| blob | 39d8e908b8d8e9902bef81a22913b21862a9df8e |
1 ;; -----------------------------------------------------------------------
2 ;;
3 ;; Copyright 1994-2008 H. Peter Anvin - All Rights Reserved
4 ;;
5 ;; This program is free software; you can redistribute it and/or modify
6 ;; it under the terms of the GNU General Public License as published by
7 ;; the Free Software Foundation, Inc., 53 Temple Place Ste 330,
8 ;; Boston MA 02111-1307, USA; either version 2 of the License, or
9 ;; (at your option) any later version; incorporated herein by reference.
10 ;;
11 ;; -----------------------------------------------------------------------
13 ;;
14 ;; runkernel.inc
15 ;;
16 ;; Common code for running a Linux kernel
17 ;;
19 ;
20 ; Hook macros, that may or may not be defined
21 ;
22 %ifndef HAVE_SPECIAL_APPEND
23 %macro SPECIAL_APPEND 0
24 %endmacro
25 %endif
27 %ifndef HAVE_UNLOAD_PREP
28 %macro UNLOAD_PREP 0
29 %endmacro
30 %endif
32 ;
33 ; A Linux kernel consists of three parts: boot sector, setup code, and
34 ; kernel code. The boot sector is never executed when using an external
35 ; booting utility, but it contains some status bytes that are necessary.
36 ;
37 ; First check that our kernel is at least 1K, or else it isn't long
38 ; enough to have the appropriate headers.
39 ;
40 ; We used to require the kernel to be 64K or larger, but it has gotten
41 ; popular to use the Linux kernel format for other things, which may
42 ; not be so large.
43 ;
44 ; Additionally, we used to have a test for 8 MB or smaller. Equally
45 ; obsolete.
46 ;
47 is_linux_kernel:
48 and dx,dx
49 jnz kernel_sane
50 cmp ax,1024 ; Bootsect + 1 setup sect
51 jb kernel_corrupt
52 kernel_sane: push ax
53 push dx
54 push si
55 mov si,loading_msg
56 call cwritestr
57 ;
58 ; Now start transferring the kernel
59 ;
60 push word real_mode_seg
61 pop es
63 movzx eax,ax ; Fix this by using a 32-bit
64 shl edx,16 ; register for the kernel size
65 or eax,edx
66 mov [KernelSize],eax
67 add eax,SECTOR_SIZE-1
68 shr eax,SECTOR_SHIFT
69 mov [KernelSects],eax ; Total sectors in kernel
71 ;
72 ; Now, if we transfer these straight, we'll hit 64K boundaries. Hence we
73 ; have to see if we're loading more than 64K, and if so, load it step by
74 ; step.
75 ;
77 ;
78 ; Start by loading the bootsector/setup code, to see if we need to
79 ; do something funky. It should fit in the first 32K (loading 64K won't
80 ; work since we might have funny stuff up near the end of memory).
81 ; If we have larger than 32K clusters, yes, we're hosed.
82 ;
83 call abort_check ; Check for abort key
84 mov ecx,8000h >> SECTOR_SHIFT ; Half a moby (32K)
85 cmp ecx,[KernelSects]
86 jna .normalkernel
87 mov ecx,[KernelSects]
88 .normalkernel:
89 sub [KernelSects],ecx
90 xor bx,bx
91 pop si ; Cluster pointer on stack
92 call getfssec
93 cmp word [es:bs_bootsign],0AA55h
94 jne kernel_corrupt ; Boot sec signature missing
96 ;
97 ; Save the cluster pointer for later...
98 ;
99 push si
100 ;
101 ; Get the BIOS' idea of what the size of high memory is.
102 ;
103 call highmemsize
104 ;
105 ; Construct the command line (append options have already been copied)
106 ;
107 construct_cmdline:
108 mov di,[CmdLinePtr]
109 mov si,boot_image ; BOOT_IMAGE=
110 mov cx,boot_image_len
111 rep movsb
112 mov si,KernelCName ; Unmangled kernel name
113 mov cx,[KernelCNameLen]
114 rep movsb
115 mov al,' ' ; Space
116 stosb
118 SPECIAL_APPEND ; Module-specific hook
120 mov si,[CmdOptPtr] ; Options from user input
121 call strcpy
123 ;
124 ; Scan through the command line for anything that looks like we might be
125 ; interested in. The original version of this code automatically assumed
126 ; the first option was BOOT_IMAGE=, but that is no longer certain.
127 ;
128 mov si,cmd_line_here
129 xor ax,ax
130 mov [InitRDPtr],ax ; No initrd= option (yet)
131 push es ; Set DS <- real_mode_seg
132 pop ds
133 get_next_opt: lodsb
134 and al,al
135 jz cmdline_end
136 cmp al,' '
137 jbe get_next_opt
138 dec si
139 mov eax,[si]
140 cmp eax,'vga='
141 je is_vga_cmd
142 cmp eax,'mem='
143 je is_mem_cmd
144 %if IS_PXELINUX
145 cmp eax,'keep' ; Is it "keeppxe"?
146 jne .notkeep
147 cmp dword [si+3],'ppxe'
148 jne .notkeep
149 cmp byte [si+7],' ' ; Must be whitespace or EOS
150 ja .notkeep
151 or byte [cs:KeepPXE],1
152 .notkeep:
153 %endif
154 push es ; Save ES -> real_mode_seg
155 push cs
156 pop es ; Set ES <- normal DS
157 mov di,initrd_cmd
158 mov cx,initrd_cmd_len
159 repe cmpsb
160 jne .not_initrd
162 cmp al,' '
163 jbe .noramdisk
164 mov [cs:InitRDPtr],si
165 jmp .not_initrd
166 .noramdisk:
167 xor ax,ax
168 mov [cs:InitRDPtr],ax
169 .not_initrd: pop es ; Restore ES -> real_mode_seg
170 skip_this_opt: lodsb ; Load from command line
171 cmp al,' '
172 ja skip_this_opt
173 dec si
174 jmp short get_next_opt
175 is_vga_cmd:
176 add si,4
177 mov eax,[si-1]
178 mov bx,-1
179 cmp eax,'=nor' ; vga=normal
180 je vc0
181 dec bx ; bx <- -2
182 cmp eax,'=ext' ; vga=ext
183 je vc0
184 dec bx ; bx <- -3
185 cmp eax,'=ask' ; vga=ask
186 je vc0
187 call parseint ; vga=<number>
188 jc skip_this_opt ; Not an integer
189 vc0: mov [bs_vidmode],bx ; Set video mode
190 jmp short skip_this_opt
191 is_mem_cmd:
192 add si,4
193 call parseint
194 jc skip_this_opt ; Not an integer
195 %if HIGHMEM_SLOP != 0
196 sub ebx,HIGHMEM_SLOP
197 %endif
198 mov [cs:HighMemSize],ebx
199 jmp short skip_this_opt
200 cmdline_end:
201 push cs ; Restore standard DS
202 pop ds
203 sub si,cmd_line_here
204 mov [CmdLineLen],si ; Length including final null
205 ;
206 ; Now check if we have a large kernel, which needs to be loaded high
207 ;
208 prepare_header:
209 mov dword [RamdiskMax], HIGHMEM_MAX ; Default initrd limit
210 cmp dword [es:su_header],HEADER_ID ; New setup code ID
211 jne old_kernel ; Old kernel, load low
212 mov ax,[es:su_version]
213 mov [KernelVersion],ax
214 cmp ax,0200h ; Setup code version 2.0
215 jb old_kernel ; Old kernel, load low
216 cmp ax,0201h ; Version 2.01+?
217 jb new_kernel ; If 2.00, skip this step
218 ; Set up the heap (assuming loading high for now)
219 mov word [es:su_heapend],linux_stack-512
220 or byte [es:su_loadflags],80h ; Let the kernel know we care
221 cmp ax,0203h ; Version 2.03+?
222 jb new_kernel ; Not 2.03+
223 mov eax,[es:su_ramdisk_max]
224 mov [RamdiskMax],eax ; Set the ramdisk limit
226 ;
227 ; We definitely have a new-style kernel. Let the kernel know who we are,
228 ; and that we are clueful
229 ;
230 new_kernel:
231 mov byte [es:su_loader],my_id ; Show some ID
232 xor eax,eax
233 mov [es:su_ramdisklen],eax ; No initrd loaded yet
235 ;
236 ; About to load the kernel. This is a modern kernel, so use the boot flags
237 ; we were provided.
238 ;
239 mov al,[es:su_loadflags]
240 mov [LoadFlags],al
241 ;
242 ; Load the kernel. We always load it at 100000h even if we're supposed to
243 ; load it "low"; for a "low" load we copy it down to low memory right before
244 ; jumping to it.
245 ;
246 read_kernel:
247 movzx ax,byte [es:bs_setupsecs] ; Setup sectors
248 and ax,ax
249 jnz .sects_ok
250 mov al,4 ; 0 = 4 setup sectors
251 .sects_ok:
252 mov [SetupSecs],ax
254 mov si,KernelCName ; Print kernel name part of
255 call cwritestr ; "Loading" message
256 mov si,dotdot_msg ; Print dots
257 call cwritestr
259 mov eax,[HighMemSize]
260 sub eax,100000h ; Load address
261 cmp eax,[KernelSize]
262 jb no_high_mem ; Not enough high memory
263 ;
264 ; Move the stuff beyond the setup code to high memory at 100000h
265 ;
266 movzx esi,word [SetupSecs] ; Setup sectors
267 inc si ; plus 1 boot sector
268 shl si,9 ; Convert to bytes
269 mov ecx,8000h ; 32K
270 sub ecx,esi ; Number of bytes to copy
271 push ecx
272 add esi,(real_mode_seg << 4) ; Pointer to source
273 mov edi,100000h ; Copy to address 100000h
275 call bcopy ; Transfer to high memory
277 ; On exit EDI -> where to load the rest
279 mov si,dot_msg ; Progress report
280 call cwritestr
281 call abort_check
283 pop ecx ; Number of bytes in the initial portion
284 pop si ; Restore file handle/cluster pointer
285 mov eax,[KernelSize]
286 sub eax,8000h ; Amount of kernel not yet loaded
287 jbe high_load_done ; Zero left (tiny kernel)
289 xor dx,dx ; No padding needed
290 mov bx,dot_pause ; Print dots...
291 call load_high ; Copy the file
293 high_load_done:
294 mov [KernelEnd],edi
295 mov ax,real_mode_seg ; Set to real mode seg
296 mov es,ax
298 mov si,dot_msg
299 call cwritestr
301 ;
302 ; Now see if we have an initial RAMdisk; if so, do requisite computation
303 ; We know we have a new kernel; the old_kernel code already will have objected
304 ; if we tried to load initrd using an old kernel
305 ;
306 load_initrd:
307 cmp word [InitRDPtr],0
308 jz nk_noinitrd
309 call parse_load_initrd
310 nk_noinitrd:
311 ;
312 ; Abandon hope, ye that enter here! We do no longer permit aborts.
313 ;
314 call abort_check ; Last chance!!
316 mov si,ready_msg
317 call cwritestr
319 call vgaclearmode ; We can't trust ourselves after this
321 UNLOAD_PREP ; Module-specific hook
323 ;
324 ; Now, if we were supposed to load "low", copy the kernel down to 10000h
325 ; and the real mode stuff to 90000h. We assume that all bzImage kernels are
326 ; capable of starting their setup from a different address.
327 ;
328 mov ax,real_mode_seg
329 mov es,ax
330 mov fs,ax
332 ;
333 ; Copy command line. Unfortunately, the old kernel boot protocol requires
334 ; the command line to exist in the 9xxxxh range even if the rest of the
335 ; setup doesn't.
336 ;
337 setup_command_line:
338 cli ; In case of hooked interrupts
339 mov dx,[KernelVersion]
340 test byte [LoadFlags],LOAD_HIGH
341 jz need_high_cmdline
342 cmp dx,0202h ; Support new cmdline protocol?
343 jb need_high_cmdline
344 ; New cmdline protocol
345 ; Store 32-bit (flat) pointer to command line
346 ; This is the "high" location, since we have bzImage
347 mov dword [fs:su_cmd_line_ptr],(real_mode_seg << 4)+cmd_line_here
348 jmp in_proper_place
350 need_high_cmdline:
351 ;
352 ; Copy command line down to fit in high conventional memory
353 ; -- this happens if we have a zImage kernel or the protocol
354 ; is less than 2.02.
355 ;
356 mov si,cmd_line_here
357 mov di,old_cmd_line_here
358 mov [fs:kern_cmd_magic],word CMD_MAGIC ; Store magic
359 mov [fs:kern_cmd_offset],di ; Store pointer
360 mov word [HeapEnd],old_linux_stack
361 mov ax,255 ; Max cmdline limit
362 cmp dx,0201h
363 jb .adjusted
364 ; Protocol 2.01+
365 mov word [fs:su_heapend],old_linux_stack-512
366 jbe .adjusted
367 ; Protocol 2.02+
368 ; Note that the only reason we would end up here is
369 ; because we have a zImage, so we anticipate the move
370 ; to 90000h already...
371 mov dword [fs:su_cmd_line_ptr],0x90000+old_cmd_line_here
372 mov ax,4095 ; 2.02+ allow a higher limit
373 .adjusted:
375 mov cx,[CmdLineLen]
376 cmp cx,ax
377 jna .len_ok
378 mov cx,ax ; Truncate the command line
379 .len_ok:
380 fs rep movsb
381 stosb ; Final null, note AL=0 already
382 cmp dx,0200h
383 jb .nomovesize
384 mov [es:su_movesize],di ; Tell the kernel what to move
385 .nomovesize:
387 test byte [LoadFlags],LOAD_HIGH
388 jnz in_proper_place ; If high load, we're done
390 ;
391 ; Loading low; we can't assume it's safe to run in place.
392 ;
393 ; Copy real_mode stuff up to 90000h
394 ;
395 mov ax,9000h
396 mov es,ax
397 mov cx,di ; == su_movesize (from above)
398 add cx,3 ; Round up
399 shr cx,2 ; Convert to dwords
400 xor si,si
401 xor di,di
402 fs rep movsd ; Copy setup + boot sector
403 ;
404 ; Some kernels in the 1.2 ballpark but pre-bzImage have more than 4
405 ; setup sectors, but the boot protocol had not yet been defined. They
406 ; rely on a signature to figure out if they need to copy stuff from
407 ; the "protected mode" kernel area. Unfortunately, we used that area
408 ; as a transfer buffer, so it's going to find the signature there.
409 ; Hence, zero the low 32K beyond the setup area.
410 ;
411 mov di,[SetupSecs]
412 inc di ; Setup + boot sector
413 mov cx,32768/512 ; Sectors/32K
414 sub cx,di ; Remaining sectors
415 shl di,9 ; Sectors -> bytes
416 shl cx,7 ; Sectors -> dwords
417 xor eax,eax
418 rep stosd ; Clear region
419 ;
420 ; Copy the kernel down to the "low" location (the kernel will then
421 ; move itself again, sigh.)
422 ;
423 mov ecx,[KernelSize]
424 mov esi,100000h
425 mov edi,10000h
426 call bcopy
428 ;
429 ; Now everything is where it needs to be...
430 ;
431 ; When we get here, es points to the final segment, either
432 ; 9000h or real_mode_seg
433 ;
434 in_proper_place:
436 ;
437 ; If the default root device is set to FLOPPY (0000h), change to
438 ; /dev/fd0 (0200h)
439 ;
440 cmp word [es:bs_rootdev],byte 0
441 jne root_not_floppy
442 mov word [es:bs_rootdev],0200h
443 root_not_floppy:
445 ;
446 ; Copy the disk table to high memory, then re-initialize the floppy
447 ; controller
448 ;
449 %if IS_SYSLINUX || IS_MDSLINUX
450 lgs si,[cs:fdctab]
451 mov di,[cs:HeapEnd]
452 mov cx,6
453 gs rep movsw
454 mov [cs:fdctab],word linux_fdctab ; Save new floppy tab pos
455 mov [cs:fdctab+2],es
456 %endif
458 call cleanup_hardware
459 ;
460 ; If we're debugging, wait for a keypress so we can read any debug messages
461 ;
462 %ifdef debug
463 xor ax,ax
464 int 16h
465 %endif
466 ;
467 ; Set up segment registers and the Linux real-mode stack
468 ; Note: es == the real mode segment
469 ;
471 cli
472 mov bx,es
473 mov ds,bx
474 mov fs,bx
475 mov gs,bx
476 mov ss,bx
477 mov sp,strict word linux_stack
478 ; Point HeapEnd to the immediate of the instruction above
479 HeapEnd equ $-2 ; Self-modifying code! Fun!
481 ;
482 ; We're done... now RUN THAT KERNEL!!!!
483 ; Setup segment == real mode segment + 020h; we need to jump to offset
484 ; zero in the real mode segment.
485 ;
486 add bx,020h
487 push bx
488 push word 0h
489 retf
491 ;
492 ; Load an older kernel. Older kernels always have 4 setup sectors, can't have
493 ; initrd, and are always loaded low.
494 ;
495 old_kernel:
496 xor ax,ax
497 cmp word [InitRDPtr],ax ; Old kernel can't have initrd
498 je .load
499 mov si,err_oldkernel
500 jmp abort_load
501 .load:
502 mov byte [LoadFlags],al ; Always low
503 mov word [KernelVersion],ax ; Version 0.00
504 jmp read_kernel
506 ;
507 ; parse_load_initrd
508 ;
509 ; Parse an initrd= option and load the initrds. Note that we load
510 ; from the high end of memory first, so we parse this option from
511 ; left to right.
512 ;
513 parse_load_initrd:
514 push es
515 push ds
516 mov ax,real_mode_seg
517 mov ds,ax
518 push cs
519 pop es ; DS == real_mode_seg, ES == CS
521 mov si,[cs:InitRDPtr]
522 .find_end:
523 lodsb
524 cmp al,' '
525 ja .find_end
526 ; Now SI points to one character beyond the
527 ; byte that ended this option.
529 .get_chunk:
530 dec si
532 ; DS:SI points to a termination byte
534 xor ax,ax
535 xchg al,[si] ; Zero-terminate
536 push si ; Save ending byte address
537 push ax ; Save ending byte
539 .find_start:
540 dec si
541 cmp si,[cs:InitRDPtr]
542 je .got_start
543 cmp byte [si],','
544 jne .find_start
546 ; It's a comma byte
547 inc si
549 .got_start:
550 push si
551 mov di,InitRD ; Target buffer for mangled name
552 call mangle_name
553 call loadinitrd
554 pop si
556 pop ax
557 pop di
558 mov [di],al ; Restore ending byte
560 cmp si,[cs:InitRDPtr]
561 ja .get_chunk
563 pop ds
564 pop es
565 ret
567 ;
568 ; Load RAM disk into high memory
569 ;
570 ; Input: InitRD - set to the mangled name of the initrd
571 ;
572 loadinitrd:
573 push ds
574 push es
575 mov ax,cs ; CS == DS == ES
576 mov ds,ax
577 mov es,ax
578 mov si,InitRD
579 mov di,InitRDCName
580 call unmangle_name ; Create human-readable name
581 sub di,InitRDCName
582 mov [InitRDCNameLen],di
583 mov di,InitRD
584 call searchdir ; Look for it in directory
585 jz .notthere
587 mov cx,dx
588 shl ecx,16
589 mov cx,ax ; ECX <- ram disk length
591 mov ax,real_mode_seg
592 mov es,ax
594 push ecx ; Bytes to load
595 mov edx,[HighMemSize] ; End of memory
596 dec edx
597 mov eax,[RamdiskMax] ; Highest address allowed by kernel
598 cmp edx,eax
599 jna .memsize_ok
600 mov edx,eax ; Adjust to fit inside limit
601 .memsize_ok:
602 inc edx
603 and dx,0F000h ; Round down to 4K boundary
604 sub edx,ecx ; Subtract size of ramdisk
605 and dx,0F000h ; Round down to 4K boundary
606 cmp edx,[KernelEnd] ; Are we hitting the kernel image?
607 jb no_high_mem
609 cmp dword [es:su_ramdisklen],0
610 je .highest
611 ; The total length has to include the padding between
612 ; different ramdisk files, so consider "the length" the
613 ; total amount we're about to adjust the base pointer.
614 mov ecx,[es:su_ramdiskat]
615 sub ecx,edx
616 .highest:
617 add [es:su_ramdisklen],ecx
619 mov [es:su_ramdiskat],edx ; Load address
620 mov edi,edx ; initrd load address
622 dec edx ; Note: RamdiskMax is addr-1
623 mov [RamdiskMax],edx ; Next initrd loaded here
625 push si
626 mov si,crlfloading_msg ; Write "Loading "
627 call cwritestr
628 mov si,InitRDCName ; Write ramdisk name
629 call cwritestr
630 mov si,dotdot_msg ; Write dots
631 call cwritestr
632 pop si
634 pop eax ; Bytes to load
635 mov dx,0FFFh ; Pad to page
636 mov bx,dot_pause ; Print dots...
637 call load_high ; Load the file
639 pop es
640 pop ds
641 ret
643 .notthere:
644 mov si,err_noinitrd
645 call cwritestr
646 mov si,InitRDCName
647 call cwritestr
648 mov si,crlf_msg
649 jmp abort_load
651 no_high_mem: ; Error routine
652 mov si,err_nohighmem
653 jmp abort_load
655 ret
657 section .data
658 crlfloading_msg db CR, LF
659 loading_msg db 'Loading ', 0
660 dotdot_msg db '.'
661 dot_msg db '.', 0
662 ready_msg db 'ready.', CR, LF, 0
663 err_oldkernel db 'Cannot load a ramdisk with an old kernel image.'
664 db CR, LF, 0
665 err_noinitrd db CR, LF, 'Could not find ramdisk image: ', 0
666 err_nohighmem db 'Not enough memory to load specified kernel.', CR, LF, 0
668 boot_image db 'BOOT_IMAGE='
669 boot_image_len equ $-boot_image
671 section .bss
672 alignb 4
673 RamdiskMax resd 1 ; Highest address for ramdisk
674 KernelSize resd 1 ; Size of kernel in bytes
675 KernelSects resd 1 ; Size of kernel in sectors
676 KernelEnd resd 1 ; Ending address of the kernel image
677 CmdLineLen resw 1 ; Length of command line including null
678 SetupSecs resw 1 ; Number of setup sectors
679 InitRDPtr resw 1 ; Pointer to initrd= option in command line
680 KernelVersion resw 1 ; Kernel protocol version
681 LoadFlags resb 1 ; Loadflags from kernel