Re: [Xen-devel] [PATCH v3 08/16] x86: add multiboot2 protocol support

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

>>> @@ -34,6 +57,42 @@ multiboot1_header_start:       /*** MULTIBOOT1 HEADER 
>>> ****/
>>>          .long   -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
>>>  multiboot1_header_end:
>>>
>>> +/*** MULTIBOOT2 HEADER ****/
>>> +/* Some ideas are taken from grub-2.00/grub-core/tests/boot/kernel-i386.S 
>>> file. */
>>> +        .align  MULTIBOOT2_HEADER_ALIGN
>>> +
>>> +multiboot2_header_start:
>>> +        /* Magic number indicating a Multiboot2 header. */
>>> +        .long   MULTIBOOT2_HEADER_MAGIC
>>> +        /* Architecture: i386. */
>>> +        .long   MULTIBOOT2_ARCHITECTURE_I386
>>> +        /* Multiboot2 header length. */
>>> +        .long   multiboot2_header_end - multiboot2_header_start
>>> +        /* Multiboot2 header checksum. */
>>> +        .long   -(MULTIBOOT2_HEADER_MAGIC + MULTIBOOT2_ARCHITECTURE_I386 + 
>>> \
>>> +                        (multiboot2_header_end - multiboot2_header_start))
>>> +
>>> +        /* Multiboot2 information request tag. */
>>> +        mb2ht_init MB2_HT(INFORMATION_REQUEST), MB2_HT(REQUIRED), \
>>> +                   MB2_TT(BASIC_MEMINFO), MB2_TT(MMAP)
>>> +
>>> +        /* Align modules at page boundry. */
>>> +        mb2ht_init MB2_HT(MODULE_ALIGN), MB2_HT(REQUIRED)
>>> +
>>> +        /* Console flags tag. */
>>> +        mb2ht_init MB2_HT(CONSOLE_FLAGS), MB2_HT(OPTIONAL), \
>>> +                   MULTIBOOT2_CONSOLE_FLAGS_EGA_TEXT_SUPPORTED
>>> +
>>> +        /* Framebuffer tag. */
>>> +        mb2ht_init MB2_HT(FRAMEBUFFER), MB2_HT(OPTIONAL), \
>>> +                   0, /* Number of the columns - no preference. */ \
>>> +                   0, /* Number of the lines - no preference. */ \
>>> +                   0  /* Number of bits per pixel - no preference. */
>>> +
>>> +        /* Multiboot2 header end tag. */
>>> +        mb2ht_init MB2_HT(END), MB2_HT(REQUIRED)
>>> +multiboot2_header_end:
>> Imo "end" labels should always preferably be .L-prefixed, to avoid
>> them getting used by a consumer instead of another "proper" label
>> starting whatever comes next.
> Make sense, however, I am in line with multiboot1_header_end label here.
> So, if we wish .L here then we should change multiboot1_header_end label
> above too. Of course in separate patch.

The multiboot1 header is very specifically not a local label, so you can
distinguish the actual header from the 3 nops following it in the
disassembly.

~Andrew

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel