The definition of bpb's num_total_sectors_16 and num_total_sectors_32
is that either the 16-bit field is non-zero and is used (in which case
eg mkfs.fat sets the 32-bit field to zero), or it is zero and the
32-bit field is used. Therefore, a BPB is invalid only if *both*
fields are zero; having one field as zero and the other as non-zero is
the case to be expected. (Indeed, according to Microsoft's specification
one of the fields *must* be zero, and the other non-zero.)
This affects all users of grub_chainloader_patch_bpb which are in
chainloader.c, freedos.c, and ntldr.c
Some descriptions of the semantics of these two fields:
https://www.win.tue.nl/~aeb/linux/fs/fat/fat-1.html
The old 2-byte fields "total number of sectors" and "number of
sectors per FAT" are now zero; this information is now found in
the new 4-byte fields.
(Here given in the FAT32 EBPB section but the total sectors 16/32 bit
fields semantic is true of FAT12 and FAT16 too.)
https://wiki.osdev.org/FAT#BPB_.28BIOS_Parameter_Block.29
19 | 2 | The total sectors in the logical volume. If this value is 0,
it means there are more than 65535 sectors in the volume, and the actual
count is stored in "Large Sectors (bytes 32-35).
32 | 4 | Large amount of sector on media. This field is set if there
are more than 65535 sectors in the volume.
(Doesn't specify what the "large" field is set to when unused, but as
mentioned mkfs.fat sets it to zero then.)
https://technet.microsoft.com/en-us/library/cc976796.aspx
0x13 | WORD | 0x0000 |
Small Sectors . The number of sectors on the volume represented in 16
bits (< 65,536). For volumes larger than 65,536 sectors, this field
has a value of zero and the Large Sectors field is used instead.
0x20 | DWORD | 0x01F03E00 |
Large Sectors . If the value of the Small Sectors field is zero, this
field contains the total number of sectors in the FAT16 volume. If the
value of the Small Sectors field is not zero, the value of this field
is zero.
https://staff.washington.edu/dittrich/misc/fatgen103.pdf page 10
BPB_TotSec16 | 19 | 2 |
This field is the old 16-bit total count of sectors on the volume.
This count includes the count of all sectors in all four regions of the
volume. This field can be 0; if it is 0, then BPB_TotSec32 must be
non-zero. For FAT32 volumes, this field must be 0. For FAT12 and
FAT16 volumes, this field contains the sector count, and
BPB_TotSec32 is 0 if the total sector count “fits” (is less than
0x10000).
BPB_TotSec32 | 32 | 4 |
This field is the new 32-bit total count of sectors on the volume.
This count includes the count of all sectors in all four regions of the
volume. This field can be 0; if it is 0, then BPB_TotSec16 must be
non-zero. For FAT32 volumes, this field must be non-zero. For
FAT12/FAT16 volumes, this field contains the sector count if
BPB_TotSec16 is 0 (count is greater than or equal to 0x10000).
(This specifies that an unused BPB_TotSec32 field is set to zero.)
By the way fix offsets in include/grub/fat.h.
Tested with lDebug booted in qemu via grub2's
FreeDOS direct loading support, refer to
https://bitbucket.org/ecm/ldosboot + https://bitbucket.org/ecm/ldebug
Signed-off-by: C. Masloch <pushbx@38.de>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
struct ... foo = { 0, } is valid initializer, but older GCC emits
warning which is fatal error due to -Werror=missing-field-initializer.
So simply use full initializer to avoid these errors. This was fixed
probably in GCC 4.7.
See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=36750
Currently, if "linux" fails, the "goto fail;" in grub_cmd_initrd sends us
into grub_initrd_close() without grub_initrd_init() being called, and thus
it never clears initrd_ctx->components. grub_initrd_close() then frees that
address, which is stale data from the stack. If the stack happens to have a
stale *address* there that matches a recent allocation, then you'll get a
double free later.
So initialize the memory up front.
Signed-off-by: Peter Jones <pjones@redhat.com>
* include/grub/i386/relocator.h (grub_relocator16_state):
New member ebp.
* grub-core/lib/i386/relocator.c (grub_relocator16_ebp): New extern
variable.
(grub_relocator16_boot): Handle %ebp.
* grub-core/lib/i386/relocator16.S: Likewise.
* grub-core/loader/i386/pc/freedos.c:
Load BPB to pass kernel which partition to load from.
Check that kernel file is not too large.
Set register dl to BIOS unit number as well.
with DMA.
* grub-core/commands/boot.c (grub_loader_noreturn): Rename to ...
(grub_loader_flags): ... this. All users updated.
(grub_loader_boot): Check for GRUB_LOADER_FLAG_NORETURN.
* grub-core/loader/i386/pc/pxechainloader.c (grub_cmd_pxechain): Mark
loader as GRUB_LOADER_FLAG_PXE_NOT_UNLOAD.
* grub-core/net/drivers/i386/pc/pxe.c (grub_pxe_shutdown): New
function.
(grub_pxe_restore): Likewise.
(fini_hnd): New var.
(GRUB_MOD_INIT): Register shutdown hook.
(GRUB_MOD_FINI): Shutdown and unregister shutdown hook.
* include/grub/loader.h (GRUB_LOADER_FLAG_NORETURN): New const.
(GRUB_LOADER_FLAG_PXE_NOT_UNLOAD): Likewise.
(grub_loader_set): Rename second argument to flags.
* grub-core/loader/i386/pc/pxechainloader.c: New file.
* grub-core/net/drivers/i386/pc/pxe.c (grub_pxe_get_cached): New
function.
(grub_pc_net_config_real): Use grub_pxe_get_cached.
* include/grub/i386/pc/pxe.h (grub_pxe_get_cached): New proto.
(grub_fat_bpb): Moved to ...
* include/grub/fat.h (grub_fat_bpb): ... here. New file.
* grub-core/loader/i386/pc/chainloader.c: Include grub/fat.h and
grub/ntfs.h.
* include/grub/i386/pc/chainloader.h (grub_chainloader_flags_t):
Moved from here...
* grub-core/loader/i386/pc/chainloader.c (grub_chainloader_flags_t): ...
here.
* grub-core/loader/i386/pc/chainloader.c (grub_chainloader_patch_bpb):
New function.
(grub_chainloader_cmd): Patch BPB if --bpb is given.
(GRUB_MOD_INIT): Show --bpb.
* grub-core/loader/i386/pc/ntldr.c (grub_cmd_ntldr): Patch BPB.
* grub-core/normal/main.c (features): New variable.
(GRUB_MOD_INIT): Set feature_* variables.
* include/grub/i386/pc/chainloader.h (grub_chainloader_patch_bpb): New
proto.
* include/grub/ntfs.h (grub_ntfs_bpb): New field bios_drive.
* grub-core/loader/i386/linux.c (GRUB_LINUX_CL_END_OFFSET): Removed.
(maximal_cmdline_size): New variable.
(allocate_pages): Use maximal_cmdline_size.
(grub_cmd_linux): Set and use maximal_cmdline_size.
* grub-core/loader/i386/pc/linux.c (GRUB_LINUX_CL_END_OFFSET): Removed.
(allocate_pages): Use maximal_cmdline_size.
(grub_cmd_linux): Set and use maximal_cmdline_size.
* include/grub/i386/linux.h (GRUB_LINUX_SETUP_MOVE_SIZE): Removed.
(linux_kernel_header): Add fields kernel_alignment, relocatable, pad
and cmdline_size.
