efi.c

linux 内核源代码

/************************************************************
 * EFI GUID Partition Table handling
 * Per Intel EFI Specification v1.02
 * http://developer.intel.com/technology/efi/efi.htm
 * efi.[ch] by Matt Domsch <[e-mail]>
 *   Copyright 2000,2001,2002,2004 Dell Inc.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *
 * TODO:
 *
 * Changelog:
 * Mon Nov 09 2004 Matt Domsch <[e-mail]>
 * - test for valid PMBR and valid PGPT before ever reading
 *   AGPT, allow override with 'gpt' kernel command line option.
 * - check for first/last_usable_lba outside of size of disk
 *
 * Tue  Mar 26 2002 Matt Domsch <[e-mail]>
 * - Ported to 2.5.7-pre1 and 2.5.7-dj2
 * - Applied patch to avoid fault in alternate header handling
 * - cleaned up find_valid_gpt
 * - On-disk structure and copy in memory is *always* LE now - 
 *   swab fields as needed
 * - remove print_gpt_header()
 * - only use first max_p partition entries, to keep the kernel minor number
 *   and partition numbers tied.
 *
 * Mon  Feb 04 2002 Matt Domsch <[e-mail]>
 * - Removed __PRIPTR_PREFIX - not being used
 *
 * Mon  Jan 14 2002 Matt Domsch <[e-mail]>
 * - Ported to 2.5.2-pre11 + library crc32 patch Linus applied
 *
 * Thu Dec 6 2001 Matt Domsch <[e-mail]>
 * - Added compare_gpts().
 * - moved le_efi_guid_to_cpus() back into this file.  GPT is the only
 *   thing that keeps EFI GUIDs on disk.
 * - Changed gpt structure names and members to be simpler and more Linux-like.
 * 
 * Wed Oct 17 2001 Matt Domsch <[e-mail]>
 * - Removed CONFIG_DEVFS_VOLUMES_UUID code entirely per Martin Wilck
 *
 * Wed Oct 10 2001 Matt Domsch <[e-mail]>
 * - Changed function comments to DocBook style per Andreas Dilger suggestion.
 *
 * Mon Oct 08 2001 Matt Domsch <[e-mail]>
 * - Change read_lba() to use the page cache per Al Viro's work.
 * - print u64s properly on all architectures
 * - fixed debug_printk(), now Dprintk()
 *
 * Mon Oct 01 2001 Matt Domsch <[e-mail]>
 * - Style cleanups
 * - made most functions static
 * - Endianness addition
 * - remove test for second alternate header, as it's not per spec,
 *   and is unnecessary.  There's now a method to read/write the last
 *   sector of an odd-sized disk from user space.  No tools have ever
 *   been released which used this code, so it's effectively dead.
 * - Per Asit Mallick of Intel, added a test for a valid PMBR.
 * - Added kernel command line option 'gpt' to override valid PMBR test.
 *
 * Wed Jun  6 2001 Martin Wilck <[e-mail]>
 * - added devfs volume UUID support (/dev/volumes/uuids) for
 *   mounting file systems by the partition GUID. 
 *
 * Tue Dec  5 2000 Matt Domsch <[e-mail]>
 * - Moved crc32() to linux/lib, added efi_crc32().
 *
 * Thu Nov 30 2000 Matt Domsch <[e-mail]>
 * - Replaced Intel's CRC32 function with an equivalent
 *   non-license-restricted version.
 *
 * Wed Oct 25 2000 Matt Domsch <[e-mail]>
 * - Fixed the last_lba() call to return the proper last block
 *
 * Thu Oct 12 2000 Matt Domsch <[e-mail]>
 * - Thanks to Andries Brouwer for his debugging assistance.
 * - Code works, detects all the partitions.
 *
 ************************************************************/
#include <linux/crc32.h>
#include "check.h"
#include "efi.h"

#undef EFI_DEBUG
#ifdef EFI_DEBUG
#define Dprintk(x...) printk(KERN_DEBUG x)
#else
#define Dprintk(x...)
#endif

/* This allows a kernel command line option 'gpt' to override
 * the test for invalid PMBR.  Not __initdata because reloading
 * the partition tables happens after init too.
 */
static int force_gpt;
static int __init
force_gpt_fn(char *str)
{
	force_gpt = 1;
	return 1;
}
__setup("gpt", force_gpt_fn);


/**
 * efi_crc32() - EFI version of crc32 function
 * @buf: buffer to calculate crc32 of
 * @len - length of buf
 *
 * Description: Returns EFI-style CRC32 value for @buf
 * 
 * This function uses the little endian Ethernet polynomial
 * but seeds the function with ~0, and xor's with ~0 at the end.
 * Note, the EFI Specification, v1.02, has a reference to
 * Dr. Dobbs Journal, May 1994 (actually it's in May 1992).
 */
static inline u32
efi_crc32(const void *buf, unsigned long len)
{
	return (crc32(~0L, buf, len) ^ ~0L);
}

/**
 * last_lba(): return number of last logical block of device
 * @bdev: block device
 * 
 * Description: Returns last LBA value on success, 0 on error.
 * This is stored (by sd and ide-geometry) in
 *  the part[0] entry for this disk, and is the number of
 *  physical sectors available on the disk.
 */
static u64
last_lba(struct block_device *bdev)
{
	if (!bdev || !bdev->bd_inode)
		return 0;
	return (bdev->bd_inode->i_size >> 9) - 1ULL;
}

static inline int
pmbr_part_valid(struct partition *part)
{
        if (part->sys_ind == EFI_PMBR_OSTYPE_EFI_GPT &&
            le32_to_cpu(part->start_sect) == 1UL)
                return 1;
        return 0;
}

/**
 * is_pmbr_valid(): test Protective MBR for validity
 * @mbr: pointer to a legacy mbr structure
 *
 * Description: Returns 1 if PMBR is valid, 0 otherwise.
 * Validity depends on two things:
 *  1) MSDOS signature is in the last two bytes of the MBR
 *  2) One partition of type 0xEE is found
 */
static int
is_pmbr_valid(legacy_mbr *mbr)
{
	int i;
	if (!mbr || le16_to_cpu(mbr->signature) != MSDOS_MBR_SIGNATURE)
                return 0;
	for (i = 0; i < 4; i++)
		if (pmbr_part_valid(&mbr->partition_record[i]))
                        return 1;
	return 0;
}

/**
 * read_lba(): Read bytes from disk, starting at given LBA
 * @bdev
 * @lba
 * @buffer
 * @size_t
 *
 * Description:  Reads @count bytes from @bdev into @buffer.
 * Returns number of bytes read on success, 0 on error.
 */
static size_t
read_lba(struct block_device *bdev, u64 lba, u8 * buffer, size_t count)
{
	size_t totalreadcount = 0;

	if (!bdev || !buffer || lba > last_lba(bdev))
                return 0;

	while (count) {
		int copied = 512;
		Sector sect;
		unsigned char *data = read_dev_sector(bdev, lba++, &sect);
		if (!data)
			break;
		if (copied > count)
			copied = count;
		memcpy(buffer, data, copied);
		put_dev_sector(sect);
		buffer += copied;
		totalreadcount +=copied;
		count -= copied;
	}
	return totalreadcount;
}

/**
 * alloc_read_gpt_entries(): reads partition entries from disk
 * @bdev
 * @gpt - GPT header
 * 
 * Description: Returns ptes on success,  NULL on error.
 * Allocates space for PTEs based on information found in @gpt.
 * Notes: remember to free pte when you're done!
 */
static gpt_entry *
alloc_read_gpt_entries(struct block_device *bdev, gpt_header *gpt)
{
	size_t count;
	gpt_entry *pte;
	if (!bdev || !gpt)
		return NULL;

	count = le32_to_cpu(gpt->num_partition_entries) *
                le32_to_cpu(gpt->sizeof_partition_entry);
	if (!count)
		return NULL;
	pte = kzalloc(count, GFP_KERNEL);
	if (!pte)
		return NULL;

	if (read_lba(bdev, le64_to_cpu(gpt->partition_entry_lba),
                     (u8 *) pte,
		     count) < count) {
		kfree(pte);
                pte=NULL;
		return NULL;
	}
	return pte;
}

/**
 * alloc_read_gpt_header(): Allocates GPT header, reads into it from disk
 * @bdev
 * @lba is the Logical Block Address of the partition table
 * 
 * Description: returns GPT header on success, NULL on error.   Allocates
 * and fills a GPT header starting at @ from @bdev.
 * Note: remember to free gpt when finished with it.
 */
static gpt_header *
alloc_read_gpt_header(struct block_device *bdev, u64 lba)
{
	gpt_header *gpt;
	if (!bdev)
		return NULL;

	gpt = kzalloc(sizeof (gpt_header), GFP_KERNEL);
	if (!gpt)
		return NULL;

	if (read_lba(bdev, lba, (u8 *) gpt,
		     sizeof (gpt_header)) < sizeof (gpt_header)) {
		kfree(gpt);
                gpt=NULL;
		return NULL;
	}

	return gpt;
}

/**
 * is_gpt_valid() - tests one GPT header and PTEs for validity
 * @bdev
 * @lba is the logical block address of the GPT header to test
 * @gpt is a GPT header ptr, filled on return.
 * @ptes is a PTEs ptr, filled on return.
 *
 * Description: returns 1 if valid,  0 on error.
 * If valid, returns pointers to newly allocated GPT header and PTEs.
 */
static int
is_gpt_valid(struct block_device *bdev, u64 lba,
	     gpt_header **gpt, gpt_entry **ptes)
{
	u32 crc, origcrc;
	u64 lastlba;

	if (!bdev || !gpt || !ptes)
		return 0;
	if (!(*gpt = alloc_read_gpt_header(bdev, lba)))
		return 0;

	/* Check the GUID Partition Table signature */
	if (le64_to_cpu((*gpt)->signature) != GPT_HEADER_SIGNATURE) {
		Dprintk("GUID Partition Table Header signature is wrong:"
			"%lld != %lld\n",
			(unsigned long long)le64_to_cpu((*gpt)->signature),
			(unsigned long long)GPT_HEADER_SIGNATURE);
		goto fail;
	}

	/* Check the GUID Partition Table CRC */
	origcrc = le32_to_cpu((*gpt)->header_crc32);
	(*gpt)->header_crc32 = 0;
	crc = efi_crc32((const unsigned char *) (*gpt), le32_to_cpu((*gpt)->header_size));

	if (crc != origcrc) {