[RFC PATCH bpf-next v3 09/10] libbpf: Add common attr support for map_create

[Leon Hwang <leon.hwang@linux.dev>]

With the previous commit adding common attribute support for
BPF_MAP_CREATE, it is now possible to retrieve detailed error messages
when map creation fails by using the 'log_buf' field from the common
attributes.

Extend 'bpf_map_create_opts' with these new fields, 'log_buf', 'log_size'
, 'log_level' and 'log_true_size', allowing users to capture and inspect
those log messages.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 tools/lib/bpf/bpf.c | 17 +++++++++++++++--
 tools/lib/bpf/bpf.h |  9 +++++++--
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 9cd79beb13a2d..ca66fcdb3f49f 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -203,10 +203,13 @@ int bpf_map_create(enum bpf_map_type map_type,
 		   __u32 key_size,
 		   __u32 value_size,
 		   __u32 max_entries,
-		   const struct bpf_map_create_opts *opts)
+		   struct bpf_map_create_opts *opts)
 {
 	const size_t attr_sz = offsetofend(union bpf_attr, excl_prog_hash_size);
+	const size_t common_attrs_sz = sizeof(struct bpf_common_attr);
+	struct bpf_common_attr common_attrs;
 	union bpf_attr attr;
+	const char *log_buf;
 	int fd;
 
 	bump_rlimit_memlock();
@@ -239,7 +242,17 @@ int bpf_map_create(enum bpf_map_type map_type,
 	attr.excl_prog_hash = ptr_to_u64(OPTS_GET(opts, excl_prog_hash, NULL));
 	attr.excl_prog_hash_size = OPTS_GET(opts, excl_prog_hash_size, 0);
 
-	fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, attr_sz);
+	log_buf = OPTS_GET(opts, log_buf, NULL);
+	if (log_buf && feat_supported(NULL, FEAT_EXTENDED_SYSCALL)) {
+		memset(&common_attrs, 0, common_attrs_sz);
+		common_attrs.log_buf = ptr_to_u64(log_buf);
+		common_attrs.log_size = OPTS_GET(opts, log_size, 0);
+		common_attrs.log_level = OPTS_GET(opts, log_level, 0);
+		fd = sys_bpf_ext_fd(BPF_MAP_CREATE, &attr, attr_sz, &common_attrs, common_attrs_sz);
+		OPTS_SET(opts, log_true_size, common_attrs.log_true_size);
+	} else {
+		fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, attr_sz);
+	}
 	return libbpf_err_errno(fd);
 }
 
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index e983a3e40d612..77d475e7274a0 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -57,16 +57,21 @@ struct bpf_map_create_opts {
 
 	const void *excl_prog_hash;
 	__u32 excl_prog_hash_size;
+
+	const char *log_buf;
+	__u32 log_size;
+	__u32 log_level;
+	__u32 log_true_size;
 	size_t :0;
 };
-#define bpf_map_create_opts__last_field excl_prog_hash_size
+#define bpf_map_create_opts__last_field log_true_size
 
 LIBBPF_API int bpf_map_create(enum bpf_map_type map_type,
 			      const char *map_name,
 			      __u32 key_size,
 			      __u32 value_size,
 			      __u32 max_entries,
-			      const struct bpf_map_create_opts *opts);
+			      struct bpf_map_create_opts *opts);
 
 struct bpf_prog_load_opts {
 	size_t sz; /* size of this struct for forward/backward compatibility */
-- 
2.51.0