[EventPipe][UserEvents] Add copy of user_events structs (#116930)

* [EventPipe][UserEvents] Add copy of user_events structs

* Use hex representation

* Various compiler warnings

__attribute__((__packed__)) isn't declared in src/native
uint8_t __reserved as a field name will somehow be interpreted as
unsigned char

Author: mdh1418

src/native/eventpipe/ep-session-provider.c

@@ -7,10 +7,6 @@
 #include "ep-session-provider.h"
 #include "ep-rt.h"
 
-#if HAVE_LINUX_USER_EVENTS_H
-#include <linux/user_events.h> // DIAG_IOCSREG
-#endif // HAVE_LINUX_USER_EVENTS_H
-
 #if HAVE_SYS_IOCTL_H
 #include <sys/ioctl.h> // session_register_tracepoint
 #endif // HAVE_SYS_IOCTL_H
@@ -149,7 +145,7 @@ session_provider_event_filter_alloc (const EventPipeProviderEventFilter *event_f
  * EventPipeSessionProviderTracepoint.
  */
 
-#if HAVE_LINUX_USER_EVENTS_H && HAVE_SYS_IOCTL_H
+#if HAVE_SYS_IOCTL_H
 static
 bool
 session_provider_tracepoint_register (
@@ -194,7 +190,7 @@ session_provider_tracepoint_unregister (
 
 	return true;
 }
-#else // HAVE_LINUX_USER_EVENTS_H && HAVE_SYS_IOCTL_H
+#else // HAVE_SYS_IOCTL_H
 static
 bool
 session_provider_tracepoint_register (
@@ -214,7 +210,7 @@ session_provider_tracepoint_unregister (
 	// Not Supported
 	return false;
 }
-#endif // HAVE_LINUX_USER_EVENTS_H && HAVE_SYS_IOCTL_H
+#endif // HAVE_SYS_IOCTL_H
 
 /*
  *  ep_session_provider_register_tracepoints

src/native/eventpipe/ep-session-provider.h

@@ -11,6 +11,67 @@
 #endif
 #include "ep-getter-setter.h"
 
+#if HAVE_LINUX_USER_EVENTS_H
+#include <linux/user_events.h> // DIAG_IOCSREG
+#else // HAVE_LINUX_USER_EVENTS_H
+/*
+ * Describes an event registration and stores the results of the registration.
+ * This structure is passed to the DIAG_IOCSREG ioctl, callers at a minimum
+ * must set the size and name_args before invocation.
+ */
+struct user_reg {
+
+	/* Input: Size of the user_reg structure being used */
+	uint32_t size;
+
+	/* Input: Bit in enable address to use */
+	uint8_t enable_bit;
+
+	/* Input: Enable size in bytes at address */
+	uint8_t enable_size;
+
+	/* Input: Flags to use, if any */
+	uint16_t flags;
+
+	/* Input: Address to update when enabled */
+	uint64_t enable_addr;
+
+	/* Input: Pointer to string with event name, description and flags */
+	uint64_t name_args;
+
+	/* Output: Index of the event to use when writing data */
+	uint32_t write_index;
+};
+
+/*
+ * Describes an event unregister, callers must set the size, address and bit.
+ * This structure is passed to the DIAG_IOCSUNREG ioctl to disable bit updates.
+ */
+struct user_unreg {
+	/* Input: Size of the user_unreg structure being used */
+	uint32_t size;
+
+	/* Input: Bit to unregister */
+	uint8_t disable_bit;
+
+	/* Input: Reserved, set to 0 */
+	uint8_t _reserved;
+
+	/* Input: Reserved, set to 0 */
+	uint16_t _reserved2;
+
+	/* Input: Address to unregister */
+	uint64_t disable_addr;
+};
+
+/* Request to register a user_event */
+#define DIAG_IOCSREG 0xC0082A00
+
+/* Requests to unregister a user_event */
+#define DIAG_IOCSUNREG 0x40082A02
+
+#endif // HAVE_LINUX_USER_EVENTS_H
+
 /*
  * EventPipeSessionProviderTracepoint.
  */