4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Based on bootsect.S and setup.S
7 * modified by more people than can be counted
9 * Rewritten as a common file by H. Peter Anvin (Apr 2007)
11 * BIG FAT NOTE: We're in real mode using 64k segments. Therefore segment
12 * addresses must be multiplied by 16 to obtain their respective linear
13 * addresses. To avoid confusion, linear addresses are written using leading
14 * hex while segment addresses are written as segment:offset.
18 #include <asm/segment.h>
19 #include <generated/utsrelease.h>
22 #include <asm/page_types.h>
23 #include <asm/setup.h>
28 BOOTSEG = 0x07C0 /* original address of boot-sector */
29 SYSSEG = 0x1000 /* historical load address >> 4 */
32 #define SVGA_MODE ASK_VGA
44 .section ".bstext", "ax"
46 .global bootsect_start
49 # Normalize the start address
50 ljmp $BOOTSEG, $start2
61 movw $bugger_off_msg, %si
73 # Allow the user to press a key, then reboot
78 # int 0x19 should never return. In case it does anyway,
79 # invoke the BIOS reset code...
82 .section ".bsdata", "a"
84 .ascii "Direct booting from floppy is no longer supported.\r\n"
85 .ascii "Please use a boot loader program instead.\r\n"
87 .ascii "Remove disk and press any key to reboot . . .\r\n"
91 # Kernel attributes; used by setup. This is part 1 of the
92 # header, from the old boot sector.
94 .section ".header", "a"
97 setup_sects: .byte 0 /* Filled in by build.c */
98 root_flags: .word ROOT_RDONLY
99 syssize: .long 0 /* Filled in by build.c */
100 ram_size: .word 0 /* Obsolete */
101 vid_mode: .word SVGA_MODE
102 root_dev: .word 0 /* Filled in by build.c */
103 boot_flag: .word 0xAA55
105 # offset 512, entry point
109 # Explicitly enter this as bytes, or the assembler
110 # tries to generate a 3-byte jump here, which causes
111 # everything else to push off to the wrong offset.
112 .byte 0xeb # short (2-byte) jump
113 .byte start_of_setup-1f
116 # Part 2 of the header, from the old setup.S
118 .ascii "HdrS" # header signature
119 .word 0x020a # header version number (>= 0x0105)
120 # or else old loadlin-1.5 will fail)
121 .globl realmode_swtch
122 realmode_swtch: .word 0, 0 # default_switch, SETUPSEG
123 start_sys_seg: .word SYSSEG # obsolete and meaningless, but just
124 # in case something decided to "use" it
125 .word kernel_version-512 # pointing to kernel version string
126 # above section of header is compatible
127 # with loadlin-1.5 (header v1.5). Don't
130 type_of_loader: .byte 0 # 0 means ancient bootloader, newer
131 # bootloaders know to change this.
132 # See Documentation/x86/boot.txt for
135 # flags, unused bits must be zero (RFU) bit within loadflags
137 LOADED_HIGH = 1 # If set, the kernel is loaded high
138 CAN_USE_HEAP = 0x80 # If set, the loader also has set
139 # heap_end_ptr to tell how much
140 # space behind setup.S can be used for
142 # Only the loader knows what is free
145 setup_move_size: .word 0x8000 # size to move, when setup is not
146 # loaded at 0x90000. We will move setup
147 # to 0x90000 then just before jumping
148 # into the kernel. However, only the
149 # loader knows how much data behind
150 # us also needs to be loaded.
152 code32_start: # here loaders can put a different
153 # start address for 32-bit code.
154 .long 0x100000 # 0x100000 = default for big kernel
156 ramdisk_image: .long 0 # address of loaded ramdisk image
157 # Here the loader puts the 32-bit
158 # address where it loaded the image.
159 # This only will be read by the kernel.
161 ramdisk_size: .long 0 # its size in bytes
166 heap_end_ptr: .word _end+STACK_SIZE-512
167 # (Header version 0x0201 or later)
168 # space from here (exclusive) down to
169 # end of setup code can be used by setup
170 # for local heap purposes.
173 .byte 0 # Extended boot loader version
175 .byte 0 # Extended boot loader type
177 cmd_line_ptr: .long 0 # (Header version 0x0202 or later)
178 # If nonzero, a 32-bit pointer
179 # to the kernel command line.
180 # The command line should be
181 # located between the start of
182 # setup and the end of low
183 # memory (0xa0000), or it may
184 # get overwritten before it
185 # gets read. If this field is
186 # used, there is no longer
187 # anything magical about the
188 # 0x90000 segment; the setup
189 # can be located anywhere in
190 # low memory 0x10000 or higher.
192 ramdisk_max: .long 0x7fffffff
193 # (Header version 0x0203 or later)
194 # The highest safe address for
195 # the contents of an initrd
196 # The current kernel allows up to 4 GB,
197 # but leave it at 2 GB to avoid
198 # possible bootloader bugs.
200 kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment
201 #required for protected mode
203 #ifdef CONFIG_RELOCATABLE
204 relocatable_kernel: .byte 1
206 relocatable_kernel: .byte 0
208 min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment
211 cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line,
212 #added with boot protocol
215 hardware_subarch: .long 0 # subarchitecture, added with 2.07
216 # default to 0 for normal x86 PC
218 hardware_subarch_data: .quad 0
220 payload_offset: .long ZO_input_data
221 payload_length: .long ZO_z_input_len
223 setup_data: .quad 0 # 64-bit physical pointer to
224 # single linked list of
227 pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr
229 #define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset)
230 #define VO_INIT_SIZE (VO__end - VO__text)
231 #if ZO_INIT_SIZE > VO_INIT_SIZE
232 #define INIT_SIZE ZO_INIT_SIZE
234 #define INIT_SIZE VO_INIT_SIZE
236 init_size: .long INIT_SIZE # kernel initialization size
238 # End of setup header #####################################################
240 .section ".entrytext", "ax"
242 #ifdef SAFE_RESET_DISK_CONTROLLER
243 # Reset the disk controller.
244 movw $0x0000, %ax # Reset disk controller
245 movb $0x80, %dl # All disks
254 # Apparently some ancient versions of LILO invoked the kernel with %ss != %ds,
255 # which happened to work by accident for the old code. Recalculate the stack
256 # pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the
257 # stack behind its own code, so we can't blindly put it directly past the heap.
260 cmpw %ax, %dx # %ds == %ss?
262 je 2f # -> assume %sp is reasonably set
264 # Invalid %ss, make up a new stack
266 testb $CAN_USE_HEAP, loadflags
268 movw heap_end_ptr, %dx
269 1: addw $STACK_SIZE, %dx
271 xorw %dx, %dx # Prevent wraparound
273 2: # Now %dx should point to the end of our stack space
274 andw $~3, %dx # dword align (might as well...)
276 movw $0xfffc, %dx # Make sure we're not zero
278 movzwl %dx, %esp # Clear upper half of %esp
279 sti # Now we should have a working stack
281 # We will have entered with %cs = %ds+0x20, normalize %cs so
282 # it is on par with the other segments.
288 # Check signature at end of setup
289 cmpl $0x5a5aaa55, setup_sig
293 movw $__bss_start, %di
300 # Jump to C code (should not return)
303 # Setup corrupt somehow...
305 movl $setup_corrupt, %eax
317 .section ".initdata", "a"
320 .string "No setup signature found...\n"