[Qemu-devel] [Bug 1512134] Re: Multiboot v1 memory map offset wrong

[Tristan Parisot]

I forgot to tell how i detected the issue:
I print all the fields, and in "type", i had the size of  the next entry (and 
in size, i have always zero, which corresponds to the high part of addr)

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https://bugs.launchpad.net/bugs/1512134

Title:
  Multiboot v1 memory map offset wrong

Status in QEMU:
  New

Bug description:
  I'm developping a multiboot kernel for multiboot v1
  My multiboot header contains the V1 magic (0x1BADB002) and the flags 
0x00010243  (with enabled memory detection, and boot loader name)

  
  When booted in multiboot,
  Qemu gives me two pointers:
  unsigned long mmap_length;
  unsigned long mmap_addr;

  mmap_addr shall points to this structure:
  struct multiboot_mmap_entry
  {
  multiboot_uint32_t size;
  multiboot_uint64_t addr;
  multiboot_uint64_t len;
  multiboot_uint32_t type;
  } 

  
  According to the multiboot v1 specification, mmap_addr should not point  to 
the start of this structure, but instead, should point to the "addr "field.

  Work-arround:
  Detect if qemu is used using bootloader_name field.
  If it is, do NOT apply a -4 offset to mmap_addr

  http://git.savannah.gnu.org/cgit/grub.git/tree/doc/multiboot.texi?h=multiboot

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