main.c

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/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright (C) 1991, 1992 Linus Torvalds
 *   Copyright 2007 rPath, Inc. - All Rights Reserved
 *   Copyright 2009 Intel Corporation; author H. Peter Anvin
 *
 *   This file is part of the Linux kernel, and is made available under
 *   the terms of the GNU General Public License version 2.
 *
 * ----------------------------------------------------------------------- */

/*
 * 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;
    }
}

/*
 * Query the keyboard lock status as given by the BIOS, and
 * set the keyboard repeat rate to maximum.  Unclear why the latter
 * is done here; this might be possible to kill off as stale code.
 */
static void keyboard_init(void)
{
    struct biosregs ireg, oreg;
    initregs(&ireg);

    ireg.ah = 0x02;     /* Get keyboard status */
    intcall(0x16, &ireg, &oreg);
    boot_params.kbd_status = oreg.al;

    ireg.ax = 0x0305;   /* Set keyboard repeat rate */
    intcall(0x16, &ireg, NULL);
}

/*
 * Get Intel SpeedStep (IST) information.
 */
static void query_ist(void)
{
    struct biosregs ireg, oreg;

    /* Some older BIOSes apparently crash on this call, so filter
       it from machines too old to have SpeedStep at all. */
    if (cpu.level < 6)
        return;

    initregs(&ireg);
    ireg.ax  = 0xe980;   /* IST Support */
    ireg.edx = 0x47534943;   /* Request value */
    intcall(0x15, &ireg, &oreg);

    boot_params.ist_info.signature  = oreg.eax;
    boot_params.ist_info.command    = oreg.ebx;
    boot_params.ist_info.event      = oreg.ecx;
    boot_params.ist_info.perf_level = oreg.edx;
}

/*
 * Tell the BIOS what CPU mode we intend to run in.
 */
static void set_bios_mode(void)
{
#ifdef CONFIG_X86_64
    struct biosregs ireg;

    initregs(&ireg);
    ireg.ax = 0xec00;
    ireg.bx = 2;
    intcall(0x15, &ireg, NULL);
#endif
}

static void init_heap(void)
{
    char *stack_end;

    if (boot_params.hdr.loadflags & CAN_USE_HEAP) {
        asm("leal %P1(%%esp),%0"
            : "=r" (stack_end) : "i" (-STACK_SIZE));

        heap_end = (char *)
            ((size_t)boot_params.hdr.heap_end_ptr + 0x200);
        if (heap_end > stack_end)
            heap_end = stack_end;
    } else {
        /* Boot protocol 2.00 only, no heap available */
        puts("WARNING: Ancient bootloader, some functionality "
             "may be limited!\n");
    }
}

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

    /* Initialize the early-boot console */
    console_init();
    if (cmdline_find_option_bool("debug"))
        puts("early console in setup code\n");

    /* End of heap check */
    init_heap();

    /* 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?) and query the lock flags */
    keyboard_init();

    /* Query MCA information */
    query_mca();

    /* 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

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

    /* Do the last things and invoke protected mode */
    go_to_protected_mode();
}