Merge tag 'trace-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from Steven Rostedt:

 - New user_events interface. User space can register an event with the
   kernel describing the format of the event. Then it will receive a
   byte in a page mapping that it can check against. A privileged task
   can then enable that event like any other event, which will change
   the mapped byte to true, telling the user space application to start
   writing the event to the tracing buffer.

 - Add new "ftrace_boot_snapshot" kernel command line parameter. When
   set, the tracing buffer will be saved in the snapshot buffer at boot
   up when the kernel hands things over to user space. This will keep
   the traces that happened at boot up available even if user space boot
   up has tracing as well.

 - Have TRACE_EVENT_ENUM() also update trace event field type
   descriptions. Thus if a static array defines its size with an enum,
   the user space trace event parsers can still know how to parse that
   array.

 - Add new TRACE_CUSTOM_EVENT() macro. This acts the same as the
   TRACE_EVENT() macro, but will attach to an existing tracepoint. This
   will make one tracepoint be able to trace different content and not
   be stuck at only what the original TRACE_EVENT() macro exports.

 - Fixes to tracing error logging.

 - Better saving of cmdlines to PIDs when tracing (use the wakeup events
   for mapping).

* tag 'trace-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (30 commits)
  tracing: Have type enum modifications copy the strings
  user_events: Add trace event call as root for low permission cases
  tracing/user_events: Use alloc_pages instead of kzalloc() for register pages
  tracing: Add snapshot at end of kernel boot up
  tracing: Have TRACE_DEFINE_ENUM affect trace event types as well
  tracing: Fix strncpy warning in trace_events_synth.c
  user_events: Prevent dyn_event delete racing with ioctl add/delete
  tracing: Add TRACE_CUSTOM_EVENT() macro
  tracing: Move the defines to create TRACE_EVENTS into their own files
  tracing: Add sample code for custom trace events
  tracing: Allow custom events to be added to the tracefs directory
  tracing: Fix last_cmd_set() string management in histogram code
  user_events: Fix potential uninitialized pointer while parsing field
  tracing: Fix allocation of last_cmd in last_cmd_set()
  user_events: Add documentation file
  user_events: Add sample code for typical usage
  user_events: Add self-test for validator boundaries
  user_events: Add self-test for perf_event integration
  user_events: Add self-test for dynamic_events integration
  user_events: Add self-test for ftrace integration
  ...

5 files changed, 760 insertions, 0 deletions

diff --git a/tools/testing/selftests/user_events/Makefile b/tools/testing/selftests/user_events/Makefile
new file mode 100644
index 000000000000..c765d8635d9a
--- /dev/null
+++ b/tools/testing/selftests/user_events/Makefile
@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: GPL-2.0
+CFLAGS += -Wl,-no-as-needed -Wall -I../../../../usr/include
+LDLIBS += -lrt -lpthread -lm
+
+TEST_GEN_PROGS = ftrace_test dyn_test perf_test
+
+TEST_FILES := settings
+
+include ../lib.mk
diff --git a/tools/testing/selftests/user_events/dyn_test.c b/tools/testing/selftests/user_events/dyn_test.c
new file mode 100644
index 000000000000..d6265d14cd51
--- /dev/null
+++ b/tools/testing/selftests/user_events/dyn_test.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * User Events Dyn Events Test Program
+ *
+ * Copyright (c) 2021 Beau Belgrave <beaub@linux.microsoft.com>
+ */
+
+#include <errno.h>
+#include <linux/user_events.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "../kselftest_harness.h"
+
+const char *dyn_file = "/sys/kernel/debug/tracing/dynamic_events";
+const char *clear = "!u:__test_event";
+
+static int Append(const char *value)
+{
+	int fd = open(dyn_file, O_RDWR | O_APPEND);
+	int ret = write(fd, value, strlen(value));
+
+	close(fd);
+	return ret;
+}
+
+#define CLEAR() \
+do { \
+	int ret = Append(clear); \
+	if (ret == -1) \
+		ASSERT_EQ(ENOENT, errno); \
+} while (0)
+
+#define TEST_PARSE(x) \
+do { \
+	ASSERT_NE(-1, Append(x)); \
+	CLEAR(); \
+} while (0)
+
+#define TEST_NPARSE(x) ASSERT_EQ(-1, Append(x))
+
+FIXTURE(user) {
+};
+
+FIXTURE_SETUP(user) {
+	CLEAR();
+}
+
+FIXTURE_TEARDOWN(user) {
+	CLEAR();
+}
+
+TEST_F(user, basic_types) {
+	/* All should work */
+	TEST_PARSE("u:__test_event u64 a");
+	TEST_PARSE("u:__test_event u32 a");
+	TEST_PARSE("u:__test_event u16 a");
+	TEST_PARSE("u:__test_event u8 a");
+	TEST_PARSE("u:__test_event char a");
+	TEST_PARSE("u:__test_event unsigned char a");
+	TEST_PARSE("u:__test_event int a");
+	TEST_PARSE("u:__test_event unsigned int a");
+	TEST_PARSE("u:__test_event short a");
+	TEST_PARSE("u:__test_event unsigned short a");
+	TEST_PARSE("u:__test_event char[20] a");
+	TEST_PARSE("u:__test_event unsigned char[20] a");
+	TEST_PARSE("u:__test_event char[0x14] a");
+	TEST_PARSE("u:__test_event unsigned char[0x14] a");
+	/* Bad size format should fail */
+	TEST_NPARSE("u:__test_event char[aa] a");
+	/* Large size should fail */
+	TEST_NPARSE("u:__test_event char[9999] a");
+	/* Long size string should fail */
+	TEST_NPARSE("u:__test_event char[0x0000000000001] a");
+}
+
+TEST_F(user, loc_types) {
+	/* All should work */
+	TEST_PARSE("u:__test_event __data_loc char[] a");
+	TEST_PARSE("u:__test_event __data_loc unsigned char[] a");
+	TEST_PARSE("u:__test_event __rel_loc char[] a");
+	TEST_PARSE("u:__test_event __rel_loc unsigned char[] a");
+}
+
+TEST_F(user, size_types) {
+	/* Should work */
+	TEST_PARSE("u:__test_event struct custom a 20");
+	/* Size not specified on struct should fail */
+	TEST_NPARSE("u:__test_event struct custom a");
+	/* Size specified on non-struct should fail */
+	TEST_NPARSE("u:__test_event char a 20");
+}
+
+TEST_F(user, flags) {
+	/* Should work */
+	TEST_PARSE("u:__test_event:BPF_ITER u32 a");
+	/* Forward compat */
+	TEST_PARSE("u:__test_event:BPF_ITER,FLAG_FUTURE u32 a");
+}
+
+TEST_F(user, matching) {
+	/* Register */
+	ASSERT_NE(-1, Append("u:__test_event struct custom a 20"));
+	/* Should not match */
+	TEST_NPARSE("!u:__test_event struct custom b");
+	/* Should match */
+	TEST_PARSE("!u:__test_event struct custom a");
+	/* Multi field reg */
+	ASSERT_NE(-1, Append("u:__test_event u32 a; u32 b"));
+	/* Non matching cases */
+	TEST_NPARSE("!u:__test_event u32 a");
+	TEST_NPARSE("!u:__test_event u32 b");
+	TEST_NPARSE("!u:__test_event u32 a; u32 ");
+	TEST_NPARSE("!u:__test_event u32 a; u32 a");
+	/* Matching case */
+	TEST_PARSE("!u:__test_event u32 a; u32 b");
+	/* Register */
+	ASSERT_NE(-1, Append("u:__test_event u32 a; u32 b"));
+	/* Ensure trailing semi-colon case */
+	TEST_PARSE("!u:__test_event u32 a; u32 b;");
+}
+
+int main(int argc, char **argv)
+{
+	return test_harness_run(argc, argv);
+}
diff --git a/tools/testing/selftests/user_events/ftrace_test.c b/tools/testing/selftests/user_events/ftrace_test.c
new file mode 100644
index 000000000000..a80fb5ef61d5
--- /dev/null
+++ b/tools/testing/selftests/user_events/ftrace_test.c
@@ -0,0 +1,452 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * User Events FTrace Test Program
+ *
+ * Copyright (c) 2021 Beau Belgrave <beaub@linux.microsoft.com>
+ */
+
+#include <errno.h>
+#include <linux/user_events.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "../kselftest_harness.h"
+
+const char *data_file = "/sys/kernel/debug/tracing/user_events_data";
+const char *status_file = "/sys/kernel/debug/tracing/user_events_status";
+const char *enable_file = "/sys/kernel/debug/tracing/events/user_events/__test_event/enable";
+const char *trace_file = "/sys/kernel/debug/tracing/trace";
+const char *fmt_file = "/sys/kernel/debug/tracing/events/user_events/__test_event/format";
+
+static int trace_bytes(void)
+{
+	int fd = open(trace_file, O_RDONLY);
+	char buf[256];
+	int bytes = 0, got;
+
+	if (fd == -1)
+		return -1;
+
+	while (true) {
+		got = read(fd, buf, sizeof(buf));
+
+		if (got == -1)
+			return -1;
+
+		if (got == 0)
+			break;
+
+		bytes += got;
+	}
+
+	close(fd);
+
+	return bytes;
+}
+
+static int skip_until_empty_line(FILE *fp)
+{
+	int c, last = 0;
+
+	while (true) {
+		c = getc(fp);
+
+		if (c == EOF)
+			break;
+
+		if (last == '\n' && c == '\n')
+			return 0;
+
+		last = c;
+	}
+
+	return -1;
+}
+
+static int get_print_fmt(char *buffer, int len)
+{
+	FILE *fp = fopen(fmt_file, "r");
+	char *newline;
+
+	if (!fp)
+		return -1;
+
+	/* Read until empty line (Skip Common) */
+	if (skip_until_empty_line(fp) < 0)
+		goto err;
+
+	/* Read until empty line (Skip Properties) */
+	if (skip_until_empty_line(fp) < 0)
+		goto err;
+
+	/* Read in print_fmt: */
+	if (fgets(buffer, len, fp) == NULL)
+		goto err;
+
+	newline = strchr(buffer, '\n');
+
+	if (newline)
+		*newline = '\0';
+
+	fclose(fp);
+
+	return 0;
+err:
+	fclose(fp);
+
+	return -1;
+}
+
+static int clear(void)
+{
+	int fd = open(data_file, O_RDWR);
+
+	if (fd == -1)
+		return -1;
+
+	if (ioctl(fd, DIAG_IOCSDEL, "__test_event") == -1)
+		if (errno != ENOENT)
+			return -1;
+
+	close(fd);
+
+	return 0;
+}
+
+static int check_print_fmt(const char *event, const char *expected)
+{
+	struct user_reg reg = {0};
+	char print_fmt[256];
+	int ret;
+	int fd;
+
+	/* Ensure cleared */
+	ret = clear();
+
+	if (ret != 0)
+		return ret;
+
+	fd = open(data_file, O_RDWR);
+
+	if (fd == -1)
+		return fd;
+
+	reg.size = sizeof(reg);
+	reg.name_args = (__u64)event;
+
+	/* Register should work */
+	ret = ioctl(fd, DIAG_IOCSREG, &reg);
+
+	close(fd);
+
+	if (ret != 0)
+		return ret;
+
+	/* Ensure correct print_fmt */
+	ret = get_print_fmt(print_fmt, sizeof(print_fmt));
+
+	if (ret != 0)
+		return ret;
+
+	return strcmp(print_fmt, expected);
+}
+
+FIXTURE(user) {
+	int status_fd;
+	int data_fd;
+	int enable_fd;
+};
+
+FIXTURE_SETUP(user) {
+	self->status_fd = open(status_file, O_RDONLY);
+	ASSERT_NE(-1, self->status_fd);
+
+	self->data_fd = open(data_file, O_RDWR);
+	ASSERT_NE(-1, self->data_fd);
+
+	self->enable_fd = -1;
+}
+
+FIXTURE_TEARDOWN(user) {
+	close(self->status_fd);
+	close(self->data_fd);
+
+	if (self->enable_fd != -1) {
+		write(self->enable_fd, "0", sizeof("0"));
+		close(self->enable_fd);
+	}
+
+	ASSERT_EQ(0, clear());
+}
+
+TEST_F(user, register_events) {
+	struct user_reg reg = {0};
+	int page_size = sysconf(_SC_PAGESIZE);
+	char *status_page;
+
+	reg.size = sizeof(reg);
+	reg.name_args = (__u64)"__test_event u32 field1; u32 field2";
+
+	status_page = mmap(NULL, page_size, PROT_READ, MAP_SHARED,
+			   self->status_fd, 0);
+
+	/* Register should work */
+	ASSERT_EQ(0, ioctl(self->data_fd, DIAG_IOCSREG, &reg));
+	ASSERT_EQ(0, reg.write_index);
+	ASSERT_NE(0, reg.status_index);
+
+	/* Multiple registers should result in same index */
+	ASSERT_EQ(0, ioctl(self->data_fd, DIAG_IOCSREG, &reg));
+	ASSERT_EQ(0, reg.write_index);
+	ASSERT_NE(0, reg.status_index);
+
+	/* Ensure disabled */
+	self->enable_fd = open(enable_file, O_RDWR);
+	ASSERT_NE(-1, self->enable_fd);
+	ASSERT_NE(-1, write(self->enable_fd, "0", sizeof("0")))
+
+	/* MMAP should work and be zero'd */
+	ASSERT_NE(MAP_FAILED, status_page);
+	ASSERT_NE(NULL, status_page);
+	ASSERT_EQ(0, status_page[reg.status_index]);
+
+	/* Enable event and ensure bits updated in status */
+	ASSERT_NE(-1, write(self->enable_fd, "1", sizeof("1")))
+	ASSERT_EQ(EVENT_STATUS_FTRACE, status_page[reg.status_index]);
+
+	/* Disable event and ensure bits updated in status */
+	ASSERT_NE(-1, write(self->enable_fd, "0", sizeof("0")))
+	ASSERT_EQ(0, status_page[reg.status_index]);
+
+	/* File still open should return -EBUSY for delete */
+	ASSERT_EQ(-1, ioctl(self->data_fd, DIAG_IOCSDEL, "__test_event"));
+	ASSERT_EQ(EBUSY, errno);
+
+	/* Delete should work only after close */
+	close(self->data_fd);
+	self->data_fd = open(data_file, O_RDWR);
+	ASSERT_EQ(0, ioctl(self->data_fd, DIAG_IOCSDEL, "__test_event"));
+
+	/* Unmap should work */
+	ASSERT_EQ(0, munmap(status_page, page_size));
+}
+
+TEST_F(user, write_events) {
+	struct user_reg reg = {0};
+	struct iovec io[3];
+	__u32 field1, field2;
+	int before = 0, after = 0;
+
+	reg.size = sizeof(reg);
+	reg.name_args = (__u64)"__test_event u32 field1; u32 field2";
+
+	field1 = 1;
+	field2 = 2;
+
+	io[0].iov_base = &reg.write_index;
+	io[0].iov_len = sizeof(reg.write_index);
+	io[1].iov_base = &field1;
+	io[1].iov_len = sizeof(field1);
+	io[2].iov_base = &field2;
+	io[2].iov_len = sizeof(field2);
+
+	/* Register should work */
+	ASSERT_EQ(0, ioctl(self->data_fd, DIAG_IOCSREG, &reg));
+	ASSERT_EQ(0, reg.write_index);
+	ASSERT_NE(0, reg.status_index);
+
+	/* Write should fail on invalid slot with ENOENT */
+	io[0].iov_base = &field2;
+	io[0].iov_len = sizeof(field2);
+	ASSERT_EQ(-1, writev(self->data_fd, (const struct iovec *)io, 3));
+	ASSERT_EQ(ENOENT, errno);
+	io[0].iov_base = &reg.write_index;
+	io[0].iov_len = sizeof(reg.write_index);
+
+	/* Enable event */
+	self->enable_fd = open(enable_file, O_RDWR);
+	ASSERT_NE(-1, write(self->enable_fd, "1", sizeof("1")))
+
+	/* Write should make it out to ftrace buffers */
+	before = trace_bytes();
+	ASSERT_NE(-1, writev(self->data_fd, (const struct iovec *)io, 3));
+	after = trace_bytes();
+	ASSERT_GT(after, before);
+}
+
+TEST_F(user, write_fault) {
+	struct user_reg reg = {0};
+	struct iovec io[2];
+	int l = sizeof(__u64);
+	void *anon;
+
+	reg.size = sizeof(reg);
+	reg.name_args = (__u64)"__test_event u64 anon";
+
+	anon = mmap(NULL, l, PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	ASSERT_NE(MAP_FAILED, anon);
+
+	io[0].iov_base = &reg.write_index;
+	io[0].iov_len = sizeof(reg.write_index);
+	io[1].iov_base = anon;
+	io[1].iov_len = l;
+
+	/* Register should work */
+	ASSERT_EQ(0, ioctl(self->data_fd, DIAG_IOCSREG, &reg));
+	ASSERT_EQ(0, reg.write_index);
+	ASSERT_NE(0, reg.status_index);
+
+	/* Write should work normally */
+	ASSERT_NE(-1, writev(self->data_fd, (const struct iovec *)io, 2));
+
+	/* Faulted data should zero fill and work */
+	ASSERT_EQ(0, madvise(anon, l, MADV_DONTNEED));
+	ASSERT_NE(-1, writev(self->data_fd, (const struct iovec *)io, 2));
+	ASSERT_EQ(0, munmap(anon, l));
+}
+
+TEST_F(user, write_validator) {
+	struct user_reg reg = {0};
+	struct iovec io[3];
+	int loc, bytes;
+	char data[8];
+	int before = 0, after = 0;
+
+	reg.size = sizeof(reg);
+	reg.name_args = (__u64)"__test_event __rel_loc char[] data";
+
+	/* Register should work */
+	ASSERT_EQ(0, ioctl(self->data_fd, DIAG_IOCSREG, &reg));
+	ASSERT_EQ(0, reg.write_index);
+	ASSERT_NE(0, reg.status_index);
+
+	io[0].iov_base = &reg.write_index;
+	io[0].iov_len = sizeof(reg.write_index);
+	io[1].iov_base = &loc;
+	io[1].iov_len = sizeof(loc);
+	io[2].iov_base = data;
+	bytes = snprintf(data, sizeof(data), "Test") + 1;
+	io[2].iov_len = bytes;
+
+	/* Undersized write should fail */
+	ASSERT_EQ(-1, writev(self->data_fd, (const struct iovec *)io, 1));
+	ASSERT_EQ(EINVAL, errno);
+
+	/* Enable event */
+	self->enable_fd = open(enable_file, O_RDWR);
+	ASSERT_NE(-1, write(self->enable_fd, "1", sizeof("1")))
+
+	/* Full in-bounds write should work */
+	before = trace_bytes();
+	loc = DYN_LOC(0, bytes);
+	ASSERT_NE(-1, writev(self->data_fd, (const struct iovec *)io, 3));
+	after = trace_bytes();
+	ASSERT_GT(after, before);
+
+	/* Out of bounds write should fault (offset way out) */
+	loc = DYN_LOC(1024, bytes);
+	ASSERT_EQ(-1, writev(self->data_fd, (const struct iovec *)io, 3));
+	ASSERT_EQ(EFAULT, errno);
+
+	/* Out of bounds write should fault (offset 1 byte out) */
+	loc = DYN_LOC(1, bytes);
+	ASSERT_EQ(-1, writev(self->data_fd, (const struct iovec *)io, 3));
+	ASSERT_EQ(EFAULT, errno);
+
+	/* Out of bounds write should fault (size way out) */
+	loc = DYN_LOC(0, bytes + 1024);
+	ASSERT_EQ(-1, writev(self->data_fd, (const struct iovec *)io, 3));
+	ASSERT_EQ(EFAULT, errno);
+
+	/* Out of bounds write should fault (size 1 byte out) */
+	loc = DYN_LOC(0, bytes + 1);
+	ASSERT_EQ(-1, writev(self->data_fd, (const struct iovec *)io, 3));
+	ASSERT_EQ(EFAULT, errno);
+
+	/* Non-Null should fault */
+	memset(data, 'A', sizeof(data));
+	loc = DYN_LOC(0, bytes);
+	ASSERT_EQ(-1, writev(self->data_fd, (const struct iovec *)io, 3));
+	ASSERT_EQ(EFAULT, errno);
+}
+
+TEST_F(user, print_fmt) {
+	int ret;
+
+	ret = check_print_fmt("__test_event __rel_loc char[] data",
+			      "print fmt: \"data=%s\", __get_rel_str(data)");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event __data_loc char[] data",
+			      "print fmt: \"data=%s\", __get_str(data)");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event s64 data",
+			      "print fmt: \"data=%lld\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event u64 data",
+			      "print fmt: \"data=%llu\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event s32 data",
+			      "print fmt: \"data=%d\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event u32 data",
+			      "print fmt: \"data=%u\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event int data",
+			      "print fmt: \"data=%d\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event unsigned int data",
+			      "print fmt: \"data=%u\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event s16 data",
+			      "print fmt: \"data=%d\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event u16 data",
+			      "print fmt: \"data=%u\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event short data",
+			      "print fmt: \"data=%d\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event unsigned short data",
+			      "print fmt: \"data=%u\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event s8 data",
+			      "print fmt: \"data=%d\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event u8 data",
+			      "print fmt: \"data=%u\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event char data",
+			      "print fmt: \"data=%d\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event unsigned char data",
+			      "print fmt: \"data=%u\", REC->data");
+	ASSERT_EQ(0, ret);
+
+	ret = check_print_fmt("__test_event char[4] data",
+			      "print fmt: \"data=%s\", REC->data");
+	ASSERT_EQ(0, ret);
+}
+
+int main(int argc, char **argv)
+{
+	return test_harness_run(argc, argv);
+}
diff --git a/tools/testing/selftests/user_events/perf_test.c b/tools/testing/selftests/user_events/perf_test.c
new file mode 100644
index 000000000000..26851d51d6bb
--- /dev/null
+++ b/tools/testing/selftests/user_events/perf_test.c
@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * User Events Perf Events Test Program
+ *
+ * Copyright (c) 2021 Beau Belgrave <beaub@linux.microsoft.com>
+ */
+
+#include <errno.h>
+#include <linux/user_events.h>
+#include <linux/perf_event.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <asm/unistd.h>
+
+#include "../kselftest_harness.h"
+
+const char *data_file = "/sys/kernel/debug/tracing/user_events_data";
+const char *status_file = "/sys/kernel/debug/tracing/user_events_status";
+const char *id_file = "/sys/kernel/debug/tracing/events/user_events/__test_event/id";
+const char *fmt_file = "/sys/kernel/debug/tracing/events/user_events/__test_event/format";
+
+struct event {
+	__u32 index;
+	__u32 field1;
+	__u32 field2;
+};
+
+static long perf_event_open(struct perf_event_attr *pe, pid_t pid,
+			    int cpu, int group_fd, unsigned long flags)
+{
+	return syscall(__NR_perf_event_open, pe, pid, cpu, group_fd, flags);
+}
+
+static int get_id(void)
+{
+	FILE *fp = fopen(id_file, "r");
+	int ret, id = 0;
+
+	if (!fp)
+		return -1;
+
+	ret = fscanf(fp, "%d", &id);
+	fclose(fp);
+
+	if (ret != 1)
+		return -1;
+
+	return id;
+}
+
+static int get_offset(void)
+{
+	FILE *fp = fopen(fmt_file, "r");
+	int ret, c, last = 0, offset = 0;
+
+	if (!fp)
+		return -1;
+
+	/* Read until empty line */
+	while (true) {
+		c = getc(fp);
+
+		if (c == EOF)
+			break;
+
+		if (last == '\n' && c == '\n')
+			break;
+
+		last = c;
+	}
+
+	ret = fscanf(fp, "\tfield:u32 field1;\toffset:%d;", &offset);
+	fclose(fp);
+
+	if (ret != 1)
+		return -1;
+
+	return offset;
+}
+
+FIXTURE(user) {
+	int status_fd;
+	int data_fd;
+};
+
+FIXTURE_SETUP(user) {
+	self->status_fd = open(status_file, O_RDONLY);
+	ASSERT_NE(-1, self->status_fd);
+
+	self->data_fd = open(data_file, O_RDWR);
+	ASSERT_NE(-1, self->data_fd);
+}
+
+FIXTURE_TEARDOWN(user) {
+	close(self->status_fd);
+	close(self->data_fd);
+}
+
+TEST_F(user, perf_write) {
+	struct perf_event_attr pe = {0};
+	struct user_reg reg = {0};
+	int page_size = sysconf(_SC_PAGESIZE);
+	char *status_page;
+	struct event event;
+	struct perf_event_mmap_page *perf_page;
+	int id, fd, offset;
+	__u32 *val;
+
+	reg.size = sizeof(reg);
+	reg.name_args = (__u64)"__test_event u32 field1; u32 field2";
+
+	status_page = mmap(NULL, page_size, PROT_READ, MAP_SHARED,
+			   self->status_fd, 0);
+	ASSERT_NE(MAP_FAILED, status_page);
+
+	/* Register should work */
+	ASSERT_EQ(0, ioctl(self->data_fd, DIAG_IOCSREG, &reg));
+	ASSERT_EQ(0, reg.write_index);
+	ASSERT_NE(0, reg.status_index);
+	ASSERT_EQ(0, status_page[reg.status_index]);
+
+	/* Id should be there */
+	id = get_id();
+	ASSERT_NE(-1, id);
+	offset = get_offset();
+	ASSERT_NE(-1, offset);
+
+	pe.type = PERF_TYPE_TRACEPOINT;
+	pe.size = sizeof(pe);
+	pe.config = id;
+	pe.sample_type = PERF_SAMPLE_RAW;
+	pe.sample_period = 1;
+	pe.wakeup_events = 1;
+
+	/* Tracepoint attach should work */
+	fd = perf_event_open(&pe, 0, -1, -1, 0);
+	ASSERT_NE(-1, fd);
+
+	perf_page = mmap(NULL, page_size * 2, PROT_READ, MAP_SHARED, fd, 0);
+	ASSERT_NE(MAP_FAILED, perf_page);
+
+	/* Status should be updated */
+	ASSERT_EQ(EVENT_STATUS_PERF, status_page[reg.status_index]);
+
+	event.index = reg.write_index;
+	event.field1 = 0xc001;
+	event.field2 = 0xc01a;
+
+	/* Ensure write shows up at correct offset */
+	ASSERT_NE(-1, write(self->data_fd, &event, sizeof(event)));
+	val = (void *)(((char *)perf_page) + perf_page->data_offset);
+	ASSERT_EQ(PERF_RECORD_SAMPLE, *val);
+	/* Skip over header and size, move to offset */
+	val += 3;
+	val = (void *)((char *)val) + offset;
+	/* Ensure correct */
+	ASSERT_EQ(event.field1, *val++);
+	ASSERT_EQ(event.field2, *val++);
+}
+
+int main(int argc, char **argv)
+{
+	return test_harness_run(argc, argv);
+}
diff --git a/tools/testing/selftests/user_events/settings b/tools/testing/selftests/user_events/settings
new file mode 100644
index 000000000000..ba4d85f74cd6
--- /dev/null
+++ b/tools/testing/selftests/user_events/settings
@@ -0,0 +1 @@
+timeout=90