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main.c

/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright (C) 1991, 1992 Linus Torvalds
 *   Copyright 2007 rPath, Inc. - All Rights Reserved
 *
 *   This file is part of the Linux kernel, and is made available under
 *   the terms of the GNU General Public License version 2.
 *
 * ----------------------------------------------------------------------- */

/*
 * arch/i386/boot/main.c
 *
 * Main module for the real-mode kernel code
 */

#include "boot.h"

struct boot_params boot_params __attribute__((aligned(16)));

char *HEAP = _end;
char *heap_end = _end;        /* Default end of heap = no heap */

/*
 * Copy the header into the boot parameter block.  Since this
 * screws up the old-style command line protocol, adjust by
 * filling in the new-style command line pointer instead.
 */

static void copy_boot_params(void)
{
      struct old_cmdline {
            u16 cl_magic;
            u16 cl_offset;
      };
      const struct old_cmdline * const oldcmd =
            (const struct old_cmdline *)OLD_CL_ADDRESS;

      BUILD_BUG_ON(sizeof boot_params != 4096);
      memcpy(&boot_params.hdr, &hdr, sizeof hdr);

      if (!boot_params.hdr.cmd_line_ptr &&
          oldcmd->cl_magic == OLD_CL_MAGIC) {
            /* Old-style command line protocol. */
            u16 cmdline_seg;

            /* Figure out if the command line falls in the region
               of memory that an old kernel would have copied up
               to 0x90000... */
            if (oldcmd->cl_offset < boot_params.hdr.setup_move_size)
                  cmdline_seg = ds();
            else
                  cmdline_seg = 0x9000;

            boot_params.hdr.cmd_line_ptr =
                  (cmdline_seg << 4) + oldcmd->cl_offset;
      }
}

/*
 * Set the keyboard repeat rate to maximum.  Unclear why this
 * is done here; this might be possible to kill off as stale code.
 */
static void keyboard_set_repeat(void)
{
      u16 ax = 0x0305;
      u16 bx = 0;
      asm volatile("int $0x16"
                 : "+a" (ax), "+b" (bx)
                 : : "ecx", "edx", "esi", "edi");
}

/*
 * Get Intel SpeedStep (IST) information.
 */
static void query_ist(void)
{
      asm("int $0x15"
          : "=a" (boot_params.ist_info.signature),
            "=b" (boot_params.ist_info.command),
            "=c" (boot_params.ist_info.event),
            "=d" (boot_params.ist_info.perf_level)
          : "a" (0x0000e980),  /* IST Support */
            "d" (0x47534943)); /* Request value */
}

/*
 * Tell the BIOS what CPU mode we intend to run in.
 */
static void set_bios_mode(void)
{
#ifdef CONFIG_X86_64
      u32 eax, ebx;

      eax = 0xec00;
      ebx = 2;
      asm volatile("int $0x15"
                 : "+a" (eax), "+b" (ebx)
                 : : "ecx", "edx", "esi", "edi");
#endif
}

void main(void)
{
      /* First, copy the boot header into the "zeropage" */
      copy_boot_params();

      /* End of heap check */
      if (boot_params.hdr.loadflags & CAN_USE_HEAP) {
            heap_end = (char *)(boot_params.hdr.heap_end_ptr
                            +0x200-STACK_SIZE);
      } else {
            /* Boot protocol 2.00 only, no heap available */
            puts("WARNING: Ancient bootloader, some functionality "
                 "may be limited!\n");
      }

      /* Make sure we have all the proper CPU support */
      if (validate_cpu()) {
            puts("Unable to boot - please use a kernel appropriate "
                 "for your CPU.\n");
            die();
      }

      /* Tell the BIOS what CPU mode we intend to run in. */
      set_bios_mode();

      /* Detect memory layout */
      detect_memory();

      /* Set keyboard repeat rate (why?) */
      keyboard_set_repeat();

      /* Set the video mode */
      set_video();

      /* Query MCA information */
      query_mca();

      /* Voyager */
#ifdef CONFIG_X86_VOYAGER
      query_voyager();
#endif

      /* Query Intel SpeedStep (IST) information */
      query_ist();

      /* Query APM information */
#if defined(CONFIG_APM) || defined(CONFIG_APM_MODULE)
      query_apm_bios();
#endif

      /* Query EDD information */
#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
      query_edd();
#endif
      /* Do the last things and invoke protected mode */
      go_to_protected_mode();
}

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