[PATCH bpf-next 0/2] tools/bpf: changes of libbpf debug interfaces

[PATCH bpf-next 0/2] tools/bpf: changes of libbpf debug interfaces

[Yonghong Song]

These are concrete patches responding to my comments for
Magnus's patch. Specifically, Patch #1 used global functions
to facilitate pr_* macros in the header files so they
are available in different C files.
Patch #2 simplified libbpf_set_print() takes only one print
function and the print function has a "level" argument.

Yonghong Song (2):
  tools/bpf: move libbpf pr_* debug print functions to headers
  tools/bpf: simplify libbpf API function libbpf_set_print()

 tools/lib/bpf/btf.c                           | 97 +++++++++----------
 tools/lib/bpf/btf.h                           |  7 +-
 tools/lib/bpf/libbpf.c                        | 45 +++++----
 tools/lib/bpf/libbpf.h                        | 20 ++--
 tools/lib/bpf/test_libbpf.cpp                 |  4 +-
 tools/lib/bpf/util.h                          | 32 ++++++
 tools/perf/util/bpf-loader.c                  | 32 +++---
 tools/testing/selftests/bpf/test_btf.c        |  7 +-
 .../testing/selftests/bpf/test_libbpf_open.c  | 36 ++++---
 tools/testing/selftests/bpf/test_progs.c      | 20 +++-
 10 files changed, 166 insertions(+), 134 deletions(-)
 create mode 100644 tools/lib/bpf/util.h

-- 
2.17.1

[PATCH bpf-next 1/2] tools/bpf: move libbpf pr_* debug print functions to headers

[Yonghong Song]

A global function libbpf_dprint, which is invisible
outside the shared library, is defined to print based
on levels. The pr_warning, pr_info and pr_debug
macros are moved into the newly created header
common.h. So any .c file including common.h can
use these macros directly.

Currently btf__new and btf_ext__new API has an argument getting
__pr_debug function pointer into btf.c so the debugging information
can be printed there. This patch removed this parameter
from btf__new and btf_ext__new and directly using pr_debug in btf.c.

Another global function libbpf_dprint_level_available, also
invisible outside the shared library, can test
whether a particular level debug printing is
available or not. It is used in btf.c to
test whether DEBUG level debug printing is availabl or not,
based on which the log buffer will be allocated when loading
btf to the kernel.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 tools/lib/bpf/btf.c           | 97 +++++++++++++++++------------------
 tools/lib/bpf/btf.h           |  7 +--
 tools/lib/bpf/libbpf.c        | 46 ++++++++++++-----
 tools/lib/bpf/libbpf.h        |  6 +++
 tools/lib/bpf/test_libbpf.cpp |  2 +-
 tools/lib/bpf/util.h          | 32 ++++++++++++
 6 files changed, 120 insertions(+), 70 deletions(-)
 create mode 100644 tools/lib/bpf/util.h

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index d682d3b8f7b9..159104ec31dc 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -9,8 +9,9 @@
 #include <linux/btf.h>
 #include "btf.h"
 #include "bpf.h"
+#include "libbpf.h"
+#include "util.h"
 
-#define elog(fmt, ...) { if (err_log) err_log(fmt, ##__VA_ARGS__); }
 #define max(a, b) ((a) > (b) ? (a) : (b))
 #define min(a, b) ((a) < (b) ? (a) : (b))
 
@@ -107,54 +108,54 @@ static int btf_add_type(struct btf *btf, struct btf_type *t)
 	return 0;
 }
 
-static int btf_parse_hdr(struct btf *btf, btf_print_fn_t err_log)
+static int btf_parse_hdr(struct btf *btf)
 {
 	const struct btf_header *hdr = btf->hdr;
 	__u32 meta_left;
 
 	if (btf->data_size < sizeof(struct btf_header)) {
-		elog("BTF header not found\n");
+		pr_debug("BTF header not found\n");
 		return -EINVAL;
 	}
 
 	if (hdr->magic != BTF_MAGIC) {
-		elog("Invalid BTF magic:%x\n", hdr->magic);
+		pr_debug("Invalid BTF magic:%x\n", hdr->magic);
 		return -EINVAL;
 	}
 
 	if (hdr->version != BTF_VERSION) {
-		elog("Unsupported BTF version:%u\n", hdr->version);
+		pr_debug("Unsupported BTF version:%u\n", hdr->version);
 		return -ENOTSUP;
 	}
 
 	if (hdr->flags) {
-		elog("Unsupported BTF flags:%x\n", hdr->flags);
+		pr_debug("Unsupported BTF flags:%x\n", hdr->flags);
 		return -ENOTSUP;
 	}
 
 	meta_left = btf->data_size - sizeof(*hdr);
 	if (!meta_left) {
-		elog("BTF has no data\n");
+		pr_debug("BTF has no data\n");
 		return -EINVAL;
 	}
 
 	if (meta_left < hdr->type_off) {
-		elog("Invalid BTF type section offset:%u\n", hdr->type_off);
+		pr_debug("Invalid BTF type section offset:%u\n", hdr->type_off);
 		return -EINVAL;
 	}
 
 	if (meta_left < hdr->str_off) {
-		elog("Invalid BTF string section offset:%u\n", hdr->str_off);
+		pr_debug("Invalid BTF string section offset:%u\n", hdr->str_off);
 		return -EINVAL;
 	}
 
 	if (hdr->type_off >= hdr->str_off) {
-		elog("BTF type section offset >= string section offset. No type?\n");
+		pr_debug("BTF type section offset >= string section offset. No type?\n");
 		return -EINVAL;
 	}
 
 	if (hdr->type_off & 0x02) {
-		elog("BTF type section is not aligned to 4 bytes\n");
+		pr_debug("BTF type section is not aligned to 4 bytes\n");
 		return -EINVAL;
 	}
 
@@ -163,7 +164,7 @@ static int btf_parse_hdr(struct btf *btf, btf_print_fn_t err_log)
 	return 0;
 }
 
-static int btf_parse_str_sec(struct btf *btf, btf_print_fn_t err_log)
+static int btf_parse_str_sec(struct btf *btf)
 {
 	const struct btf_header *hdr = btf->hdr;
 	const char *start = btf->nohdr_data + hdr->str_off;
@@ -171,7 +172,7 @@ static int btf_parse_str_sec(struct btf *btf, btf_print_fn_t err_log)
 
 	if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_NAME_OFFSET ||
 	    start[0] || end[-1]) {
-		elog("Invalid BTF string section\n");
+		pr_debug("Invalid BTF string section\n");
 		return -EINVAL;
 	}
 
@@ -180,7 +181,7 @@ static int btf_parse_str_sec(struct btf *btf, btf_print_fn_t err_log)
 	return 0;
 }
 
-static int btf_parse_type_sec(struct btf *btf, btf_print_fn_t err_log)
+static int btf_parse_type_sec(struct btf *btf)
 {
 	struct btf_header *hdr = btf->hdr;
 	void *nohdr_data = btf->nohdr_data;
@@ -219,7 +220,7 @@ static int btf_parse_type_sec(struct btf *btf, btf_print_fn_t err_log)
 		case BTF_KIND_RESTRICT:
 			break;
 		default:
-			elog("Unsupported BTF_KIND:%u\n",
+			pr_debug("Unsupported BTF_KIND:%u\n",
 			     BTF_INFO_KIND(t->info));
 			return -EINVAL;
 		}
@@ -363,7 +364,7 @@ void btf__free(struct btf *btf)
 	free(btf);
 }
 
-struct btf *btf__new(__u8 *data, __u32 size, btf_print_fn_t err_log)
+struct btf *btf__new(__u8 *data, __u32 size)
 {
 	__u32 log_buf_size = 0;
 	char *log_buf = NULL;
@@ -376,7 +377,7 @@ struct btf *btf__new(__u8 *data, __u32 size, btf_print_fn_t err_log)
 
 	btf->fd = -1;
 
-	if (err_log) {
+	if (libbpf_dprint_level_available(LIBBPF_DEBUG)) {
 		log_buf = malloc(BPF_LOG_BUF_SIZE);
 		if (!log_buf) {
 			err = -ENOMEM;
@@ -400,21 +401,21 @@ struct btf *btf__new(__u8 *data, __u32 size, btf_print_fn_t err_log)
 
 	if (btf->fd == -1) {
 		err = -errno;
-		elog("Error loading BTF: %s(%d)\n", strerror(errno), errno);
+		pr_debug("Error loading BTF: %s(%d)\n", strerror(errno), errno);
 		if (log_buf && *log_buf)
-			elog("%s\n", log_buf);
+			pr_debug("%s\n", log_buf);
 		goto done;
 	}
 
-	err = btf_parse_hdr(btf, err_log);
+	err = btf_parse_hdr(btf);
 	if (err)
 		goto done;
 
-	err = btf_parse_str_sec(btf, err_log);
+	err = btf_parse_str_sec(btf);
 	if (err)
 		goto done;
 
-	err = btf_parse_type_sec(btf, err_log);
+	err = btf_parse_type_sec(btf);
 
 done:
 	free(log_buf);
@@ -491,7 +492,7 @@ int btf__get_from_id(__u32 id, struct btf **btf)
 		goto exit_free;
 	}
 
-	*btf = btf__new((__u8 *)(long)btf_info.btf, btf_info.btf_size, NULL);
+	*btf = btf__new((__u8 *)(long)btf_info.btf, btf_info.btf_size);
 	if (IS_ERR(*btf)) {
 		err = PTR_ERR(*btf);
 		*btf = NULL;
@@ -514,8 +515,7 @@ struct btf_ext_sec_copy_param {
 
 static int btf_ext_copy_info(struct btf_ext *btf_ext,
 			     __u8 *data, __u32 data_size,
-			     struct btf_ext_sec_copy_param *ext_sec,
-			     btf_print_fn_t err_log)
+			     struct btf_ext_sec_copy_param *ext_sec)
 {
 	const struct btf_ext_header *hdr = (struct btf_ext_header *)data;
 	const struct btf_ext_info_sec *sinfo;
@@ -529,14 +529,14 @@ static int btf_ext_copy_info(struct btf_ext *btf_ext,
 	data_size -= hdr->hdr_len;
 
 	if (ext_sec->off & 0x03) {
-		elog(".BTF.ext %s section is not aligned to 4 bytes\n",
+		pr_debug(".BTF.ext %s section is not aligned to 4 bytes\n",
 		     ext_sec->desc);
 		return -EINVAL;
 	}
 
 	if (data_size < ext_sec->off ||
 	    ext_sec->len > data_size - ext_sec->off) {
-		elog("%s section (off:%u len:%u) is beyond the end of the ELF section .BTF.ext\n",
+		pr_debug("%s section (off:%u len:%u) is beyond the end of the ELF section .BTF.ext\n",
 		     ext_sec->desc, ext_sec->off, ext_sec->len);
 		return -EINVAL;
 	}
@@ -546,7 +546,7 @@ static int btf_ext_copy_info(struct btf_ext *btf_ext,
 
 	/* At least a record size */
 	if (info_left < sizeof(__u32)) {
-		elog(".BTF.ext %s record size not found\n", ext_sec->desc);
+		pr_debug(".BTF.ext %s record size not found\n", ext_sec->desc);
 		return -EINVAL;
 	}
 
@@ -554,7 +554,7 @@ static int btf_ext_copy_info(struct btf_ext *btf_ext,
 	record_size = *(__u32 *)info;
 	if (record_size < ext_sec->min_rec_size ||
 	    record_size & 0x03) {
-		elog("%s section in .BTF.ext has invalid record size %u\n",
+		pr_debug("%s section in .BTF.ext has invalid record size %u\n",
 		     ext_sec->desc, record_size);
 		return -EINVAL;
 	}
@@ -564,7 +564,7 @@ static int btf_ext_copy_info(struct btf_ext *btf_ext,
 
 	/* If no records, return failure now so .BTF.ext won't be used. */
 	if (!info_left) {
-		elog("%s section in .BTF.ext has no records", ext_sec->desc);
+		pr_debug("%s section in .BTF.ext has no records", ext_sec->desc);
 		return -EINVAL;
 	}
 
@@ -574,14 +574,14 @@ static int btf_ext_copy_info(struct btf_ext *btf_ext,
 		__u32 num_records;
 
 		if (info_left < sec_hdrlen) {
-			elog("%s section header is not found in .BTF.ext\n",
+			pr_debug("%s section header is not found in .BTF.ext\n",
 			     ext_sec->desc);
 			return -EINVAL;
 		}
 
 		num_records = sinfo->num_info;
 		if (num_records == 0) {
-			elog("%s section has incorrect num_records in .BTF.ext\n",
+			pr_debug("%s section has incorrect num_records in .BTF.ext\n",
 			     ext_sec->desc);
 			return -EINVAL;
 		}
@@ -589,7 +589,7 @@ static int btf_ext_copy_info(struct btf_ext *btf_ext,
 		total_record_size = sec_hdrlen +
 				    (__u64)num_records * record_size;
 		if (info_left < total_record_size) {
-			elog("%s section has incorrect num_records in .BTF.ext\n",
+			pr_debug("%s section has incorrect num_records in .BTF.ext\n",
 			     ext_sec->desc);
 			return -EINVAL;
 		}
@@ -610,8 +610,7 @@ static int btf_ext_copy_info(struct btf_ext *btf_ext,
 }
 
 static int btf_ext_copy_func_info(struct btf_ext *btf_ext,
-				  __u8 *data, __u32 data_size,
-				  btf_print_fn_t err_log)
+				  __u8 *data, __u32 data_size)
 {
 	const struct btf_ext_header *hdr = (struct btf_ext_header *)data;
 	struct btf_ext_sec_copy_param param = {
@@ -622,12 +621,11 @@ static int btf_ext_copy_func_info(struct btf_ext *btf_ext,
 		.desc = "func_info"
 	};
 
-	return btf_ext_copy_info(btf_ext, data, data_size, &param, err_log);
+	return btf_ext_copy_info(btf_ext, data, data_size, &param);
 }
 
 static int btf_ext_copy_line_info(struct btf_ext *btf_ext,
-				  __u8 *data, __u32 data_size,
-				  btf_print_fn_t err_log)
+				  __u8 *data, __u32 data_size)
 {
 	const struct btf_ext_header *hdr = (struct btf_ext_header *)data;
 	struct btf_ext_sec_copy_param param = {
@@ -638,37 +636,36 @@ static int btf_ext_copy_line_info(struct btf_ext *btf_ext,
 		.desc = "line_info",
 	};
 
-	return btf_ext_copy_info(btf_ext, data, data_size, &param, err_log);
+	return btf_ext_copy_info(btf_ext, data, data_size, &param);
 }
 
-static int btf_ext_parse_hdr(__u8 *data, __u32 data_size,
-			     btf_print_fn_t err_log)
+static int btf_ext_parse_hdr(__u8 *data, __u32 data_size)
 {
 	const struct btf_ext_header *hdr = (struct btf_ext_header *)data;
 
 	if (data_size < offsetof(struct btf_ext_header, func_info_off) ||
 	    data_size < hdr->hdr_len) {
-		elog("BTF.ext header not found");
+		pr_debug("BTF.ext header not found");
 		return -EINVAL;
 	}
 
 	if (hdr->magic != BTF_MAGIC) {
-		elog("Invalid BTF.ext magic:%x\n", hdr->magic);
+		pr_debug("Invalid BTF.ext magic:%x\n", hdr->magic);
 		return -EINVAL;
 	}
 
 	if (hdr->version != BTF_VERSION) {
-		elog("Unsupported BTF.ext version:%u\n", hdr->version);
+		pr_debug("Unsupported BTF.ext version:%u\n", hdr->version);
 		return -ENOTSUP;
 	}
 
 	if (hdr->flags) {
-		elog("Unsupported BTF.ext flags:%x\n", hdr->flags);
+		pr_debug("Unsupported BTF.ext flags:%x\n", hdr->flags);
 		return -ENOTSUP;
 	}
 
 	if (data_size == hdr->hdr_len) {
-		elog("BTF.ext has no data\n");
+		pr_debug("BTF.ext has no data\n");
 		return -EINVAL;
 	}
 
@@ -685,12 +682,12 @@ void btf_ext__free(struct btf_ext *btf_ext)
 	free(btf_ext);
 }
 
-struct btf_ext *btf_ext__new(__u8 *data, __u32 size, btf_print_fn_t err_log)
+struct btf_ext *btf_ext__new(__u8 *data, __u32 size)
 {
 	struct btf_ext *btf_ext;
 	int err;
 
-	err = btf_ext_parse_hdr(data, size, err_log);
+	err = btf_ext_parse_hdr(data, size);
 	if (err)
 		return ERR_PTR(err);
 
@@ -698,13 +695,13 @@ struct btf_ext *btf_ext__new(__u8 *data, __u32 size, btf_print_fn_t err_log)
 	if (!btf_ext)
 		return ERR_PTR(-ENOMEM);
 
-	err = btf_ext_copy_func_info(btf_ext, data, size, err_log);
+	err = btf_ext_copy_func_info(btf_ext, data, size);
 	if (err) {
 		btf_ext__free(btf_ext);
 		return ERR_PTR(err);
 	}
 
-	err = btf_ext_copy_line_info(btf_ext, data, size, err_log);
+	err = btf_ext_copy_line_info(btf_ext, data, size);
 	if (err) {
 		btf_ext__free(btf_ext);
 		return ERR_PTR(err);
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index b0610dcdae6b..b1e8e54cc21d 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -55,11 +55,8 @@ struct btf_ext_header {
 	__u32	line_info_len;
 };
 
-typedef int (*btf_print_fn_t)(const char *, ...)
-	__attribute__((format(printf, 1, 2)));
-
 LIBBPF_API void btf__free(struct btf *btf);
-LIBBPF_API struct btf *btf__new(__u8 *data, __u32 size, btf_print_fn_t err_log);
+LIBBPF_API struct btf *btf__new(__u8 *data, __u32 size);
 LIBBPF_API __s32 btf__find_by_name(const struct btf *btf,
 				   const char *type_name);
 LIBBPF_API const struct btf_type *btf__type_by_id(const struct btf *btf,
@@ -70,7 +67,7 @@ LIBBPF_API int btf__fd(const struct btf *btf);
 LIBBPF_API const char *btf__name_by_offset(const struct btf *btf, __u32 offset);
 LIBBPF_API int btf__get_from_id(__u32 id, struct btf **btf);
 
-struct btf_ext *btf_ext__new(__u8 *data, __u32 size, btf_print_fn_t err_log);
+struct btf_ext *btf_ext__new(__u8 *data, __u32 size);
 void btf_ext__free(struct btf_ext *btf_ext);
 int btf_ext__reloc_func_info(const struct btf *btf,
 			     const struct btf_ext *btf_ext,
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 2ccde17957e6..1c7e25ebbe85 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -42,6 +42,7 @@
 #include "bpf.h"
 #include "btf.h"
 #include "str_error.h"
+#include "util.h"
 
 #ifndef EM_BPF
 #define EM_BPF 247
@@ -69,16 +70,6 @@ static __printf(1, 2) libbpf_print_fn_t __pr_warning = __base_pr;
 static __printf(1, 2) libbpf_print_fn_t __pr_info = __base_pr;
 static __printf(1, 2) libbpf_print_fn_t __pr_debug;
 
-#define __pr(func, fmt, ...)	\
-do {				\
-	if ((func))		\
-		(func)("libbpf: " fmt, ##__VA_ARGS__); \
-} while (0)
-
-#define pr_warning(fmt, ...)	__pr(__pr_warning, fmt, ##__VA_ARGS__)
-#define pr_info(fmt, ...)	__pr(__pr_info, fmt, ##__VA_ARGS__)
-#define pr_debug(fmt, ...)	__pr(__pr_debug, fmt, ##__VA_ARGS__)
-
 void libbpf_set_print(libbpf_print_fn_t warn,
 		      libbpf_print_fn_t info,
 		      libbpf_print_fn_t debug)
@@ -88,6 +79,35 @@ void libbpf_set_print(libbpf_print_fn_t warn,
 	__pr_debug = debug;
 }
 
+__printf(2, 3)
+void libbpf_dprint(enum libbpf_print_level level, const char *format, ...)
+{
+	va_list args;
+
+	va_start(args, format);
+	if (level == LIBBPF_WARN) {
+		if (__pr_warning)
+			__pr_warning(format, args);
+	} else if (level == LIBBPF_INFO) {
+		if (__pr_info)
+			__pr_info(format, args);
+	} else {
+		if (__pr_debug)
+			__pr_debug(format, args);
+	}
+	va_end(args);
+}
+
+bool libbpf_dprint_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 {	\
@@ -839,8 +859,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 		else if (strcmp(name, "maps") == 0)
 			obj->efile.maps_shndx = idx;
 		else if (strcmp(name, BTF_ELF_SEC) == 0) {
-			obj->btf = btf__new(data->d_buf, data->d_size,
-					    __pr_debug);
+			obj->btf = btf__new(data->d_buf, data->d_size);
 			if (IS_ERR(obj->btf)) {
 				pr_warning("Error loading ELF section %s: %ld. Ignored and continue.\n",
 					   BTF_ELF_SEC, PTR_ERR(obj->btf));
@@ -915,8 +934,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 				 BTF_EXT_ELF_SEC, BTF_ELF_SEC);
 		} else {
 			obj->btf_ext = btf_ext__new(btf_ext_data->d_buf,
-						    btf_ext_data->d_size,
-						    __pr_debug);
+						    btf_ext_data->d_size);
 			if (IS_ERR(obj->btf_ext)) {
 				pr_warning("Error loading ELF section %s: %ld. Ignored and continue.\n",
 					   BTF_EXT_ELF_SEC,
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 62ae6cb93da1..4e21971101c9 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -47,6 +47,12 @@ enum libbpf_errno {
 
 LIBBPF_API int libbpf_strerror(int err, char *buf, size_t size);
 
+enum libbpf_print_level {
+        LIBBPF_WARN,
+        LIBBPF_INFO,
+        LIBBPF_DEBUG,
+};
+
 /*
  * __printf is defined in include/linux/compiler-gcc.h. However,
  * it would be better if libbpf.h didn't depend on Linux header files.
diff --git a/tools/lib/bpf/test_libbpf.cpp b/tools/lib/bpf/test_libbpf.cpp
index abf3fc25c9fa..be67f5ea2c19 100644
--- a/tools/lib/bpf/test_libbpf.cpp
+++ b/tools/lib/bpf/test_libbpf.cpp
@@ -14,5 +14,5 @@ int main(int argc, char *argv[])
     bpf_prog_get_fd_by_id(0);
 
     /* btf.h */
-    btf__new(NULL, 0, NULL);
+    btf__new(NULL, 0);
 }
diff --git a/tools/lib/bpf/util.h b/tools/lib/bpf/util.h
new file mode 100644
index 000000000000..b07657600f7c
--- /dev/null
+++ b/tools/lib/bpf/util.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+/* Copyright (c) 2019 Facebook */
+
+#ifndef __LIBBPF_COMMON_H
+#define __LIBBPF_COMMON_H
+
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern void libbpf_dprint(enum libbpf_print_level level,
+			  const char *format, ...)
+	__attribute__((format(printf, 2, 3)));
+
+extern bool libbpf_dprint_level_available(enum libbpf_print_level level);
+
+#define __pr(level, fmt, ...)	\
+do {				\
+	libbpf_dprint(level, "libbpf: " fmt, ##__VA_ARGS__);	\
+} while (0)
+
+#define pr_warning(fmt, ...)	__pr(LIBBPF_WARN, fmt, ##__VA_ARGS__)
+#define pr_info(fmt, ...)	__pr(LIBBPF_INFO, fmt, ##__VA_ARGS__)
+#define pr_debug(fmt, ...)	__pr(LIBBPF_DEBUG, fmt, ##__VA_ARGS__)
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif
-- 
2.17.1

[PATCH bpf-next 2/2] tools/bpf: simplify libbpf API function libbpf_set_print()

[Yonghong Song]

Currently, the libbpf API function libbpf_set_print()
takes three function pointer parameters for warning, info
and debug printout respectively.

This patch changes the API to have just one function pointer
parameter and the function pointer has one additional
parameter "debugging level". So if in the future, if
the debug level is increased, the function signature
won't change.

The libbpf internal function libbpf_dprint_level_available()
previous is able to return whether a particular debug level
(warning, info or debug) is available or not.
With this change, there is only one function for debug
printout, so no easy way to test whether a particular
level is supported or not. This function is only used
for btf.c to allocate for log buffers. Such a compromise
should be acceptable. The function is changed to
libbpf_dprint_available().

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 tools/lib/bpf/btf.c                           |  2 +-
 tools/lib/bpf/libbpf.c                        | 37 +++++--------------
 tools/lib/bpf/libbpf.h                        | 14 ++-----
 tools/lib/bpf/test_libbpf.cpp                 |  2 +-
 tools/lib/bpf/util.h                          |  2 +-
 tools/perf/util/bpf-loader.c                  | 32 ++++++----------
 tools/testing/selftests/bpf/test_btf.c        |  7 ++--
 .../testing/selftests/bpf/test_libbpf_open.c  | 36 +++++++++---------
 tools/testing/selftests/bpf/test_progs.c      | 20 +++++++++-
 9 files changed, 67 insertions(+), 85 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 159104ec31dc..4bbf7f363c50 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -377,7 +377,7 @@ struct btf *btf__new(__u8 *data, __u32 size)
 
 	btf->fd = -1;
 
-	if (libbpf_dprint_level_available(LIBBPF_DEBUG)) {
+	if (libbpf_dprint_available()) {
 		log_buf = malloc(BPF_LOG_BUF_SIZE);
 		if (!log_buf) {
 			err = -ENOMEM;
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 1c7e25ebbe85..38a2e71ea369 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -54,8 +54,8 @@
 
 #define __printf(a, b)	__attribute__((format(printf, a, b)))
 
-__printf(1, 2)
-static int __base_pr(const char *format, ...)
+__printf(2, 3)
+static int __base_pr(enum libbpf_print_level level, const char *format, ...)
 {
 	va_list args;
 	int err;
@@ -66,17 +66,11 @@ static int __base_pr(const char *format, ...)
 	return err;
 }
 
-static __printf(1, 2) libbpf_print_fn_t __pr_warning = __base_pr;
-static __printf(1, 2) libbpf_print_fn_t __pr_info = __base_pr;
-static __printf(1, 2) libbpf_print_fn_t __pr_debug;
+static __printf(2, 3) libbpf_print_fn_t __libbpf_pr = __base_pr;
 
-void libbpf_set_print(libbpf_print_fn_t warn,
-		      libbpf_print_fn_t info,
-		      libbpf_print_fn_t debug)
+void libbpf_set_print(libbpf_print_fn_t fn)
 {
-	__pr_warning = warn;
-	__pr_info = info;
-	__pr_debug = debug;
+	__libbpf_pr = fn;
 }
 
 __printf(2, 3)
@@ -85,27 +79,14 @@ void libbpf_dprint(enum libbpf_print_level level, const char *format, ...)
 	va_list args;
 
 	va_start(args, format);
-	if (level == LIBBPF_WARN) {
-		if (__pr_warning)
-			__pr_warning(format, args);
-	} else if (level == LIBBPF_INFO) {
-		if (__pr_info)
-			__pr_info(format, args);
-	} else {
-		if (__pr_debug)
-			__pr_debug(format, args);
-	}
+	if (__libbpf_pr)
+		__libbpf_pr(level, format, args);
 	va_end(args);
 }
 
-bool libbpf_dprint_level_available(enum libbpf_print_level level)
+bool libbpf_dprint_available(void)
 {
-	if (level == LIBBPF_WARN)
-		return !!__pr_warning;
-	else if (level == LIBBPF_INFO)
-		return !!__pr_info;
-	else
-		return !!__pr_debug;
+	return !!__libbpf_pr;
 }
 
 #define STRERR_BUFSIZE  128
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 4e21971101c9..f8f27f1bb6bf 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -53,17 +53,11 @@ enum libbpf_print_level {
         LIBBPF_DEBUG,
 };
 
-/*
- * __printf is defined in include/linux/compiler-gcc.h. However,
- * it would be better if libbpf.h didn't depend on Linux header files.
- * So instead of __printf, here we use gcc attribute directly.
- */
-typedef int (*libbpf_print_fn_t)(const char *, ...)
-	__attribute__((format(printf, 1, 2)));
+typedef int (*libbpf_print_fn_t)(enum libbpf_print_level level,
+				 const char *, ...)
+	__attribute__((format(printf, 2, 3)));
 
-LIBBPF_API void libbpf_set_print(libbpf_print_fn_t warn,
-				 libbpf_print_fn_t info,
-				 libbpf_print_fn_t debug);
+LIBBPF_API void libbpf_set_print(libbpf_print_fn_t fn);
 
 /* Hide internal to user */
 struct bpf_object;
diff --git a/tools/lib/bpf/test_libbpf.cpp b/tools/lib/bpf/test_libbpf.cpp
index be67f5ea2c19..fc134873bb6d 100644
--- a/tools/lib/bpf/test_libbpf.cpp
+++ b/tools/lib/bpf/test_libbpf.cpp
@@ -8,7 +8,7 @@
 int main(int argc, char *argv[])
 {
     /* libbpf.h */
-    libbpf_set_print(NULL, NULL, NULL);
+    libbpf_set_print(NULL);
 
     /* bpf.h */
     bpf_prog_get_fd_by_id(0);
diff --git a/tools/lib/bpf/util.h b/tools/lib/bpf/util.h
index b07657600f7c..6b93ebf61ea6 100644
--- a/tools/lib/bpf/util.h
+++ b/tools/lib/bpf/util.h
@@ -14,7 +14,7 @@ extern void libbpf_dprint(enum libbpf_print_level level,
 			  const char *format, ...)
 	__attribute__((format(printf, 2, 3)));
 
-extern bool libbpf_dprint_level_available(enum libbpf_print_level level);
+extern bool libbpf_dprint_available(void);
 
 #define __pr(level, fmt, ...)	\
 do {				\
diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 2f3eb6d293ee..c492f3a2acdc 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -24,21 +24,17 @@
 #include "llvm-utils.h"
 #include "c++/clang-c.h"
 
-#define DEFINE_PRINT_FN(name, level) \
-static int libbpf_##name(const char *fmt, ...)	\
-{						\
-	va_list args;				\
-	int ret;				\
-						\
-	va_start(args, fmt);			\
-	ret = veprintf(level, verbose, pr_fmt(fmt), args);\
-	va_end(args);				\
-	return ret;				\
-}
+static int libbpf_perf_dprint(enum libbpf_print_level level __attribute__((unused)),
+			      const char *fmt, ...)
+{
+	va_list args;
+	int ret;
 
-DEFINE_PRINT_FN(warning, 1)
-DEFINE_PRINT_FN(info, 1)
-DEFINE_PRINT_FN(debug, 1)
+	va_start(args, fmt);
+	ret = veprintf(1, verbose, pr_fmt(fmt), args);
+	va_end(args);
+	return ret;
+}
 
 struct bpf_prog_priv {
 	bool is_tp;
@@ -59,9 +55,7 @@ bpf__prepare_load_buffer(void *obj_buf, size_t obj_buf_sz, const char *name)
 	struct bpf_object *obj;
 
 	if (!libbpf_initialized) {
-		libbpf_set_print(libbpf_warning,
-				 libbpf_info,
-				 libbpf_debug);
+		libbpf_set_print(libbpf_perf_dprint);
 		libbpf_initialized = true;
 	}
 
@@ -79,9 +73,7 @@ struct bpf_object *bpf__prepare_load(const char *filename, bool source)
 	struct bpf_object *obj;
 
 	if (!libbpf_initialized) {
-		libbpf_set_print(libbpf_warning,
-				 libbpf_info,
-				 libbpf_debug);
+		libbpf_set_print(libbpf_perf_dprint);
 		libbpf_initialized = true;
 	}
 
diff --git a/tools/testing/selftests/bpf/test_btf.c b/tools/testing/selftests/bpf/test_btf.c
index 179f1d8ec5bf..aebaeff5a5a0 100644
--- a/tools/testing/selftests/bpf/test_btf.c
+++ b/tools/testing/selftests/bpf/test_btf.c
@@ -54,8 +54,9 @@ static int count_result(int err)
 
 #define __printf(a, b)	__attribute__((format(printf, a, b)))
 
-__printf(1, 2)
-static int __base_pr(const char *format, ...)
+__printf(2, 3)
+static int __base_pr(enum libbpf_print_level level __attribute__((unused)),
+		     const char *format, ...)
 {
 	va_list args;
 	int err;
@@ -5650,7 +5651,7 @@ int main(int argc, char **argv)
 		return err;
 
 	if (args.always_log)
-		libbpf_set_print(__base_pr, __base_pr, __base_pr);
+		libbpf_set_print(__base_pr);
 
 	if (args.raw_test)
 		err |= test_raw();
diff --git a/tools/testing/selftests/bpf/test_libbpf_open.c b/tools/testing/selftests/bpf/test_libbpf_open.c
index 8fcd1c076add..b9ff3bf76544 100644
--- a/tools/testing/selftests/bpf/test_libbpf_open.c
+++ b/tools/testing/selftests/bpf/test_libbpf_open.c
@@ -34,23 +34,22 @@ static void usage(char *argv[])
 	printf("\n");
 }
 
-#define DEFINE_PRINT_FN(name, enabled) \
-static int libbpf_##name(const char *fmt, ...)  	\
-{							\
-        va_list args;					\
-        int ret;					\
-							\
-        va_start(args, fmt);				\
-	if (enabled) {					\
-		fprintf(stderr, "[" #name "] ");	\
-		ret = vfprintf(stderr, fmt, args);	\
-	}						\
-        va_end(args);					\
-        return ret;					\
+static bool debug = 0;
+static int libbpf_debug_print(enum libbpf_print_level level,
+			      const char *fmt, ...)
+{
+	va_list args;
+	int ret;
+
+	if (level == LIBBPF_DEBUG && !debug)
+		return 0;
+
+	va_start(args, fmt);
+	fprintf(stderr, "[%d] ", level);
+	ret = vfprintf(stderr, fmt, args);
+	va_end(args);
+	return ret;
 }
-DEFINE_PRINT_FN(warning, 1)
-DEFINE_PRINT_FN(info, 1)
-DEFINE_PRINT_FN(debug, 1)
 
 #define EXIT_FAIL_LIBBPF EXIT_FAILURE
 #define EXIT_FAIL_OPTION 2
@@ -120,15 +119,14 @@ int main(int argc, char **argv)
 	int longindex = 0;
 	int opt;
 
-	libbpf_set_print(libbpf_warning, libbpf_info, NULL);
+	libbpf_set_print(libbpf_debug_print);
 
 	/* Parse commands line args */
 	while ((opt = getopt_long(argc, argv, "hDq",
 				  long_options, &longindex)) != -1) {
 		switch (opt) {
 		case 'D':
-			libbpf_set_print(libbpf_warning, libbpf_info,
-					 libbpf_debug);
+			debug = 1;
 			break;
 		case 'q': /* Use in scripting mode */
 			verbose = 0;
diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index d8940b8b2f8d..294beff3374e 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -10,6 +10,7 @@
 #include <string.h>
 #include <assert.h>
 #include <stdlib.h>
+#include <stdarg.h>
 #include <time.h>
 
 #include <linux/types.h>
@@ -1783,6 +1784,21 @@ static void test_task_fd_query_tp(void)
 				   "sys_enter_read");
 }
 
+static int libbpf_debug_print(enum libbpf_print_level level,
+			      const char *format, ...)
+{
+	va_list args;
+	int ret;
+
+	if (level == LIBBPF_DEBUG)
+		return 0;
+
+	va_start(args, format);
+	ret = vfprintf(stderr, format, args);
+	va_end(args);
+	return ret;
+}
+
 static void test_reference_tracking()
 {
 	const char *file = "./test_sk_lookup_kern.o";
@@ -1809,9 +1825,9 @@ static void test_reference_tracking()
 
 		/* Expect verifier failure if test name has 'fail' */
 		if (strstr(title, "fail") != NULL) {
-			libbpf_set_print(NULL, NULL, NULL);
+			libbpf_set_print(NULL);
 			err = !bpf_program__load(prog, "GPL", 0);
-			libbpf_set_print(printf, printf, NULL);
+			libbpf_set_print(libbpf_debug_print);
 		} else {
 			err = bpf_program__load(prog, "GPL", 0);
 		}
-- 
2.17.1