selftests/bpf: Add vmlinux.h selftest exercising tracing of syscalls

Add vmlinux.h generation to selftest/bpf's Makefile. Use it from newly added
test_vmlinux to trace nanosleep syscall using 5 different types of programs:
  - tracepoint;
  - raw tracepoint;
  - raw tracepoint w/ direct memory reads (tp_btf);
  - kprobe;
  - fentry.

These programs are realistic variants of real-life tracing programs,
excercising vmlinux.h's usage with tracing applications.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200313172336.1879637-5-andriin@fb.com

tools/testing/selftests/bpf/Makefile

@@ -136,7 +136,7 @@ VMLINUX_BTF_PATHS := $(if $(O),$(O)/vmlinux)				\
 		     ../../../../vmlinux				\
 		     /sys/kernel/btf/vmlinux				\
 		     /boot/vmlinux-$(shell uname -r)
-VMLINUX_BTF:= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
+VMLINUX_BTF := $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
 
 $(OUTPUT)/runqslower: $(BPFOBJ)
 	$(Q)$(MAKE) $(submake_extras) -C $(TOOLSDIR)/bpf/runqslower	\
@@ -177,6 +177,10 @@ $(BUILD_DIR)/libbpf $(BUILD_DIR)/bpftool $(INCLUDE_DIR):
 	$(call msg,MKDIR,,$@)
 	mkdir -p $@
 
+$(INCLUDE_DIR)/vmlinux.h: $(VMLINUX_BTF) | $(BPFTOOL) $(INCLUDE_DIR)
+	$(call msg,GEN,,$@)
+	$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
+
 # Get Clang's default includes on this system, as opposed to those seen by
 # '-target bpf'. This fixes "missing" files on some architectures/distros,
 # such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc.
@@ -285,6 +289,7 @@ $(TRUNNER_BPF_PROGS_DIR)$(if $2,-)$2-bpfobjs := y
 $(TRUNNER_BPF_OBJS): $(TRUNNER_OUTPUT)/%.o:				\
 		     $(TRUNNER_BPF_PROGS_DIR)/%.c			\
 		     $(TRUNNER_BPF_PROGS_DIR)/*.h			\
+		     $$(INCLUDE_DIR)/vmlinux.h				\
 		     $$(BPFOBJ) | $(TRUNNER_OUTPUT)
 	$$(call $(TRUNNER_BPF_BUILD_RULE),$$<,$$@,			\
 					  $(TRUNNER_BPF_CFLAGS),	\

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+
+#include <test_progs.h>
+#include <time.h>
+#include "test_vmlinux.skel.h"
+
+#define MY_TV_NSEC 1337
+
+static void nsleep()
+{
+	struct timespec ts = { .tv_nsec = MY_TV_NSEC };
+
+	(void)nanosleep(&ts, NULL);
+}
+
+void test_vmlinux(void)
+{
+	int duration = 0, err;
+	struct test_vmlinux* skel;
+	struct test_vmlinux__bss *bss;
+
+	skel = test_vmlinux__open_and_load();
+	if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
+		return;
+	bss = skel->bss;
+
+	err = test_vmlinux__attach(skel);
+	if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
+		goto cleanup;
+
+	/* trigger everything */
+	nsleep();
+
+	CHECK(!bss->tp_called, "tp", "not called\n");
+	CHECK(!bss->raw_tp_called, "raw_tp", "not called\n");
+	CHECK(!bss->tp_btf_called, "tp_btf", "not called\n");
+	CHECK(!bss->kprobe_called, "kprobe", "not called\n");
+	CHECK(!bss->fentry_called, "fentry", "not called\n");
+
+cleanup:
+	test_vmlinux__destroy(skel);
+}

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+
+#include "vmlinux.h"
+#include <asm/unistd.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+
+#define MY_TV_NSEC 1337
+
+bool tp_called = false;
+bool raw_tp_called = false;
+bool tp_btf_called = false;
+bool kprobe_called = false;
+bool fentry_called = false;
+
+SEC("tp/syscalls/sys_enter_nanosleep")
+int handle__tp(struct trace_event_raw_sys_enter *args)
+{
+	struct __kernel_timespec *ts;
+
+	if (args->id != __NR_nanosleep)
+		return 0;
+
+	ts = (void *)args->args[0];
+	if (BPF_CORE_READ(ts, tv_nsec) != MY_TV_NSEC)
+		return 0;
+
+	tp_called = true;
+	return 0;
+}
+
+SEC("raw_tp/sys_enter")
+int BPF_PROG(handle__raw_tp, struct pt_regs *regs, long id)
+{
+	struct __kernel_timespec *ts;
+
+	if (id != __NR_nanosleep)
+		return 0;
+
+	ts = (void *)PT_REGS_PARM1_CORE(regs);
+	if (BPF_CORE_READ(ts, tv_nsec) != MY_TV_NSEC)
+		return 0;
+
+	raw_tp_called = true;
+	return 0;
+}
+
+SEC("tp_btf/sys_enter")
+int BPF_PROG(handle__tp_btf, struct pt_regs *regs, long id)
+{
+	struct __kernel_timespec *ts;
+
+	if (id != __NR_nanosleep)
+		return 0;
+
+	ts = (void *)PT_REGS_PARM1_CORE(regs);
+	if (BPF_CORE_READ(ts, tv_nsec) != MY_TV_NSEC)
+		return 0;
+
+	tp_btf_called = true;
+	return 0;
+}
+
+SEC("kprobe/hrtimer_nanosleep")
+int BPF_KPROBE(handle__kprobe,
+	       ktime_t rqtp, enum hrtimer_mode mode, clockid_t clockid)
+{
+	if (rqtp == MY_TV_NSEC)
+		kprobe_called = true;
+	return 0;
+}
+
+SEC("fentry/hrtimer_nanosleep")
+int BPF_PROG(handle__fentry,
+	     ktime_t rqtp, enum hrtimer_mode mode, clockid_t clockid)
+{
+	if (rqtp == MY_TV_NSEC)
+		fentry_called = true;
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";