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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 0x020a # 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
404
405# End of setup header #####################################################
406
407 .section ".entrytext", "ax"
408start_of_setup:
409#ifdef SAFE_RESET_DISK_CONTROLLER
410# Reset the disk controller.
411 movw $0x0000, %ax # Reset disk controller
412 movb $0x80, %dl # All disks
413 int $0x13
414#endif
415
416# Force %es = %ds
417 movw %ds, %ax
418 movw %ax, %es
419 cld
420
421# Apparently some ancient versions of LILO invoked the kernel with %ss != %ds,
422# which happened to work by accident for the old code. Recalculate the stack
423# pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the
424# stack behind its own code, so we can't blindly put it directly past the heap.
425
426 movw %ss, %dx
427 cmpw %ax, %dx # %ds == %ss?
428 movw %sp, %dx
429 je 2f # -> assume %sp is reasonably set
430
431 # Invalid %ss, make up a new stack
432 movw $_end, %dx
433 testb $CAN_USE_HEAP, loadflags
434 jz 1f
435 movw heap_end_ptr, %dx
4361: addw $STACK_SIZE, %dx
437 jnc 2f
438 xorw %dx, %dx # Prevent wraparound
439
4402: # Now %dx should point to the end of our stack space
441 andw $~3, %dx # dword align (might as well...)
442 jnz 3f
443 movw $0xfffc, %dx # Make sure we're not zero
4443: movw %ax, %ss
445 movzwl %dx, %esp # Clear upper half of %esp
446 sti # Now we should have a working stack
447
448# We will have entered with %cs = %ds+0x20, normalize %cs so
449# it is on par with the other segments.
450 pushw %ds
451 pushw $6f
452 lretw
4536:
454
455# Check signature at end of setup
456 cmpl $0x5a5aaa55, setup_sig
457 jne setup_bad
458
459# Zero the bss
460 movw $__bss_start, %di
461 movw $_end+3, %cx
462 xorl %eax, %eax
463 subw %di, %cx
464 shrw $2, %cx
465 rep; stosl
466
467# Jump to C code (should not return)
468 calll main
469
470# Setup corrupt somehow...
471setup_bad:
472 movl $setup_corrupt, %eax
473 calll puts
474 # Fall through...
475
476 .globl die
477 .type die, @function
478die:
479 hlt
480 jmp die
481
482 .size die, .-die
483
484 .section ".initdata", "a"
485setup_corrupt:
486 .byte 7
487 .string "No setup signature found...\n"
488
489 .data
490dummy: .long 0
1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * header.S
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 *
7 * Based on bootsect.S and setup.S
8 * modified by more people than can be counted
9 *
10 * Rewritten as a common file by H. Peter Anvin (Apr 2007)
11 *
12 * BIG FAT NOTE: We're in real mode using 64k segments. Therefore segment
13 * addresses must be multiplied by 16 to obtain their respective linear
14 * addresses. To avoid confusion, linear addresses are written using leading
15 * hex while segment addresses are written as segment:offset.
16 *
17 */
18#include <linux/pe.h>
19#include <asm/segment.h>
20#include <asm/boot.h>
21#include <asm/page_types.h>
22#include <asm/setup.h>
23#include <asm/bootparam.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 ROOT_RDONLY
36#define ROOT_RDONLY 1
37#endif
38
39 .set salign, 0x1000
40 .set falign, 0x200
41
42 .code16
43 .section ".bstext", "ax"
44#ifdef CONFIG_EFI_STUB
45 # "MZ", MS-DOS header
46 .word MZ_MAGIC
47 .org 0x38
48 #
49 # Offset to the PE header.
50 #
51 .long LINUX_PE_MAGIC
52 .long pe_header
53pe_header:
54 .long PE_MAGIC
55
56coff_header:
57#ifdef CONFIG_X86_32
58 .set image_file_add_flags, IMAGE_FILE_32BIT_MACHINE
59 .set pe_opt_magic, PE_OPT_MAGIC_PE32
60 .word IMAGE_FILE_MACHINE_I386
61#else
62 .set image_file_add_flags, 0
63 .set pe_opt_magic, PE_OPT_MAGIC_PE32PLUS
64 .word IMAGE_FILE_MACHINE_AMD64
65#endif
66 .word section_count # nr_sections
67 .long 0 # TimeDateStamp
68 .long 0 # PointerToSymbolTable
69 .long 1 # NumberOfSymbols
70 .word section_table - optional_header # SizeOfOptionalHeader
71 .word IMAGE_FILE_EXECUTABLE_IMAGE | \
72 image_file_add_flags | \
73 IMAGE_FILE_DEBUG_STRIPPED | \
74 IMAGE_FILE_LINE_NUMS_STRIPPED # Characteristics
75
76optional_header:
77 .word pe_opt_magic
78 .byte 0x02 # MajorLinkerVersion
79 .byte 0x14 # MinorLinkerVersion
80
81 .long ZO__data # SizeOfCode
82
83 .long ZO__end - ZO__data # SizeOfInitializedData
84 .long 0 # SizeOfUninitializedData
85
86 .long setup_size + ZO_efi_pe_entry # AddressOfEntryPoint
87
88 .long setup_size # BaseOfCode
89#ifdef CONFIG_X86_32
90 .long 0 # data
91#endif
92
93extra_header_fields:
94#ifdef CONFIG_X86_32
95 .long 0 # ImageBase
96#else
97 .quad 0 # ImageBase
98#endif
99 .long salign # SectionAlignment
100 .long falign # FileAlignment
101 .word 0 # MajorOperatingSystemVersion
102 .word 0 # MinorOperatingSystemVersion
103 .word LINUX_EFISTUB_MAJOR_VERSION # MajorImageVersion
104 .word LINUX_EFISTUB_MINOR_VERSION # MinorImageVersion
105 .word 0 # MajorSubsystemVersion
106 .word 0 # MinorSubsystemVersion
107 .long 0 # Win32VersionValue
108
109 .long setup_size + ZO__end # SizeOfImage
110
111 .long salign # SizeOfHeaders
112 .long 0 # CheckSum
113 .word IMAGE_SUBSYSTEM_EFI_APPLICATION # Subsystem (EFI application)
114 .word IMAGE_DLL_CHARACTERISTICS_NX_COMPAT # DllCharacteristics
115#ifdef CONFIG_X86_32
116 .long 0 # SizeOfStackReserve
117 .long 0 # SizeOfStackCommit
118 .long 0 # SizeOfHeapReserve
119 .long 0 # SizeOfHeapCommit
120#else
121 .quad 0 # SizeOfStackReserve
122 .quad 0 # SizeOfStackCommit
123 .quad 0 # SizeOfHeapReserve
124 .quad 0 # SizeOfHeapCommit
125#endif
126 .long 0 # LoaderFlags
127 .long (section_table - .) / 8 # NumberOfRvaAndSizes
128
129 .quad 0 # ExportTable
130 .quad 0 # ImportTable
131 .quad 0 # ResourceTable
132 .quad 0 # ExceptionTable
133 .quad 0 # CertificationTable
134 .quad 0 # BaseRelocationTable
135
136 # Section table
137section_table:
138 .ascii ".setup"
139 .byte 0
140 .byte 0
141 .long pecompat_fstart - salign # VirtualSize
142 .long salign # VirtualAddress
143 .long pecompat_fstart - salign # SizeOfRawData
144 .long salign # PointerToRawData
145
146 .long 0, 0, 0
147 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
148 IMAGE_SCN_MEM_READ | \
149 IMAGE_SCN_MEM_DISCARDABLE # Characteristics
150
151#ifdef CONFIG_EFI_MIXED
152 .asciz ".compat"
153
154 .long pecompat_fsize # VirtualSize
155 .long pecompat_fstart # VirtualAddress
156 .long pecompat_fsize # SizeOfRawData
157 .long pecompat_fstart # PointerToRawData
158
159 .long 0, 0, 0
160 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
161 IMAGE_SCN_MEM_READ | \
162 IMAGE_SCN_MEM_DISCARDABLE # Characteristics
163
164 /*
165 * Put the IA-32 machine type and the associated entry point address in
166 * the .compat section, so loaders can figure out which other execution
167 * modes this image supports.
168 */
169 .pushsection ".pecompat", "a", @progbits
170 .balign salign
171 .globl pecompat_fstart
172pecompat_fstart:
173 .byte 0x1 # Version
174 .byte 8 # Size
175 .word IMAGE_FILE_MACHINE_I386 # PE machine type
176 .long setup_size + ZO_efi32_pe_entry # Entrypoint
177 .byte 0x0 # Sentinel
178 .popsection
179#else
180 .set pecompat_fstart, setup_size
181#endif
182 .ascii ".text"
183 .byte 0
184 .byte 0
185 .byte 0
186 .long ZO__data
187 .long setup_size
188 .long ZO__data # Size of initialized data
189 # on disk
190 .long setup_size
191 .long 0 # PointerToRelocations
192 .long 0 # PointerToLineNumbers
193 .word 0 # NumberOfRelocations
194 .word 0 # NumberOfLineNumbers
195 .long IMAGE_SCN_CNT_CODE | \
196 IMAGE_SCN_MEM_READ | \
197 IMAGE_SCN_MEM_EXECUTE # Characteristics
198
199 .ascii ".data\0\0\0"
200 .long ZO__end - ZO__data # VirtualSize
201 .long setup_size + ZO__data # VirtualAddress
202 .long ZO__edata - ZO__data # SizeOfRawData
203 .long setup_size + ZO__data # PointerToRawData
204
205 .long 0, 0, 0
206 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
207 IMAGE_SCN_MEM_READ | \
208 IMAGE_SCN_MEM_WRITE # Characteristics
209
210 .set section_count, (. - section_table) / 40
211#endif /* CONFIG_EFI_STUB */
212
213 # Kernel attributes; used by setup. This is part 1 of the
214 # header, from the old boot sector.
215
216 .section ".header", "a"
217 .globl sentinel
218sentinel: .byte 0xff, 0xff /* Used to detect broken loaders */
219
220 .globl hdr
221hdr:
222 .byte setup_sects - 1
223root_flags: .word ROOT_RDONLY
224syssize: .long ZO__edata / 16
225ram_size: .word 0 /* Obsolete */
226vid_mode: .word SVGA_MODE
227root_dev: .word 0 /* Default to major/minor 0/0 */
228boot_flag: .word 0xAA55
229
230 # offset 512, entry point
231
232 .globl _start
233_start:
234 # Explicitly enter this as bytes, or the assembler
235 # tries to generate a 3-byte jump here, which causes
236 # everything else to push off to the wrong offset.
237 .byte 0xeb # short (2-byte) jump
238 .byte start_of_setup-1f
2391:
240
241 # Part 2 of the header, from the old setup.S
242
243 .ascii "HdrS" # header signature
244 .word 0x020f # header version number (>= 0x0105)
245 # or else old loadlin-1.5 will fail)
246 .globl realmode_swtch
247realmode_swtch: .word 0, 0 # default_switch, SETUPSEG
248start_sys_seg: .word SYSSEG # obsolete and meaningless, but just
249 # in case something decided to "use" it
250 .word kernel_version-512 # pointing to kernel version string
251 # above section of header is compatible
252 # with loadlin-1.5 (header v1.5). Don't
253 # change it.
254
255type_of_loader: .byte 0 # 0 means ancient bootloader, newer
256 # bootloaders know to change this.
257 # See Documentation/arch/x86/boot.rst for
258 # assigned ids
259
260# flags, unused bits must be zero (RFU) bit within loadflags
261loadflags:
262 .byte LOADED_HIGH # The kernel is to be loaded high
263
264setup_move_size: .word 0x8000 # size to move, when setup is not
265 # loaded at 0x90000. We will move setup
266 # to 0x90000 then just before jumping
267 # into the kernel. However, only the
268 # loader knows how much data behind
269 # us also needs to be loaded.
270
271code32_start: # here loaders can put a different
272 # start address for 32-bit code.
273 .long 0x100000 # 0x100000 = default for big kernel
274
275ramdisk_image: .long 0 # address of loaded ramdisk image
276 # Here the loader puts the 32-bit
277 # address where it loaded the image.
278 # This only will be read by the kernel.
279
280ramdisk_size: .long 0 # its size in bytes
281
282bootsect_kludge:
283 .long 0 # obsolete
284
285heap_end_ptr: .word _end+STACK_SIZE-512
286 # (Header version 0x0201 or later)
287 # space from here (exclusive) down to
288 # end of setup code can be used by setup
289 # for local heap purposes.
290
291ext_loader_ver:
292 .byte 0 # Extended boot loader version
293ext_loader_type:
294 .byte 0 # Extended boot loader type
295
296cmd_line_ptr: .long 0 # (Header version 0x0202 or later)
297 # If nonzero, a 32-bit pointer
298 # to the kernel command line.
299 # The command line should be
300 # located between the start of
301 # setup and the end of low
302 # memory (0xa0000), or it may
303 # get overwritten before it
304 # gets read. If this field is
305 # used, there is no longer
306 # anything magical about the
307 # 0x90000 segment; the setup
308 # can be located anywhere in
309 # low memory 0x10000 or higher.
310
311initrd_addr_max: .long 0x7fffffff
312 # (Header version 0x0203 or later)
313 # The highest safe address for
314 # the contents of an initrd
315 # The current kernel allows up to 4 GB,
316 # but leave it at 2 GB to avoid
317 # possible bootloader bugs.
318
319kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment
320 #required for protected mode
321 #kernel
322#ifdef CONFIG_RELOCATABLE
323relocatable_kernel: .byte 1
324#else
325relocatable_kernel: .byte 0
326#endif
327min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment
328
329xloadflags:
330#ifdef CONFIG_X86_64
331# define XLF0 XLF_KERNEL_64 /* 64-bit kernel */
332#else
333# define XLF0 0
334#endif
335
336#if defined(CONFIG_RELOCATABLE) && defined(CONFIG_X86_64)
337 /* kernel/boot_param/ramdisk could be loaded above 4g */
338# define XLF1 XLF_CAN_BE_LOADED_ABOVE_4G
339#else
340# define XLF1 0
341#endif
342
343#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
344# ifdef CONFIG_EFI_MIXED
345# define XLF23 (XLF_EFI_HANDOVER_32|XLF_EFI_HANDOVER_64)
346# else
347# ifdef CONFIG_X86_64
348# define XLF23 XLF_EFI_HANDOVER_64 /* 64-bit EFI handover ok */
349# else
350# define XLF23 XLF_EFI_HANDOVER_32 /* 32-bit EFI handover ok */
351# endif
352# endif
353#else
354# define XLF23 0
355#endif
356
357#if defined(CONFIG_X86_64) && defined(CONFIG_EFI) && defined(CONFIG_KEXEC_CORE)
358# define XLF4 XLF_EFI_KEXEC
359#else
360# define XLF4 0
361#endif
362
363#ifdef CONFIG_X86_64
364#ifdef CONFIG_X86_5LEVEL
365#define XLF56 (XLF_5LEVEL|XLF_5LEVEL_ENABLED)
366#else
367#define XLF56 XLF_5LEVEL
368#endif
369#else
370#define XLF56 0
371#endif
372
373 .word XLF0 | XLF1 | XLF23 | XLF4 | XLF56
374
375cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line,
376 #added with boot protocol
377 #version 2.06
378
379hardware_subarch: .long 0 # subarchitecture, added with 2.07
380 # default to 0 for normal x86 PC
381
382hardware_subarch_data: .quad 0
383
384payload_offset: .long ZO_input_data
385payload_length: .long ZO_z_input_len
386
387setup_data: .quad 0 # 64-bit physical pointer to
388 # single linked list of
389 # struct setup_data
390
391pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr
392
393#
394# Getting to provably safe in-place decompression is hard. Worst case
395# behaviours need to be analyzed. Here let's take the decompression of
396# a gzip-compressed kernel as example, to illustrate it:
397#
398# The file layout of gzip compressed kernel is:
399#
400# magic[2]
401# method[1]
402# flags[1]
403# timestamp[4]
404# extraflags[1]
405# os[1]
406# compressed data blocks[N]
407# crc[4] orig_len[4]
408#
409# ... resulting in +18 bytes overhead of uncompressed data.
410#
411# (For more information, please refer to RFC 1951 and RFC 1952.)
412#
413# Files divided into blocks
414# 1 bit (last block flag)
415# 2 bits (block type)
416#
417# 1 block occurs every 32K -1 bytes or when there 50% compression
418# has been achieved. The smallest block type encoding is always used.
419#
420# stored:
421# 32 bits length in bytes.
422#
423# fixed:
424# magic fixed tree.
425# symbols.
426#
427# dynamic:
428# dynamic tree encoding.
429# symbols.
430#
431#
432# The buffer for decompression in place is the length of the uncompressed
433# data, plus a small amount extra to keep the algorithm safe. The
434# compressed data is placed at the end of the buffer. The output pointer
435# is placed at the start of the buffer and the input pointer is placed
436# where the compressed data starts. Problems will occur when the output
437# pointer overruns the input pointer.
438#
439# The output pointer can only overrun the input pointer if the input
440# pointer is moving faster than the output pointer. A condition only
441# triggered by data whose compressed form is larger than the uncompressed
442# form.
443#
444# The worst case at the block level is a growth of the compressed data
445# of 5 bytes per 32767 bytes.
446#
447# The worst case internal to a compressed block is very hard to figure.
448# The worst case can at least be bounded by having one bit that represents
449# 32764 bytes and then all of the rest of the bytes representing the very
450# very last byte.
451#
452# All of which is enough to compute an amount of extra data that is required
453# to be safe. To avoid problems at the block level allocating 5 extra bytes
454# per 32767 bytes of data is sufficient. To avoid problems internal to a
455# block adding an extra 32767 bytes (the worst case uncompressed block size)
456# is sufficient, to ensure that in the worst case the decompressed data for
457# block will stop the byte before the compressed data for a block begins.
458# To avoid problems with the compressed data's meta information an extra 18
459# bytes are needed. Leading to the formula:
460#
461# extra_bytes = (uncompressed_size >> 12) + 32768 + 18
462#
463# Adding 8 bytes per 32K is a bit excessive but much easier to calculate.
464# Adding 32768 instead of 32767 just makes for round numbers.
465#
466# Above analysis is for decompressing gzip compressed kernel only. Up to
467# now 6 different decompressor are supported all together. And among them
468# xz stores data in chunks and has maximum chunk of 64K. Hence safety
469# margin should be updated to cover all decompressors so that we don't
470# need to deal with each of them separately. Please check
471# the description in lib/decompressor_xxx.c for specific information.
472#
473# extra_bytes = (uncompressed_size >> 12) + 65536 + 128
474#
475# LZ4 is even worse: data that cannot be further compressed grows by 0.4%,
476# or one byte per 256 bytes. OTOH, we can safely get rid of the +128 as
477# the size-dependent part now grows so fast.
478#
479# extra_bytes = (uncompressed_size >> 8) + 65536
480#
481# ZSTD compressed data grows by at most 3 bytes per 128K, and only has a 22
482# byte fixed overhead but has a maximum block size of 128K, so it needs a
483# larger margin.
484#
485# extra_bytes = (uncompressed_size >> 8) + 131072
486
487#define ZO_z_extra_bytes ((ZO_z_output_len >> 8) + 131072)
488#if ZO_z_output_len > ZO_z_input_len
489# define ZO_z_extract_offset (ZO_z_output_len + ZO_z_extra_bytes - \
490 ZO_z_input_len)
491#else
492# define ZO_z_extract_offset ZO_z_extra_bytes
493#endif
494
495/*
496 * The extract_offset has to be bigger than ZO head section. Otherwise when
497 * the head code is running to move ZO to the end of the buffer, it will
498 * overwrite the head code itself.
499 */
500#if (ZO__ehead - ZO_startup_32) > ZO_z_extract_offset
501# define ZO_z_min_extract_offset ((ZO__ehead - ZO_startup_32 + 4095) & ~4095)
502#else
503# define ZO_z_min_extract_offset ((ZO_z_extract_offset + 4095) & ~4095)
504#endif
505
506#define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_min_extract_offset)
507
508#define VO_INIT_SIZE (VO__end - VO__text)
509#if ZO_INIT_SIZE > VO_INIT_SIZE
510# define INIT_SIZE ZO_INIT_SIZE
511#else
512# define INIT_SIZE VO_INIT_SIZE
513#endif
514
515 .macro __handover_offset
516#ifndef CONFIG_EFI_HANDOVER_PROTOCOL
517 .long 0
518#elif !defined(CONFIG_X86_64)
519 .long ZO_efi32_stub_entry
520#else
521 /* Yes, this is really how we defined it :( */
522 .long ZO_efi64_stub_entry - 0x200
523#ifdef CONFIG_EFI_MIXED
524 .if ZO_efi32_stub_entry != ZO_efi64_stub_entry - 0x200
525 .error "32-bit and 64-bit EFI entry points do not match"
526 .endif
527#endif
528#endif
529 .endm
530
531init_size: .long INIT_SIZE # kernel initialization size
532handover_offset: __handover_offset
533kernel_info_offset: .long ZO_kernel_info
534
535# End of setup header #####################################################
536
537 .section ".entrytext", "ax"
538start_of_setup:
539# Force %es = %ds
540 movw %ds, %ax
541 movw %ax, %es
542 cld
543
544# Apparently some ancient versions of LILO invoked the kernel with %ss != %ds,
545# which happened to work by accident for the old code. Recalculate the stack
546# pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the
547# stack behind its own code, so we can't blindly put it directly past the heap.
548
549 movw %ss, %dx
550 cmpw %ax, %dx # %ds == %ss?
551 movw %sp, %dx
552 je 2f # -> assume %sp is reasonably set
553
554 # Invalid %ss, make up a new stack
555 movw $_end, %dx
556 testb $CAN_USE_HEAP, loadflags
557 jz 1f
558 movw heap_end_ptr, %dx
5591: addw $STACK_SIZE, %dx
560 jnc 2f
561 xorw %dx, %dx # Prevent wraparound
562
5632: # Now %dx should point to the end of our stack space
564 andw $~3, %dx # dword align (might as well...)
565 jnz 3f
566 movw $0xfffc, %dx # Make sure we're not zero
5673: movw %ax, %ss
568 movzwl %dx, %esp # Clear upper half of %esp
569 sti # Now we should have a working stack
570
571# We will have entered with %cs = %ds+0x20, normalize %cs so
572# it is on par with the other segments.
573 pushw %ds
574 pushw $6f
575 lretw
5766:
577
578# Check signature at end of setup
579 cmpl $0x5a5aaa55, setup_sig
580 jne setup_bad
581
582# Zero the bss
583 movw $__bss_start, %di
584 movw $_end+3, %cx
585 xorl %eax, %eax
586 subw %di, %cx
587 shrw $2, %cx
588 rep; stosl
589
590# Jump to C code (should not return)
591 calll main
592
593# Setup corrupt somehow...
594setup_bad:
595 movl $setup_corrupt, %eax
596 calll puts
597 # Fall through...
598
599 .globl die
600 .type die, @function
601die:
602 hlt
603 jmp die
604
605 .size die, .-die
606
607 .section ".initdata", "a"
608setup_corrupt:
609 .byte 7
610 .string "No setup signature found...\n"