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Message-Id: <1190084206.12429.20.camel@caritas-dev.intel.com>
Date: Tue, 18 Sep 2007 10:56:46 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: Andi Kleen <ak@...e.de>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
akpm@...ux-foundation.org, Yinghai Lu <yhlu.kernel@...il.com>,
Chandramouli Narayanan <mouli@...ux.intel.com>,
linux-kernel@...r.kernel.org
Subject: Re: [RFC -mm 2/2] i386/x86_64 boot: document for 32 bit
boot protocol
On Mon, 2007-09-17 at 18:48 -0700, H. Peter Anvin wrote:
> Huang, Ying wrote:
> >
> > OK, I will check the actual structure, and change the document
> > accordingly.
> >
>
> The best would probably be to fix zero-page.txt (and probably rename it
> something saner.)
Does the patch appended with the mail seems better?
If it is desired, I can move the zero page description into
zero-page.txt, and refer to it in 32-bit boot protocol description.
I delete the hd0_info and hd1_info from the zero page. If it is
undesired, I will move them back.
The field in zero page is fairly complex (such as struct edd_info). Do
you think it is necessary to document every field inside the first level
field, until the primary data type? Or we just provide the C struct
name?
Best Regards,
Huang Ying
---
Index: linux-2.6.23-rc4/Documentation/i386/boot.txt
===================================================================
--- linux-2.6.23-rc4.orig/Documentation/i386/boot.txt 2007-09-18 10:40:34.000000000 +0800
+++ linux-2.6.23-rc4/Documentation/i386/boot.txt 2007-09-18 10:46:13.000000000 +0800
@@ -2,7 +2,7 @@
----------------------------
H. Peter Anvin <hpa@...or.com>
- Last update 2007-05-23
+ Last update 2007-09-14
On the i386 platform, the Linux kernel uses a rather complicated boot
convention. This has evolved partially due to historical aspects, as
@@ -42,6 +42,9 @@
Protocol 2.06: (Kernel 2.6.22) Added a field that contains the size of
the boot command line
+Protocol 2.07: (kernel 2.6.23) Added a field of 64-bit physical
+ pointer to single linked list of struct setup_data.
+ Added 32-bit boot protocol.
**** MEMORY LAYOUT
@@ -168,6 +171,9 @@
0234/1 2.05+ relocatable_kernel Whether kernel is relocatable or not
0235/3 N/A pad2 Unused
0238/4 2.06+ cmdline_size Maximum size of the kernel command line
+023c/4 N/A pad3 Unused
+0240/8 2.07+ setup_data 64-bit physical pointer to linked list
+ of struct setup_data
(1) For backwards compatibility, if the setup_sects field contains 0, the
real value is 4.
@@ -480,6 +486,36 @@
cmdline_size characters. With protocol version 2.05 and earlier, the
maximum size was 255.
+Field name: setup_data
+Type: write (obligatory)
+Offset/size: 0x240/8
+Protocol: 2.07+
+
+ The 64-bit physical pointer to NULL terminated single linked list of
+ struct setup_data. This is used to define a more extensible boot
+ parameters passing mechanism. The definition of struct setup_data is
+ as follow:
+
+ struct setup_data {
+ u64 next;
+ u32 type;
+ u32 len;
+ u8 data[0];
+ } __attribute__((packed));
+
+ Where, the next is a 64-bit physical pointer to the next node of
+ linked list, the next field of the last node is 0; the type is used
+ to identify the contents of data; the len is the length of data
+ field; the data holds the real payload.
+
+ With this field, to add a new boot parameter written by bootloader,
+ it is not needed to add a new field to real mode header, just add a
+ new setup_data type is sufficient. But to add a new boot parameter
+ read by bootloader, it is still needed to add a new field.
+
+ TODO: Where is the safe place to place the linked list of struct
+ setup_data?
+
**** THE KERNEL COMMAND LINE
@@ -753,3 +789,57 @@
After completing your hook, you should jump to the address
that was in this field before your boot loader overwrote it
(relocated, if appropriate.)
+
+
+**** SETUP DATA TYPES
+
+
+**** 32-bit BOOT PROTOCOL
+
+For machine with some new BIOS other than legacy BIOS, such as EFI,
+LinuxBIOS, etc, and kexec, the 16-bit real mode setup code in kernel
+based on legacy BIOS can not be used, so a 32-bit boot protocol need
+to be defined.
+
+In 32-bit boot protocol, the first step in loading a Linux kernel
+should still be to load the real-mode code and then examine the kernel
+header at offset 0x01f1. But, it is not necessary to load all
+real-mode code, just first 4K bytes traditionally known as "zero page"
+is needed.
+
+In addition to read/modify/write kernel header of the zero page as
+that of 16-bit boot protocol, the boot loader should fill the
+following additional fields of the zero page too.
+
+Offset Proto Name Meaning
+/Size
+
+000/040 2.07+ screen_info Text mode or frame buffer information
+ (struct screen_info)
+040/014 2.07+ apm_bios_info APM BIOS information (struct apm_bios_info)
+060/010 2.07+ ist_info Intel SpeedStep (IST) BIOS support information
+ (struct ist_info)
+0A0/010 2.07+ sys_desc_table System description table (struct sys_desc_table)
+140/080 2.07+ edid_info Video mode setup (struct edid_info)
+1C0/020 2.07+ efi_info EFI 32 information (struct efi_info)
+1E0/004 2.07+ alk_mem_k Alternative mem check, in KB
+1E4/004 2.07+ scratch Scratch field for the kernel setup code
+1E8/001 2.07+ e820_entries Number of entries in e820_map (below)
+1E9/001 2.07+ eddbuf_entries Number of entries in eddbuf (below)
+1EA/001 2.07+ edd_mbr_sig_buf_entries Number of entries in edd_mbr_sig_buffer
+ (below)
+290/040 2.07+ edd_mbr_sig_buffer EDD MBR signatures
+2D0/A00 2.07+ e820_map E820 memory map table
+ (array of struct e820entry)
+D00/1EC 2.07+ eddbuf EDD data (array of struct edd_info)
+
+After loading and setuping the zero page, the boot loader can load the
+32/64-bit kernel in the same way as that of 16-bit boot protocol.
+
+In 32-bit boot protocol, the kernel is started by jumping to the
+32-bit kernel entry point, which is the start address of loaded
+32/64-bit kernel.
+
+At entry, the CPU must be in 32-bit protected mode with paging
+disabled; the CS and DS must be 4G flat segments; %esi holds the base
+address of the "zero page"; %esp, %ebp, %edi should be zero.
-
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