Currently multiboot2 protocol loads image exactly at address specified in
ELF or multiboot2 header. This solution works quite well on legacy BIOS
platforms. It is possible because memory regions are placed at predictable
addresses (though I was not able to find any spec which says that it is
strong requirement, so, it looks that it is just a goodwill of hardware
designers). However, EFI platforms are more volatile. Even if required
memory regions live at specific addresses then they are sometimes simply
not free (e.g. used by boot/runtime services on Dell PowerEdge R820 and
OVMF). This means that you are not able to just set up final image
destination on build time. You have to provide method to relocate image
contents to real load address which is usually different than load address
specified in ELF and multiboot2 headers.
This patch provides all needed machinery to do self relocation in image code.
First of all GRUB2 reads min_addr (min. load addr), max_addr (max. load addr),
align (required image alignment), preference (it says which memory regions are
preferred by image, e.g. none, low, high) from multiboot_header_tag_relocatable
header tag contained in binary (at this stage load addresses from multiboot2
and/or ELF headers are ignored). Later loader tries to fulfill request (not only
that one) and if it succeeds then it informs image about real load address via
multiboot_tag_load_base_addr tag. At this stage GRUB2 role is finished. Starting
from now executable must cope with relocations itself using whole static and
dynamic knowledge provided by boot loader.
This patch does not provide functionality which could do relocations using
ELF relocation data. However, I was asked by Konrad Rzeszutek Wilk and Vladimir
'phcoder' Serbinenko to investigate that thing. It looks that relevant machinery
could be added to existing code (including this patch) without huge effort.
Additionally, ELF relocation could live in parallel with self relocation provided
by this patch. However, during research I realized that first of all we should
establish the details how ELF relocatable image should look like and how it should
be build. At least to build proper test/example files.
So, this patch just provides support for self relocatable images. If ELF file
with relocs is loaded then GRUB2 complains loudly and ignores it. Support for
such files will be added later.
This patch was tested with Xen image which uses that functionality. However, this Xen
feature is still under development and new patchset will be released in about 2-3 weeks.
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Vladimir Serbinenko <phcoder@gmail.com>
Add tags used to pass ImageHandle to loaded image if requested.
It is used by at least ExitBootServices() function.
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Vladimir Serbinenko <phcoder@gmail.com>
Add grub_relocator64_efi relocator. It will be used on EFI 64-bit platforms
when multiboot2 compatible image requests MULTIBOOT_TAG_TYPE_EFI_BS. Relocator
will set lower parts of %rax and %rbx accordingly to multiboot2 specification.
On the other hand processor mode, just before jumping into loaded image, will
be set accordingly to Unified Extensible Firmware Interface Specification,
Version 2.4 Errata B, section 2.3.4, x64 Platforms, boot services. This way
loaded image will be able to use EFI boot services without any issues.
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Vladimir Serbinenko <phcoder@gmail.com>
Video multiboot support.
* include/grub/multiboot.h (grub_multiboot_set_accepts_video):
New prototype.
* include/multiboot.h: Resynced with multiboot specification.
* include/multiboot2.h: Likewise.
* loader/i386/multiboot.c (UNSUPPORTED_FLAGS): Support video flags.
(grub_multiboot): Parse MULTIBOOT_VIDEO_MODE fields.
* loader/i386/multiboot_mbi.c (DEFAULT_VIDEO_MODE): New constant.
(HAS_VGA_TEXT): Likewise.
(accepts_video): New variable.
(grub_multiboot_set_accepts_video): New function.
(grub_multiboot_get_mbi_size): Account for video structures.
(set_video_mode): New function.
(retrieve_video_parameters): Likewise.
(grub_multiboot_make_mbi): Fill video fields.
* include/multiboot2.h (multiboot_word): Rename from this ...
(multiboot2_word): ... to this. Update all users.
(multiboot_header): Rename from this ...
(multiboot2_header): ... to this. Update all users.
(multiboot_tag_header): Rename from this ...
(multiboot2_tag_header): ... to this. Update all users.
(multiboot_tag_start): Rename from this ...
(multiboot2_tag_start): ... to this. Update all users.
(multiboot_tag_name): Rename from this ...
(multiboot2_tag_name): ... to this. Update all users.
(multiboot_tag_module): Rename from this ...
(multiboot2_tag_module): ... to this. Update all users.
(multiboot_tag_memory): Rename from this ...
(multiboot2_tag_memory): ... to this. Update all users.
(multiboot_tag_unused): Rename from this ...
(multiboot2_tag_unused): ... to this. Update all users.
(multiboot_tag_end): Rename from this ...
(multiboot2_tag_end): ... to this. Update all users.
* include/grub/multiboot2.h: Provide compatibility defines for
multiboot2.h.
* include/multiboot2.h: Include stdint.h only if needed, using
angle brackets.
* loader/i386/pc/multiboot2.c: Include multiboot2.h after
grub/multiboot2.h.
* loader/ieee1275/multiboot2.c: Likewise.
* loader/multiboot2.c: Likewise.
* loader/multiboot_loader.c: Likewise.
* include/multiboot2.h (struct multiboot_header): Add `flags' member as
per specification.
* loader/multiboot2.c (grub_multiboot2): Fix Multiboot2 header check.
* loader/multiboot_loader.c (find_multi_boot2_header): New function
(based on find_multi_boot1_header).
(grub_rescue_cmd_multiboot_loader): Check for Multiboot2 header,
using find_multi_boot2_header(), and abort if neither Multiboot or
Multiboot headers were found.
for powerpc & i386-pc. This patch was more so started by Hollis
Blanchard getting multiboot 2 working for powerpc and I added to it
and cleaned it up.
One of the ideas with this patch is to keep everything under one
command for the user. So instead of having a "multiboot2" & "module2"
command, I created a proxy like mechanism so that you have only one
command for both multiboot 1 & 2 ... "multiboot". This is where
"loader/multiboot_loader.c" comes from. I could have integrated things
more but I figure the current approach will less likely break
anything.
So if your OS is multiboot 2 capable, the user would do the following
to load it up from a grub prompt:
grub> multiboot <location of kernel> <kernel args>
grub> module <some image> <multiboot tag> <image arguments>
grub> module <isome mage> <multiboot tag> <image arguments>
grub .....
The other thing that this patch does is it begins to make the
multiboot 1 code a bit more architecture agnostic so IF someone wanted
to implement it on another architecture they can.
A bit of file moving around and definition renaming is also apart of
this patch. I have also taken the time to make sure that it does not
break multiboot 1 loading on i386-pc. But mulitboot 2 may still need a
little more testing and work for i386-pc. Powerpc multiboot 2 has been
heavily tested and does work.
Daniel Kiper