Merge branch 'libbpf: error reporting changes for v1.0'

Andrii Nakryiko says:

====================

Implement error reporting changes discussed in "Libbpf: the road to v1.0"
([0]) document.

Libbpf gets a new API, libbpf_set_strict_mode() which accepts a set of flags
that turn on a set of libbpf 1.0 changes, that might be potentially breaking.
It's possible to opt-in into all current and future 1.0 features by specifying
LIBBPF_STRICT_ALL flag.

When some of the 1.0 "features" are requested, libbpf APIs might behave
differently. In this patch set a first set of changes are implemented, all
related to the way libbpf returns errors. See individual patches for details.

Patch #1 adds a no-op libbpf_set_strict_mode() functionality to enable
updating selftests.

Patch #2 gets rid of all the bad code patterns that will break in libbpf 1.0
(exact -1 comparison for low-level APIs, direct IS_ERR() macro usage to check
pointer-returning APIs for error, etc). These changes make selftest work in
both legacy and 1.0 libbpf modes. Selftests also opt-in into 100% libbpf 1.0
mode to automatically gain all the subsequent changes, which will come in
follow up patches.

Patch #3 streamlines error reporting for low-level APIs wrapping bpf() syscall.

Patch #4 streamlines errors for all the rest APIs.

Patch #5 ensures that BPF skeletons propagate errors properly as well, as
currently on error some APIs will return NULL with no way of checking exact
error code.

  [0] https://docs.google.com/document/d/1UyjTZuPFWiPFyKk1tV5an11_iaRuec6U-ZESZ54nNTY

v1->v2:
  - move libbpf_set_strict_mode() implementation to patch #1, where it belongs
    (Alexei);
  - add acks, slight rewording of commit messages.
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 11 insertions, 11 deletions

diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
index 1dca41a24f75..10911a8cad0f 100644
--- a/tools/lib/bpf/linker.c
+++ b/tools/lib/bpf/linker.c
@@ -220,16 +220,16 @@ struct bpf_linker *bpf_linker__new(const char *filename, struct bpf_linker_opts
 	int err;
 
 	if (!OPTS_VALID(opts, bpf_linker_opts))
-		return NULL;
+		return errno = EINVAL, NULL;
 
 	if (elf_version(EV_CURRENT) == EV_NONE) {
 		pr_warn_elf("libelf initialization failed");
-		return NULL;
+		return errno = EINVAL, NULL;
 	}
 
 	linker = calloc(1, sizeof(*linker));
 	if (!linker)
-		return NULL;
+		return errno = ENOMEM, NULL;
 
 	linker->fd = -1;
 
@@ -241,7 +241,7 @@ struct bpf_linker *bpf_linker__new(const char *filename, struct bpf_linker_opts
 
 err_out:
 	bpf_linker__free(linker);
-	return NULL;
+	return errno = -err, NULL;
 }
 
 static struct dst_sec *add_dst_sec(struct bpf_linker *linker, const char *sec_name)
@@ -444,10 +444,10 @@ int bpf_linker__add_file(struct bpf_linker *linker, const char *filename,
 	int err = 0;
 
 	if (!OPTS_VALID(opts, bpf_linker_file_opts))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	if (!linker->elf)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	err = err ?: linker_load_obj_file(linker, filename, opts, &obj);
 	err = err ?: linker_append_sec_data(linker, &obj);
@@ -467,7 +467,7 @@ int bpf_linker__add_file(struct bpf_linker *linker, const char *filename,
 	if (obj.fd >= 0)
 		close(obj.fd);
 
-	return err;
+	return libbpf_err(err);
 }
 
 static bool is_dwarf_sec_name(const char *name)
@@ -2548,11 +2548,11 @@ int bpf_linker__finalize(struct bpf_linker *linker)
 	int err, i;
 
 	if (!linker->elf)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	err = finalize_btf(linker);
 	if (err)
-		return err;
+		return libbpf_err(err);
 
 	/* Finalize strings */
 	strs_sz = strset__data_size(linker->strtab_strs);
@@ -2584,14 +2584,14 @@ int bpf_linker__finalize(struct bpf_linker *linker)
 	if (elf_update(linker->elf, ELF_C_NULL) < 0) {
 		err = -errno;
 		pr_warn_elf("failed to finalize ELF layout");
-		return err;
+		return libbpf_err(err);
 	}
 
 	/* Write out final ELF contents */
 	if (elf_update(linker->elf, ELF_C_WRITE) < 0) {
 		err = -errno;
 		pr_warn_elf("failed to write ELF contents");
-		return err;
+		return libbpf_err(err);
 	}
 
 	elf_end(linker->elf);