@@ -528,6 +528,66 @@ The physical address to which the boot loader should jump in order to
start running the operating system.
@end table
+@subsection EFI i386 entry address tag of Multiboot2 header
+
+@example
+@group
+ +-------------------+
+u16 | type = 8 |
+u16 | flags |
+u32 | size |
+u32 | entry_addr |
+ +-------------------+
+@end group
+@end example
+
+All of the address fields in this tag are physical addresses.
+The meaning of each is as follows:
+
+@table @code
+
+@item entry_addr
+The physical address to which the boot loader should jump in order to
+start running EFI i386 compatible operating system code.
+@end table
+
+This tag is taken into account only on EFI i386 platforms
+when Multiboot2 image header contains EFI boot services tag.
+Then entry point specified in ELF header and the entry address
+tag of Multiboot2 header are ignored.
+
+@subsection EFI amd64 entry address tag of Multiboot2 header
+
+@example
+@group
+ +-------------------+
+u16 | type = 9 |
+u16 | flags |
+u32 | size |
+u32 | entry_addr |
+ +-------------------+
+@end group
+@end example
+
+All of the address fields in this tag are physical addresses (paging
+mode is enabled and any memory space defined by the UEFI memory map
+is identity mapped, hence, virtual address equals physical address;
+Unified Extensible Firmware Interface Specification, Version 2.6,
+section 2.3.4, x64 Platforms, boot services). The meaning of each
+is as follows:
+
+@table @code
+
+@item entry_addr
+The physical address to which the boot loader should jump in order to
+start running EFI amd64 compatible operating system code.
+@end table
+
+This tag is taken into account only on EFI amd64 platforms
+when Multiboot2 image header contains EFI boot services tag.
+Then entry point specified in ELF header and the entry address
+tag of Multiboot2 header are ignored.
+
@node Console header tags
@subsection Flags tag
@@ -708,6 +768,70 @@ The OS image must leave interrupts disabled until it sets up its own
On EFI system boot services must be terminated.
+@section EFI i386 machine state with boot services enabled
+
+When the boot loader invokes the 32-bit operating system on EFI i386
+platform and EFI boot services tag together with EFI i386 entry address
+tag are present in the image Multiboot2 header, the machine must have the
+following state:
+
+@table @samp
+@item EAX
+Must contain the magic value @samp{0x36d76289}; the presence of this
+value indicates to the operating system that it was loaded by a
+Multiboot2-compliant boot loader (e.g. as opposed to another type of
+boot loader that the operating system can also be loaded from).
+
+@item EBX
+Must contain the 32-bit physical address of the Multiboot2
+information structure provided by the boot loader (@pxref{Boot
+information format}).
+@end table
+
+All other processor registers, flag bits and state are set accordingly
+to Unified Extensible Firmware Interface Specification, Version 2.6,
+section 2.3.2, IA-32 Platforms, boot services.
+
+@section EFI amd64 machine state with boot services enabled
+
+When the boot loader invokes the 64-bit operating system on EFI amd64
+platform and EFI boot services tag together with EFI amd64 entry address
+tag are present in the image Multiboot2 header, the machine must have the
+following state:
+
+@table @samp
+@item EAX
+Must contain the magic value @samp{0x36d76289}; the presence of this
+value indicates to the operating system that it was loaded by a
+Multiboot2-compliant boot loader (e.g. as opposed to another type of
+boot loader that the operating system can also be loaded from).
+
+@item EBX
+Must contain the 64-bit physical address (paging mode is enabled and any
+memory space defined by the UEFI memory map is identity mapped, hence,
+virtual address equals physical address; Unified Extensible Firmware
+Interface Specification, Version 2.6, section 2.3.4, x64 Platforms, boot
+services) of the Multiboot2 information structure provided by the boot
+loader (@pxref{Boot information format}).
+@end table
+
+All other processor registers, flag bits and state are set accordingly
+to Unified Extensible Firmware Interface Specification, Version 2.6,
+section 2.3.4, x64 Platforms, boot services.
+
+The bootloader must not load any part of the kernel, the modules, the Multiboot2
+information structure, etc. higher than 4 GiB - 1. This requirement is put in
+force because most of currently specified tags supports 32-bit addresses only.
+Additionally, some kernels, even if they run on EFI 64-bit platform, still
+execute some parts of its initialization code in 32-bit mode.
+
+Note: If at some point there is a need for full 64-bit mode support in Multiboot2
+protocol then it should be designed very carefully. Especially it should be taken
+into account that 32-bit and 64-bit mode code should coexist in an image without
+any issue. The image should have a chance to inform the bootloader that it supports
+full 64-bit mode. If it is the case then the bootloader should provide 64-bit tags
+if it is desired and possible. Otherwise 32-bit tags should be used.
+
@node Boot information format
@section Boot information
@subsection Boot information format
@@ -69,6 +69,8 @@
#define MULTIBOOT_HEADER_TAG_FRAMEBUFFER 5
#define MULTIBOOT_HEADER_TAG_MODULE_ALIGN 6
#define MULTIBOOT_HEADER_TAG_EFI_BS 7
+#define MULTIBOOT_HEADER_TAG_ENTRY_ADDRESS_EFI32 8
+#define MULTIBOOT_HEADER_TAG_ENTRY_ADDRESS_EFI64 9
#define MULTIBOOT_ARCHITECTURE_I386 0
#define MULTIBOOT_ARCHITECTURE_MIPS32 4
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com> --- v3 - suggestions/fixes: - replace u_virt with u32 (suggested by Andrei Borzenkov and Toomas Soome), - change RAX/RBX to EAX/EBX in "EFI amd64 machine state with boot services enabled" section, - describe the kernel, the modules, etc. load addresses limitation in "EFI amd64 machine state with boot services enabled" section, - replace Multiboot-compliant with Multiboot2-compliant. v2 - suggestions/fixes: - clarify physical address meaning for EFI amd64 mode with boot services enabled (suggested by Andrew Cooper). --- doc/multiboot.texi | 124 ++++++++++++++++++++++++++++++++++++++++++++++++++++ doc/multiboot2.h | 2 + 2 files changed, 126 insertions(+)