[PATCH v11 5/5] ring-buffer/selftest: Add ring-buffer mapping test

[Vincent Donnefort]

This test maps a ring-buffer and validate the meta-page after reset and
after emitting few events.

Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
Cc: linux-kselftest@xxxxxxxxxxxxxxx
Signed-off-by: Vincent Donnefort <vdonnefort@xxxxxxxxxx>

diff --git a/tools/testing/selftests/ring-buffer/Makefile b/tools/testing/selftests/ring-buffer/Makefile
new file mode 100644
index 000000000000..627c5fa6d1ab
--- /dev/null
+++ b/tools/testing/selftests/ring-buffer/Makefile
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0
+CFLAGS += -Wl,-no-as-needed -Wall
+CFLAGS += $(KHDR_INCLUDES)
+CFLAGS += -D_GNU_SOURCE
+
+TEST_GEN_PROGS = map_test
+
+include ../lib.mk
diff --git a/tools/testing/selftests/ring-buffer/config b/tools/testing/selftests/ring-buffer/config
new file mode 100644
index 000000000000..ef8214661612
--- /dev/null
+++ b/tools/testing/selftests/ring-buffer/config
@@ -0,0 +1 @@
+CONFIG_FTRACE=y
diff --git a/tools/testing/selftests/ring-buffer/map_test.c b/tools/testing/selftests/ring-buffer/map_test.c
new file mode 100644
index 000000000000..49107e8da5e9
--- /dev/null
+++ b/tools/testing/selftests/ring-buffer/map_test.c
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Ring-buffer memory mapping tests
+ *
+ * Copyright (c) 2024 Vincent Donnefort <vdonnefort@xxxxxxxxxx>
+ */
+#include <fcntl.h>
+#include <sched.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <linux/trace_mmap.h>
+
+#include <sys/mman.h>
+#include <sys/ioctl.h>
+
+#include "../user_events/user_events_selftests.h" /* share tracefs setup */
+#include "../kselftest_harness.h"
+
+#define TRACEFS_ROOT "/sys/kernel/tracing"
+
+static int __tracefs_write(const char *path, const char *value)
+{
+	FILE *file;
+
+	file = fopen(path, "w");
+	if (!file)
+		return -1;
+
+	fputs(value, file);
+	fclose(file);
+
+	return 0;
+}
+
+static int __tracefs_write_int(const char *path, int value)
+{
+	char *str;
+	int ret;
+
+	if (asprintf(&str, "%d", value) < 0)
+		return -1;
+
+	ret = __tracefs_write(path, str);
+
+	free(str);
+
+	return ret;
+}
+
+#define tracefs_write_int(path, value) \
+	ASSERT_EQ(__tracefs_write_int((path), (value)), 0)
+
+static int tracefs_reset(void)
+{
+	if (__tracefs_write_int(TRACEFS_ROOT"/tracing_on", 0))
+		return -1;
+	if (__tracefs_write_int(TRACEFS_ROOT"/trace", 0))
+		return -1;
+	if (__tracefs_write(TRACEFS_ROOT"/set_event", ""))
+		return -1;
+
+	return 0;
+}
+
+FIXTURE(map) {
+	struct trace_buffer_meta	*meta;
+	void				*data;
+	int				cpu_fd;
+	bool				umount;
+};
+
+FIXTURE_VARIANT(map) {
+	int	subbuf_size;
+};
+
+FIXTURE_VARIANT_ADD(map, subbuf_size_4k) {
+	.subbuf_size = 4,
+};
+
+FIXTURE_VARIANT_ADD(map, subbuf_size_8k) {
+	.subbuf_size = 8,
+};
+
+FIXTURE_SETUP(map)
+{
+	int cpu = sched_getcpu(), page_size = getpagesize();
+	unsigned long meta_len, data_len;
+	char *cpu_path, *message;
+	bool fail, umount;
+	cpu_set_t cpu_mask;
+	void *map;
+
+	if (!tracefs_enabled(&message, &fail, &umount)) {
+		if (fail) {
+			TH_LOG("Tracefs setup failed: %s", message);
+			ASSERT_FALSE(fail);
+		}
+		SKIP(return, "Skipping: %s", message);
+	}
+
+	self->umount = umount;
+
+	ASSERT_GE(cpu, 0);
+
+	ASSERT_EQ(tracefs_reset(), 0);
+
+	tracefs_write_int(TRACEFS_ROOT"/buffer_subbuf_size_kb", variant->subbuf_size);
+
+	ASSERT_GE(asprintf(&cpu_path,
+			   TRACEFS_ROOT"/per_cpu/cpu%d/trace_pipe_raw",
+			   cpu), 0);
+
+	self->cpu_fd = open(cpu_path, O_RDONLY | O_NONBLOCK);
+	ASSERT_GE(self->cpu_fd, 0);
+	free(cpu_path);
+
+	map = mmap(NULL, page_size, PROT_READ, MAP_SHARED, self->cpu_fd, 0);
+	ASSERT_NE(map, MAP_FAILED);
+	self->meta = (struct trace_buffer_meta *)map;
+
+	meta_len = self->meta->meta_page_size;
+	data_len = self->meta->subbuf_size * self->meta->nr_subbufs;
+
+	map = mmap(NULL, data_len, PROT_READ, MAP_SHARED, self->cpu_fd, meta_len);
+	ASSERT_NE(map, MAP_FAILED);
+	self->data = map;
+
+	/*
+	 * Ensure generated events will be found on this very same ring-buffer.
+	 */
+	CPU_ZERO(&cpu_mask);
+	CPU_SET(cpu, &cpu_mask);
+	ASSERT_EQ(sched_setaffinity(0, sizeof(cpu_mask), &cpu_mask), 0);
+}
+
+FIXTURE_TEARDOWN(map)
+{
+	tracefs_reset();
+
+	if (self->umount)
+		tracefs_unmount();
+
+	munmap(self->data, self->meta->subbuf_size * self->meta->nr_subbufs);
+	munmap(self->meta, self->meta->meta_page_size);
+	close(self->cpu_fd);
+}
+
+TEST_F(map, meta_page_check)
+{
+	int cnt = 0;
+
+	ASSERT_EQ(self->meta->entries, 0);
+	ASSERT_EQ(self->meta->overrun, 0);
+	ASSERT_EQ(self->meta->read, 0);
+	ASSERT_EQ(self->meta->subbufs_touched, 0);
+	ASSERT_EQ(self->meta->subbufs_lost, 0);
+	ASSERT_EQ(self->meta->subbufs_read, 0);
+
+	ASSERT_EQ(self->meta->reader.id, 0);
+	ASSERT_EQ(self->meta->reader.read, 0);
+
+	ASSERT_EQ(ioctl(self->cpu_fd, TRACE_MMAP_IOCTL_GET_READER), 0);
+	ASSERT_EQ(self->meta->reader.id, 0);
+
+	tracefs_write_int(TRACEFS_ROOT"/tracing_on", 1);
+	for (int i = 0; i < 16; i++)
+		tracefs_write_int(TRACEFS_ROOT"/trace_marker", i);
+again:
+	ASSERT_EQ(ioctl(self->cpu_fd, TRACE_MMAP_IOCTL_GET_READER), 0);
+
+	ASSERT_EQ(self->meta->entries, 16);
+	ASSERT_EQ(self->meta->overrun, 0);
+	ASSERT_EQ(self->meta->read, 16);
+	/* subbufs_touched doesn't take into account the commit page */
+	ASSERT_EQ(self->meta->subbufs_touched, 0);
+	ASSERT_EQ(self->meta->subbufs_lost, 0);
+	ASSERT_EQ(self->meta->subbufs_read, 1);
+
+	ASSERT_EQ(self->meta->reader.id, 1);
+
+	if (!(cnt++))
+		goto again;
+}
+
+TEST_HARNESS_MAIN
-- 
2.43.0.275.g3460e3d667-goog