linux-kernel - Re: [RFC -mm 2/2] i386/x86_64 boot: document for 32 bit boot protocol

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Message-Id: <1190078003.12429.8.camel@caritas-dev.intel.com>
Date:	Tue, 18 Sep 2007 09:13:23 +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 08:29 -0700, H. Peter Anvin wrote:
> Huang, Ying wrote:
> > This patch defines a 32-bit boot protocol and adds corresponding
> > document.
> > +
> > +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	Type		Description
> > +------  ----		-----------
> > +    0	32 bytes	struct screen_info, SCREEN_INFO
> > +			ATTENTION, overlaps the following !!!
> > +    2	unsigned short	EXT_MEM_K, extended memory size in Kb (from int 0x15)
> > + 0x20	unsigned short	CL_MAGIC, commandline magic number (=0xA33F)
> > + 0x22	unsigned short	CL_OFFSET, commandline offset
> > +			Address of commandline is calculated:
> > +			  0x90000 + contents of CL_OFFSET
> > +			(only taken, when CL_MAGIC = 0xA33F)
> > + 0x40	20 bytes	struct apm_bios_info, APM_BIOS_INFO
> > + 0x60	16 bytes	Intel SpeedStep (IST) BIOS support information
> > + 0x80	16 bytes	hd0-disk-parameter from intvector 0x41
> > + 0x90	16 bytes	hd1-disk-parameter from intvector 0x46
> > +
> > + 0xa0	16 bytes	System description table truncated to 16 bytes.
> > +			( struct sys_desc_table_struct )
> > + 0xb0 - 0x13f		Free. Add more parameters here if you really need them.
> > + 0x140- 0x1be		EDID_INFO Video mode setup
> > +
> > +0x1c4	unsigned long	EFI system table pointer
> > +0x1c8	unsigned long	EFI memory descriptor size
> > +0x1cc	unsigned long	EFI memory descriptor version
> > +0x1d0	unsigned long	EFI memory descriptor map pointer
> > +0x1d4	unsigned long	EFI memory descriptor map size
> > +0x1e0	unsigned long	ALT_MEM_K, alternative mem check, in Kb
> > +0x1e4	unsigned long	Scratch field for the kernel setup code
> > +0x1e8	char		number of entries in E820MAP (below)
> > +0x1e9	unsigned char	number of entries in EDDBUF (below)
> > +0x1ea	unsigned char	number of entries in EDD_MBR_SIG_BUFFER (below)
> > +0x290 - 0x2cf		EDD_MBR_SIG_BUFFER (edd.S)
> > +0x2d0 - 0xd00		E820MAP
> > +0xd00 - 0xeff		EDDBUF (edd.S) for disk signature read sector
> > +0xd00 - 0xeeb		EDDBUF (edd.S) for edd data
> > +
> > +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.
> 
> This is just replicating the "zero-page.txt" document, which can best be
> described as a "total lie" -- compare with the actual structure.

OK, I will check the actual structure, and change the document
accordingly.

Best Regards,
Huang Ying
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