Previous commits described this behaviour, but did not
actually implement it. :)

Signed-off-by: Shao Miller <shao.miller@yrdsb.edu.on.ca>

In order to consolidate the installer option-parsing system,
we add the --mbr (-m), --active (-a), and --force (-f)
options from the DOS, Win32, and mtools installers to
libinstaller.

Since the -m and -a options are not currently valid for the
Linux 'syslinux' and 'extlinux' installers, we add error
messages to both of these.  The -f option is allowed but
does nothing for them.

Signed-off-by: Shao Miller <shao.miller@yrdsb.edu.on.ca>

It appears that the glibc version of asprintf() is braindamaged, and
doesn't set the target pointer to NULL in the event of an error (only
returns -1).  Therefore we need to check the return value.  Just in
case someone else made the *opposite* error, also check the pointer.

Bleh.  The glibc documentation states that *BSD sets the pointer to
NULL, but instead of following that, the glibc people put
warn_unused_result on asprintf.  Sigh.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

If we are on a loop device, set bsHidden based on the loopback device
offset.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Put the btrfs boot code right after the boot sector (they are really
one image anyway).  Align the ADV with the end of the boot region, so
we can locate it for modification as necessary, and the offset don't
end up shifting with different boot image sizes.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Do the appropriate thing for various error cases, so that the
migration code actually does the right thing.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

- Be able to modify the ADV either in extlinux.sys or ldlinux.sys
- Be able to preserve the ADV from extlinux.sys
- Remove extlinux.sys when installing ldlinux.sys

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

modify_adv() should be used by any installer which uses the common
CLI, so it should go into syslxopt.c.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

Install an empty ADV in the Windows installer to keep it from being
broken.  In order to do that, separate the Unix-specific ADV I/O
functions from the generic data structure manipulation.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>