[PATCH bpf-next 2/2] selftests/bpf: Add PROG_TEST_RUN selftest for BPF_PROG_TYPE_KPROBE

[Daniel Xu <dxu@xxxxxxxxx>]

This commit adds a selftest to test that we can both PROG_TEST_RUN a
kprobe prog and set its context.

Signed-off-by: Daniel Xu <dxu@xxxxxxxxx>
---
 .../selftests/bpf/prog_tests/kprobe_ctx.c     | 57 +++++++++++++++++++
 .../testing/selftests/bpf/progs/kprobe_ctx.c  | 33 +++++++++++
 2 files changed, 90 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/kprobe_ctx.c
 create mode 100644 tools/testing/selftests/bpf/progs/kprobe_ctx.c

diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_ctx.c b/tools/testing/selftests/bpf/prog_tests/kprobe_ctx.c
new file mode 100644
index 000000000000..260966fd4506
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/kprobe_ctx.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <linux/ptrace.h>
+#include "kprobe_ctx.skel.h"
+
+/*
+ * x86_64 happens to be one of the architectures that exports the
+ * kernel `struct pt_regs` to userspace ABI. For the architectures
+ * that don't, users will have to extract `struct pt_regs` from vmlinux
+ * BTF in order to use BPF_PROG_TYPE_KPROBE's BPF_PROG_RUN functionality.
+ *
+ * We choose to only test x86 here to keep the test simple.
+ */
+void test_kprobe_ctx(void)
+{
+#ifdef __x86_64__
+	struct pt_regs regs = {
+		.rdi = 1,
+		.rsi = 2,
+		.rdx = 3,
+		.rcx = 4,
+		.r8 = 5,
+	};
+
+	LIBBPF_OPTS(bpf_test_run_opts, tattr,
+		.ctx_in = &regs,
+		.ctx_size_in = sizeof(regs),
+	);
+
+	struct kprobe_ctx *skel = NULL;
+	int prog_fd;
+	int err;
+
+	skel = kprobe_ctx__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		return;
+
+	skel->bss->expected_p1 = (void *)1;
+	skel->bss->expected_p2 = (void *)2;
+	skel->bss->expected_p3 = (void *)3;
+	skel->bss->expected_p4 = (void *)4;
+	skel->bss->expected_p5 = (void *)5;
+
+	prog_fd = bpf_program__fd(skel->progs.prog);
+	err = bpf_prog_test_run_opts(prog_fd, &tattr);
+	if (!ASSERT_OK(err, "bpf_prog_test_run"))
+		goto cleanup;
+
+	if (!ASSERT_TRUE(skel->bss->ret, "ret"))
+		goto cleanup;
+
+	if (!ASSERT_GT(tattr.duration, 0, "duration"))
+		goto cleanup;
+cleanup:
+	kprobe_ctx__destroy(skel);
+#endif
+}
diff --git a/tools/testing/selftests/bpf/progs/kprobe_ctx.c b/tools/testing/selftests/bpf/progs/kprobe_ctx.c
new file mode 100644
index 000000000000..98063c549930
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/kprobe_ctx.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+volatile void *expected_p1;
+volatile void *expected_p2;
+volatile void *expected_p3;
+volatile void *expected_p4;
+volatile void *expected_p5;
+volatile bool ret = false;
+
+SEC("kprobe/this_function_does_not_exist")
+int prog(struct pt_regs *ctx)
+{
+	void *p1, *p2, *p3, *p4, *p5;
+
+	p1 = (void *)PT_REGS_PARM1(ctx);
+	p2 = (void *)PT_REGS_PARM2(ctx);
+	p3 = (void *)PT_REGS_PARM3(ctx);
+	p4 = (void *)PT_REGS_PARM4(ctx);
+	p5 = (void *)PT_REGS_PARM5(ctx);
+
+	if (p1 != expected_p1 || p2 != expected_p2 || p3 != expected_p3 ||
+	    p4 != expected_p4 || p5 != expected_p5)
+		return 0;
+
+	ret = true;
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.36.1