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authorH. Peter Anvin <hpa@zytor.com>2008-05-30 20:16:20 -0400
committerH. Peter Anvin <hpa@zytor.com>2008-05-30 20:16:20 -0400
commit4039feb5bae72a5fed9ba6bc1a9cfd8dfe0a8613 (patch)
treee590d48fd0fe7cf6379d816836854f5005e0c7d9
parent3b6b9293d0f8e1b11630102013ca2a1dcef17d44 (diff)
x86: update Documentation/i386/boot.txt
Document QUIET_FLAG, correct the definition of several fields, make it clear this applies to the entire x86 architecture, not just i386. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
-rw-r--r--Documentation/i386/boot.txt79
1 files changed, 46 insertions, 33 deletions
diff --git a/Documentation/i386/boot.txt b/Documentation/i386/boot.txt
index 95ad15c3b01f..147bfe511cdd 100644
--- a/Documentation/i386/boot.txt
+++ b/Documentation/i386/boot.txt
@@ -1,17 +1,14 @@
1 THE LINUX/I386 BOOT PROTOCOL 1 THE LINUX/x86 BOOT PROTOCOL
2 ---------------------------- 2 ---------------------------
3 3
4 H. Peter Anvin <hpa@zytor.com> 4On the x86 platform, the Linux kernel uses a rather complicated boot
5 Last update 2007-05-23
6
7On the i386 platform, the Linux kernel uses a rather complicated boot
8convention. This has evolved partially due to historical aspects, as 5convention. This has evolved partially due to historical aspects, as
9well as the desire in the early days to have the kernel itself be a 6well as the desire in the early days to have the kernel itself be a
10bootable image, the complicated PC memory model and due to changed 7bootable image, the complicated PC memory model and due to changed
11expectations in the PC industry caused by the effective demise of 8expectations in the PC industry caused by the effective demise of
12real-mode DOS as a mainstream operating system. 9real-mode DOS as a mainstream operating system.
13 10
14Currently, the following versions of the Linux/i386 boot protocol exist. 11Currently, the following versions of the Linux/x86 boot protocol exist.
15 12
16Old kernels: zImage/Image support only. Some very early kernels 13Old kernels: zImage/Image support only. Some very early kernels
17 may not even support a command line. 14 may not even support a command line.
@@ -372,10 +369,17 @@ Protocol: 2.00+
372 - If 0, the protected-mode code is loaded at 0x10000. 369 - If 0, the protected-mode code is loaded at 0x10000.
373 - If 1, the protected-mode code is loaded at 0x100000. 370 - If 1, the protected-mode code is loaded at 0x100000.
374 371
372 Bit 5 (write): QUIET_FLAG
373 - If 0, print early messages.
374 - If 1, suppress early messages.
375 This requests to the kernel (decompressor and early
376 kernel) to not write early messages that require
377 accessing the display hardware directly.
378
375 Bit 6 (write): KEEP_SEGMENTS 379 Bit 6 (write): KEEP_SEGMENTS
376 Protocol: 2.07+ 380 Protocol: 2.07+
377 - if 0, reload the segment registers in the 32bit entry point. 381 - If 0, reload the segment registers in the 32bit entry point.
378 - if 1, do not reload the segment registers in the 32bit entry point. 382 - If 1, do not reload the segment registers in the 32bit entry point.
379 Assume that %cs %ds %ss %es are all set to flat segments with 383 Assume that %cs %ds %ss %es are all set to flat segments with
380 a base of 0 (or the equivalent for their environment). 384 a base of 0 (or the equivalent for their environment).
381 385
@@ -504,7 +508,7 @@ Protocol: 2.06+
504 maximum size was 255. 508 maximum size was 255.
505 509
506Field name: hardware_subarch 510Field name: hardware_subarch
507Type: write 511Type: write (optional, defaults to x86/PC)
508Offset/size: 0x23c/4 512Offset/size: 0x23c/4
509Protocol: 2.07+ 513Protocol: 2.07+
510 514
@@ -520,11 +524,13 @@ Protocol: 2.07+
520 0x00000002 Xen 524 0x00000002 Xen
521 525
522Field name: hardware_subarch_data 526Field name: hardware_subarch_data
523Type: write 527Type: write (subarch-dependent)
524Offset/size: 0x240/8 528Offset/size: 0x240/8
525Protocol: 2.07+ 529Protocol: 2.07+
526 530
527 A pointer to data that is specific to hardware subarch 531 A pointer to data that is specific to hardware subarch
532 This field is currently unused for the default x86/PC environment,
533 do not modify.
528 534
529Field name: payload_offset 535Field name: payload_offset
530Type: read 536Type: read
@@ -545,6 +551,34 @@ Protocol: 2.08+
545 551
546 The length of the payload. 552 The length of the payload.
547 553
554Field name: setup_data
555Type: write (special)
556Offset/size: 0x250/8
557Protocol: 2.09+
558
559 The 64-bit physical pointer to NULL terminated single linked list of
560 struct setup_data. This is used to define a more extensible boot
561 parameters passing mechanism. The definition of struct setup_data is
562 as follow:
563
564 struct setup_data {
565 u64 next;
566 u32 type;
567 u32 len;
568 u8 data[0];
569 };
570
571 Where, the next is a 64-bit physical pointer to the next node of
572 linked list, the next field of the last node is 0; the type is used
573 to identify the contents of data; the len is the length of data
574 field; the data holds the real payload.
575
576 This list may be modified at a number of points during the bootup
577 process. Therefore, when modifying this list one should always make
578 sure to consider the case where the linked list already contains
579 entries.
580
581
548**** THE IMAGE CHECKSUM 582**** THE IMAGE CHECKSUM
549 583
550From boot protocol version 2.08 onwards the CRC-32 is calculated over 584From boot protocol version 2.08 onwards the CRC-32 is calculated over
@@ -553,6 +587,7 @@ initial remainder of 0xffffffff. The checksum is appended to the
553file; therefore the CRC of the file up to the limit specified in the 587file; therefore the CRC of the file up to the limit specified in the
554syssize field of the header is always 0. 588syssize field of the header is always 0.
555 589
590
556**** THE KERNEL COMMAND LINE 591**** THE KERNEL COMMAND LINE
557 592
558The kernel command line has become an important way for the boot 593The kernel command line has become an important way for the boot
@@ -584,28 +619,6 @@ command line is entered using the following protocol:
584 covered by setup_move_size, so you may need to adjust this 619 covered by setup_move_size, so you may need to adjust this
585 field. 620 field.
586 621
587Field name: setup_data
588Type: write (obligatory)
589Offset/size: 0x250/8
590Protocol: 2.09+
591
592 The 64-bit physical pointer to NULL terminated single linked list of
593 struct setup_data. This is used to define a more extensible boot
594 parameters passing mechanism. The definition of struct setup_data is
595 as follow:
596
597 struct setup_data {
598 u64 next;
599 u32 type;
600 u32 len;
601 u8 data[0];
602 };
603
604 Where, the next is a 64-bit physical pointer to the next node of
605 linked list, the next field of the last node is 0; the type is used
606 to identify the contents of data; the len is the length of data
607 field; the data holds the real payload.
608
609 622
610**** MEMORY LAYOUT OF THE REAL-MODE CODE 623**** MEMORY LAYOUT OF THE REAL-MODE CODE
611 624