The way we load the Linux and PE/COFF image headers depends on a fixed
placement of the COFF header at offset 0x40 into the file. This is
a reasonable default, given that this is where Linux emits it today.
However, in order to comply with the PE/COFF spec, which allows this
header to appear anywhere in the file, let's ensure that we read the
header from where it actually appears in the file if it is not located
at offset 0x40.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Xen has its own version of the image header, to account for the
additional PE/COFF header fields. Since we are adding references to
those in the shared EFI loader code, update the common definitions
and drop the Xen specific one which no longer has a purpose.
Since in both cases, the call to grub_arch_efi_linux_check_image() is
preceded by a load of the image header, let's move the load into that
function, and rename it to grub_arch_efi_linux_load_image_header().
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
The PE/COFF spec permits the COFF signature and file header to appear
anywhere in the file, and the actual offset is recorded in 4 byte
little endian field at offset 0x3c of the image.
When GRUB is emitted as a PE/COFF binary, we reuse the 128 byte MS-DOS
stub (even for non-x86 architectures), putting the COFF signature and
file header at offset 0x80. However, other PE/COFF images may use
different values, and non-x86 Linux kernels use an offset of 0x40
instead.
So let's get rid of the grub_pe32_header struct from pe32.h, given that
it does not represent anything defined by the PE/COFF spec. Instead,
introduce a minimal struct grub_msdos_image_header type based on the
PE/COFF spec's description of the image header, and use the offset
recorded at file position 0x3c to discover the actual location of the PE
signature and the COFF image header.
The remaining fields are moved into a struct grub_pe_image_header,
which we will use later to access COFF header fields of arbitrary
images (and which may therefore appear at different offsets)
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
The "ARM\x64" magic number in the file header identifies an image as one
that implements the bare metal boot protocol, allowing the loader to
simply move the file to a suitably aligned address in memory, with
sufficient headroom for the trailing .bss segment (the required memory
size is described in the header as well).
Note of this matters for GRUB, as it only supports EFI boot. EFI does
not care about this magic number, and nor should GRUB: this prevents us
from booting other PE linux images, such as the generic EFI zboot
decompressor, which is a pure PE/COFF image, and does not implement the
bare metal boot protocol.
So drop the magic number check.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Ard Biesheuvel