bpftool: Use libbpf_get_error() to check error

Currently, LIBBPF_STRICT_ALL mode is enabled by default for
bpftool which means on error cases, some libbpf APIs would
return NULL pointers. This makes IS_ERR check failed to detect
such cases and result in segfault error. Use libbpf_get_error()
instead like we do in libbpf itself.

Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211115012436.3143318-1-hengqi.chen@gmail.com

tools/bpf/bpftool/btf.c

@@ -421,8 +421,9 @@ static int dump_btf_c(const struct btf *btf,
 	int err = 0, i;
 
 	d = btf_dump__new(btf, btf_dump_printf, NULL, NULL);
-	if (IS_ERR(d))
-		return PTR_ERR(d);
+	err = libbpf_get_error(d);
+	if (err)
+		return err;
 
 	printf("#ifndef __VMLINUX_H__\n");
 	printf("#define __VMLINUX_H__\n");
@@ -549,8 +550,8 @@ static int do_dump(int argc, char **argv)
 		}
 
 		btf = btf__parse_split(*argv, base ?: base_btf);
-		if (IS_ERR(btf)) {
-			err = -PTR_ERR(btf);
+		err = libbpf_get_error(btf);
+		if (err) {
 			btf = NULL;
 			p_err("failed to load BTF from %s: %s",
 			      *argv, strerror(err));

tools/bpf/bpftool/gen.c

@@ -219,8 +219,9 @@ static int codegen_datasecs(struct bpf_object *obj, const char *obj_name)
 	int i, err = 0;
 
 	d = btf_dump__new(btf, codegen_btf_dump_printf, NULL, NULL);
-	if (IS_ERR(d))
-		return PTR_ERR(d);
+	err = libbpf_get_error(d);
+	if (err)
+		return err;
 
 	bpf_object__for_each_map(map, obj) {
 		/* only generate definitions for memory-mapped internal maps */
@@ -719,10 +720,11 @@ static int do_skeleton(int argc, char **argv)
 		get_obj_name(obj_name, file);
 	opts.object_name = obj_name;
 	obj = bpf_object__open_mem(obj_data, file_sz, &opts);
-	if (IS_ERR(obj)) {
+	err = libbpf_get_error(obj);
+	if (err) {
 		char err_buf[256];
 
-		libbpf_strerror(PTR_ERR(obj), err_buf, sizeof(err_buf));
+		libbpf_strerror(err, err_buf, sizeof(err_buf));
 		p_err("failed to open BPF object file: %s", err_buf);
 		obj = NULL;
 		goto out;

tools/bpf/bpftool/iter.c

@@ -46,7 +46,8 @@ static int do_pin(int argc, char **argv)
 	}
 
 	obj = bpf_object__open(objfile);
-	if (IS_ERR(obj)) {
+	err = libbpf_get_error(obj);
+	if (err) {
 		p_err("can't open objfile %s", objfile);
 		goto close_map_fd;
 	}
@@ -64,8 +65,8 @@ static int do_pin(int argc, char **argv)
 	}
 
 	link = bpf_program__attach_iter(prog, &iter_opts);
-	if (IS_ERR(link)) {
-		err = PTR_ERR(link);
+	err = libbpf_get_error(link);
+	if (err) {
 		p_err("attach_iter failed for program %s",
 		      bpf_program__name(prog));
 		goto close_obj;

tools/bpf/bpftool/map.c

@@ -812,7 +812,7 @@ static struct btf *get_map_kv_btf(const struct bpf_map_info *info)
 	if (info->btf_vmlinux_value_type_id) {
 		if (!btf_vmlinux) {
 			btf_vmlinux = libbpf_find_kernel_btf();
-			if (IS_ERR(btf_vmlinux))
+			if (libbpf_get_error(btf_vmlinux))
 				p_err("failed to get kernel btf");
 		}
 		return btf_vmlinux;
@@ -832,13 +832,13 @@ static struct btf *get_map_kv_btf(const struct bpf_map_info *info)
 
 static void free_map_kv_btf(struct btf *btf)
 {
-	if (!IS_ERR(btf) && btf != btf_vmlinux)
+	if (!libbpf_get_error(btf) && btf != btf_vmlinux)
 		btf__free(btf);
 }
 
 static void free_btf_vmlinux(void)
 {
-	if (!IS_ERR(btf_vmlinux))
+	if (!libbpf_get_error(btf_vmlinux))
 		btf__free(btf_vmlinux);
 }
 
@@ -863,8 +863,8 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
 
 	if (wtr) {
 		btf = get_map_kv_btf(info);
-		if (IS_ERR(btf)) {
-			err = PTR_ERR(btf);
+		err = libbpf_get_error(btf);
+		if (err) {
 			goto exit_free;
 		}
 

tools/bpf/bpftool/struct_ops.c

@@ -32,7 +32,7 @@ static const struct btf *get_btf_vmlinux(void)
 		return btf_vmlinux;
 
 	btf_vmlinux = libbpf_find_kernel_btf();
-	if (IS_ERR(btf_vmlinux))
+	if (libbpf_get_error(btf_vmlinux))
 		p_err("struct_ops requires kernel CONFIG_DEBUG_INFO_BTF=y");
 
 	return btf_vmlinux;
@@ -45,7 +45,7 @@ static const char *get_kern_struct_ops_name(const struct bpf_map_info *info)
 	const char *st_ops_name;
 
 	kern_btf = get_btf_vmlinux();
-	if (IS_ERR(kern_btf))
+	if (libbpf_get_error(kern_btf))
 		return "<btf_vmlinux_not_found>";
 
 	t = btf__type_by_id(kern_btf, info->btf_vmlinux_value_type_id);
@@ -63,7 +63,7 @@ static __s32 get_map_info_type_id(void)
 		return map_info_type_id;
 
 	kern_btf = get_btf_vmlinux();
-	if (IS_ERR(kern_btf)) {
+	if (libbpf_get_error(kern_btf)) {
 		map_info_type_id = PTR_ERR(kern_btf);
 		return map_info_type_id;
 	}
@@ -415,7 +415,7 @@ static int do_dump(int argc, char **argv)
 	}
 
 	kern_btf = get_btf_vmlinux();
-	if (IS_ERR(kern_btf))
+	if (libbpf_get_error(kern_btf))
 		return -1;
 
 	if (!json_output) {
@@ -495,7 +495,7 @@ static int do_register(int argc, char **argv)
 	file = GET_ARG();
 
 	obj = bpf_object__open(file);
-	if (IS_ERR_OR_NULL(obj))
+	if (libbpf_get_error(obj))
 		return -1;
 
 	set_max_rlimit();
@@ -516,7 +516,7 @@ static int do_register(int argc, char **argv)
 			continue;
 
 		link = bpf_map__attach_struct_ops(map);
-		if (IS_ERR(link)) {
+		if (libbpf_get_error(link)) {
 			p_err("can't register struct_ops %s: %s",
 			      bpf_map__name(map),
 			      strerror(-PTR_ERR(link)));
@@ -596,7 +596,7 @@ int do_struct_ops(int argc, char **argv)
 
 	err = cmd_select(cmds, argc, argv, do_help);
 
-	if (!IS_ERR(btf_vmlinux))
+	if (!libbpf_get_error(btf_vmlinux))
 		btf__free(btf_vmlinux);
 
 	return err;