The virtual filesystem that we provide to expose downloaded images
will erroneously interpret filenames with redundant path separators
such as ".\filename" as an attempt to open the directory, rather than
an attempt to open "filename".
This shows up most obviously when chainloading from one iPXE into
another iPXE, when the inner iPXE may end up attempting to open
".\autoexec.ipxe" from the outer iPXE's virtual filesystem. (The
erroneously opened file will have a zero length and will therefore be
ignored, but is still confusing.)
Fix by discarding any dot or backslash characters after a potential
initial backslash. This is very liberal and will accept some
syntactically invalid paths, but this is acceptable since our virtual
filesystem does not implement directories anyway.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
iPXE allows individual raw files to be automatically wrapped with
suitable CPIO headers and injected into the magic initrd image as
exposed to a booted Linux kernel. This feature is currently limited
to placing files within directories that already exist in the initrd
filesystem.
Remove this limitation by adding the ability for iPXE to construct
CPIO headers for parent directories as needed, under control of the
"mkdir=<n>" command-line argument. For example:
initrd config.ign /usr/share/oem/config.ign mkdir=1
will create CPIO headers for the "/usr/share/oem" directory as well as
for the "/usr/share/oem/config.ign" file itself.
This simplifies the process of booting operating systems such as
Flatcar Linux, which otherwise require the single "config.ign" file to
be manually wrapped up as a CPIO archive solely in order to create the
relevant parent directory entries.
The value <n> may be used to control the number of parent directory
entries that are created. For example, "mkdir=2" would cause up to
two parent directories to be created (i.e. "/usr/share" and
"/usr/share/oem" in the above example). A negative value such as
"mkdir=-1" may be used to create all parent directories up to the root
of the tree.
Do not create any parent directory entries by default, since doing so
would potentially cause the modes and ownership information for
existing directories to be overwritten.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Most image flags are independent values: any combination of flags may
be set for any image, and the flags for one image are independent of
the flags for any other image. The "selected" flag does not follow
this pattern: at most one image may be marked as selected at any time.
When invoking a kernel via the UEFI shim, there will be multiple
"special" images: the selected kernel itself, the shim image, and
potentially a shim-signed GRUB binary to be used as a crutch to assist
shim in loading the kernel (since current versions of the UEFI shim
are not capable of directly loading a Linux kernel).
Remove the "selected" image flag and replace it with a general concept
of an image tag with the same semantics: a given tag may be assigned
to at most one image, an image may be found by its tag only while the
image is currently registered, and a tag will survive unregistration
and reregistration of an image (if it has not already been assigned to
a new image). For visual consistency, also replace the current image
pointer with a current image tag.
The image pointer stored within the image tag holds only a weak
reference to the image, since the selection of an image should not
prevent that image from being freed. (The strong reference to the
currently executing image is held locally within the execution scope
of image_exec(), and is logically separate from the current image
pointer.)
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Versions 15.4 and earlier of the UEFI shim are incapable of correctly
parsing the command line in order to extract the second stage loader
filename, and will always attempt to load "grubx64.efi" or equivalent.
Versions 15.3 and later of the UEFI shim are currently incapable of
loading a Linux kernel directly anyway, since the kernel does not
include SBAT metadata. These versions will require a genuine
shim-signed GRUB binary to be used as a crutch to assist shim in
loading a Linux kernel.
This leaves versions 15.2 and earlier of the UEFI shim (as currently
used in e.g. RHEL7) as being capable of directly loading a Linux
kernel, but incorrectly attempting to load it using the filename
"grubx64.efi" or equivalent. To support the bugs in these older
versions of the UEFI shim, allow the currently selected image to be
opened via any filename of the form "grub*.efi".
Signed-off-by: Michael Brown <mcb30@ipxe.org>
When invoking a kernel via the UEFI shim, the kernel (and potentially
also a helper binary such as GRUB) must be accessible via the virtual
filesystem exposed via EFI_SIMPLE_FILE_SYSTEM_PROTOCOL but must not be
present in the magic initrd constructed from all registered images.
Allow for images to be flagged as hidden, which will cause them to be
excluded from API-level lists of all images such as the virtual
filesystem directory contents, the magic initrd, or the Multiboot
module list. Hidden images remain visible to iPXE commands including
"imgstat", which will show a "[HIDDEN]" flag for such images.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Show the original filename as used by the consumer when calling our
EFI_SIMPLE_FILE_SYSTEM_PROTOCOL's Open() method.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Try searching for a matching registered image before checking for
fixed filenames (such as "initrd.magic" for the dynamically generated
magic initrd file). This minimises surprise by ensuring that an
explicitly downloaded image will always be used verbatim.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
As documented in commits 6a004be ("[efi] Support the initrd
autodetection mechanism in newer Linux kernels") and 04e60a2 ("[efi]
Omit EFI_LOAD_FILE2_PROTOCOL for a zero-length initrd"), the choice in
Linux of using a fixed device path requires bootloaders to allow for
the fact that a previous bootloader may have already installed a
handle with the fixed device path.
We currently deal with this situation by reusing the existing handle,
replacing the EFI_LOAD_FILE2_PROTOCOL instance with our own. Simplify
the code by instead uninstalling the EFI_DEVICE_PATH_PROTOCOL instance
from the existing handle (if present), thereby allowing the creation
of a new handle to succeed.
Create the new handle only if we have a non-empty initrd to provide.
This works around bugs in bootloaders such as the systemd EFI stub
that fail to allow for the existence of multiple-bootloader chains.
(The workaround is not comprehensive: if the user has downloaded other
images in iPXE before invoking the systemd Unified Kernel Image (UKI),
then the systemd EFI stub will still crash and burn since it fails to
allow for the fact that a previous bootloader has already installed a
handle with the fixed device path.)
Signed-off-by: Michael Brown <mcb30@ipxe.org>
We unregister script images during their execution, to prevent a
"boot" command from re-executing the containing script. This also has
the side effect of preventing executing scripts from showing up within
the Linux magic initrd image (or the Multiboot module list).
Additional logic in bzimage.c and efi_file.c prevents a currently
executing kernel from showing up within the magic initrd image.
Similar logic in multiboot.c prevents the Multiboot kernel from
showing up as a Multiboot module.
This still leaves some corner cases that are not covered correctly.
For example: when using a gzip-compressed kernel image, nothing will
currently hide the original compressed image from the magic initrd.
Fix by moving the logic that temporarily unregisters the current image
from script_exec() to image_exec(), so that it applies to all image
types, and simplify the magic initrd and Multiboot module list
construction logic on the basis that no further filtering of the
registered image list is necessary.
This change has the side effect of hiding currently executing EFI
images from the virtual filesystem exposed by iPXE. For example, when
using iPXE to boot wimboot, the wimboot binary itself will no longer
be visible within the virtual filesystem.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
When the Linux kernel is being used with no initrd, iPXE will still
provide a zero-length initrd.magic file within the virtual filesystem.
As of commit 6a004be ("[efi] Support the initrd autodetection
mechanism in newer Linux kernels"), this zero-length file will also be
exposed via an EFI_LOAD_FILE2_PROTOCOL instance on a handle with a
fixed device path.
The correct handling of zero-length files via EFI_LOAD_FILE2_PROTOCOL
is unfortunately not well defined.
Linux expects the first call to LoadFile() to always fail with
EFI_BUFFER_TOO_SMALL. When the initrd is genuinely zero-length, iPXE
will return success since the buffer is not too small to hold the
(zero-length) file. This causes Linux to immediately report a
spurious EFI_LOAD_ERROR boot failure.
We could change the logic in iPXE's efi_file_load() to always return
EFI_BUFFER_TOO_SMALL if Buffer is NULL on entry. Since the correct
behaviour of LoadFile() in the corner case of a zero-length file is
left undefined by the UEFI specification, this would be permissible.
Unfortunately this approach would not fix the problem. If we return
EFI_BUFFER_TOO_SMALL and set the file length to zero, then Linux will
call the boot services AllocatePages() method with a zero length. In
at least the EDK2 implementation, this combination of parameters will
cause AllocatePages() to return EFI_OUT_OF_RESOURCES, and Linux will
again report a boot failure.
Another approach would be to install the initrd device path handle
only if we have a non-empty initrd to offer. Unfortunately this would
lead to a failure in yet another corner case: if a previous bootloader
has installed an initrd device path handle (e.g. to pass a boot script
to iPXE) then we must not leave that initrd in place, since then our
loaded kernel would end up seeing the wrong initrd content.
The cleanest fix seems to be to ensure that the initrd device path
handle is installed with the EFI_DEVICE_PATH_PROTOCOL instance present
but with the EFI_LOAD_FILE2_PROTOCOL instance absent (and forcibly
uninstalled if necessary), matching the state in which we leave the
handle after uninstalling our virtual filesystem. Linux will then not
find any handle that supports EFI_LOAD_FILE2_PROTOCOL within the fixed
device path, and so will fall through to trying other mechanisms to
locate the initrd.
Reported-by: Chris Bradshaw <cwbshaw@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Linux 5.7 added the ability to autodetect an initrd by searching for a
handle via a fixed vendor-specific "Linux initrd device path" and then
locating and using the EFI_LOAD_FILE2_PROTOCOL instance on that
handle.
This maps quite naturally onto our existing concept of a "magic
initrd" as introduced for EFI in commit e5f0255 ("[efi] Provide an
"initrd.magic" file for use by UEFI kernels").
Add an EFI_LOAD_FILE2_PROTOCOL instance to our EFI virtual files
(backed by simply calling the existing EFI_SIMPLE_FILE_SYSTEM_PROTOCOL
method to read from the file), and install the protocol instance for
the "initrd.magic" virtual file onto a new device handle that also
provides the Linux initrd device path.
The design choice in Linux of using a single fixed device path makes
this unfortunately messy to support, since device paths must be unique
within a system. When multiple bootloaders are used (e.g. GRUB
loading iPXE loading Linux) then only one bootloader can ever install
the device path onto a handle. Subsequent bootloaders must locate the
existing handle and replace the load file protocol instance with their
own.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Show the requested range when a caller reads from a virtual file via
the EFI_SIMPLE_FILE_SYSTEM_PROTOCOL interface.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Provide a file "initrd.magic" via the EFI_SIMPLE_FILE_SYSTEM_PROTOCOL
that contains the initrd file as constructed for BIOS bzImage kernels
(including injected files with CPIO headers constructed by iPXE).
This allows BIOS and UEFI kernels to obtain the exact same initramfs
image, by adding "initrd=initrd.magic" to the kernel command line.
For example:
#!ipxe
kernel boot/vmlinuz initrd=initrd.magic
initrd boot/initrd.img
initrd boot/modules/e1000.ko /lib/modules/e1000.ko
initrd boot/modules/af_packet.ko /lib/modules/af_packet.ko
boot
Do not include the "initrd.magic" file within the root directory
listing, since doing so would break software such as wimboot that
processes all files within the root directory.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Restructure the EFI_SIMPLE_FILE_SYSTEM_PROTOCOL implementation to
allow for the existence of virtual files that are not simply backed by
a single underlying image.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Dump the existing openers of a protocol whenever we are unable to open
a protocol using attributes of BY_DEVICE, EXCLUSIVE, or
BY_CHILD_CONTROLLER.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
efi_file_install() and efi_download_install() are both used to install
onto existing handles. There is therefore no need to allow for each
of their calls to InstallMultipleProtocolInterfaces() to create a new
handle.
By passing the handle directly (rather than a pointer to the handle),
we avoid potential confusion (and erroneous debug message colours).
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The EFI FAT filesystem driver has a bug: if a block device contains no
FAT filesystem but does have an EFI_SIMPLE_FILE_SYSTEM_PROTOCOL
instance, the FAT driver will assume that it must have previously
installed the EFI_SIMPLE_FILE_SYSTEM_PROTOCOL. This causes the FAT
driver to claim control of our device, and to refuse to stop driving
it, which prevents us from later uninstalling correctly.
Work around this bug by opening the disk I/O protocol ourselves,
thereby preventing the FAT driver from opening it.
Note that the alternative approach of opening the block I/O protocol
(and thereby in theory preventing DiskIo from attaching to the block
I/O protocol) causes an endless loop of calls to our DRIVER_STOP
method when starting the EFI shell. I have no idea why this is.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Exploit the redefinition of iPXE error codes to include a "platform
error code" to allow for meaningful conversion of EFI_STATUS values to
iPXE errors and vice versa.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Expose iPXE's images as a UEFI file system, allowing the booted image
to access all images downloaded by iPXE.
This functionality is complementary to the custom iPXE download
protocol. The iPXE download protocol allows a booted image to utilise
iPXE to download arbitrary URIs, but requires the booted image to
specifically support the custom iPXE download protocol. The new
functionality limits the booted image to accessing only files that
were already downloaded by iPXE (e.g. as part of a script), but can
work with any generic UEFI image (e.g. the UEFI shell). Both
protocols are provided simultaneously, and are attached to the SNP
device handle.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown