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>
* grub-core/loader/i386/multiboot_mbi.c (grub_multiboot_get_mbi_size):
Take VBE info into account even if only text is supported.
(fill_vbe_info): Take into account the case when only VGA text
is supported.
* include/grub/multiboot.h (GRUB_MACHINE_HAS_VBE): Set to zero
on coreboot, multiboot and qemu.
* grub-core/loader/multiboot_mbi2.c (grub_multiboot_load): Declare
new tags as supported.
(acpiv2_size): New function.
(grub_multiboot_get_mbi_size): Take new tags into account.
(grub_multiboot_make_mbi): Add new tags.
* include/grub/multiboot.h (GRUB_MACHINE_HAS_ACPI): New definition.
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/grub/multiboot.h (struct grub_multiboot_header): Move
from here ...
* include/multiboot.h (struct multiboot_header): ... to here. Update
all users.
* include/grub/multiboot.h (struct grub_multiboot_info): Move
from here ...
* include/multiboot.h (struct multiboot_info): ... to here. Update
all users.
* include/grub/multiboot.h (struct grub_multiboot_mmap_entry): Move
from here ...
* include/multiboot.h (struct multiboot_mmap_entry): ... to here.
Update all users.
* include/grub/multiboot.h (struct grub_mod_list): Move
from here ...
* include/multiboot.h (struct multiboot_mod_list): ... to here.
Update all users.
* conf/i386-pc.rmk (kernel_img_SOURCES): Add `kern/i386/pc/mmap.c'.
* include/grub/i386/pc/init.h (GRUB_MACHINE_MEMORY_AVAILABLE)
(GRUB_MACHINE_MEMORY_RESERVED): New macros.
(grub_machine_mmap_iterate): New function declaration.
* include/grub/multiboot.h (struct grub_multiboot_mmap_entry): New
structure.
(GRUB_MMAP_MEMORY_AVAILABLE, GRUB_MMAP_MEMORY_RESERVED): New
macros.
* kern/i386/pc/init.c (grub_machine_init): Replace hardcoded region
type check value with `GRUB_MACHINE_MEMORY_AVAILABLE'.
Move e820 parsing from here ...
* kern/i386/pc/mmap.c: New file.
(grub_machine_mmap_iterate): ... to here.
* include/grub/i386/coreboot/memory.h: Remove `<grub/err.h>'.
(GRUB_LINUXBIOS_MEMORY_AVAILABLE): Rename (for consistency) to ...
(GRUB_MACHINE_MEMORY_AVAILABLE): ... this. Update all users.
(grub_available_iterate): Redeclare to return `void', and redeclare
its hook to use grub_uint64_t as addr and size parameters, and rename
to ...
(grub_machine_mmap_iterate): ... this. Update all users.
* kern/i386/coreboot/mmap.c (grub_mmap_iterate): Simplify parser loop
to make it more readable. Rename to ...
(grub_machine_mmap_iterate): ... this.
* loader/i386/pc/multiboot.c (mmap_addr, mmap_length): New variables.
(grub_get_multiboot_mmap_len, grub_fill_multiboot_mmap): New functions.
(grub_multiboot): Allocate an extra region after the payload, and fill
it with a Multiboot memory map. Adjust a.out loader to calculate size
with the extra space.
(grub_multiboot_load_elf32): Adjust elf32 loader to calculate size
with the extra space.
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.
