xref: /openbmc/linux/arch/x86/boot/header.S (revision 95e9fd10)
1/*
2 *	header.S
3 *
4 *	Copyright (C) 1991, 1992 Linus Torvalds
5 *
6 *	Based on bootsect.S and setup.S
7 *	modified by more people than can be counted
8 *
9 *	Rewritten as a common file by H. Peter Anvin (Apr 2007)
10 *
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.
15 *
16 */
17
18#include <asm/segment.h>
19#include <generated/utsrelease.h>
20#include <asm/boot.h>
21#include <asm/e820.h>
22#include <asm/page_types.h>
23#include <asm/setup.h>
24#include "boot.h"
25#include "voffset.h"
26#include "zoffset.h"
27
28BOOTSEG		= 0x07C0		/* original address of boot-sector */
29SYSSEG		= 0x1000		/* historical load address >> 4 */
30
31#ifndef SVGA_MODE
32#define SVGA_MODE ASK_VGA
33#endif
34
35#ifndef RAMDISK
36#define RAMDISK 0
37#endif
38
39#ifndef ROOT_RDONLY
40#define ROOT_RDONLY 1
41#endif
42
43	.code16
44	.section ".bstext", "ax"
45
46	.global bootsect_start
47bootsect_start:
48#ifdef CONFIG_EFI_STUB
49	# "MZ", MS-DOS header
50	.byte 0x4d
51	.byte 0x5a
52#endif
53
54	# Normalize the start address
55	ljmp	$BOOTSEG, $start2
56
57start2:
58	movw	%cs, %ax
59	movw	%ax, %ds
60	movw	%ax, %es
61	movw	%ax, %ss
62	xorw	%sp, %sp
63	sti
64	cld
65
66	movw	$bugger_off_msg, %si
67
68msg_loop:
69	lodsb
70	andb	%al, %al
71	jz	bs_die
72	movb	$0xe, %ah
73	movw	$7, %bx
74	int	$0x10
75	jmp	msg_loop
76
77bs_die:
78	# Allow the user to press a key, then reboot
79	xorw	%ax, %ax
80	int	$0x16
81	int	$0x19
82
83	# int 0x19 should never return.  In case it does anyway,
84	# invoke the BIOS reset code...
85	ljmp	$0xf000,$0xfff0
86
87#ifdef CONFIG_EFI_STUB
88	.org	0x3c
89	#
90	# Offset to the PE header.
91	#
92	.long	pe_header
93#endif /* CONFIG_EFI_STUB */
94
95	.section ".bsdata", "a"
96bugger_off_msg:
97	.ascii	"Direct floppy boot is not supported. "
98	.ascii	"Use a boot loader program instead.\r\n"
99	.ascii	"\n"
100	.ascii	"Remove disk and press any key to reboot ...\r\n"
101	.byte	0
102
103#ifdef CONFIG_EFI_STUB
104pe_header:
105	.ascii	"PE"
106	.word 	0
107
108coff_header:
109#ifdef CONFIG_X86_32
110	.word	0x14c				# i386
111#else
112	.word	0x8664				# x86-64
113#endif
114	.word	3				# nr_sections
115	.long	0 				# TimeDateStamp
116	.long	0				# PointerToSymbolTable
117	.long	1				# NumberOfSymbols
118	.word	section_table - optional_header	# SizeOfOptionalHeader
119#ifdef CONFIG_X86_32
120	.word	0x306				# Characteristics.
121						# IMAGE_FILE_32BIT_MACHINE |
122						# IMAGE_FILE_DEBUG_STRIPPED |
123						# IMAGE_FILE_EXECUTABLE_IMAGE |
124						# IMAGE_FILE_LINE_NUMS_STRIPPED
125#else
126	.word	0x206				# Characteristics
127						# IMAGE_FILE_DEBUG_STRIPPED |
128						# IMAGE_FILE_EXECUTABLE_IMAGE |
129						# IMAGE_FILE_LINE_NUMS_STRIPPED
130#endif
131
132optional_header:
133#ifdef CONFIG_X86_32
134	.word	0x10b				# PE32 format
135#else
136	.word	0x20b 				# PE32+ format
137#endif
138	.byte	0x02				# MajorLinkerVersion
139	.byte	0x14				# MinorLinkerVersion
140
141	# Filled in by build.c
142	.long	0				# SizeOfCode
143
144	.long	0				# SizeOfInitializedData
145	.long	0				# SizeOfUninitializedData
146
147	# Filled in by build.c
148	.long	0x0000				# AddressOfEntryPoint
149
150	.long	0x0200				# BaseOfCode
151#ifdef CONFIG_X86_32
152	.long	0				# data
153#endif
154
155extra_header_fields:
156#ifdef CONFIG_X86_32
157	.long	0				# ImageBase
158#else
159	.quad	0				# ImageBase
160#endif
161	.long	0x20				# SectionAlignment
162	.long	0x20				# FileAlignment
163	.word	0				# MajorOperatingSystemVersion
164	.word	0				# MinorOperatingSystemVersion
165	.word	0				# MajorImageVersion
166	.word	0				# MinorImageVersion
167	.word	0				# MajorSubsystemVersion
168	.word	0				# MinorSubsystemVersion
169	.long	0				# Win32VersionValue
170
171	#
172	# The size of the bzImage is written in tools/build.c
173	#
174	.long	0				# SizeOfImage
175
176	.long	0x200				# SizeOfHeaders
177	.long	0				# CheckSum
178	.word	0xa				# Subsystem (EFI application)
179	.word	0				# DllCharacteristics
180#ifdef CONFIG_X86_32
181	.long	0				# SizeOfStackReserve
182	.long	0				# SizeOfStackCommit
183	.long	0				# SizeOfHeapReserve
184	.long	0				# SizeOfHeapCommit
185#else
186	.quad	0				# SizeOfStackReserve
187	.quad	0				# SizeOfStackCommit
188	.quad	0				# SizeOfHeapReserve
189	.quad	0				# SizeOfHeapCommit
190#endif
191	.long	0				# LoaderFlags
192	.long	0x6				# NumberOfRvaAndSizes
193
194	.quad	0				# ExportTable
195	.quad	0				# ImportTable
196	.quad	0				# ResourceTable
197	.quad	0				# ExceptionTable
198	.quad	0				# CertificationTable
199	.quad	0				# BaseRelocationTable
200
201	# Section table
202section_table:
203	#
204	# The offset & size fields are filled in by build.c.
205	#
206	.ascii	".setup"
207	.byte	0
208	.byte	0
209	.long	0
210	.long	0x0				# startup_{32,64}
211	.long	0				# Size of initialized data
212						# on disk
213	.long	0x0				# startup_{32,64}
214	.long	0				# PointerToRelocations
215	.long	0				# PointerToLineNumbers
216	.word	0				# NumberOfRelocations
217	.word	0				# NumberOfLineNumbers
218	.long	0x60500020			# Characteristics (section flags)
219
220	#
221	# The EFI application loader requires a relocation section
222	# because EFI applications must be relocatable. The .reloc
223	# offset & size fields are filled in by build.c.
224	#
225	.ascii	".reloc"
226	.byte	0
227	.byte	0
228	.long	0
229	.long	0
230	.long	0				# SizeOfRawData
231	.long	0				# PointerToRawData
232	.long	0				# PointerToRelocations
233	.long	0				# PointerToLineNumbers
234	.word	0				# NumberOfRelocations
235	.word	0				# NumberOfLineNumbers
236	.long	0x42100040			# Characteristics (section flags)
237
238	#
239	# The offset & size fields are filled in by build.c.
240	#
241	.ascii	".text"
242	.byte	0
243	.byte	0
244	.byte	0
245	.long	0
246	.long	0x0				# startup_{32,64}
247	.long	0				# Size of initialized data
248						# on disk
249	.long	0x0				# startup_{32,64}
250	.long	0				# PointerToRelocations
251	.long	0				# PointerToLineNumbers
252	.word	0				# NumberOfRelocations
253	.word	0				# NumberOfLineNumbers
254	.long	0x60500020			# Characteristics (section flags)
255
256#endif /* CONFIG_EFI_STUB */
257
258	# Kernel attributes; used by setup.  This is part 1 of the
259	# header, from the old boot sector.
260
261	.section ".header", "a"
262	.globl	hdr
263hdr:
264setup_sects:	.byte 0			/* Filled in by build.c */
265root_flags:	.word ROOT_RDONLY
266syssize:	.long 0			/* Filled in by build.c */
267ram_size:	.word 0			/* Obsolete */
268vid_mode:	.word SVGA_MODE
269root_dev:	.word 0			/* Filled in by build.c */
270boot_flag:	.word 0xAA55
271
272	# offset 512, entry point
273
274	.globl	_start
275_start:
276		# Explicitly enter this as bytes, or the assembler
277		# tries to generate a 3-byte jump here, which causes
278		# everything else to push off to the wrong offset.
279		.byte	0xeb		# short (2-byte) jump
280		.byte	start_of_setup-1f
2811:
282
283	# Part 2 of the header, from the old setup.S
284
285		.ascii	"HdrS"		# header signature
286		.word	0x020b		# header version number (>= 0x0105)
287					# or else old loadlin-1.5 will fail)
288		.globl realmode_swtch
289realmode_swtch:	.word	0, 0		# default_switch, SETUPSEG
290start_sys_seg:	.word	SYSSEG		# obsolete and meaningless, but just
291					# in case something decided to "use" it
292		.word	kernel_version-512 # pointing to kernel version string
293					# above section of header is compatible
294					# with loadlin-1.5 (header v1.5). Don't
295					# change it.
296
297type_of_loader:	.byte	0		# 0 means ancient bootloader, newer
298					# bootloaders know to change this.
299					# See Documentation/x86/boot.txt for
300					# assigned ids
301
302# flags, unused bits must be zero (RFU) bit within loadflags
303loadflags:
304LOADED_HIGH	= 1			# If set, the kernel is loaded high
305CAN_USE_HEAP	= 0x80			# If set, the loader also has set
306					# heap_end_ptr to tell how much
307					# space behind setup.S can be used for
308					# heap purposes.
309					# Only the loader knows what is free
310		.byte	LOADED_HIGH
311
312setup_move_size: .word  0x8000		# size to move, when setup is not
313					# loaded at 0x90000. We will move setup
314					# to 0x90000 then just before jumping
315					# into the kernel. However, only the
316					# loader knows how much data behind
317					# us also needs to be loaded.
318
319code32_start:				# here loaders can put a different
320					# start address for 32-bit code.
321		.long	0x100000	# 0x100000 = default for big kernel
322
323ramdisk_image:	.long	0		# address of loaded ramdisk image
324					# Here the loader puts the 32-bit
325					# address where it loaded the image.
326					# This only will be read by the kernel.
327
328ramdisk_size:	.long	0		# its size in bytes
329
330bootsect_kludge:
331		.long	0		# obsolete
332
333heap_end_ptr:	.word	_end+STACK_SIZE-512
334					# (Header version 0x0201 or later)
335					# space from here (exclusive) down to
336					# end of setup code can be used by setup
337					# for local heap purposes.
338
339ext_loader_ver:
340		.byte	0		# Extended boot loader version
341ext_loader_type:
342		.byte	0		# Extended boot loader type
343
344cmd_line_ptr:	.long	0		# (Header version 0x0202 or later)
345					# If nonzero, a 32-bit pointer
346					# to the kernel command line.
347					# The command line should be
348					# located between the start of
349					# setup and the end of low
350					# memory (0xa0000), or it may
351					# get overwritten before it
352					# gets read.  If this field is
353					# used, there is no longer
354					# anything magical about the
355					# 0x90000 segment; the setup
356					# can be located anywhere in
357					# low memory 0x10000 or higher.
358
359ramdisk_max:	.long 0x7fffffff
360					# (Header version 0x0203 or later)
361					# The highest safe address for
362					# the contents of an initrd
363					# The current kernel allows up to 4 GB,
364					# but leave it at 2 GB to avoid
365					# possible bootloader bugs.
366
367kernel_alignment:  .long CONFIG_PHYSICAL_ALIGN	#physical addr alignment
368						#required for protected mode
369						#kernel
370#ifdef CONFIG_RELOCATABLE
371relocatable_kernel:    .byte 1
372#else
373relocatable_kernel:    .byte 0
374#endif
375min_alignment:		.byte MIN_KERNEL_ALIGN_LG2	# minimum alignment
376pad3:			.word 0
377
378cmdline_size:   .long   COMMAND_LINE_SIZE-1     #length of the command line,
379                                                #added with boot protocol
380                                                #version 2.06
381
382hardware_subarch:	.long 0			# subarchitecture, added with 2.07
383						# default to 0 for normal x86 PC
384
385hardware_subarch_data:	.quad 0
386
387payload_offset:		.long ZO_input_data
388payload_length:		.long ZO_z_input_len
389
390setup_data:		.quad 0			# 64-bit physical pointer to
391						# single linked list of
392						# struct setup_data
393
394pref_address:		.quad LOAD_PHYSICAL_ADDR	# preferred load addr
395
396#define ZO_INIT_SIZE	(ZO__end - ZO_startup_32 + ZO_z_extract_offset)
397#define VO_INIT_SIZE	(VO__end - VO__text)
398#if ZO_INIT_SIZE > VO_INIT_SIZE
399#define INIT_SIZE ZO_INIT_SIZE
400#else
401#define INIT_SIZE VO_INIT_SIZE
402#endif
403init_size:		.long INIT_SIZE		# kernel initialization size
404handover_offset:	.long 0x30		# offset to the handover
405						# protocol entry point
406
407# End of setup header #####################################################
408
409	.section ".entrytext", "ax"
410start_of_setup:
411# Force %es = %ds
412	movw	%ds, %ax
413	movw	%ax, %es
414	cld
415
416# Apparently some ancient versions of LILO invoked the kernel with %ss != %ds,
417# which happened to work by accident for the old code.  Recalculate the stack
418# pointer if %ss is invalid.  Otherwise leave it alone, LOADLIN sets up the
419# stack behind its own code, so we can't blindly put it directly past the heap.
420
421	movw	%ss, %dx
422	cmpw	%ax, %dx	# %ds == %ss?
423	movw	%sp, %dx
424	je	2f		# -> assume %sp is reasonably set
425
426	# Invalid %ss, make up a new stack
427	movw	$_end, %dx
428	testb	$CAN_USE_HEAP, loadflags
429	jz	1f
430	movw	heap_end_ptr, %dx
4311:	addw	$STACK_SIZE, %dx
432	jnc	2f
433	xorw	%dx, %dx	# Prevent wraparound
434
4352:	# Now %dx should point to the end of our stack space
436	andw	$~3, %dx	# dword align (might as well...)
437	jnz	3f
438	movw	$0xfffc, %dx	# Make sure we're not zero
4393:	movw	%ax, %ss
440	movzwl	%dx, %esp	# Clear upper half of %esp
441	sti			# Now we should have a working stack
442
443# We will have entered with %cs = %ds+0x20, normalize %cs so
444# it is on par with the other segments.
445	pushw	%ds
446	pushw	$6f
447	lretw
4486:
449
450# Check signature at end of setup
451	cmpl	$0x5a5aaa55, setup_sig
452	jne	setup_bad
453
454# Zero the bss
455	movw	$__bss_start, %di
456	movw	$_end+3, %cx
457	xorl	%eax, %eax
458	subw	%di, %cx
459	shrw	$2, %cx
460	rep; stosl
461
462# Jump to C code (should not return)
463	calll	main
464
465# Setup corrupt somehow...
466setup_bad:
467	movl	$setup_corrupt, %eax
468	calll	puts
469	# Fall through...
470
471	.globl	die
472	.type	die, @function
473die:
474	hlt
475	jmp	die
476
477	.size	die, .-die
478
479	.section ".initdata", "a"
480setup_corrupt:
481	.byte	7
482	.string	"No setup signature found...\n"
483
484	.data
485dummy:	.long	0
486