[RFC][PATCH 2.4] EDD 4-byte MBR disk signature for the boot disk

From: Matt Domsch
Date: Fri Oct 10 2003 - 09:08:52 EST

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For comment. -Matt
--
Matt Domsch
Sr. Software Engineer, Lead Engineer
Dell Linux Solutions www.dell.com/linux
Linux on Dell mailing lists @ http://lists.us.dell.com

You can import this changeset into BK by piping this whole message to
'| bk receive [path to repository]' or apply the patch as usual.

===================================================================

ChangeSet@xxxxxx, 2003-10-10 08:50:32-05:00, Matt_Domsch@xxxxxxxx
EDD: read disk80 MBR signature, export through edd module

There are 4 bytes in the MSDOS master boot record, at offset 0x228,
which may contain a per-system-unique signature. By writing into this
signature from a tool that makes real-mode int13 calls a unique
signature such as "BOOT" for the boot disk (int13 dev 80h), Linux may
then retrieve this information and use it to compare against disks it
knows as named /dev/[hs]d[a-z].

This is useful in the case where the BIOS is not EDD3.0 compliant,
thus doesn't provide the PCI bus/dev/fn and IDE/SCSI location of the
boot disk, yet you need to know which disk is the boot disk.

This patch retrieves the signature from the disk in setup.S and stores
it in a space reserved in the empty_zero_page, copies it somewhere
safe in setup.c, and exports it via
/proc/bios/edd/int13_disk80/mbr_signature in edd.c. Code is covered
under CONFIG_EDD=[ym].

Documentation/i386/zero-page.txt | 4 +++-
arch/i386/boot/setup.S | 21 +++++++++++++++++++++
arch/i386/kernel/edd.c | 27 +++++++++++++++++++++++++--
arch/i386/kernel/i386_ksyms.c | 1 +
arch/i386/kernel/setup.c | 3 +++
include/asm-i386/edd.h | 7 ++++++-
6 files changed, 59 insertions(+), 4 deletions(-)

diff -Nru a/Documentation/i386/zero-page.txt b/Documentation/i386/zero-page.txt
--- a/Documentation/i386/zero-page.txt Fri Oct 10 09:01:41 2003
+++ b/Documentation/i386/zero-page.txt Fri Oct 10 09:01:41 2003
@@ -66,8 +66,10 @@
0x21c unsigned long INITRD_SIZE, size in bytes of ramdisk image
0x220 4 bytes (setup.S)
0x224 unsigned short setup.S heap end pointer
+0x228 4 bytes DISK80_SIG_BUFFER (setup.S)
0x2d0 - 0x600 E820MAP
-0x600 - 0x7D4 EDDBUF (setup.S)
+0x600 - 0x800 EDDBUF (setup.S) for disk signature read sector
+0x600 - 0x7d4 EDDBUF (setup.S)

0x800 string, 2K max COMMAND_LINE, the kernel commandline as
copied using CL_OFFSET.
diff -Nru a/arch/i386/boot/setup.S b/arch/i386/boot/setup.S
--- a/arch/i386/boot/setup.S Fri Oct 10 09:01:41 2003
+++ b/arch/i386/boot/setup.S Fri Oct 10 09:01:41 2003
@@ -49,6 +49,8 @@
* by Matt Domsch <Matt_Domsch@xxxxxxxx> October 2002
* conformant to T13 Committee www.t13.org
* projects 1572D, 1484D, 1386D, 1226DT
+ * disk signature read by Matt Domsch <Matt_Domsch@xxxxxxxx>
+ * and Andrew Wilks <Andrew_Wilks@xxxxxxxx> September 2003
*/

#include <linux/config.h>
@@ -549,6 +551,25 @@
#endif

#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
+# Read the first sector of device 80h and store the 4-byte signature
+ movl $0xFFFFFFFF, %eax
+ movl %eax, (DISK80_SIG_BUFFER) # assume failure
+ movb $READ_SECTORS, %ah
+ movb $1, %al # read 1 sector
+ movb $0x80, %dl # from device 80
+ movb $0, %dh # at head 0
+ movw $1, %cx # cylinder 0, sector 0
+ pushw %es
+ pushw %ds
+ popw %es
+ movw $EDDBUF, %bx
+ int $0x13
+ jc disk_sig_done
+ movl (EDDBUF+MBR_SIG_OFFSET), %eax
+ movl %eax, (DISK80_SIG_BUFFER) # store success
+disk_sig_done:
+ popw %es
+
# Do the BIOS Enhanced Disk Drive calls
# This consists of two calls:
# int 13h ah=41h "Check Extensions Present"
diff -Nru a/arch/i386/kernel/edd.c b/arch/i386/kernel/edd.c
--- a/arch/i386/kernel/edd.c Fri Oct 10 09:01:41 2003
+++ b/arch/i386/kernel/edd.c Fri Oct 10 09:01:41 2003
@@ -1,7 +1,8 @@
/*
* linux/arch/i386/kernel/edd.c
- * Copyright (C) 2002 Dell Computer Corporation
+ * Copyright (C) 2002, 2003 Dell, Inc.
* by Matt Domsch <Matt_Domsch@xxxxxxxx>
+ * disk80 signature by Matt Domsch, Andrew Wilks, and Sandeep K. Shandilya
*
* BIOS Enhanced Disk Drive Services (EDD)
* conformant to T13 Committee www.t13.org
@@ -27,7 +28,6 @@
/*
* TODO:
* - move edd.[ch] to better locations if/when one is decided
- * - keep current with 2.5 EDD code changes
*/

#include <linux/module.h>
@@ -333,6 +333,18 @@
}

static int
+edd_show_disk80_sig(char *page, char **start, off_t off, int count, int *eof, void *data)
+{
+ char *p = page;
+ if ( !page || off) {
+ return proc_calc_metrics(page, start, off, count, eof, 0);
+ }
+
+ p += snprintf(p, left, "0x%08x\n", edd_disk80_sig);
+ return proc_calc_metrics(page, start, off, count, eof, (p - page));
+}
+
+static int
edd_show_extensions(char *page, char **start, off_t off, int count, int *eof, void *data)
{
struct edd_info *info = data;
@@ -491,6 +503,15 @@
return 1;
}

+static int
+edd_has_disk80_sig(struct edd_device *edev)
+{
+ struct edd_info *info = edd_dev_get_info(edev);
+ if (!edev || !info)
+ return 0;
+ return info->device == 0x80;
+}
+
static EDD_DEVICE_ATTR(raw_data, edd_show_raw_data, NULL);
static EDD_DEVICE_ATTR(version, edd_show_version, NULL);
static EDD_DEVICE_ATTR(extensions, edd_show_extensions, NULL);
@@ -505,6 +526,7 @@
edd_has_default_sectors_per_track);
static EDD_DEVICE_ATTR(interface, edd_show_interface,edd_has_edd30);
static EDD_DEVICE_ATTR(host_bus, edd_show_host_bus, edd_has_edd30);
+static EDD_DEVICE_ATTR(mbr_signature, edd_show_disk80_sig, edd_has_disk80_sig);

static struct edd_attribute *def_attrs[] = {
&edd_attr_raw_data,
@@ -517,6 +539,7 @@
&edd_attr_default_sectors_per_track,
&edd_attr_interface,
&edd_attr_host_bus,
+ &edd_attr_mbr_signature,
NULL,
};

diff -Nru a/arch/i386/kernel/i386_ksyms.c b/arch/i386/kernel/i386_ksyms.c
--- a/arch/i386/kernel/i386_ksyms.c Fri Oct 10 09:01:41 2003
+++ b/arch/i386/kernel/i386_ksyms.c Fri Oct 10 09:01:41 2003
@@ -185,4 +185,5 @@
#ifdef CONFIG_EDD_MODULE
EXPORT_SYMBOL(edd);
EXPORT_SYMBOL(eddnr);
+EXPORT_SYMBOL(edd_disk80_sig);
#endif
diff -Nru a/arch/i386/kernel/setup.c b/arch/i386/kernel/setup.c
--- a/arch/i386/kernel/setup.c Fri Oct 10 09:01:41 2003
+++ b/arch/i386/kernel/setup.c Fri Oct 10 09:01:41 2003
@@ -212,6 +212,7 @@
#define KERNEL_START (*(unsigned long *) (PARAM+0x214))
#define INITRD_START (*(unsigned long *) (PARAM+0x218))
#define INITRD_SIZE (*(unsigned long *) (PARAM+0x21c))
+#define DISK80_SIGNATURE_BUFFER (*(unsigned int*) (PARAM+DISKSIG_BUFFER))
#define EDD_NR (*(unsigned char *) (PARAM+EDDNR))
#define EDD_BUF ((struct edd_info *) (PARAM+EDDBUF))
#define COMMAND_LINE ((char *) (PARAM+2048))
@@ -721,6 +722,7 @@
#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
unsigned char eddnr;
struct edd_info edd[EDDMAXNR];
+unsigned int edd_disk80_sig;
/**
* copy_edd() - Copy the BIOS EDD information
* from empty_zero_page into a safe place.
@@ -730,6 +732,7 @@
{
eddnr = EDD_NR;
memcpy(edd, EDD_BUF, sizeof(edd));
+ edd_disk80_sig = DISK80_SIGNATURE_BUFFER;
}
#else
static inline void copy_edd(void) {}
diff -Nru a/include/asm-i386/edd.h b/include/asm-i386/edd.h
--- a/include/asm-i386/edd.h Fri Oct 10 09:01:41 2003
+++ b/include/asm-i386/edd.h Fri Oct 10 09:01:41 2003
@@ -1,6 +1,6 @@
/*
* linux/include/asm-i386/edd.h
- * Copyright (C) 2002 Dell Computer Corporation
+ * Copyright (C) 2002, 2003 Dell, Inc.
* by Matt Domsch <Matt_Domsch@xxxxxxxx>
*
* structures and definitions for the int 13h, ax={41,48}h
@@ -41,6 +41,10 @@
#define EDDMAGIC1 0x55AA
#define EDDMAGIC2 0xAA55

+#define READ_SECTORS 0x02
+#define MBR_SIG_OFFSET 0x1B8
+#define DISK80_SIG_BUFFER 0x228
+
#ifndef __ASSEMBLY__

#define EDD_EXT_FIXED_DISK_ACCESS (1 << 0)
@@ -167,6 +171,7 @@

extern struct edd_info edd[EDDMAXNR];
extern unsigned char eddnr;
+extern unsigned int edd_disk80_sig;
#endif /*!__ASSEMBLY__ */

#endif /* _ASM_I386_EDD_H */

===================================================================

This BitKeeper patch contains the following changesets:
1.1182
## Wrapped with gzip_uu ##

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Next message: Stuart Longland: "Re: 2.7 thoughts"
Previous message: Trond Myklebust: "Re: statfs() / statvfs() syscall ballsup..."
Next in thread: Jamie Lokier: "Re: [RFC][PATCH 2.4] EDD 4-byte MBR disk signature for the boot disk"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]