linux/arch/x86/boot/main.c
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   1/* -*- linux-c -*- ------------------------------------------------------- *
   2 *
   3 *   Copyright (C) 1991, 1992 Linus Torvalds
   4 *   Copyright 2007 rPath, Inc. - All Rights Reserved
   5 *
   6 *   This file is part of the Linux kernel, and is made available under
   7 *   the terms of the GNU General Public License version 2.
   8 *
   9 * ----------------------------------------------------------------------- */
  10
  11/*
  12 * Main module for the real-mode kernel code
  13 */
  14
  15#include "boot.h"
  16
  17struct boot_params boot_params __attribute__((aligned(16)));
  18
  19char *HEAP = _end;
  20char *heap_end = _end;          /* Default end of heap = no heap */
  21
  22/*
  23 * Copy the header into the boot parameter block.  Since this
  24 * screws up the old-style command line protocol, adjust by
  25 * filling in the new-style command line pointer instead.
  26 */
  27
  28static void copy_boot_params(void)
  29{
  30        struct old_cmdline {
  31                u16 cl_magic;
  32                u16 cl_offset;
  33        };
  34        const struct old_cmdline * const oldcmd =
  35                (const struct old_cmdline *)OLD_CL_ADDRESS;
  36
  37        BUILD_BUG_ON(sizeof boot_params != 4096);
  38        memcpy(&boot_params.hdr, &hdr, sizeof hdr);
  39
  40        if (!boot_params.hdr.cmd_line_ptr &&
  41            oldcmd->cl_magic == OLD_CL_MAGIC) {
  42                /* Old-style command line protocol. */
  43                u16 cmdline_seg;
  44
  45                /* Figure out if the command line falls in the region
  46                   of memory that an old kernel would have copied up
  47                   to 0x90000... */
  48                if (oldcmd->cl_offset < boot_params.hdr.setup_move_size)
  49                        cmdline_seg = ds();
  50                else
  51                        cmdline_seg = 0x9000;
  52
  53                boot_params.hdr.cmd_line_ptr =
  54                        (cmdline_seg << 4) + oldcmd->cl_offset;
  55        }
  56}
  57
  58/*
  59 * Set the keyboard repeat rate to maximum.  Unclear why this
  60 * is done here; this might be possible to kill off as stale code.
  61 */
  62static void keyboard_set_repeat(void)
  63{
  64        u16 ax = 0x0305;
  65        u16 bx = 0;
  66        asm volatile("int $0x16"
  67                     : "+a" (ax), "+b" (bx)
  68                     : : "ecx", "edx", "esi", "edi");
  69}
  70
  71/*
  72 * Get Intel SpeedStep (IST) information.
  73 */
  74static void query_ist(void)
  75{
  76        /* Some older BIOSes apparently crash on this call, so filter
  77           it from machines too old to have SpeedStep at all. */
  78        if (cpu.level < 6)
  79                return;
  80
  81        asm("int $0x15"
  82            : "=a" (boot_params.ist_info.signature),
  83              "=b" (boot_params.ist_info.command),
  84              "=c" (boot_params.ist_info.event),
  85              "=d" (boot_params.ist_info.perf_level)
  86            : "a" (0x0000e980),  /* IST Support */
  87              "d" (0x47534943)); /* Request value */
  88}
  89
  90/*
  91 * Tell the BIOS what CPU mode we intend to run in.
  92 */
  93static void set_bios_mode(void)
  94{
  95#ifdef CONFIG_X86_64
  96        u32 eax, ebx;
  97
  98        eax = 0xec00;
  99        ebx = 2;
 100        asm volatile("int $0x15"
 101                     : "+a" (eax), "+b" (ebx)
 102                     : : "ecx", "edx", "esi", "edi");
 103#endif
 104}
 105
 106static void init_heap(void)
 107{
 108        char *stack_end;
 109
 110        if (boot_params.hdr.loadflags & CAN_USE_HEAP) {
 111                asm("leal %P1(%%esp),%0"
 112                    : "=r" (stack_end) : "i" (-STACK_SIZE));
 113
 114                heap_end = (char *)
 115                        ((size_t)boot_params.hdr.heap_end_ptr + 0x200);
 116                if (heap_end > stack_end)
 117                        heap_end = stack_end;
 118        } else {
 119                /* Boot protocol 2.00 only, no heap available */
 120                puts("WARNING: Ancient bootloader, some functionality "
 121                     "may be limited!\n");
 122        }
 123}
 124
 125void main(void)
 126{
 127        /* First, copy the boot header into the "zeropage" */
 128        copy_boot_params();
 129
 130        /* End of heap check */
 131        init_heap();
 132
 133        /* Make sure we have all the proper CPU support */
 134        if (validate_cpu()) {
 135                puts("Unable to boot - please use a kernel appropriate "
 136                     "for your CPU.\n");
 137                die();
 138        }
 139
 140        /* Tell the BIOS what CPU mode we intend to run in. */
 141        set_bios_mode();
 142
 143        /* Detect memory layout */
 144        detect_memory();
 145
 146        /* Set keyboard repeat rate (why?) */
 147        keyboard_set_repeat();
 148
 149        /* Query MCA information */
 150        query_mca();
 151
 152        /* Query Intel SpeedStep (IST) information */
 153        query_ist();
 154
 155        /* Query APM information */
 156#if defined(CONFIG_APM) || defined(CONFIG_APM_MODULE)
 157        query_apm_bios();
 158#endif
 159
 160        /* Query EDD information */
 161#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
 162        query_edd();
 163#endif
 164
 165        /* Set the video mode */
 166        set_video();
 167
 168        /* Parse command line for 'quiet' and pass it to decompressor. */
 169        if (cmdline_find_option_bool("quiet"))
 170                boot_params.hdr.loadflags |= QUIET_FLAG;
 171
 172        /* Do the last things and invoke protected mode */
 173        go_to_protected_mode();
 174}
 175
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