The RISC-V ABI document outlines ELF header structure and relocation
information. Pull the respective magic numbers into our elf header
so we can make use of them.
Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
The PE format defines magic numbers as well as relocation identifiers for
RISC-V. Add them to our include file, so we can make use of them.
Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Some architectures want to boot Linux as plain UEFI binary. Today that
really only encompasses ARM and AArch64, but going forward more
architectures may adopt that model.
So rename our internal API accordingly.
Signed-off-by: Alexander Graf <agraf@suse.de>
Acked-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
There are a few spots in the PE generation code for EFI binaries that uses
the section alignment rather than file alignment, even though the alignment
is really only file bound.
Replace those cases with the file alignment constant instead.
Reported-by: Daniel Kiper <dkiper@net-space.pl>
Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Julien ROBIN <julien.robin28@free.fr>
There is UEFI firmware popping up in the wild now that implements stricter
permission checks using NX and write protect page table entry bits.
This means that firmware now may fail to load binaries if its individual
sections are not page aligned, as otherwise it can not ensure permission
boundaries.
So let's bump all efi section alignments up to 4k (EFI page size). That way
we will stay compatible going forward.
Unfortunately our internals can't deal very well with a mismatch of alignment
between the virtual and file offsets, so we have to also pad our target
binary a bit.
Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Julien ROBIN <julien.robin28@free.fr>
The efi-arm case was defining its own header size calculation, even though it's
100% identical to the common EFI32_HEADER_SIZE definition.
So let's clean it up to use the common define.
Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Julien ROBIN <julien.robin28@free.fr>
This patch allows to have bigger kernels. If the kernel grows, then it will
overwrite the initrd when it is extracted.
Signed-off-by: Guillaume GARDET <guillaume.gardet@arm.com>
Acked-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
A certain amount of dynamic space is required for the handover from
GRUB/Linux-EFI-stub. This entails things like initrd addresses,
address-cells entries and associated strings.
But move this into a proper centralised #define rather than live-code
it in the loader.
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
uboot_disk_write() is currently lacking the write support
to storage devices because, historically, those devices did not
implement block_write() in U-Boot.
The solution has been tested using a patched U-Boot loading
and booting GRUB in a QEMU vexpress-a9 environment.
The disk write operations were triggered with GRUB's save_env
command.
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
The value of tpm_handle changes between successive calls to grub_tpm_handle_find(),
as instead of simply copying the stored pointer we end up taking the address of
said pointer when using the cached value of grub_tpm_handle.
This causes grub_efi_open_protocol() to return a nullptr in grub_tpm2_execute()
and grub_tpm2_log_event(). Said nullptr goes unchecked and
efi_call_5(tpm->hash_log_extend_event,...) ends up jumping to 0x0, Qemu crashes
once video ROM is reached at 0xb0000.
This patch seems to do the trick of fixing that bug, but we should also ensure
that all calls to grub_efi_open_protocol() are checked so that we don't start
executing low memory.
Signed-off-by: Max Tottenham <mtottenh@akamai.com>
Reviewed-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Commit b07feb8746 (verifiers: Rename
verify module to pgp module) renamed the "verify" module to "pgp", but
the GRUB_MOD_INIT and GRUB_MOD_FINI macros were left as "verify", which
broke the emu target build; and file_filter_test still referred to the
now non-existent "verify" module. Fix both of these.
Signed-off-by: Colin Watson <cjwatson@ubuntu.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Add support for multiple, shared, early initrd images. These early
images will be loaded in the order declared, and all will be loaded
before the initrd image.
While many classes of data can be provided by early images, the
immediate use case would be for distributions to provide CPU
microcode to mitigate the Meltdown and Spectre vulnerabilities.
Xen has also support to load microcode updates provided as additional
modules by the bootloader.
There are two environment variables provided for declaring the early
images.
* GRUB_EARLY_INITRD_LINUX_STOCK is for the distribution declare
images that are provided by the distribution or installed packages.
If undeclared, this will default to a set of common microcode image
names.
* GRUB_EARLY_INITRD_LINUX_CUSTOM is for user created images. User
images will be loaded after the stock images.
These separate configurations allow the distribution and user to
declare different image sets without clobbering each other.
This also makes a minor update to ensure that UUID partition labels
stay disabled when no initrd image is found, even if early images are
present.
This is basically a copy of a698240d "grub-mkconfig/10_linux: Support
multiple early initrd images" by Matthew S. Turnbull.
Signed-off-by: Peter Große <pegro@friiks.de>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
We should not try to copy any memory area which is outside of the original
fdt. If this extra memory is controlled by a hypervisor this might end
with a crash.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Describe the behaviour of GRUB when the TPM module is in use.
Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Add support for performing basic TPM measurements. Right now this only
supports extending PCRs statically and only on UEFI. In future we might
want to have some sort of mechanism for choosing which events get logged
to which PCRs, but this seems like a good default policy and we can wait
to see whether anyone has a use case before adding more complexity.
Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Pass all commands executed by GRUB to the verifiers layer. Most verifiers will
ignore this, but some (such as the TPM verifier) want to be able to measure and
log each command executed in order to ensure that the boot state is as expected.
Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Support platform i386/xen_pvh in configure.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Add xen_pvh support to grub-install.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Support mkimage for xen_pvh.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
In order to avoid using plain integers for the ELF notes use the
available Xen include instead.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
This solves the build failing with "Error: no symbol table and no
.moddeps section"
Also see:
- 6371e9c104
- https://savannah.gnu.org/bugs/?49012
Signed-off-by: Hans van Kranenburg <hans@knorrie.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Add the modifications to the build system needed to build a xen_pvh
grub.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Add all usable memory regions to grub memory management and add the
needed mmap iterate code, which will be used by grub core (e.g.
grub-core/lib/relocator.c or grub-core/mmap/mmap.c).
As we are running in 32-bit mode don't add memory above 4GB.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Initialize the needed Xen specific data. This is:
- the Xen start of day page containing the console and Xenstore ring
page PFN and event channel
- the grant table
- the shared info page
Write back the possibly modified memory map to the hypervisor in case
the guest is reading it from there again.
Set the RSDP address for the guest from the start_info page passed
as boot parameter.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Retrieve the memory map from the hypervisor and normalize it to contain
no overlapping entries and to be sorted by address.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Add the needed code to setup the hypercall page for calling into the
Xen hypervisor.
Import the XEN_HVM_DEBUGCONS_IOPORT define from Xen unstable into
include/xen/arch-x86/xen.h
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Add the code for the Xen PVH mode boot entry.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Add the hooks to current code needed for Xen PVH. They will be filled
with code later when the related functionality is being added.
loader/i386/linux.c needs to include machine/kernel.h now as it needs
to get GRUB_KERNEL_USE_RSDP_ADDR from there. This in turn requires to
add an empty kernel.h header for some i386 platforms (efi, coreboot,
ieee1275, xen) and for x86_64 efi.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
include/grub/offsets.h needs some defines for Xen PVH mode.
Add them. While at it line up the values in the surrounding lines to
start at the same column.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
grub_xen_ptr2mfn() returns the machine frame number for a given pointer
value. For Xen-PVH guests this is just the PFN. Add the PVH specific
variant.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Rearrange grub-core/kern/xen/init.c to prepare adding PVH mode support
to it. This includes putting some code under #ifdef GRUB_MACHINE_XEN
as it will not be used when running as PVH.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
With Xen PVH mode adding a new machine type the machine related headers
need to be present for the build to succeed. Most of the headers just
need to include the related common i386 headers. Add those to the tree.
Note that xen_pvh/int.h needs to include pc/int_types.h instead of
pc/int.h in order to avoid the definition of grub_bios_interrupt().
xen_pvh/memory.h needs to include coreboot/memory.h (like some other
<machine>/memory.h do as well) as this contains just the needed stubs.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Some common code needs to be special cased for Xen PVH mode. This hits
mostly Xen PV mode specific areas.
Split include/grub/i386/pc/int_types.h off from
include/grub/i386/pc/int.h to support including this file later from
xen_pvh code without the grub_bios_interrupt definition.
Move definition of struct grub_e820_mmap_entry from
grub-core/mmap/i386/pc/mmap.c to include/grub/i386/memory.h in order
to make it usable from xen_pvh code.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Initialize the grant tab in a dedicated function. This will enable
using it for PVH guests, too.
Call the new function from grub_machine_init() as this will later
be common between Xen PV and Xen PVH mode.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Xen PVH guests will have the RSDP at an arbitrary address. Support that
by passing the RSDP address via the boot parameters to Linux.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
In order to support grub2 in Xen PVH environment some additional Xen
headers are needed as grub2 will be started in PVH mode requiring to
use several HVM hypercalls and structures.
Add the needed headers from Xen 4.10 being the first Xen version with
full (not only experimental) PVH guest support.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
ARM Xen fallout cleanup after commit ca0a4f689 (verifiers: File type for
fine-grained signature-verification controlling).
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Ross Philipson <ross.philipson@oracle.com>
Xen fallout cleanup after commit ca0a4f689 (verifiers: File type for
fine-grained signature-verification controlling).
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Ross Philipson <ross.philipson@oracle.com>
The grub_ieee1275_parse_bootpath() function (commit a661a32, ofnet: Initialize
structs in bootpath parser) introduces a build regression on SPARC:
cc1: warnings being treated as errors
net/drivers/ieee1275/ofnet.c: In function 'grub_ieee1275_parse_bootpath':
net/drivers/ieee1275/ofnet.c:156: error: missing initializer
net/drivers/ieee1275/ofnet.c:156: error: (near initialization for 'client_addr.type')
net/drivers/ieee1275/ofnet.c:156: error: missing initializer
net/drivers/ieee1275/ofnet.c:156: error: (near initialization for 'gateway_addr.type')
net/drivers/ieee1275/ofnet.c:156: error: missing initializer
net/drivers/ieee1275/ofnet.c:156: error: (near initialization for 'subnet_mask.type')
net/drivers/ieee1275/ofnet.c:157: error: missing initializer
net/drivers/ieee1275/ofnet.c:157: error: (near initialization for 'hw_addr.type')
make[3]: *** [net/drivers/ieee1275/ofnet_module-ofnet.o] Error 1
Initialize the entire structure.
More info can be found here:
http://lists.gnu.org/archive/html/grub-devel/2018-03/msg00034.html
Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
- Adds zstd support to the btrfs module.
- Adds a test case for btrfs zstd support.
- Changes top_srcdir to srcdir in the btrfs module's lzo include
following comments from Daniel Kiper about the zstd include.
Tested on Ubuntu-18.04 with a btrfs /boot partition with and without zstd
compression. A test case was also added to the test suite that fails before
the patch, and passes after.
Signed-off-by: Nick Terrell <terrelln@fb.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
- Import zstd-1.3.6 from upstream
- Add zstd's module.c file
- Add the zstd module to Makefile.core.def
Import zstd-1.3.6 from upstream [1]. Only the files need for decompression
are imported. I used the latest zstd release, which includes patches [2] to
build cleanly in GRUB.
I included the script used to import zstd-1.3.6 below at the bottom of the
commit message.
Upstream zstd commit hash: 4fa456d7f12f8b27bd3b2f5dfd4f46898cb31c24
Upstream zstd commit name: Merge pull request #1354 from facebook/dev
Zstd requires some posix headers, which it gets from posix_wrap.
This can be checked by inspecting the .Po files generated by automake,
which contain the header dependencies. After building run the command
`cat grub-core/lib/zstd/.deps-core/*.Po` to see the dependencies [3].
The only OS dependencies are:
- stddef.h, which is already a dependency in posix_wrap, and used for size_t
by lzo and xz.
- stdarg.h, which comes from the grub/misc.h header, and we don't use in zstd.
All the types like uint64_t are typedefed to grub_uint64_t under the hood.
The only exception is size_t, which comes from stddef.h. This is already the
case for lzo and xz. I don't think there are any cross-compilation concerns,
because cross-compilers provide their own system headers (and it would already
be broken).
[1] https://github.com/facebook/zstd/releases/tag/v1.3.6
[2] https://github.com/facebook/zstd/pull/1344
[3] https://gist.github.com/terrelln/7a16b92f5a1b3aecf980f944b4a966c4
```
curl -L -O https://github.com/facebook/zstd/releases/download/v1.3.6/zstd-1.3.6.tar.gz
curl -L -O https://github.com/facebook/zstd/releases/download/v1.3.6/zstd-1.3.6.tar.gz.sha256
sha256sum --check zstd-1.3.6.tar.gz.sha256
tar xzf zstd-1.3.6.tar.gz
SRC_LIB="zstd-1.3.6/lib"
DST_LIB="grub-core/lib/zstd"
rm -rf $DST_LIB
mkdir -p $DST_LIB
cp $SRC_LIB/zstd.h $DST_LIB/
cp $SRC_LIB/common/*.[hc] $DST_LIB/
cp $SRC_LIB/decompress/*.[hc] $DST_LIB/
rm $DST_LIB/{pool.[hc],threading.[hc]}
rm -rf zstd-1.3.6*
echo SUCCESS!
```
Signed-off-by: Nick Terrell <terrelln@fb.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
An error emerged as when I was testing the verifiers branch, so instead
of putting it in pgp prefix, the verifiers is used to reflect what the
patch is based on.
While running verify_detached, grub aborts with error.
verify_detached /@/.snapshots/1/snapshot/boot/grub/grub.cfg
/@/.snapshots/1/snapshot/boot/grub/grub.cfg.sig
alloc magic is broken at 0x7beea660: 0
Aborted. Press any key to exit.
The error is caused by sig file descriptor been closed twice, first time
in grub_verify_signature() to which it is passed as parameter. Second in
grub_cmd_verify_signature() or in whichever opens the sig file
descriptor. The second close is not consider as bug to me either, as in
common rule of what opens a file has to close it to avoid file
descriptor leakage.
After all the design of grub_verify_signature() makes it difficult to keep
a good trace on opened file descriptor from it's caller. Let's refine
the application interface to accept file path rather than descriptor, in
this way the caller doesn't have to care about closing the descriptor by
delegating it to grub_verify_signature() with full tracing to opened
file descriptor by itself.
Also making it clear that sig descriptor is not referenced in error
returning path of grub_verify_signature_init(), so it can be closed
directly by it's caller. This also makes delegating it to
grub_pubkey_close() infeasible to help in relieving file descriptor
leakage as it has to depend on uncertainty of ctxt fields in error
returning path.
Signed-off-by: Michael Chang <mchang@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
grub_file_filter_disable_compression() no longer exists.
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Without this fix, building xen_boot.c omits:
loader/arm64/xen_boot.c: In function ‘xen_boot_binary_load’:
loader/arm64/xen_boot.c:370:7: error: too few arguments to function ‘grub_create_loader_cmdline’
grub_create_loader_cmdline (argc - 1, argv + 1, binary->cmdline,
^~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from loader/arm64/xen_boot.c:36:0:
../include/grub/lib/cmdline.h:29:12: note: declared here
grub_err_t grub_create_loader_cmdline (int argc, char *argv[], char *buf,
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
The verifiers framework changed the grub_file_open() interface, breaking all
non-x86 linux loaders. Add file types to the grub_file_open() calls to make
them build again.
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
The verifiers framework changed the API of grub_file_open(), but did not
fix up all users. Add the file type GRUB_FILE_TYPE_DEVICE_TREE_IMAGE
to the "devicetree" command handler call.
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
The API change of grub_file_open() for adding verifiers did not include
a type for device tree blobs. Add GRUB_FILE_TYPE_DEVICE_TREE_IMAGE to
the grub_file_type enum.
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
verify.h was added without include guards. This means compiling anything
including both include/grub/verify.h and include/grub/lib/cmdline.h fails
(at least grub-core/loader/arm64/linux.c.
Add the necessary include guard.
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Device tree (DTB) lengths are being padded to a multiple of 4 bytes
rather than the target-specific pointer size. This causes objects
following OBJ_TYPE_DTB objects to be incorrectly parsed during GRUB
execution on arm64.
Fix by using ALIGN_ADDR(), not ALIGN_UP().
Signed-by-off: Matthew Daley <mattd@bugfuzz.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Alexander Graf