grub-2.06 fails to load 64bit Multiboot2 ELF with regions above 4GiB

[Baksik, Fred [USA]]

GRUB2 fails to load a Multiboot2 ELF with loadable regions above 4GiB.  The error seen is “segment crosses 4 GiB border”.

 

The 4 GiB border check was added as part of “multiboot2: Add support for relocatable images” commit a620876e3b32e4ea0c9a7b3541fcb9a4dd4fb9eb.

I believe this check should only apply when the multiboot2 image supports relocation via the MULTIBOOT_HEADER_TAG_RELOCATABLE tag.

 

Subject: [PATCH] multiboot2: check 4GiB limit for relocatable images only

 

---

grub-core/loader/multiboot_elfxx.c | 9 +++++----

1 file changed, 5 insertions(+), 4 deletions(-)

 

diff --git a/grub-core/loader/multiboot_elfxx.c b/grub-core/loader/multiboot_elfxx.c

index f2318e0..0ac11f0 100644

--- a/grub-core/loader/multiboot_elfxx.c

+++ b/grub-core/loader/multiboot_elfxx.c

@@ -92,10 +92,6 @@ CONCAT(grub_multiboot_load_elf, XX) (mbi_load_data_t *mld)

    highest_load = grub_max (highest_load, phdr(i)->p_paddr + phdr(i)->p_memsz);

       }

-#ifdef MULTIBOOT_LOAD_ELF64

-  if (highest_load >= 0x100000000)

-    return grub_error (GRUB_ERR_BAD_OS, "segment crosses 4 GiB border");

-#endif

   if (mld->relocatable)

     {

@@ -106,6 +102,11 @@ CONCAT(grub_multiboot_load_elf, XX) (mbi_load_data_t *mld)

              (long) mld->align, mld->preference, load_size,

              mld->avoid_efi_boot_services);

+#ifdef MULTIBOOT_LOAD_ELF64

+      if (highest_load >= 0x100000000)

+        return grub_error (GRUB_ERR_BAD_OS, "segment crosses 4 GiB border");

+#endif

+

       if (load_size > mld->max_addr || mld->min_addr > mld->max_addr - load_size)

    return grub_error (GRUB_ERR_BAD_OS, "invalid min/max address and/or load size");

--

2.31.1

 

Fred Baksik
Sr Prin Software Engineer
Systems | Mission

Mercury Systems
6675 Shiloh Road East, Alpharetta, GA 30005
+1 978.967.3405 office

fred.baksik@mrcy.com | mrcy.com