[PATCH bpf-next v5 8/9] libbpf: Add common attr support for map_create

[Leon Hwang]

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.hw...@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