[RESEND PATCH bpf-next v4 8/9] 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.

Introduce a new struct bpf_syscall_common_attr_opts, which wraps these
new fields, 'log_buf', 'log_size', 'log_level', and 'log_true_size'.

Extend 'bpf_map_create_opts' with a new field, 'cattr_opts', allowing
users to capture and inspect those log messages.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 tools/lib/bpf/bpf.c | 15 ++++++++++++++-
 tools/lib/bpf/bpf.h | 17 ++++++++++++++++-
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 689ade4a822b..4a1ba4951785 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -207,6 +207,9 @@ int bpf_map_create(enum bpf_map_type map_type,
 		   const 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_syscall_common_attr_opts *cattr_opts;
+	struct bpf_common_attr common_attrs;
 	union bpf_attr attr;
 	int fd;
 
@@ -240,7 +243,17 @@ 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);
+	cattr_opts = OPTS_GET(opts, cattr_opts, NULL);
+	if (cattr_opts && feat_supported(NULL, FEAT_EXTENDED_SYSCALL)) {
+		memset(&common_attrs, 0, common_attrs_sz);
+		common_attrs.log_buf = ptr_to_u64(OPTS_GET(cattr_opts, log_buf, NULL));
+		common_attrs.log_size = OPTS_GET(cattr_opts, log_size, 0);
+		common_attrs.log_level = OPTS_GET(cattr_opts, log_level, 0);
+		fd = sys_bpf_ext_fd(BPF_MAP_CREATE, &attr, attr_sz, &common_attrs, common_attrs_sz);
+		OPTS_SET(cattr_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 1f9c28d27795..6f544c205b89 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -37,6 +37,18 @@ extern "C" {
 
 LIBBPF_API int libbpf_set_memlock_rlim(size_t memlock_bytes);
 
+struct bpf_syscall_common_attr_opts {
+	size_t sz; /* size of this struct for forward/backward compatibility */
+
+	const char *log_buf;
+	__u32 log_size;
+	__u32 log_level;
+	__u32 log_true_size;
+
+	size_t :0;
+};
+#define bpf_syscall_common_attr_opts__last_field log_true_size
+
 struct bpf_map_create_opts {
 	size_t sz; /* size of this struct for forward/backward compatibility */
 
@@ -57,9 +69,12 @@ struct bpf_map_create_opts {
 
 	const void *excl_prog_hash;
 	__u32 excl_prog_hash_size;
+
+	struct bpf_syscall_common_attr_opts *cattr_opts;
+
 	size_t :0;
 };
-#define bpf_map_create_opts__last_field excl_prog_hash_size
+#define bpf_map_create_opts__last_field cattr_opts
 
 LIBBPF_API int bpf_map_create(enum bpf_map_type map_type,
 			      const char *map_name,
-- 
2.52.0