[PATCH v3 2/2] libbpf: Fix the incorrect register read for syscalls on x86_64

[<Kenta.Tada@sony.com>]

Add a selftest to verify the behavior of PT_REGS_xxx.

Signed-off-by: Kenta Tada <Kenta.Tada@sony.com>
---
 .../bpf/prog_tests/bpf_syscall_macro_test.c   | 60 +++++++++++++++++++
 .../bpf/progs/test_bpf_syscall_macro.c        | 52 ++++++++++++++++
 2 files changed, 112 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/bpf_syscall_macro_test.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_bpf_syscall_macro.c

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_syscall_macro_test.c b/tools/testing/selftests/bpf/prog_tests/bpf_syscall_macro_test.c
new file mode 100644
index 000000000000..cd7133954210
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_syscall_macro_test.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright 2022 Sony Group Corporation */
+#include <sys/prctl.h>
+#include <test_progs.h>
+#include "test_bpf_syscall_macro.skel.h"
+
+void serial_test_bpf_syscall_macro(void)
+{
+	struct test_bpf_syscall_macro *skel = NULL;
+	int err;
+	int duration = 0;
+	int exp_arg1 = 1001;
+	unsigned long exp_arg2 = 12;
+	unsigned long exp_arg3 = 13;
+	unsigned long exp_arg4 = 14;
+	unsigned long exp_arg5 = 15;
+
+	/* check whether it can load program */
+	skel = test_bpf_syscall_macro__open_and_load();
+	if (CHECK(!skel, "skel_open_and_load", "skeleton open_and_load failed\n"))
+		goto cleanup;
+
+	/* check whether it can attach kprobe */
+	err = test_bpf_syscall_macro__attach(skel);
+	if (CHECK(err, "attach_kprobe", "err %d\n", err))
+		goto cleanup;
+
+	/* check whether args of syscall are copied correctly */
+	prctl(exp_arg1, exp_arg2, exp_arg3, exp_arg4, exp_arg5);
+	if (CHECK(skel->bss->arg1 != exp_arg1, "syscall_arg1",
+		  "exp %d, got %d\n", exp_arg1, skel->bss->arg1)) {
+		goto cleanup;
+	}
+	if (CHECK(skel->bss->arg2 != exp_arg2, "syscall_arg2",
+		  "exp %ld, got %ld\n", exp_arg2, skel->bss->arg2)) {
+		goto cleanup;
+	}
+	if (CHECK(skel->bss->arg3 != exp_arg3, "syscall_arg3",
+		  "exp %ld, got %ld\n", exp_arg3, skel->bss->arg3)) {
+		goto cleanup;
+	}
+	/* it cannot copy arg4 when uses PT_REGS_PARM4 on x86_64 */
+#ifdef __x86_64__
+	if (CHECK(skel->bss->arg4_cx == exp_arg4, "syscall_arg4_from_cx",
+		  "exp %ld, got %ld\n", exp_arg4, skel->bss->arg4_cx)) {
+		goto cleanup;
+	}
+#endif
+	if (CHECK(skel->bss->arg4 != exp_arg4, "syscall_arg4",
+		  "exp %ld, got %ld\n", exp_arg4, skel->bss->arg4)) {
+		goto cleanup;
+	}
+	if (CHECK(skel->bss->arg5 != exp_arg5, "syscall_arg5",
+		  "exp %ld, got %ld\n", exp_arg5, skel->bss->arg5)) {
+		goto cleanup;
+	}
+
+cleanup:
+	test_bpf_syscall_macro__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_bpf_syscall_macro.c b/tools/testing/selftests/bpf/progs/test_bpf_syscall_macro.c
new file mode 100644
index 000000000000..002889d506cc
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_bpf_syscall_macro.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright 2022 Sony Group Corporation */
+#include <linux/bpf.h>
+#include <linux/ptrace.h>
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#if defined(__TARGET_ARCH_x86)
+#define SYS_PREFIX "__x64_"
+#elif defined(__TARGET_ARCH_s390)
+#define SYS_PREFIX "__s390x_"
+#elif defined(__TARGET_ARCH_arm64)
+#define SYS_PREFIX "__arm64_"
+#else
+#define SYS_PREFIX ""
+#endif
+
+int arg1 = 0;
+unsigned long arg2 = 0;
+unsigned long arg3 = 0;
+unsigned long arg4_cx = 0;
+unsigned long arg4 = 0;
+unsigned long arg5 = 0;
+
+SEC("kprobe/" SYS_PREFIX "sys_prctl")
+int BPF_KPROBE(handle_sys_prctl)
+{
+	struct pt_regs *real_regs;
+	int orig_arg1;
+	unsigned long orig_arg2, orig_arg3, orig_arg4_cx, orig_arg4, orig_arg5;
+
+	real_regs = (struct pt_regs *)PT_REGS_PARM1(ctx);
+	bpf_probe_read_kernel(&orig_arg1, sizeof(orig_arg1), &PT_REGS_PARM1_SYSCALL(real_regs));
+	bpf_probe_read_kernel(&orig_arg2, sizeof(orig_arg2), &PT_REGS_PARM2_SYSCALL(real_regs));
+	bpf_probe_read_kernel(&orig_arg3, sizeof(orig_arg3), &PT_REGS_PARM3_SYSCALL(real_regs));
+	bpf_probe_read_kernel(&orig_arg4_cx, sizeof(orig_arg4_cx), &PT_REGS_PARM4(real_regs));
+	bpf_probe_read_kernel(&orig_arg4, sizeof(orig_arg4), &PT_REGS_PARM4_SYSCALL(real_regs));
+	bpf_probe_read_kernel(&orig_arg5, sizeof(orig_arg5), &PT_REGS_PARM5_SYSCALL(real_regs));
+
+	/* copy all actual args and the wrong arg4 on x86_64 */
+	arg1 = orig_arg1;
+	arg2 = orig_arg2;
+	arg3 = orig_arg3;
+	arg4_cx = orig_arg4_cx;
+	arg4 = orig_arg4;
+	arg5 = orig_arg5;
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.32.0