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cpu.h

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/* (c) 2004 Technische Universitaet Dresden
 * This file is part of DROPS, which is distributed under the terms of the
 * GNU General Public License 2. Please see the COPYING file for details. */

#ifndef __L4_UTIL_CPU_H
#define __L4_UTIL_CPU_H

#include <l4/sys/compiler.h>

EXTERN_C_BEGIN

L4_INLINE int          l4util_cpu_has_cpuid(void);

L4_INLINE unsigned int l4util_cpu_capabilities(void);

L4_INLINE unsigned int l4util_cpu_capabilities_nocheck(void);

L4_INLINE void
l4util_cpu_cpuid(unsigned long mode,
                 unsigned long *eax, unsigned long *ebx,
                 unsigned long *ecx, unsigned long *edx);

static inline void
l4util_cpu_pause(void)
{
  __asm__ __volatile__ ("rep; nop");
}

L4_INLINE int
l4util_cpu_has_cpuid(void)
{
  unsigned long eax;

  asm volatile("pushfl                  \t\n"
               "popl %%eax              \t\n" /* get eflags */
               "movl %%eax, %%ebx       \t\n" /* save it */
               "xorl $0x200000, %%eax   \t\n" /* toggle ID bit */
               "pushl %%eax             \t\n" 
               "popfl                   \t\n" /* set again */
               "pushfl                  \t\n"
               "popl %%eax              \t\n" /* get it again */
               "xorl %%eax, %%ebx       \t\n"
               "pushl %%ebx             \t\n"
               "popfl                   \t\n" /* restore saved flags */
               : "=a" (eax)
               : /* no input */
               : "ebx");

  return eax & 0x200000;
}

L4_INLINE void
l4util_cpu_cpuid(unsigned long mode,
                 unsigned long *eax, unsigned long *ebx,
                 unsigned long *ecx, unsigned long *edx)
{
  asm volatile("cpuid"
               : "=a" (*eax),
                 "=b" (*ebx),
                 "=c" (*ecx),
                 "=d" (*edx)
               : "a"  (mode)
               : "cc");
}

L4_INLINE unsigned int
l4util_cpu_capabilities_nocheck(void)
{
  unsigned long dummy, capability;

  /* get CPU capabilities */
  l4util_cpu_cpuid(1, &dummy, &dummy, &dummy, &capability);

  return capability;
}

L4_INLINE unsigned int
l4util_cpu_capabilities(void)
{
  if (!l4util_cpu_has_cpuid())
    return 0; /* CPU has not cpuid instruction */

  return l4util_cpu_capabilities_nocheck();
}

EXTERN_C_END

#endif

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