l4/pkg/l4util/include/ARCH-amd64/cpu.h

   1 /**
   2  * \file
   3  * \brief  CPU related functions
   4  *
   5  * \author Frank Mehnert <fm3@os.inf.tu-dresden.de> */
   6
   7 /*
   8  * (c) 2004-2009 Author(s)
   9  *     economic rights: Technische Universität Dresden (Germany)
  10  * This file is part of TUD:OS and distributed under the terms of the
  11  * GNU Lesser General Public License 2.1.
  12  * Please see the COPYING-LGPL-2.1 file for details.
  13  */
  14
  15 #ifndef __L4_UTIL_CPU_H
  16 #define __L4_UTIL_CPU_H
  17
  18 #include <l4/sys/compiler.h>
  19
  20 EXTERN_C_BEGIN
  21
  22 /**
  23  * \defgroup l4util_cpu CPU related functions
  24  * \ingroup l4util_api
  25  */
  26 /*@{*/
  27
  28 /**
  29  * Check whether the CPU supports the "cpuid" instruction.
  30  *
  31  * \return 1 if it has, 0 if it has not
  32  */
  33 L4_INLINE int          l4util_cpu_has_cpuid(void);
  34
  35 /**
  36  * Returns the CPU capabilities if the "cpuid" instruction is available.
  37  *
  38  * \return CPU capabilities if the "cpuid" instruction is available,
  39  *         0 if the "cpuid" instruction is not supported.
  40  */
  41 L4_INLINE unsigned int l4util_cpu_capabilities(void);
  42
  43 /**
  44  * Returns the CPU capabilities.
  45  *
  46  * \return CPU capabilities.
  47  */
  48 L4_INLINE unsigned int l4util_cpu_capabilities_nocheck(void);
  49
  50 /**
  51  * Generic CPUID access function.
  52  */
  53 L4_INLINE void
  54 l4util_cpu_cpuid(unsigned long mode,
  55                  unsigned long *eax, unsigned long *ebx,
  56                  unsigned long *ecx, unsigned long *edx);
  57 /*@}*/
  58
  59 static inline void
  60 l4util_cpu_pause(void)
  61 {
  62   __asm__ __volatile__ ("rep; nop");
  63 }
  64
  65 L4_INLINE int
  66 l4util_cpu_has_cpuid(void)
  67 {
  68   unsigned long eax;
  69
  70   asm volatile("pushf                   \t\n"
  71                "pop %%rax               \t\n" /* get eflags */
  72                "mov %%rax, %%rbx        \t\n" /* save it */
  73                "xorq $0x200000, %%rax   \t\n" /* toggle ID bit */
  74                "push %%rax              \t\n"
  75                "popf                    \t\n" /* set again */
  76                "pushf                   \t\n"
  77                "pop %%rax               \t\n" /* get it again */
  78                "xor %%rax, %%rbx        \t\n"
  79                "push %%rbx              \t\n"
  80                "popf                    \t\n" /* restore saved flags */
  81                : "=a" (eax)
  82                : /* no input */
  83                : "rbx");
  84
  85   return eax & 0x200000;
  86 }
  87
  88 L4_INLINE void
  89 l4util_cpu_cpuid(unsigned long mode,
  90                  unsigned long *eax, unsigned long *ebx,
  91                  unsigned long *ecx, unsigned long *edx)
  92 {
  93   asm volatile("cpuid"
  94                : "=a" (*eax),
  95                  "=b" (*ebx),
  96                  "=c" (*ecx),
  97                  "=d" (*edx)
  98                : "a"  (mode)
  99                : "cc");
 100 }
 101
 102 L4_INLINE unsigned int
 103 l4util_cpu_capabilities_nocheck(void)
 104 {
 105   unsigned long dummy, capability;
 106
 107   /* get CPU capabilities */
 108   l4util_cpu_cpuid(1, &dummy, &dummy, &dummy, &capability);
 109
 110   return capability;
 111 }
 112
 113 L4_INLINE unsigned int
 114 l4util_cpu_capabilities(void)
 115 {
 116   if (!l4util_cpu_has_cpuid())
 117     return 0; /* CPU has not cpuid instruction */
 118
 119   return l4util_cpu_capabilities_nocheck();
 120 }
 121
 122 EXTERN_C_END
 123
 124 #endif
 125