);                    \n\
-                       return -1;                                          \n\
+                       return -ENOMEM;                                     \n\
                }                                                           \n\
                                                                            \n\
                #endif /* %s */                                             \n\