[PATCH bpf-next v5 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, users can now retrieve detailed error messages when map
creation fails via the log_buf field.

Introduce struct bpf_syscall_common_attr_opts with the following fields:
log_buf, log_size, log_level, and log_true_size.

Extend bpf_map_create_opts with a new field common_attr_opts, allowing
users to capture and inspect log messages on map creation failures.

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 d44e667aaf02..d65df1b7b2be 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_attr_sz = sizeof(struct bpf_common_attr);
+	struct bpf_syscall_common_attr_opts *common_attr_opts;
+	struct bpf_common_attr common_attr;
 	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);
+	common_attr_opts = OPTS_GET(opts, common_attr_opts, NULL);
+	if (common_attr_opts && feat_supported(NULL, FEAT_EXTENDED_SYSCALL)) {
+		memset(&common_attr, 0, common_attr_sz);
+		common_attr.log_buf = ptr_to_u64(OPTS_GET(common_attr_opts, log_buf, NULL));
+		common_attr.log_size = OPTS_GET(common_attr_opts, log_size, 0);
+		common_attr.log_level = OPTS_GET(common_attr_opts, log_level, 0);
+		fd = sys_bpf_ext_fd(BPF_MAP_CREATE, &attr, attr_sz, &common_attr, common_attr_sz);
+		OPTS_SET(common_attr_opts, log_true_size, common_attr.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 2c8e88ddb674..c4a26e6b71ea 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 */
+
+	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 *common_attr_opts;
+
 	size_t :0;
 };
-#define bpf_map_create_opts__last_field excl_prog_hash_size
+#define bpf_map_create_opts__last_field common_attr_opts
 
 LIBBPF_API int bpf_map_create(enum bpf_map_type map_type,
 			      const char *map_name,
-- 
2.52.0