summaryrefslogtreecommitdiffstats
path: root/arch/x86/boot/header.S
diff options
context:
space:
mode:
Diffstat (limited to 'arch/x86/boot/header.S')
-rw-r--r--arch/x86/boot/header.S661
1 files changed, 661 insertions, 0 deletions
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
new file mode 100644
index 0000000000..b04ca8e2b2
--- /dev/null
+++ b/arch/x86/boot/header.S
@@ -0,0 +1,661 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * 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 <linux/pe.h>
+#include <asm/segment.h>
+#include <asm/boot.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
+ .word MZ_MAGIC
+#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 0x38
+ #
+ # Offset to the PE header.
+ #
+ .long LINUX_PE_MAGIC
+ .long pe_header
+#endif /* CONFIG_EFI_STUB */
+
+ .section ".bsdata", "a"
+bugger_off_msg:
+ .ascii "Use a boot loader.\r\n"
+ .ascii "\n"
+ .ascii "Remove disk and press any key to reboot...\r\n"
+ .byte 0
+
+#ifdef CONFIG_EFI_STUB
+pe_header:
+ .long PE_MAGIC
+
+coff_header:
+#ifdef CONFIG_X86_32
+ .set image_file_add_flags, IMAGE_FILE_32BIT_MACHINE
+ .set pe_opt_magic, PE_OPT_MAGIC_PE32
+ .word IMAGE_FILE_MACHINE_I386
+#else
+ .set image_file_add_flags, 0
+ .set pe_opt_magic, PE_OPT_MAGIC_PE32PLUS
+ .word IMAGE_FILE_MACHINE_AMD64
+#endif
+ .word section_count # nr_sections
+ .long 0 # TimeDateStamp
+ .long 0 # PointerToSymbolTable
+ .long 1 # NumberOfSymbols
+ .word section_table - optional_header # SizeOfOptionalHeader
+ .word IMAGE_FILE_EXECUTABLE_IMAGE | \
+ image_file_add_flags | \
+ IMAGE_FILE_DEBUG_STRIPPED | \
+ IMAGE_FILE_LINE_NUMS_STRIPPED # Characteristics
+
+optional_header:
+ .word pe_opt_magic
+ .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:
+ # PE specification requires ImageBase to be 64k aligned
+ .set image_base, (LOAD_PHYSICAL_ADDR + 0xffff) & ~0xffff
+#ifdef CONFIG_X86_32
+ .long image_base # ImageBase
+#else
+ .quad image_base # ImageBase
+#endif
+ .long 0x20 # SectionAlignment
+ .long 0x20 # FileAlignment
+ .word 0 # MajorOperatingSystemVersion
+ .word 0 # MinorOperatingSystemVersion
+ .word LINUX_EFISTUB_MAJOR_VERSION # MajorImageVersion
+ .word LINUX_EFISTUB_MINOR_VERSION # 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 IMAGE_SUBSYSTEM_EFI_APPLICATION # Subsystem (EFI application)
+#ifdef CONFIG_EFI_DXE_MEM_ATTRIBUTES
+ .word IMAGE_DLL_CHARACTERISTICS_NX_COMPAT # DllCharacteristics
+#else
+ .word 0 # DllCharacteristics
+#endif
+#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 (section_table - .) / 8 # 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 IMAGE_SCN_CNT_CODE | \
+ IMAGE_SCN_MEM_READ | \
+ IMAGE_SCN_MEM_EXECUTE | \
+ IMAGE_SCN_ALIGN_16BYTES # Characteristics
+
+ #
+ # 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 IMAGE_SCN_CNT_INITIALIZED_DATA | \
+ IMAGE_SCN_MEM_READ | \
+ IMAGE_SCN_MEM_DISCARDABLE | \
+ IMAGE_SCN_ALIGN_1BYTES # Characteristics
+
+#ifdef CONFIG_EFI_MIXED
+ #
+ # The offset & size fields are filled in by build.c.
+ #
+ .asciz ".compat"
+ .long 0
+ .long 0x0
+ .long 0 # Size of initialized data
+ # on disk
+ .long 0x0
+ .long 0 # PointerToRelocations
+ .long 0 # PointerToLineNumbers
+ .word 0 # NumberOfRelocations
+ .word 0 # NumberOfLineNumbers
+ .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
+ IMAGE_SCN_MEM_READ | \
+ IMAGE_SCN_MEM_DISCARDABLE | \
+ IMAGE_SCN_ALIGN_1BYTES # Characteristics
+#endif
+
+ #
+ # 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 IMAGE_SCN_CNT_CODE | \
+ IMAGE_SCN_MEM_READ | \
+ IMAGE_SCN_MEM_EXECUTE | \
+ IMAGE_SCN_ALIGN_16BYTES # Characteristics
+
+ .set section_count, (. - section_table) / 40
+#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 0x020f # 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/arch/x86/boot.rst 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_HANDOVER_PROTOCOL
+# 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_CORE)
+# define XLF4 XLF_EFI_KEXEC
+#else
+# define XLF4 0
+#endif
+
+#ifdef CONFIG_X86_64
+#ifdef CONFIG_X86_5LEVEL
+#define XLF56 (XLF_5LEVEL|XLF_5LEVEL_ENABLED)
+#else
+#define XLF56 XLF_5LEVEL
+#endif
+#else
+#define XLF56 0
+#endif
+
+ .word XLF0 | XLF1 | XLF23 | XLF4 | XLF56
+
+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
+
+#
+# Getting to provably safe in-place decompression is hard. Worst case
+# behaviours need to be analyzed. Here let's take the decompression of
+# a gzip-compressed kernel as example, to illustrate it:
+#
+# The file layout of gzip compressed kernel is:
+#
+# magic[2]
+# method[1]
+# flags[1]
+# timestamp[4]
+# extraflags[1]
+# os[1]
+# compressed data blocks[N]
+# crc[4] orig_len[4]
+#
+# ... resulting in +18 bytes overhead of uncompressed data.
+#
+# (For more information, please refer to RFC 1951 and RFC 1952.)
+#
+# Files divided into blocks
+# 1 bit (last block flag)
+# 2 bits (block type)
+#
+# 1 block occurs every 32K -1 bytes or when there 50% compression
+# has been achieved. The smallest block type encoding is always used.
+#
+# stored:
+# 32 bits length in bytes.
+#
+# fixed:
+# magic fixed tree.
+# symbols.
+#
+# dynamic:
+# dynamic tree encoding.
+# symbols.
+#
+#
+# The buffer for decompression in place is the length of the uncompressed
+# data, plus a small amount extra to keep the algorithm safe. The
+# compressed data is placed at the end of the buffer. The output pointer
+# is placed at the start of the buffer and the input pointer is placed
+# where the compressed data starts. Problems will occur when the output
+# pointer overruns the input pointer.
+#
+# The output pointer can only overrun the input pointer if the input
+# pointer is moving faster than the output pointer. A condition only
+# triggered by data whose compressed form is larger than the uncompressed
+# form.
+#
+# The worst case at the block level is a growth of the compressed data
+# of 5 bytes per 32767 bytes.
+#
+# The worst case internal to a compressed block is very hard to figure.
+# The worst case can at least be bounded by having one bit that represents
+# 32764 bytes and then all of the rest of the bytes representing the very
+# very last byte.
+#
+# All of which is enough to compute an amount of extra data that is required
+# to be safe. To avoid problems at the block level allocating 5 extra bytes
+# per 32767 bytes of data is sufficient. To avoid problems internal to a
+# block adding an extra 32767 bytes (the worst case uncompressed block size)
+# is sufficient, to ensure that in the worst case the decompressed data for
+# block will stop the byte before the compressed data for a block begins.
+# To avoid problems with the compressed data's meta information an extra 18
+# bytes are needed. Leading to the formula:
+#
+# extra_bytes = (uncompressed_size >> 12) + 32768 + 18
+#
+# Adding 8 bytes per 32K is a bit excessive but much easier to calculate.
+# Adding 32768 instead of 32767 just makes for round numbers.
+#
+# Above analysis is for decompressing gzip compressed kernel only. Up to
+# now 6 different decompressor are supported all together. And among them
+# xz stores data in chunks and has maximum chunk of 64K. Hence safety
+# margin should be updated to cover all decompressors so that we don't
+# need to deal with each of them separately. Please check
+# the description in lib/decompressor_xxx.c for specific information.
+#
+# extra_bytes = (uncompressed_size >> 12) + 65536 + 128
+#
+# LZ4 is even worse: data that cannot be further compressed grows by 0.4%,
+# or one byte per 256 bytes. OTOH, we can safely get rid of the +128 as
+# the size-dependent part now grows so fast.
+#
+# extra_bytes = (uncompressed_size >> 8) + 65536
+#
+# ZSTD compressed data grows by at most 3 bytes per 128K, and only has a 22
+# byte fixed overhead but has a maximum block size of 128K, so it needs a
+# larger margin.
+#
+# extra_bytes = (uncompressed_size >> 8) + 131072
+
+#define ZO_z_extra_bytes ((ZO_z_output_len >> 8) + 131072)
+#if ZO_z_output_len > ZO_z_input_len
+# define ZO_z_extract_offset (ZO_z_output_len + ZO_z_extra_bytes - \
+ ZO_z_input_len)
+#else
+# define ZO_z_extract_offset ZO_z_extra_bytes
+#endif
+
+/*
+ * The extract_offset has to be bigger than ZO head section. Otherwise when
+ * the head code is running to move ZO to the end of the buffer, it will
+ * overwrite the head code itself.
+ */
+#if (ZO__ehead - ZO_startup_32) > ZO_z_extract_offset
+# define ZO_z_min_extract_offset ((ZO__ehead - ZO_startup_32 + 4095) & ~4095)
+#else
+# define ZO_z_min_extract_offset ((ZO_z_extract_offset + 4095) & ~4095)
+#endif
+
+#define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_min_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
+kernel_info_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"