LXR linux/arch/x86/boot/main.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* -*- linux-c -*- ------------------------------------------------------- *
   3 *
   4 *   Copyright (C) 1991, 1992 Linus Torvalds
   5 *   Copyright 2007 rPath, Inc. - All Rights Reserved
   6 *   Copyright 2009 Intel Corporation; author H. Peter Anvin
   7 *
   8 * ----------------------------------------------------------------------- */
   9
  10/*
  11 * Main module for the real-mode kernel code
  12 */
  13#include <linux/build_bug.h>
  14
  15#include "boot.h"
  16#include "string.h"
  17
  18struct boot_params boot_params __attribute__((aligned(16)));
  19
  20char *HEAP = _end;
  21char *heap_end = _end;          /* Default end of heap = no heap */
  22
  23/*
  24 * Copy the header into the boot parameter block.  Since this
  25 * screws up the old-style command line protocol, adjust by
  26 * filling in the new-style command line pointer instead.
  27 */
  28
  29static void copy_boot_params(void)
  30{
  31        struct old_cmdline {
  32                u16 cl_magic;
  33                u16 cl_offset;
  34        };
  35        const struct old_cmdline * const oldcmd =
  36                (const struct old_cmdline *)OLD_CL_ADDRESS;
  37
  38        BUILD_BUG_ON(sizeof(boot_params) != 4096);
  39        memcpy(&boot_params.hdr, &hdr, sizeof(hdr));
  40
  41        if (!boot_params.hdr.cmd_line_ptr &&
  42            oldcmd->cl_magic == OLD_CL_MAGIC) {
  43                /* Old-style command line protocol. */
  44                u16 cmdline_seg;
  45
  46                /* Figure out if the command line falls in the region
  47                   of memory that an old kernel would have copied up
  48                   to 0x90000... */
  49                if (oldcmd->cl_offset < boot_params.hdr.setup_move_size)
  50                        cmdline_seg = ds();
  51                else
  52                        cmdline_seg = 0x9000;
  53
  54                boot_params.hdr.cmd_line_ptr =
  55                        (cmdline_seg << 4) + oldcmd->cl_offset;
  56        }
  57}
  58
  59/*
  60 * Query the keyboard lock status as given by the BIOS, and
  61 * set the keyboard repeat rate to maximum.  Unclear why the latter
  62 * is done here; this might be possible to kill off as stale code.
  63 */
  64static void keyboard_init(void)
  65{
  66        struct biosregs ireg, oreg;
  67        initregs(&ireg);
  68
  69        ireg.ah = 0x02;         /* Get keyboard status */
  70        intcall(0x16, &ireg, &oreg);
  71        boot_params.kbd_status = oreg.al;
  72
  73        ireg.ax = 0x0305;       /* Set keyboard repeat rate */
  74        intcall(0x16, &ireg, NULL);
  75}
  76
  77/*
  78 * Get Intel SpeedStep (IST) information.
  79 */
  80static void query_ist(void)
  81{
  82        struct biosregs ireg, oreg;
  83
  84        /* Some older BIOSes apparently crash on this call, so filter
  85           it from machines too old to have SpeedStep at all. */
  86        if (cpu.level < 6)
  87                return;
  88
  89        initregs(&ireg);
  90        ireg.ax  = 0xe980;       /* IST Support */
  91        ireg.edx = 0x47534943;   /* Request value */
  92        intcall(0x15, &ireg, &oreg);
  93
  94        boot_params.ist_info.signature  = oreg.eax;
  95        boot_params.ist_info.command    = oreg.ebx;
  96        boot_params.ist_info.event      = oreg.ecx;
  97        boot_params.ist_info.perf_level = oreg.edx;
  98}
  99
 100/*
 101 * Tell the BIOS what CPU mode we intend to run in.
 102 */
 103static void set_bios_mode(void)
 104{
 105#ifdef CONFIG_X86_64
 106        struct biosregs ireg;
 107
 108        initregs(&ireg);
 109        ireg.ax = 0xec00;
 110        ireg.bx = 2;
 111        intcall(0x15, &ireg, NULL);
 112#endif
 113}
 114
 115static void init_heap(void)
 116{
 117        char *stack_end;
 118
 119        if (boot_params.hdr.loadflags & CAN_USE_HEAP) {
 120                asm("leal %P1(%%esp),%0"
 121                    : "=r" (stack_end) : "i" (-STACK_SIZE));
 122
 123                heap_end = (char *)
 124                        ((size_t)boot_params.hdr.heap_end_ptr + 0x200);
 125                if (heap_end > stack_end)
 126                        heap_end = stack_end;
 127        } else {
 128                /* Boot protocol 2.00 only, no heap available */
 129                puts("WARNING: Ancient bootloader, some functionality "
 130                     "may be limited!\n");
 131        }
 132}
 133
 134void main(void)
 135{
 136        /* First, copy the boot header into the "zeropage" */
 137        copy_boot_params();
 138
 139        /* Initialize the early-boot console */
 140        console_init();
 141        if (cmdline_find_option_bool("debug"))
 142                puts("early console in setup code\n");
 143
 144        /* End of heap check */
 145        init_heap();
 146
 147        /* Make sure we have all the proper CPU support */
 148        if (validate_cpu()) {
 149                puts("Unable to boot - please use a kernel appropriate "
 150                     "for your CPU.\n");
 151                die();
 152        }
 153
 154        /* Tell the BIOS what CPU mode we intend to run in. */
 155        set_bios_mode();
 156
 157        /* Detect memory layout */
 158        detect_memory();
 159
 160        /* Set keyboard repeat rate (why?) and query the lock flags */
 161        keyboard_init();
 162
 163        /* Query Intel SpeedStep (IST) information */
 164        query_ist();
 165
 166        /* Query APM information */
 167#if defined(CONFIG_APM) || defined(CONFIG_APM_MODULE)
 168        query_apm_bios();
 169#endif
 170
 171        /* Query EDD information */
 172#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
 173        query_edd();
 174#endif
 175
 176        /* Set the video mode */
 177        set_video();
 178
 179        /* Do the last things and invoke protected mode */
 180        go_to_protected_mode();
 181}
 182