tools/bpf: print out btf log at LIBBPF_WARN level

Currently, the btf log is allocated and printed out in case
of error at LIBBPF_DEBUG level.
Such logs from kernel are very important for debugging.
For example, bpf syscall BPF_PROG_LOAD command can get
verifier logs back to user space. In function load_program()
of libbpf.c, the log buffer is allocated unconditionally
and printed out at pr_warning() level.

Let us do the similar thing here for btf. Allocate buffer
unconditionally and print out error logs at pr_warning() level.
This can reduce one global function and
optimize for common situations where pr_warning()
is activated either by default or by user supplied
debug output function.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/lib/bpf/btf.c

@@ -377,16 +377,15 @@ struct btf *btf__new(__u8 *data, __u32 size)
 
 	btf->fd = -1;
 
-	if (libbpf_print_level_available(LIBBPF_DEBUG)) {
-		log_buf = malloc(BPF_LOG_BUF_SIZE);
-		if (!log_buf) {
-			err = -ENOMEM;
-			goto done;
-		}
-		*log_buf = 0;
-		log_buf_size = BPF_LOG_BUF_SIZE;
+	log_buf = malloc(BPF_LOG_BUF_SIZE);
+	if (!log_buf) {
+		err = -ENOMEM;
+		goto done;
 	}
 
+	*log_buf = 0;
+	log_buf_size = BPF_LOG_BUF_SIZE;
+
 	btf->data = malloc(size);
 	if (!btf->data) {
 		err = -ENOMEM;
@@ -401,9 +400,9 @@ struct btf *btf__new(__u8 *data, __u32 size)
 
 	if (btf->fd == -1) {
 		err = -errno;
-		pr_debug("Error loading BTF: %s(%d)\n", strerror(errno), errno);
+		pr_warning("Error loading BTF: %s(%d)\n", strerror(errno), errno);
 		if (log_buf && *log_buf)
-			pr_debug("%s\n", log_buf);
+			pr_warning("%s\n", log_buf);
 		goto done;
 	}
 

tools/lib/bpf/libbpf.c

@@ -98,16 +98,6 @@ void libbpf_print(enum libbpf_print_level level, const char *format, ...)
 	va_end(args);
 }
 
-bool libbpf_print_level_available(enum libbpf_print_level level)
-{
-	if (level == LIBBPF_WARN)
-		return !!__pr_warning;
-	else if (level == LIBBPF_INFO)
-		return !!__pr_info;
-	else
-		return !!__pr_debug;
-}
-
 #define STRERR_BUFSIZE  128
 
 #define CHECK_ERR(action, err, out) do {	\

tools/lib/bpf/libbpf_util.h

@@ -14,8 +14,6 @@ extern void libbpf_print(enum libbpf_print_level level,
 			 const char *format, ...)
 	__attribute__((format(printf, 2, 3)));
 
-extern bool libbpf_print_level_available(enum libbpf_print_level level);
-
 #define __pr(level, fmt, ...)	\
 do {				\
 	libbpf_print(level, "libbpf: " fmt, ##__VA_ARGS__);	\