Urgh, and now actually add the files :-)

include/grub/i386/tsc.h

@@ -0,0 +1,80 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2008  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef KERNEL_CPU_TSC_HEADER
+#define KERNEL_CPU_TSC_HEADER   1
+
+#include <grub/types.h>
+
+/* Read the TSC value, which increments with each CPU clock cycle. */
+static __inline grub_uint64_t
+grub_get_tsc (void)
+{
+  grub_uint32_t lo, hi;
+
+  /* The CPUID instruction is a 'serializing' instruction, and
+     avoids out-of-order execution of the RDTSC instruction. */
+  __asm__ __volatile__ ("xorl %%eax, %%eax\n\t"
+                        "cpuid":::"%rax", "%rbx", "%rcx", "%rdx");
+  /* Read TSC value.  We cannot use "=A", since this would use
+     %rax on x86_64. */
+  __asm__ __volatile__ ("rdtsc":"=a" (lo), "=d" (hi));
+
+  return (((grub_uint64_t) hi) << 32) | lo;
+}
+
+static __inline int
+grub_cpu_is_cpuid_supported (void)
+{
+  grub_uint32_t id_supported;
+
+  __asm__ ("pushfl\n\t"
+           "popl %%eax             /* Get EFLAGS into EAX */\n\t"
+           "movl %%eax, %%ecx      /* Save original flags in ECX */\n\t"
+           "xorl $0x200000, %%eax  /* Flip ID bit in EFLAGS */\n\t"
+           "pushl %%eax            /* Store modified EFLAGS on stack */\n\t"
+           "popfl                  /* Replace current EFLAGS */\n\t"
+           "pushfl                 /* Read back the EFLAGS */\n\t"
+           "popl %%eax             /* Get EFLAGS into EAX */\n\t"
+           "xorl %%ecx, %%eax      /* Check if flag could be modified */\n\t"
+           : "=a" (id_supported)
+           : /* No inputs.  */
+           : /* Clobbered:  */ "%rcx");
+
+  return id_supported != 0;
+}
+
+static __inline int
+grub_cpu_is_tsc_supported (void)
+{
+  if (! grub_cpu_is_cpuid_supported ())
+    return 0;
+
+  grub_uint32_t features;
+  __asm__ ("movl $1, %%eax\n\t"
+           "cpuid"
+           : "=d" (features)
+           : /* No inputs.  */
+           : /* Clobbered:  */ "%rax", "%rbx", "%rcx");
+  return (features & (1 << 4)) != 0;
+}
+
+void grub_tsc_init (void);
+grub_uint64_t grub_tsc_get_time_ms (void);
+
+#endif /* ! KERNEL_CPU_TSC_HEADER */