root/arch/x86/boot/main.c

DEFINITIONS

1. copy_boot_params
2. keyboard_set_repeat
3. query_ist
4. set_bios_mode
5. init_heap
6. main

/* -*- 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.
 *
 * ----------------------------------------------------------------------- */

/*
 * 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)
{
        /* 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;

        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
}

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();

        /* 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?) */
        keyboard_set_repeat();

        /* 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

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

        /* Parse command line for 'quiet' and pass it to decompressor. */
        if (cmdline_find_option_bool("quiet"))
                boot_params.hdr.loadflags |= QUIET_FLAG;

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