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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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