diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index cb106e8c42cb..1cac02bfa599 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -6584,7 +6584,7 @@ static int bpf_object__read_kallsyms_file(struct bpf_object *obj)
 }
 
 static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name,
-			    __u16 kind, struct btf **res_btf,
+			    __u16 kind, bool is_weak, struct btf **res_btf,
 			    int *res_btf_fd)
 {
 	int i, id, btf_fd, err;
@@ -6608,6 +6608,9 @@ static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name,
 				break;
 		}
 	}
+	if (is_weak && id == -ENOENT)
+		return 0;
+
 	if (id <= 0) {
 		pr_warn("extern (%s ksym) '%s': failed to find BTF ID in kernel BTF(s).\n",
 			__btf_kind_str(kind), ksym_name);
@@ -6627,11 +6630,19 @@ static int bpf_object__resolve_ksym_var_btf_id(struct bpf_object *obj,
 	const char *targ_var_name;
 	int id, btf_fd = 0, err;
 	struct btf *btf = NULL;
+	bool is_weak = ext->is_weak;
 
-	id = find_ksym_btf_id(obj, ext->name, BTF_KIND_VAR, &btf, &btf_fd);
+	id = find_ksym_btf_id(obj, ext->name, BTF_KIND_VAR, is_weak, &btf, &btf_fd);
 	if (id < 0)
 		return id;
 
+	if (is_weak && id == 0) {
+		ext->is_set = true;
+		ext->ksym.kernel_btf_obj_fd = 0;
+		ext->ksym.kernel_btf_id = 0;
+		return 0;
+	}
+
 	/* find local type_id */
 	local_type_id = ext->ksym.type_id;
 
@@ -6676,7 +6687,7 @@ static int bpf_object__resolve_ksym_func_btf_id(struct bpf_object *obj,
 
 	local_func_proto_id = ext->ksym.type_id;
 
-	kfunc_id = find_ksym_btf_id(obj, ext->name, BTF_KIND_FUNC,
+	kfunc_id = find_ksym_btf_id(obj, ext->name, BTF_KIND_FUNC, false,
 				    &kern_btf, &kern_btf_fd);
 	if (kfunc_id < 0) {
 		pr_warn("extern (func ksym) '%s': not found in kernel BTF\n",
diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
index 67bebd324147..12a5e5ebcc3d 100644
--- a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
@@ -6,6 +6,7 @@
 #include <bpf/btf.h>
 #include "test_ksyms_btf.skel.h"
 #include "test_ksyms_btf_null_check.skel.h"
+#include "test_ksyms_weak.skel.h"
 
 static int duration;
 
@@ -81,6 +82,44 @@ static void test_null_check(void)
 	test_ksyms_btf_null_check__destroy(skel);
 }
 
+static void test_weak_syms(void)
+{
+	struct test_ksyms_weak *skel;
+	struct test_ksyms_weak__data *data;
+
+	skel = test_ksyms_weak__open_and_load();
+	if (CHECK(skel, "skel_open_and_load",
+		  "unexpected load of a prog referencing non-existing ksyms\n")) {
+		test_ksyms_weak__destroy(skel);
+		return;
+	}
+
+	skel = test_ksyms_weak__open();
+	if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
+		return;
+
+	bpf_program__set_autoload(skel->progs.fail_handler, false);
+	if (CHECK(test_ksyms_weak__load(skel), "skel_load", "failed to load skeleton\n"))
+		goto cleanup;
+
+	if (CHECK(test_ksyms_weak__attach(skel), "skel_attach", "failed to attach skeleton\n"))
+		goto cleanup;
+
+	/* trigger tracepoint */
+	usleep(1);
+
+	data = skel->data;
+	CHECK(data->out__existing_typed != 0, "existing_typed",
+	      "failed to reference an existing typed symbol\n");
+	CHECK(data->out__existing_typeless == -1, "existing_typeless",
+	      "failed to get the address of an existing typeless symbol\n");
+	CHECK(data->out__non_existing_typeless != 0, "non_existing_typeless",
+	      "non-existing typeless symbol does not default to zero\n");
+
+cleanup:
+	test_ksyms_weak__destroy(skel);
+}
+
 void test_ksyms_btf(void)
 {
 	int percpu_datasec;
@@ -105,4 +144,7 @@ void test_ksyms_btf(void)
 
 	if (test__start_subtest("null_check"))
 		test_null_check();
+
+	if (test__start_subtest("weak_ksyms"))
+		test_weak_syms();
 }
diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_weak.c b/tools/testing/selftests/bpf/progs/test_ksyms_weak.c
new file mode 100644
index 000000000000..e956fdf3162c
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_ksyms_weak.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test weak ksyms.
+ *
+ * Copyright (c) 2021 Google
+ */
+
+#include "vmlinux.h"
+
+#include <bpf/bpf_helpers.h>
+
+int out__existing_typed = -1;
+__u64 out__existing_typeless = -1;
+
+__u64 out__non_existing_typeless = -1;
+__u64 out__non_existing_typed = -1;
+
+/* existing weak symbols */
+
+/* test existing weak symbols can be resolved. */
+extern const struct rq runqueues __ksym __weak; /* typed */
+extern const void bpf_prog_active __ksym __weak; /* typeless */
+
+
+/* non-existing weak symbols. */
+
+/* typeless symbols, default to zero. */
+extern const void bpf_link_fops1 __ksym __weak;
+
+/* typed symbols, fail verifier checks if referenced. */
+extern const int bpf_link_fops2 __ksym __weak;
+
+/* typed symbols, pass if not referenced. */
+extern const int bpf_link_fops3 __ksym __weak;
+
+SEC("raw_tp/sys_enter")
+int pass_handler(const void *ctx)
+{
+	/* tests existing symbols. */
+	struct rq *rq = (struct rq *)bpf_per_cpu_ptr(&runqueues, 0);
+	if (rq)
+		out__existing_typed = rq->cpu;
+	out__existing_typeless = (__u64)&bpf_prog_active;
+
+	/* tests non-existing symbols. */
+	out__non_existing_typeless = (__u64)&bpf_link_fops1;
+
+	return 0;
+}
+
+SEC("raw_tp/sys_exit")
+int fail_handler(const void *ctx)
+{
+	/* tests non-existing symbols. */
+	out__non_existing_typed = (__u64)&bpf_link_fops2;
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
