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	/*

	 * Prior to 2.5.64 ("[PATCH] x86-64 updates for 2.5.64-bk3"),

	 * Linux saved and restored fs and gs in these slots.  This

	 * was counterproductive, as fsbase and gsbase were never

	 * saved, so arch_prctl was presumably unreliable.

	 *

	 * These slots should never be reused without extreme caution:

	 *

	 *  - Some DOSEMU versions stash fs and gs in these slots manually,

	 *    thus overwriting anything the kernel expects to be preserved

	 *    in these slots.

	 *

	 *  - If these slots are ever needed for any other purpose,

	 *    there is some risk that very old 64-bit binaries could get

	 *    confused.  I doubt that many such binaries still work,

	 *    though, since the same patch in 2.5.64 also removed the

	 *    64-bit set_thread_area syscall, so it appears that there

	 *    is no TLS API beyond modify_ldt that works in both pre-

	 *    and post-2.5.64 kernels.

	 *

	 * If the kernel ever adds explicit fs, gs, fsbase, and gsbase

	 * save/restore, it will most likely need to be opt-in and use

	 * different context slots.

	 */

	union {

		__u16			__pad0;	/* Alias name for old (!UC_SIGCONTEXT_SS) user-space */

	};