Use image_replace() to transfer execution to the extracted image,
rather than calling image_exec() directly. This allows the original
archive image to be freed immediately if it was marked as an
automatically freeable image (e.g. via "chain --autofree").
In particular, this ensures that in the case of an archive image
containing another archive image (such as an EFI zboot kernel wrapper
image containing a gzip-compressed kernel image), the intermediate
extracted image will be freed as early as possible, since extracted
images are always marked as automatically freeable.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
An extracted image is wholly derived from the original archive image.
If the original archive image has been verified and marked as trusted,
then this trust logically extends to any image extracted from it.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Provide image_extract_exec() as a helper method to allow single-member
archive images (such as gzip compressed images) to be executed without
an explicit "imgextract" step.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Add the concept of extracting an image from an archive (which could be
a single-file archive such as a gzip-compressed file), along with an
"imgextract" command to expose this functionality to scripts.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
