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    Subject[x86 setup 29/33] Assembly header and main routine for new x86 setup code
    Date
    From: H. Peter Anvin <hpa@zytor.com>

    The assembly header and initialization code, and the main() routine.
    main.c also contains some miscellaneous very short routines.

    Signed-off-by: H. Peter Anvin <hpa@zytor.com>
    ---
    arch/i386/boot/header.S | 283 +++++++++++++++++++++++++++++++++++++++++++++++
    arch/i386/boot/main.c | 161 +++++++++++++++++++++++++++
    2 files changed, 444 insertions(+), 0 deletions(-)
    create mode 100644 arch/i386/boot/header.S
    create mode 100644 arch/i386/boot/main.c
    diff --git a/arch/i386/boot/header.S b/arch/i386/boot/header.S
    new file mode 100644
    index 0000000..6b9923f
    --- /dev/null
    +++ b/arch/i386/boot/header.S
    @@ -0,0 +1,283 @@
    +/*
    + * header.S
    + *
    + * Copyright (C) 1991, 1992 Linus Torvalds
    + *
    + * Based on bootsect.S and setup.S
    + * modified by more people than can be counted
    + *
    + * Rewritten as a common file by H. Peter Anvin (Apr 2007)
    + *
    + * BIG FAT NOTE: We're in real mode using 64k segments. Therefore segment
    + * addresses must be multiplied by 16 to obtain their respective linear
    + * addresses. To avoid confusion, linear addresses are written using leading
    + * hex while segment addresses are written as segment:offset.
    + *
    + */
    +
    +#include <asm/segment.h>
    +#include <linux/utsrelease.h>
    +#include <asm/boot.h>
    +#include <asm/e820.h>
    +#include <asm/page.h>
    +#include <asm/setup.h>
    +#include "boot.h"
    +
    +SETUPSECTS = 4 /* default nr of setup-sectors */
    +BOOTSEG = 0x07C0 /* original address of boot-sector */
    +SYSSEG = DEF_SYSSEG /* system loaded at 0x10000 (65536) */
    +SYSSIZE = DEF_SYSSIZE /* system size: # of 16-byte clicks */
    + /* to be loaded */
    +ROOT_DEV = 0 /* ROOT_DEV is now written by "build" */
    +SWAP_DEV = 0 /* SWAP_DEV is now written by "build" */
    +
    +#ifndef SVGA_MODE
    +#define SVGA_MODE ASK_VGA
    +#endif
    +
    +#ifndef RAMDISK
    +#define RAMDISK 0
    +#endif
    +
    +#ifndef ROOT_RDONLY
    +#define ROOT_RDONLY 1
    +#endif
    +
    + .code16
    + .section ".bstext", "ax"
    +
    + .global bootsect_start
    +bootsect_start:
    +
    + # Normalize the start address
    + ljmp $BOOTSEG, $start2
    +
    +start2:
    + movw %cs, %ax
    + movw %ax, %ds
    + movw %ax, %es
    + movw %ax, %ss
    + xorw %sp, %sp
    + sti
    + cld
    +
    + movw $bugger_off_msg, %si
    +
    +msg_loop:
    + lodsb
    + andb %al, %al
    + jz bs_die
    + movb $0xe, %ah
    + movw $7, %bx
    + int $0x10
    + jmp msg_loop
    +
    +bs_die:
    + # Allow the user to press a key, then reboot
    + xorw %ax, %ax
    + int $0x16
    + int $0x19
    +
    + # int 0x19 should never return. In case it does anyway,
    + # invoke the BIOS reset code...
    + ljmp $0xf000,$0xfff0
    +
    + .section ".bsdata", "a"
    +bugger_off_msg:
    + .ascii "Direct booting from floppy is no longer supported.\r\n"
    + .ascii "Please use a boot loader program instead.\r\n"
    + .ascii "\n"
    + .ascii "Remove disk and press any key to reboot . . .\r\n"
    + .byte 0
    +
    +
    + # Kernel attributes; used by setup. This is part 1 of the
    + # header, from the old boot sector.
    +
    + .section ".header", "a"
    + .globl hdr
    +hdr:
    +setup_sects: .byte SETUPSECTS
    +root_flags: .word ROOT_RDONLY
    +syssize: .long SYSSIZE
    +ram_size: .word RAMDISK
    +vid_mode: .word SVGA_MODE
    +root_dev: .word ROOT_DEV
    +boot_flag: .word 0xAA55
    +
    + # offset 512, entry point
    +
    + .globl _start
    +_start:
    + # Explicitly enter this as bytes, or the assembler
    + # tries to generate a 3-byte jump here, which causes
    + # everything else to push off to the wrong offset.
    + .byte 0xeb # short (2-byte) jump
    + .byte start_of_setup-1f
    +1:
    +
    + # Part 2 of the header, from the old setup.S
    +
    + .ascii "HdrS" # header signature
    + .word 0x0206 # header version number (>= 0x0105)
    + # or else old loadlin-1.5 will fail)
    + .globl realmode_swtch
    +realmode_swtch: .word 0, 0 # default_switch, SETUPSEG
    +start_sys_seg: .word SYSSEG
    + .word kernel_version-512 # pointing to kernel version string
    + # above section of header is compatible
    + # with loadlin-1.5 (header v1.5). Don't
    + # change it.
    +
    +type_of_loader: .byte 0 # = 0, old one (LILO, Loadlin,
    + # Bootlin, SYSLX, bootsect...)
    + # See Documentation/i386/boot.txt for
    + # assigned ids
    +
    +# flags, unused bits must be zero (RFU) bit within loadflags
    +loadflags:
    +LOADED_HIGH = 1 # If set, the kernel is loaded high
    +CAN_USE_HEAP = 0x80 # If set, the loader also has set
    + # heap_end_ptr to tell how much
    + # space behind setup.S can be used for
    + # heap purposes.
    + # Only the loader knows what is free
    +#ifndef __BIG_KERNEL__
    + .byte 0
    +#else
    + .byte LOADED_HIGH
    +#endif
    +
    +setup_move_size: .word 0x8000 # size to move, when setup is not
    + # loaded at 0x90000. We will move setup
    + # to 0x90000 then just before jumping
    + # into the kernel. However, only the
    + # loader knows how much data behind
    + # us also needs to be loaded.
    +
    +code32_start: # here loaders can put a different
    + # start address for 32-bit code.
    +#ifndef __BIG_KERNEL__
    + .long 0x1000 # 0x1000 = default for zImage
    +#else
    + .long 0x100000 # 0x100000 = default for big kernel
    +#endif
    +
    +ramdisk_image: .long 0 # address of loaded ramdisk image
    + # Here the loader puts the 32-bit
    + # address where it loaded the image.
    + # This only will be read by the kernel.
    +
    +ramdisk_size: .long 0 # its size in bytes
    +
    +bootsect_kludge:
    + .long 0 # obsolete
    +
    +heap_end_ptr: .word _end+1024 # (Header version 0x0201 or later)
    + # space from here (exclusive) down to
    + # end of setup code can be used by setup
    + # for local heap purposes.
    +
    +pad1: .word 0
    +cmd_line_ptr: .long 0 # (Header version 0x0202 or later)
    + # If nonzero, a 32-bit pointer
    + # to the kernel command line.
    + # The command line should be
    + # located between the start of
    + # setup and the end of low
    + # memory (0xa0000), or it may
    + # get overwritten before it
    + # gets read. If this field is
    + # used, there is no longer
    + # anything magical about the
    + # 0x90000 segment; the setup
    + # can be located anywhere in
    + # low memory 0x10000 or higher.
    +
    +ramdisk_max: .long (-__PAGE_OFFSET-(512 << 20)-1) & 0x7fffffff
    + # (Header version 0x0203 or later)
    + # The highest safe address for
    + # the contents of an initrd
    +
    +kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment
    + #required for protected mode
    + #kernel
    +#ifdef CONFIG_RELOCATABLE
    +relocatable_kernel: .byte 1
    +#else
    +relocatable_kernel: .byte 0
    +#endif
    +pad2: .byte 0
    +pad3: .word 0
    +
    +cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line,
    + #added with boot protocol
    + #version 2.06
    +
    +# End of setup header #####################################################
    +
    + .section ".inittext", "ax"
    +start_of_setup:
    +#ifdef SAFE_RESET_DISK_CONTROLLER
    +# Reset the disk controller.
    + movw $0x0000, %ax # Reset disk controller
    + movb $0x80, %dl # All disks
    + int $0x13
    +#endif
    +
    +# We will have entired with %cs = %ds+0x20, normalize %cs so
    +# it is on par with the other segments.
    + pushw %ds
    + pushw $setup2
    + lretw
    +
    +setup2:
    +# Force %es = %ds
    + movw %ds, %ax
    + movw %ax, %es
    + cld
    +
    +# Stack paranoia: align the stack and make sure it is good
    +# for both 16- and 32-bit references. In particular, if we
    +# were meant to have been using the full 16-bit segment, the
    +# caller might have set %sp to zero, which breaks %esp-based
    +# references.
    + andw $~3, %sp # dword align (might as well...)
    + jnz 1f
    + movw $0xfffc, %sp # Make sure we're not zero
    +1: movzwl %sp, %esp # Clear upper half of %esp
    + sti
    +
    +# Check signature at end of setup
    + cmpl $0x5a5aaa55, setup_sig
    + jne setup_bad
    +
    +# Zero the bss
    + movw $__bss_start, %di
    + movw $_end+3, %cx
    + xorl %eax, %eax
    + subw %di, %cx
    + shrw $2, %cx
    + rep; stosl
    +
    +# Jump to C code (should not return)
    + calll main
    +
    +# Setup corrupt somehow...
    +setup_bad:
    + movl $setup_corrupt, %eax
    + calll puts
    + # Fall through...
    +
    + .globl die
    + .type die, @function
    +die:
    + hlt
    + jmp die
    +
    + .size die, .-due
    +
    + .section ".initdata", "a"
    +setup_corrupt:
    + .byte 7
    + .string "No setup signature found..."
    diff --git a/arch/i386/boot/main.c b/arch/i386/boot/main.c
    new file mode 100644
    index 0000000..7f01f96
    --- /dev/null
    +++ b/arch/i386/boot/main.c
    @@ -0,0 +1,161 @@
    +/* -*- 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.
    + */
    +#define OLD_CL_MAGIC 0xA33F
    +#define OLD_CL_ADDRESS 0x20
    +
    +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_speedstep_ist(void)
    +{
    + asm("int $0x15"
    + : "=a" (boot_params.speedstep_info[0]),
    + "=b" (boot_params.speedstep_info[1]),
    + "=c" (boot_params.speedstep_info[2]),
    + "=d" (boot_params.speedstep_info[3])
    + : "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 SpeedStep IST information */
    + query_speedstep_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();
    +}
    --
    1.5.2.2
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