Re: [Xen-devel] [MULTIBOOT2 DOC PATCH 06/10] multiboot2: Add description of support for relocatable images

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 09/06/2016 21:30, Daniel Kiper wrote:
> Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
> ---
>  doc/multiboot.texi |   56 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  doc/multiboot2.h   |   24 ++++++++++++++++++++++
>  2 files changed, 80 insertions(+)
>
> diff --git a/doc/multiboot.texi b/doc/multiboot.texi
> index 130176a..f1e0e09 100644
> --- a/doc/multiboot.texi
> +++ b/doc/multiboot.texi
> @@ -359,6 +359,7 @@ executable header.
>  * Console header tags::
>  * Module alignment tag::
>  * EFI boot services tag::
> +* Relocatable header tag::
>  
>  @end menu
>  
> @@ -681,6 +682,47 @@ u32     | size = 8          |
>  This tag indicates that payload supports starting without
>  terminating boot services.
>  
> +@node Relocatable header tag
> +@subsection Relocatable header tag
> +
> +@example
> +@group
> +        +-------------------+
> +u16     | type = 10         |
> +u16     | flags             |
> +u32     | size = 24         |
> +u32     | min_addr          |
> +u32     | max_addr          |
> +u32     | align             |
> +u32     | preference        |
> +        +-------------------+
> +@end group
> +@end example
> +
> +This tag indicates that image is relocatable.
> +
> +The meaning of each field is as follows:
> +
> +@table @code
> +@item min_addr
> +Lowest possible physical address at which image should be loaded.
> +Boot loader cannot load any part of image below this address.

"The bootloader".

> +
> +@item max_addr
> +Highest possible physical address at which loaded image should end.
> +Boot loader cannot load any part of image above this address.

"The bootloader".

> +
> +@item align
> +Image alignment in memory, e.g. 4096 (know on many machines as page).

I would drop the qualification in brackets.  It isn't helpful to the
intended audience.

> +
> +@item preference
> +It contains load address placement suggestion for boot loader.
> +Boot loader should follow it. @samp{0} means none, @samp{1} means
> +load image at lowest possible address but not lower than min_addr
> +and @samp{2} means load image at highest possible address but not
> +higher than max_addr.
> +@end table
> +
>  @node Machine state
>  @section MIPS machine state
>  
> @@ -1309,6 +1351,20 @@ u64     | pointer           |
>  This tag contains pointer to EFI amd64 image handle.
>  Usually it is boot loader image handle.
>  
> +@subsection Image load base physical address
> +@example
> +@group
> +        +-------------------+
> +u32     | type = 21         |
> +u32     | size = 12         |
> +u32     | load_base_addr    |
> +        +-------------------+
> +@end group
> +@end example
> +
> +This tag contains image load base physical address. It is
> +provided only if image has relocatable header tag.
> +
>  @node Examples
>  @chapter Examples
>  
> diff --git a/doc/multiboot2.h b/doc/multiboot2.h
> index b85cb13..b181607 100644
> --- a/doc/multiboot2.h
> +++ b/doc/multiboot2.h
> @@ -62,6 +62,7 @@
>  #define MULTIBOOT_TAG_TYPE_EFI_BS            18
>  #define MULTIBOOT_TAG_TYPE_EFI32_IH          19
>  #define MULTIBOOT_TAG_TYPE_EFI64_IH          20
> +#define MULTIBOOT_TAG_TYPE_LOAD_BASE_ADDR    21
>  
>  #define MULTIBOOT_HEADER_TAG_END  0
>  #define MULTIBOOT_HEADER_TAG_INFORMATION_REQUEST  1
> @@ -73,11 +74,16 @@
>  #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_HEADER_TAG_RELOCATABLE  10
>  
>  #define MULTIBOOT_ARCHITECTURE_I386  0
>  #define MULTIBOOT_ARCHITECTURE_MIPS32  4
>  #define MULTIBOOT_HEADER_TAG_OPTIONAL 1
>  
> +#define MULTIBOOT_LOAD_PREFERENCE_NONE 0
> +#define MULTIBOOT_LOAD_PREFERENCE_LOW 1
> +#define MULTIBOOT_LOAD_PREFERENCE_HIGH 2
> +
>  #define MULTIBOOT_CONSOLE_FLAGS_CONSOLE_REQUIRED 1
>  #define MULTIBOOT_CONSOLE_FLAGS_EGA_TEXT_SUPPORTED 2
>  
> @@ -162,6 +168,17 @@ struct multiboot_header_tag_module_align
>    multiboot_uint32_t size;
>  };
>  
> +struct multiboot_header_tag_relocatable
> +{
> +  multiboot_uint16_t type;
> +  multiboot_uint16_t flags;
> +  multiboot_uint32_t size;
> +  multiboot_uint32_t min_addr;
> +  multiboot_uint32_t max_addr;

64bit multiboot2 payloads could reasonably expect to be able to have
themselves relocated about the 4G boundary.

~Andrew

> +  multiboot_uint32_t align;
> +  multiboot_uint32_t preference;
> +};
> +
>  struct multiboot_color
>  {
>    multiboot_uint8_t red;
> @@ -388,6 +405,13 @@ struct multiboot_tag_efi64_ih
>    multiboot_uint64_t pointer;
>  };
>  
> +struct multiboot_tag_load_base_addr
> +{
> +  multiboot_uint32_t type;
> +  multiboot_uint32_t size;
> +  multiboot_uint32_t load_base_addr;
> +};
> +
>  #endif /* ! ASM_FILE */
>  
>  #endif /* ! MULTIBOOT_HEADER */


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