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linux/arch/x86/boot/header.S
Matt Fleming 745c51673e x86/boot: EFI_MIXED should not prohibit loading above 4G 
commit 7d453eee36 ("x86/efi: Wire up CONFIG_EFI_MIXED") introduced a
regression for the functionality to load kernels above 4G. The relevant
(incorrect) reasoning behind this change can be seen in the commit
message,

  "The xloadflags field in the bzImage header is also updated to reflect
  that the kernel supports both entry points by setting both of
  XLF_EFI_HANDOVER_32 and XLF_EFI_HANDOVER_64 when CONFIG_EFI_MIXED=y.
  XLF_CAN_BE_LOADED_ABOVE_4G is disabled so that the kernel text is
  guaranteed to be addressable with 32-bits."

This is obviously bogus since 32-bit EFI loaders will never place the
kernel above the 4G mark. So this restriction is entirely unnecessary.

But things are worse than that - since we want to encourage people to
always compile with CONFIG_EFI_MIXED=y so that their kernels work out of
the box for both 32-bit and 64-bit firmware, commit 7d453eee36
effectively disables XLF_CAN_BE_LOADED_ABOVE_4G completely.

Remove the overzealous and superfluous restriction and restore the
XLF_CAN_BE_LOADED_ABOVE_4G functionality.

Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Link: http://lkml.kernel.org/r/1402140380-15377-1-git-send-email-matt@console-pimps.org
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2014-06-07 09:31:00 -07:00

511 lines
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/*
* 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 <generated/utsrelease.h>
#include <asm/boot.h>
#include <asm/e820.h>
#include <asm/page_types.h>
#include <asm/setup.h>
#include <asm/bootparam.h>
#include "boot.h"
#include "voffset.h"
#include "zoffset.h"
BOOTSEG = 0x07C0 /* original address of boot-sector */
SYSSEG = 0x1000 /* historical load address >> 4 */
#ifndef SVGA_MODE
#define SVGA_MODE ASK_VGA
#endif
#ifndef ROOT_RDONLY
#define ROOT_RDONLY 1
#endif
.code16
.section ".bstext", "ax"
.global bootsect_start
bootsect_start:
#ifdef CONFIG_EFI_STUB
# "MZ", MS-DOS header
.byte 0x4d
.byte 0x5a
#endif
# 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
#ifdef CONFIG_EFI_STUB
.org 0x3c
#
# Offset to the PE header.
#
.long pe_header
#endif /* CONFIG_EFI_STUB */
.section ".bsdata", "a"
bugger_off_msg:
.ascii "Direct floppy boot is not supported. "
.ascii "Use a boot loader program instead.\r\n"
.ascii "\n"
.ascii "Remove disk and press any key to reboot ...\r\n"
.byte 0
#ifdef CONFIG_EFI_STUB
pe_header:
.ascii "PE"
.word 0
coff_header:
#ifdef CONFIG_X86_32
.word 0x14c # i386
#else
.word 0x8664 # x86-64
#endif
.word 3 # nr_sections
.long 0 # TimeDateStamp
.long 0 # PointerToSymbolTable
.long 1 # NumberOfSymbols
.word section_table - optional_header # SizeOfOptionalHeader
#ifdef CONFIG_X86_32
.word 0x306 # Characteristics.
# IMAGE_FILE_32BIT_MACHINE |
# IMAGE_FILE_DEBUG_STRIPPED |
# IMAGE_FILE_EXECUTABLE_IMAGE |
# IMAGE_FILE_LINE_NUMS_STRIPPED
#else
.word 0x206 # Characteristics
# IMAGE_FILE_DEBUG_STRIPPED |
# IMAGE_FILE_EXECUTABLE_IMAGE |
# IMAGE_FILE_LINE_NUMS_STRIPPED
#endif
optional_header:
#ifdef CONFIG_X86_32
.word 0x10b # PE32 format
#else
.word 0x20b # PE32+ format
#endif
.byte 0x02 # MajorLinkerVersion
.byte 0x14 # MinorLinkerVersion
# Filled in by build.c
.long 0 # SizeOfCode
.long 0 # SizeOfInitializedData
.long 0 # SizeOfUninitializedData
# Filled in by build.c
.long 0x0000 # AddressOfEntryPoint
.long 0x0200 # BaseOfCode
#ifdef CONFIG_X86_32
.long 0 # data
#endif
extra_header_fields:
#ifdef CONFIG_X86_32
.long 0 # ImageBase
#else
.quad 0 # ImageBase
#endif
.long 0x20 # SectionAlignment
.long 0x20 # FileAlignment
.word 0 # MajorOperatingSystemVersion
.word 0 # MinorOperatingSystemVersion
.word 0 # MajorImageVersion
.word 0 # MinorImageVersion
.word 0 # MajorSubsystemVersion
.word 0 # MinorSubsystemVersion
.long 0 # Win32VersionValue
#
# The size of the bzImage is written in tools/build.c
#
.long 0 # SizeOfImage
.long 0x200 # SizeOfHeaders
.long 0 # CheckSum
.word 0xa # Subsystem (EFI application)
.word 0 # DllCharacteristics
#ifdef CONFIG_X86_32
.long 0 # SizeOfStackReserve
.long 0 # SizeOfStackCommit
.long 0 # SizeOfHeapReserve
.long 0 # SizeOfHeapCommit
#else
.quad 0 # SizeOfStackReserve
.quad 0 # SizeOfStackCommit
.quad 0 # SizeOfHeapReserve
.quad 0 # SizeOfHeapCommit
#endif
.long 0 # LoaderFlags
.long 0x6 # NumberOfRvaAndSizes
.quad 0 # ExportTable
.quad 0 # ImportTable
.quad 0 # ResourceTable
.quad 0 # ExceptionTable
.quad 0 # CertificationTable
.quad 0 # BaseRelocationTable
# Section table
section_table:
#
# The offset & size fields are filled in by build.c.
#
.ascii ".setup"
.byte 0
.byte 0
.long 0
.long 0x0 # startup_{32,64}
.long 0 # Size of initialized data
# on disk
.long 0x0 # startup_{32,64}
.long 0 # PointerToRelocations
.long 0 # PointerToLineNumbers
.word 0 # NumberOfRelocations
.word 0 # NumberOfLineNumbers
.long 0x60500020 # Characteristics (section flags)
#
# The EFI application loader requires a relocation section
# because EFI applications must be relocatable. The .reloc
# offset & size fields are filled in by build.c.
#
.ascii ".reloc"
.byte 0
.byte 0
.long 0
.long 0
.long 0 # SizeOfRawData
.long 0 # PointerToRawData
.long 0 # PointerToRelocations
.long 0 # PointerToLineNumbers
.word 0 # NumberOfRelocations
.word 0 # NumberOfLineNumbers
.long 0x42100040 # Characteristics (section flags)
#
# The offset & size fields are filled in by build.c.
#
.ascii ".text"
.byte 0
.byte 0
.byte 0
.long 0
.long 0x0 # startup_{32,64}
.long 0 # Size of initialized data
# on disk
.long 0x0 # startup_{32,64}
.long 0 # PointerToRelocations
.long 0 # PointerToLineNumbers
.word 0 # NumberOfRelocations
.word 0 # NumberOfLineNumbers
.long 0x60500020 # Characteristics (section flags)
#endif /* CONFIG_EFI_STUB */
# Kernel attributes; used by setup. This is part 1 of the
# header, from the old boot sector.
.section ".header", "a"
.globl sentinel
sentinel: .byte 0xff, 0xff /* Used to detect broken loaders */
.globl hdr
hdr:
setup_sects: .byte 0 /* Filled in by build.c */
root_flags: .word ROOT_RDONLY
syssize: .long 0 /* Filled in by build.c */
ram_size: .word 0 /* Obsolete */
vid_mode: .word SVGA_MODE
root_dev: .word 0 /* Filled in by build.c */
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 0x020d # 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 # obsolete and meaningless, but just
# in case something decided to "use" it
.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 means ancient bootloader, newer
# bootloaders know to change this.
# See Documentation/x86/boot.txt for
# assigned ids
# flags, unused bits must be zero (RFU) bit within loadflags
loadflags:
.byte LOADED_HIGH # The kernel is to be loaded high
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.
.long 0x100000 # 0x100000 = default for big kernel
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+STACK_SIZE-512
# (Header version 0x0201 or later)
# space from here (exclusive) down to
# end of setup code can be used by setup
# for local heap purposes.
ext_loader_ver:
.byte 0 # Extended boot loader version
ext_loader_type:
.byte 0 # Extended boot loader type
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.
initrd_addr_max: .long 0x7fffffff
# (Header version 0x0203 or later)
# The highest safe address for
# the contents of an initrd
# The current kernel allows up to 4 GB,
# but leave it at 2 GB to avoid
# possible bootloader bugs.
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
min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment
xloadflags:
#ifdef CONFIG_X86_64
# define XLF0 XLF_KERNEL_64 /* 64-bit kernel */
#else
# define XLF0 0
#endif
#if defined(CONFIG_RELOCATABLE) && defined(CONFIG_X86_64)
/* kernel/boot_param/ramdisk could be loaded above 4g */
# define XLF1 XLF_CAN_BE_LOADED_ABOVE_4G
#else
# define XLF1 0
#endif
#ifdef CONFIG_EFI_STUB
# ifdef CONFIG_EFI_MIXED
# define XLF23 (XLF_EFI_HANDOVER_32|XLF_EFI_HANDOVER_64)
# else
# ifdef CONFIG_X86_64
# define XLF23 XLF_EFI_HANDOVER_64 /* 64-bit EFI handover ok */
# else
# define XLF23 XLF_EFI_HANDOVER_32 /* 32-bit EFI handover ok */
# endif
# endif
#else
# define XLF23 0
#endif
#if defined(CONFIG_X86_64) && defined(CONFIG_EFI) && defined(CONFIG_KEXEC)
# define XLF4 XLF_EFI_KEXEC
#else
# define XLF4 0
#endif
.word XLF0 | XLF1 | XLF23 | XLF4
cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line,
#added with boot protocol
#version 2.06
hardware_subarch: .long 0 # subarchitecture, added with 2.07
# default to 0 for normal x86 PC
hardware_subarch_data: .quad 0
payload_offset: .long ZO_input_data
payload_length: .long ZO_z_input_len
setup_data: .quad 0 # 64-bit physical pointer to
# single linked list of
# struct setup_data
pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr
#define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset)
#define VO_INIT_SIZE (VO__end - VO__text)
#if ZO_INIT_SIZE > VO_INIT_SIZE
#define INIT_SIZE ZO_INIT_SIZE
#else
#define INIT_SIZE VO_INIT_SIZE
#endif
init_size: .long INIT_SIZE # kernel initialization size
handover_offset: .long 0 # Filled in by build.c
# End of setup header #####################################################
.section ".entrytext", "ax"
start_of_setup:
# Force %es = %ds
movw %ds, %ax
movw %ax, %es
cld
# Apparently some ancient versions of LILO invoked the kernel with %ss != %ds,
# which happened to work by accident for the old code. Recalculate the stack
# pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the
# stack behind its own code, so we can't blindly put it directly past the heap.
movw %ss, %dx
cmpw %ax, %dx # %ds == %ss?
movw %sp, %dx
je 2f # -> assume %sp is reasonably set
# Invalid %ss, make up a new stack
movw $_end, %dx
testb $CAN_USE_HEAP, loadflags
jz 1f
movw heap_end_ptr, %dx
1: addw $STACK_SIZE, %dx
jnc 2f
xorw %dx, %dx # Prevent wraparound
2: # Now %dx should point to the end of our stack space
andw $~3, %dx # dword align (might as well...)
jnz 3f
movw $0xfffc, %dx # Make sure we're not zero
3: movw %ax, %ss
movzwl %dx, %esp # Clear upper half of %esp
sti # Now we should have a working stack
# We will have entered with %cs = %ds+0x20, normalize %cs so
# it is on par with the other segments.
pushw %ds
pushw $6f
lretw
6:
# 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, .-die
.section ".initdata", "a"
setup_corrupt:
.byte 7
.string "No setup signature found...\n"
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