bpf: Add kfuncs and selftests for detecting execution context and selftests

kernel/bpf/helpers.c

@@ -4252,6 +4252,47 @@ __bpf_kfunc int bpf_task_work_schedule_resume(struct task_struct *task, struct b
 	return bpf_task_work_schedule(task, tw, map__map, callback, aux__prog, TWA_RESUME);
 }
 
+/**
+ * bpf_in_nmi_context - Check whether we are serving NMI
+ *
+ * Return: true if we are serving NMI
+ */
+__bpf_kfunc bool bpf_in_nmi_context(void)
+{
+	return in_nmi();
+}
+
+/**
+ * bpf_in_hardirq_context - Check whether we are serving hard irq
+ *
+ * Return: true if we are serving hard irq
+ */
+__bpf_kfunc bool bpf_in_hardirq_context(void)
+{
+	return in_hardirq();
+}
+
+/**
+ * bpf_in_softirq_context - Check whether we are serving soft irq
+ *
+ * Return: true if we are serving soft irq
+ */
+__bpf_kfunc bool bpf_in_softirq_context(void)
+{
+	/* in_softirq() has been deprecated */
+	return in_serving_softirq();
+}
+
+/**
+ * bpf_in_task_context - Check whether we are in task context
+ *
+ * Return: true if we are in task context
+ */
+__bpf_kfunc bool bpf_in_task_context(void)
+{
+	return in_task();
+}
+
 __bpf_kfunc_end_defs();
 
 static void bpf_task_work_cancel_scheduled(struct irq_work *irq_work)
@@ -4429,6 +4470,10 @@ BTF_ID_FLAGS(func, bpf_cgroup_read_xattr, KF_RCU)
 BTF_ID_FLAGS(func, bpf_stream_vprintk, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_task_work_schedule_signal, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_task_work_schedule_resume, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_in_softirq_context)
+BTF_ID_FLAGS(func, bpf_in_hardirq_context)
+BTF_ID_FLAGS(func, bpf_in_task_context)
+BTF_ID_FLAGS(func, bpf_in_nmi_context)
 BTF_KFUNCS_END(common_btf_ids)
 
 static const struct btf_kfunc_id_set common_kfunc_set = {

tools/testing/selftests/bpf/prog_tests/context.c

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <error.h>
+#include <test_progs.h>
+#include "context_prog.skel.h"
+
+void test_context(void)
+{
+	struct context_prog *skel = NULL;
+
+	skel = context_prog__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "loading prog fail"))
+		return;
+
+	context_prog__attach(skel);
+	getuid();
+	sleep(5);
+
+	if (!ASSERT_EQ(1, skel->bss->in_hardirq, "hardirq not triggered"))
+		goto out;
+	if (!ASSERT_EQ(1, skel->bss->in_softriq, "softirq not triggered"))
+		goto out;
+	if (!ASSERT_EQ(1, skel->bss->in_task, "task context not triggered"))
+		goto out;
+out:
+	context_prog__destroy(skel);
+}
+
+void test_bpf_context(void)
+{
+	if (test__start_subtest("context"))
+		test_context();
+}

tools/testing/selftests/bpf/progs/context_prog.c

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_misc.h"
+#include "bpf_experimental.h"
+
+int in_hardirq = 0;
+int in_softriq = 0;
+int in_task = 0;
+
+SEC("tp/irq/irq_handler_entry")
+int trace_irq_handler_entry(const void *ctx)
+{
+	in_hardirq = bpf_in_hardirq_context();
+	return 0;
+}
+
+SEC("tp/irq/softirq_entry")
+int trace_softirq_entry(const void *ctx)
+{
+	in_softriq = bpf_in_softirq_context();
+	return 0;
+}
+
+SEC("tp/syscalls/sys_enter_getuid")
+int trace_syscall(const void *ctx)
+{
+	in_task = bpf_in_task_context();
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";