tracing/user_events: Allow events to persist for perfmon_capable users

index 2984aae4a2b4..f74f3aedd49c 100644
@@ -17,6 +17,15 @@
 /* Create dynamic location entry within a 32-bit value */
 #define DYN_LOC(offset, size) ((size) << 16 | (offset))
 
+/* List of supported registration flags */
+enum user_reg_flag {
+	/* Event will not delete upon last reference closing */
+	USER_EVENT_REG_PERSIST		= 1U << 0,
+
+	/* This value or above is currently non-ABI */
+	USER_EVENT_REG_MAX		= 1U << 1,
+};
+
 /*
  * Describes an event registration and stores the results of the registration.
  * This structure is passed to the DIAG_IOCSREG ioctl, callers at a minimum

@@ -33,7 +42,7 @@ struct user_reg {
 	/* Input: Enable size in bytes at address */
 	__u8	enable_size;
 
-	/* Input: Flags for future use, set to 0 */
+	/* Input: Flags to use, if any */
 	__u16	flags;
 
 	/* Input: Address to update when enabled */

index 6f046650e527..af663de93492 100644
@@ -49,18 +49,6 @@
 #define EVENT_STATUS_PERF BIT(1)
 #define EVENT_STATUS_OTHER BIT(7)
 
-/*
- * User register flags are not allowed yet, keep them here until we are
- * ready to expose them out to the user ABI.
- */
-enum user_reg_flag {
-	/* Event will not delete upon last reference closing */
-	USER_EVENT_REG_PERSIST		= 1U << 0,
-
-	/* This value or above is currently non-ABI */
-	USER_EVENT_REG_MAX		= 1U << 1,
-};
-
 /*
  * Stores the system name, tables, and locks for a group of events. This
  * allows isolation for events by various means.

@@ -1888,10 +1876,16 @@ static int user_event_parse(struct user_event_group *group, char *name,
 	int argc = 0;
 	char **argv;
 
-	/* User register flags are not ready yet */
-	if (reg_flags != 0 || flags != NULL)
+	/* Currently don't support any text based flags */
+	if (flags != NULL)
 		return -EINVAL;
 
+	/* Persistent events require CAP_PERFMON / CAP_SYS_ADMIN */
+	if (reg_flags & USER_EVENT_REG_PERSIST) {
+		if (!perfmon_capable())
+			return -EPERM;
+	}
+
 	/* Prevent dyn_event from racing */
 	mutex_lock(&event_mutex);
 	user = find_user_event(group, name, &key);

@@ -2024,6 +2018,12 @@ static int delete_user_event(struct user_event_group *group, char *name)
 	if (!user_event_last_ref(user))
 		return -EBUSY;
 
+	/* Persistent events require CAP_PERFMON / CAP_SYS_ADMIN */
+	if (user->reg_flags & USER_EVENT_REG_PERSIST) {
+		if (!perfmon_capable())
+			return -EPERM;
+	}
+
 	return destroy_user_event(user);
 }
 

index 5125c42efe65..b95fc15496ba 100644
@@ -23,6 +23,18 @@
 const char *data_file = "/sys/kernel/tracing/user_events_data";
 const char *enable_file = "/sys/kernel/tracing/events/user_events/__abi_event/enable";
 
+static bool event_exists(void)
+{
+	int fd = open(enable_file, O_RDWR);
+
+	if (fd < 0)
+		return false;
+
+	close(fd);
+
+	return true;
+}
+
 static int change_event(bool enable)
 {
 	int fd = open(enable_file, O_RDWR);

@@ -46,7 +58,22 @@ static int change_event(bool enable)
 	return ret;
 }
 
-static int reg_enable(long *enable, int size, int bit)
+static int event_delete(void)
+{
+	int fd = open(data_file, O_RDWR);
+	int ret;
+
+	if (fd < 0)
+		return -1;
+
+	ret = ioctl(fd, DIAG_IOCSDEL, "__abi_event");
+
+	close(fd);
+
+	return ret;
+}
+
+static int reg_enable_flags(long *enable, int size, int bit, int flags)
 {
 	struct user_reg reg = {0};
 	int fd = open(data_file, O_RDWR);

@@ -57,6 +84,7 @@ static int reg_enable(long *enable, int size, int bit)
 
 	reg.size = sizeof(reg);
 	reg.name_args = (__u64)"__abi_event";
+	reg.flags = flags;
 	reg.enable_bit = bit;
 	reg.enable_addr = (__u64)enable;
 	reg.enable_size = size;

@@ -68,6 +96,11 @@ static int reg_enable(long *enable, int size, int bit)
 	return ret;
 }
 
+static int reg_enable(long *enable, int size, int bit)
+{
+	return reg_enable_flags(enable, size, bit, 0);
+}
+
 static int reg_disable(long *enable, int bit)
 {
 	struct user_unreg reg = {0};

@@ -121,6 +154,26 @@ TEST_F(user, enablement) {
 	ASSERT_EQ(0, change_event(false));
 }
 
+TEST_F(user, flags) {
+	/* USER_EVENT_REG_PERSIST is allowed */
+	ASSERT_EQ(0, reg_enable_flags(&self->check, sizeof(int), 0,
+				      USER_EVENT_REG_PERSIST));
+	ASSERT_EQ(0, reg_disable(&self->check, 0));
+
+	/* Ensure it exists after close and disable */
+	ASSERT_TRUE(event_exists());
+
+	/* Ensure we can delete it */
+	ASSERT_EQ(0, event_delete());
+
+	/* USER_EVENT_REG_MAX or above is not allowed */
+	ASSERT_EQ(-1, reg_enable_flags(&self->check, sizeof(int), 0,
+				       USER_EVENT_REG_MAX));
+
+	/* Ensure it does not exist after invalid flags */
+	ASSERT_FALSE(event_exists());
+}
+
 TEST_F(user, bit_sizes) {
 	/* Allow 0-31 bits for 32-bit */
 	ASSERT_EQ(0, reg_enable(&self->check, sizeof(int), 0));

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