com32/modules/ifcpu64.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2008 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   This program is free software; you can redistribute it and/or modify
   6  *   it under the terms of the GNU General Public License as published by
   7  *   the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
   8  *   Boston MA 02110-1301, USA; either version 2 of the License, or
   9  *   (at your option) any later version; incorporated herein by reference.
  10  *
  11  * ----------------------------------------------------------------------- */
  12
  13 /*
  14  * ifcpu64.c
  15  *
  16  * Run one command if the CPU has 64-bit support, and another if it doesn't.
  17  * Eventually this and other features should get folded into some kind
  18  * of scripting engine.
  19  *
  20  * Usage:
  21  *
  22  *    label boot_kernel
  23  *        com32 ifcpu64.c32
  24  *        append boot_kernel_64 [-- boot_kernel_32pae] -- boot_kernel_32
  25  *    label boot_kernel_32
  26  *        kernel vmlinuz_32
  27  *        append ...
  28  *    label boot_kernel_64
  29  *        kernel vmlinuz_64
  30  *        append ...
  31  */
  32
  33 #include <alloca.h>
  34 #include <stdlib.h>
  35 #include <string.h>
  36 #include <cpuid.h>
  37 #include <syslinux/boot.h>
  38
  39 static bool __constfunc cpu_has_cpuid(void)
  40 {
  41     return cpu_has_eflag(X86_EFLAGS_ID);
  42 }
  43
  44 static bool __constfunc cpu_has_level(uint32_t level)
  45 {
  46     uint32_t group;
  47     uint32_t limit;
  48
  49     if (!cpu_has_cpuid())
  50         return false;
  51
  52     group = level & 0xffff0000;
  53     limit = cpuid_eax(group);
  54
  55     if ((limit & 0xffff0000) != group)
  56         return false;
  57
  58     if (level > limit)
  59         return false;
  60
  61     return true;
  62 }
  63
  64 /* This only supports feature groups 0 and 1, corresponding to the
  65    Intel and AMD EDX bit vectors.  We can add more later if need be. */
  66 static bool __constfunc cpu_has_feature(int x)
  67 {
  68     uint32_t level = ((x & 1) << 31) | 1;
  69
  70     return cpu_has_level(level) && ((cpuid_edx(level) >> (x & 31) & 1));
  71 }
  72
  73 /* XXX: this really should be librarized */
  74 static void boot_args(char **args)
  75 {
  76     int len = 0, a = 0;
  77     char **pp;
  78     const char *p;
  79     char c, *q, *str;
  80
  81     for (pp = args; *pp; pp++)
  82         len += strlen(*pp) + 1;
  83
  84     q = str = alloca(len);
  85     for (pp = args; *pp; pp++) {
  86         p = *pp;
  87         while ((c = *p++))
  88             *q++ = c;
  89         *q++ = ' ';
  90         a = 1;
  91     }
  92     q -= a;
  93     *q = '\0';
  94
  95     if (!str[0])
  96         syslinux_run_default();
  97     else
  98         syslinux_run_command(str);
  99 }
 100
 101 int main(int argc, char *argv[])
 102 {
 103     char **args[3];
 104     int i;
 105     int n;
 106
 107     args[0] = &argv[1];
 108     n = 1;
 109     for (i = 1; i < argc; i++) {
 110         if (!strcmp(argv[i], "--")) {
 111             argv[i] = NULL;
 112             args[n++] = &argv[i + 1];
 113         }
 114         if (n >= 3)
 115             break;
 116     }
 117     while (n < 3) {
 118         args[n] = args[n - 1];
 119         n++;
 120     }
 121
 122     boot_args(cpu_has_feature(X86_FEATURE_LM) ? args[0] :
 123               cpu_has_feature(X86_FEATURE_PAE) ? args[1] : args[2]);
 124     return -1;
 125 }