unsigned long ip;
unsigned long flags;
unsigned short cs;
- unsigned short gs;
- unsigned short fs;
+ unsigned short __pad2; /* Was called gs, but was always zero. */
+ unsigned short __pad1; /* Was called fs, but was always zero. */
unsigned short ss;
unsigned long err;
unsigned long trapno;
__u64 rip;
__u64 eflags; /* RFLAGS */
__u16 cs;
- __u16 gs;
- __u16 fs;
+
+ /*
+ * 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.
+ *
+ * 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 that works in both pre- and post-2.5.64 kernels.
+ */
+ __u16 __pad2; /* Was gs. */
+ __u16 __pad1; /* Was fs. */
+
__u16 ss;
__u64 err;
__u64 trapno;
#else /* !CONFIG_X86_32 */
put_user_ex(regs->flags, &sc->flags);
put_user_ex(regs->cs, &sc->cs);
- put_user_ex(0, &sc->gs);
- put_user_ex(0, &sc->fs);
+ put_user_ex(0, &sc->__pad2);
+ put_user_ex(0, &sc->__pad1);
put_user_ex(regs->ss, &sc->ss);
#endif /* CONFIG_X86_32 */