Author: stepan Date: 2007-04-15 02:41:40 +0200 (Sun, 15 Apr 2007) New Revision: 122
Modified: openbios-devel/fs/grubfs/fat.h openbios-devel/fs/grubfs/fsys_fat.c Log: Patch from Aurelien Jarno aurelien@aurel32.net:
The current SVN version currently fails to work on machines that have strict alignment requirements, for example the SPARC target. This is due to the way the struct fat_bpb in fs/grubfs/fat.h is defined and accessed (through FAT_CVT_U16) to avoid padding. Some 16 bits fields like bytes_per_sect are thus accessed unaligned.
The patch below takes the same approach as for other structures in openbios, it declares the structure as packed, and lets GCC do the right things to access those unaligned field.
Modified: openbios-devel/fs/grubfs/fat.h =================================================================== --- openbios-devel/fs/grubfs/fat.h 2007-04-14 19:48:59 UTC (rev 121) +++ openbios-devel/fs/grubfs/fat.h 2007-04-15 00:41:40 UTC (rev 122) @@ -37,12 +37,12 @@ __s8 ignored[3]; /* Boot strap short or near jump */ __s8 system_id[8]; /* Name - can be used to special case partition manager volumes */ - __u8 bytes_per_sect[2]; /* bytes per logical sector */ + __u16 bytes_per_sect; /* bytes per logical sector */ __u8 sects_per_clust;/* sectors/cluster */ - __u8 reserved_sects[2]; /* reserved sectors */ + __u16 reserved_sects; /* reserved sectors */ __u8 num_fats; /* number of FATs */ - __u8 dir_entries[2]; /* root directory entries */ - __u8 short_sectors[2]; /* number of sectors */ + __u16 dir_entries; /* root directory entries */ + __u16 short_sectors; /* number of sectors */ __u8 media; /* media code (unused) */ __u16 fat_length; /* sectors/FAT */ __u16 secs_track; /* sectors per track */ @@ -53,15 +53,13 @@ /* The following fields are only used by FAT32 */ __u32 fat32_length; /* sectors/FAT */ __u16 flags; /* bit 8: fat mirroring, low 4: active fat */ - __u8 version[2]; /* major, minor filesystem version */ + __u16 version; /* major, minor filesystem version */ __u32 root_cluster; /* first cluster in root directory */ __u16 info_sector; /* filesystem info sector */ __u16 backup_boot; /* backup boot sector */ __u16 reserved2[6]; /* Unused */ -}; +} __attribute__ ((packed));
-#define FAT_CVT_U16(bytarr) (* (__u16*)(bytarr)) - /* * Defines how to differentiate a 12-bit and 16-bit FAT. */
Modified: openbios-devel/fs/grubfs/fsys_fat.c =================================================================== --- openbios-devel/fs/grubfs/fsys_fat.c 2007-04-14 19:48:59 UTC (rev 121) +++ openbios-devel/fs/grubfs/fsys_fat.c 2007-04-15 00:41:40 UTC (rev 122) @@ -75,23 +75,23 @@ if (bpb.sects_per_clust == 0) return 0;
- FAT_SUPER->sectsize_bits = log2 (FAT_CVT_U16 (bpb.bytes_per_sect)); + FAT_SUPER->sectsize_bits = log2 (bpb.bytes_per_sect); FAT_SUPER->clustsize_bits = FAT_SUPER->sectsize_bits + log2 (bpb.sects_per_clust);
/* Fill in info about super block */ - FAT_SUPER->num_sectors = FAT_CVT_U16 (bpb.short_sectors) - ? FAT_CVT_U16 (bpb.short_sectors) : bpb.long_sectors; + FAT_SUPER->num_sectors = bpb.short_sectors + ? bpb.short_sectors : bpb.long_sectors;
/* FAT offset and length */ - FAT_SUPER->fat_offset = FAT_CVT_U16 (bpb.reserved_sects); + FAT_SUPER->fat_offset = bpb.reserved_sects; FAT_SUPER->fat_length = bpb.fat_length ? bpb.fat_length : bpb.fat32_length;
/* Rootdir offset and length for FAT12/16 */ FAT_SUPER->root_offset = FAT_SUPER->fat_offset + bpb.num_fats * FAT_SUPER->fat_length; - FAT_SUPER->root_max = FAT_DIRENTRY_LENGTH * FAT_CVT_U16(bpb.dir_entries); + FAT_SUPER->root_max = FAT_DIRENTRY_LENGTH * bpb.dir_entries;
/* Data offset and number of clusters */ FAT_SUPER->data_offset = @@ -105,7 +105,7 @@ if (!bpb.fat_length) { /* This is a FAT32 */ - if (FAT_CVT_U16(bpb.dir_entries)) + if (bpb.dir_entries) return 0;
if (bpb.flags & 0x0080) @@ -144,8 +144,8 @@
/* Now do some sanity checks */
- if (FAT_CVT_U16(bpb.bytes_per_sect) != (1 << FAT_SUPER->sectsize_bits) - || FAT_CVT_U16(bpb.bytes_per_sect) != SECTOR_SIZE + if (bpb.bytes_per_sect != (1 << FAT_SUPER->sectsize_bits) + || bpb.bytes_per_sect != SECTOR_SIZE || bpb.sects_per_clust != (1 << (FAT_SUPER->clustsize_bits - FAT_SUPER->sectsize_bits)) || FAT_SUPER->num_clust <= 2