scx: Allow calling scx kfuncs from BPF_PROG_TYPE_SYSCALL

kernel/sched/ext.c

@@ -5282,6 +5282,8 @@ static int __init scx_init(void)
 	    (ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS,
 					     &scx_kfunc_set_any)) ||
 	    (ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING,
+					     &scx_kfunc_set_any)) ||
+            (ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL,
 					     &scx_kfunc_set_any))) {
 		pr_err("sched_ext: Failed to register kfunc sets (%d)\n", ret);
 		return ret;

tools/testing/selftests/sched_ext/Makefile

@@ -170,6 +170,7 @@ auto-test-targets :=			\
 	maximal				\
 	maybe_null			\
 	minimal				\
+	prog_run			\
 	reload_loop			\
 	select_cpu_dfl			\
 	select_cpu_dfl_nodispatch	\

tools/testing/selftests/sched_ext/prog_run.bpf.c

@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * A scheduler that validates that we can invoke sched_ext kfuncs in
+ * BPF_PROG_TYPE_SYSCALL programs.
+ *
+ * Copyright (c) 2024 Meta Platforms, Inc. and affiliates.
+ * Copyright (c) 2024 David Vernet <[email protected]>
+ */
+
+#include <scx/common.bpf.h>
+
+UEI_DEFINE(uei);
+
+char _license[] SEC("license") = "GPL";
+
+SEC("syscall")
+int BPF_PROG(prog_run_syscall)
+{
+	scx_bpf_exit(0xdeadbeef, "Exited from PROG_RUN");
+	return 0;
+}
+
+void BPF_STRUCT_OPS(prog_run_exit, struct scx_exit_info *ei)
+{
+	UEI_RECORD(uei, ei);
+}
+
+SEC(".struct_ops.link")
+struct sched_ext_ops prog_run_ops = {
+	.exit			= prog_run_exit,
+	.name			= "prog_run",
+};

tools/testing/selftests/sched_ext/prog_run.c

@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2024 Meta Platforms, Inc. and affiliates.
+ * Copyright (c) 2024 David Vernet <[email protected]>
+ */
+#include <bpf/bpf.h>
+#include <sched.h>
+#include <scx/common.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include "prog_run.bpf.skel.h"
+#include "scx_test.h"
+
+static enum scx_test_status setup(void **ctx)
+{
+	struct prog_run *skel;
+
+	skel = prog_run__open_and_load();
+	if (!skel) {
+		SCX_ERR("Failed to open and load skel");
+		return SCX_TEST_FAIL;
+	}
+	*ctx = skel;
+
+	return SCX_TEST_PASS;
+}
+
+static enum scx_test_status run(void *ctx)
+{
+	struct prog_run *skel = ctx;
+	struct bpf_link *link;
+	int prog_fd, err = 0;
+
+	prog_fd = bpf_program__fd(skel->progs.prog_run_syscall);
+	if (prog_fd < 0) {
+		SCX_ERR("Failed to get BPF_PROG_RUN prog");
+		return SCX_TEST_FAIL;
+	}
+
+        LIBBPF_OPTS(bpf_test_run_opts, topts);
+
+	link = bpf_map__attach_struct_ops(skel->maps.prog_run_ops);
+	if (!link) {
+		SCX_ERR("Failed to attach scheduler");
+		close(prog_fd);
+		return SCX_TEST_FAIL;
+	}
+
+	//err = bpf_prog_test_run_opts(prog_fd, &topts);
+	SCX_EQ(err, 0);
+
+	/* Assumes uei.kind is written last */
+	while (skel->data->uei.kind == SCX_EXIT_NONE)
+		sched_yield();
+
+	SCX_EQ(skel->data->uei.kind, SCX_EXIT_UNREG_BPF);
+	SCX_EQ(skel->data->uei.exit_code, 0xdeadbeef);
+	close(prog_fd);
+	bpf_link__destroy(link);
+
+	return SCX_TEST_PASS;
+}
+
+static void cleanup(void *ctx)
+{
+	struct prog_run *skel = ctx;
+
+	prog_run__destroy(skel);
+}
+
+struct scx_test prog_run = {
+	.name = "prog_run",
+	.description = "Verify we can call into a scheduler with BPF_PROG_RUN, and invoke kfuncs",
+	.setup = setup,
+	.run = run,
+	.cleanup = cleanup,
+};
+REGISTER_SCX_TEST(&prog_run)