On Fri, Jun 25, 2004 at 12:00:22PM -0400, Jeremy Katz wrote: > Well, for anaconda to do it the best thing is actually to get parted > doing so. Patch below against parted-1.6.11 sets the mbr_signature if it is already zero, any time msdos_write() gets called. The value set is the tv_usec field of the current time, of which three bytes are quasi-unique, but the fourth (most significant byte) is always zero for me. The boot code struct is reduced by 6 bytes, but the code ever written to it by parted is only like 50 bytes, and the EFI spec says that the boot_code portion should only be 440 bytes anyhow. Thoughts? Thanks, Matt -- Matt Domsch Sr. Software Engineer, Lead Engineer Dell Linux Solutions linux.dell.com & www.dell.com/linux Linux on Dell mailing lists @ http://lists.us.dell.com diff -urNp --exclude-from=/home/mdomsch/excludes --minimal parted-1.6.11.orig/libparted/disk_dos.c parted-1.6.11/libparted/disk_dos.c --- parted-1.6.11.orig/libparted/disk_dos.c Tue Mar 9 04:17:08 2004 +++ parted-1.6.11/libparted/disk_dos.c Fri Jun 25 17:20:32 2004 @@ -19,6 +19,7 @@ #include "config.h" +#include <sys/time.h> #include <parted/parted.h> #include <parted/debug.h> #include <parted/endian.h> @@ -107,7 +108,9 @@ struct _DosRawPartition { } __attribute__((packed)); struct _DosRawTable { - char boot_code [446]; + char boot_code [440]; + uint32_t mbr_signature; + uint16_t Unknown; DosRawPartition partitions [4]; uint16_t magic; } __attribute__((packed)); @@ -769,6 +772,16 @@ write_extended_partitions (PedDisk* disk return write_empty_table (disk, ext_part->geom.start); } +static inline uint32_t set_mbr_signature(void) +{ + struct timeval tv; + int rc; + rc = gettimeofday(&tv, NULL); + if (rc == -1) + return 0; + return (uint32_t)(tv.tv_usec & 0xFFFFFFFFUL); +} + static int msdos_write (PedDisk* disk) { @@ -786,6 +799,9 @@ msdos_write (PedDisk* disk) memcpy (table.boot_code, MBR_BOOT_CODE, sizeof (MBR_BOOT_CODE)); } + + if (!table.mbr_signature) + table.mbr_signature = set_mbr_signature(); memset (table.partitions, 0, sizeof (DosRawPartition) * 4); table.magic = PED_CPU_TO_LE16 (MSDOS_MAGIC);
Attachment:
pgpPE95JssNz6.pgp
Description: PGP signature
