// SPDX-License-Identifier: GPL-2.0-only
/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright (C) 1991, 1992 Linus Torvalds
 *   Copyright 2007 rPath, Inc. - All Rights Reserved
 *   Copyright 2009 Intel Corporation; author H. Peter Anvin
 *
 * ----------------------------------------------------------------------- */

/*
 * Main module for the real-mode kernel code
 */
#include <linux/build_bug.h>

#include "boot.h"
#include "string.h"

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

struct port_io_ops pio_ops;

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 = absolute_pointer(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) {
                stack_end = (char *) (current_stack_pointer - 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)
{
        init_default_io_ops();

        /* 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 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();
}