[PATCH 12/13] perf test: Test BPF prologue

[Wang Nan <wangnan0@huawei.com>]

This patch introduces a new BPF script to test BPF prologue. The new
script probes at null_lseek, which is the function pointer when we try
to lseek on '/dev/null'.

null_lseek is chosen because it is a function pointer, so we don't need
to consider inlining and LTO.

By extracting file->f_mode, bpf-script-test-prologue.c should know whether
the file is writable or readonly. According to llseek_loop() and
bpf-script-test-prologue.c, one forth of total lseeks should be collected.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 tools/perf/tests/Build                      |  9 +++++++-
 tools/perf/tests/bpf-script-test-prologue.c | 35 +++++++++++++++++++++++++++++
 tools/perf/tests/bpf.c                      | 34 ++++++++++++++++++++++++++++
 tools/perf/tests/llvm.c                     |  4 ++++
 tools/perf/tests/llvm.h                     |  2 ++
 5 files changed, 83 insertions(+), 1 deletion(-)
 create mode 100644 tools/perf/tests/bpf-script-test-prologue.c

diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
index f41ebf8..0ff8a97 100644
--- a/tools/perf/tests/Build
+++ b/tools/perf/tests/Build
@@ -31,7 +31,7 @@ perf-y += sample-parsing.o
 perf-y += parse-no-sample-id-all.o
 perf-y += kmod-path.o
 perf-y += thread-map.o
-perf-y += llvm.o llvm-src-base.o llvm-src-kbuild.o
+perf-y += llvm.o llvm-src-base.o llvm-src-kbuild.o llvm-src-prologue.o
 perf-y += bpf.o
 perf-y += topology.o
 
@@ -49,6 +49,13 @@ $(OUTPUT)tests/llvm-src-kbuild.c: tests/bpf-script-test-kbuild.c
 	$(Q)sed -e 's/"/\\"/g' -e 's/\(.*\)/"\1\\n"/g' $< >> $@
 	$(Q)echo ';' >> $@
 
+$(OUTPUT)tests/llvm-src-prologue.c: tests/bpf-script-test-prologue.c
+	$(call rule_mkdir)
+	$(Q)echo '#include <tests/llvm.h>' > $@
+	$(Q)echo 'const char test_llvm__bpf_test_prologue_prog[] =' >> $@
+	$(Q)sed -e 's/"/\\"/g' -e 's/\(.*\)/"\1\\n"/g' $< >> $@
+	$(Q)echo ';' >> $@
+
 ifeq ($(ARCH),$(filter $(ARCH),x86 arm arm64))
 perf-$(CONFIG_DWARF_UNWIND) += dwarf-unwind.o
 endif
diff --git a/tools/perf/tests/bpf-script-test-prologue.c b/tools/perf/tests/bpf-script-test-prologue.c
new file mode 100644
index 0000000..7230e62
--- /dev/null
+++ b/tools/perf/tests/bpf-script-test-prologue.c
@@ -0,0 +1,35 @@
+/*
+ * bpf-script-test-prologue.c
+ * Test BPF prologue
+ */
+#ifndef LINUX_VERSION_CODE
+# error Need LINUX_VERSION_CODE
+# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
+#endif
+#define SEC(NAME) __attribute__((section(NAME), used))
+
+#include <uapi/linux/fs.h>
+
+#define FMODE_READ		0x1
+#define FMODE_WRITE		0x2
+
+static void (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) =
+	(void *) 6;
+
+SEC("func=null_lseek file->f_mode offset orig")
+int bpf_func__null_lseek(void *ctx, int err, unsigned long f_mode,
+			 unsigned long offset, unsigned long orig)
+{
+	if (err)
+		return 0;
+	if (f_mode & FMODE_WRITE)
+		return 0;
+	if (offset & 1)
+		return 0;
+	if (orig == SEEK_CUR)
+		return 0;
+	return 1;
+}
+
+char _license[] SEC("license") = "GPL";
+int _version SEC("version") = LINUX_VERSION_CODE;
diff --git a/tools/perf/tests/bpf.c b/tools/perf/tests/bpf.c
index ec16f78..c7131fa 100644
--- a/tools/perf/tests/bpf.c
+++ b/tools/perf/tests/bpf.c
@@ -19,6 +19,29 @@ static int epoll_pwait_loop(void)
 	return 0;
 }
 
+#ifdef HAVE_BPF_PROLOGUE
+
+static int llseek_loop(void)
+{
+	int fds[2], i;
+
+	fds[0] = open("/dev/null", O_RDONLY);
+	fds[1] = open("/dev/null", O_RDWR);
+
+	if (fds[0] < 0 || fds[1] < 0)
+		return -1;
+
+	for (i = 0; i < NR_ITERS; i++) {
+		lseek(fds[i % 2], i, (i / 2) % 2 ? SEEK_CUR : SEEK_SET);
+		lseek(fds[(i + 1) % 2], i, (i / 2) % 2 ? SEEK_CUR : SEEK_SET);
+	}
+	close(fds[0]);
+	close(fds[1]);
+	return 0;
+}
+
+#endif
+
 static struct {
 	enum test_llvm__testcase prog_id;
 	const char *desc;
@@ -37,6 +60,17 @@ static struct {
 		&epoll_pwait_loop,
 		(NR_ITERS + 1) / 2,
 	},
+#ifdef HAVE_BPF_PROLOGUE
+	{
+		LLVM_TESTCASE_BPF_PROLOGUE,
+		"Test BPF prologue generation",
+		"[bpf_prologue_test]",
+		"fix kbuild first",
+		"check your vmlinux setting?",
+		&llseek_loop,
+		(NR_ITERS + 1) / 4,
+	},
+#endif
 };
 
 static int do_test(struct bpf_object *obj, int (*func)(void),
diff --git a/tools/perf/tests/llvm.c b/tools/perf/tests/llvm.c
index bc4cf50..7f4f7f7 100644
--- a/tools/perf/tests/llvm.c
+++ b/tools/perf/tests/llvm.c
@@ -44,6 +44,10 @@ static struct {
 		.source = test_llvm__bpf_test_kbuild_prog,
 		.desc = "Test kbuild searching",
 	},
+	[LLVM_TESTCASE_BPF_PROLOGUE] = {
+		.source = test_llvm__bpf_test_prologue_prog,
+		.desc = "Test BPF prologue generation",
+	},
 };
 
 
diff --git a/tools/perf/tests/llvm.h b/tools/perf/tests/llvm.h
index d91d8f4..5150b4d 100644
--- a/tools/perf/tests/llvm.h
+++ b/tools/perf/tests/llvm.h
@@ -6,10 +6,12 @@
 
 extern const char test_llvm__bpf_base_prog[];
 extern const char test_llvm__bpf_test_kbuild_prog[];
+extern const char test_llvm__bpf_test_prologue_prog[];
 
 enum test_llvm__testcase {
 	LLVM_TESTCASE_BASE,
 	LLVM_TESTCASE_KBUILD,
+	LLVM_TESTCASE_BPF_PROLOGUE,
 	__LLVM_TESTCASE_MAX,
 };
 
-- 
1.8.3.4