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  1. /*
  2.  * Copyright (C) 2006 Ondrej Palkovsky
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. #include <syscall/syscall.h>
  30. #include <arch/syscall.h>
  31. #include <panic.h>
  32. #include <arch/cpu.h>
  33. #include <arch/pm.h>
  34. #include <arch/asm.h>
  35.  
  36. #include <print.h>
  37. #include <arch/cpu.h>
  38.  
  39. extern void syscall_entry(void);
  40.  
  41. /** Enable & setup support for SYSCALL/SYSRET */
  42. void syscall_setup_cpu(void)
  43. {
  44.     /* Enable SYSCALL/SYSRET */
  45.     set_efer_flag(AMD_SCE_FLAG);
  46.  
  47.     /* Setup syscall entry address */
  48.    
  49.     /* This is _mess_ - the 64-bit CS is argument+16,
  50.      * the SS is argument+8. The order is:
  51.      * +0(KDATA_DES), +8(UDATA_DES), +16(UTEXT_DES)
  52.      */
  53.     write_msr(AMD_MSR_STAR,
  54.           ((__u64)(gdtselector(KDATA_DES) | PL_USER)<<48) \
  55.           | ((__u64)(gdtselector(KTEXT_DES) | PL_KERNEL)<<32));
  56.     write_msr(AMD_MSR_LSTAR, (__u64)syscall_entry);
  57.     /* Mask RFLAGS on syscall
  58.      * - disable interrupts, until we exchange the stack register
  59.      *   (mask the IE bit)
  60.      */
  61.     write_msr(AMD_MSR_SFMASK, 0x200);
  62. }
  63.