Committed, thanks. On 15.04.2014 13:58, Piotr Krysiuk wrote: > GRUB cannot determine end of BSS section of compressed image when loading > very old Linux kernels. Booting these kernels, grub_relocator32_start and > new Global Descriptor Table are placed in the area overlapping with the BSS > section of loaded image. When Linux executes, it initializes BSS also > wiping Global Descriptor Table that is still active. This leads to failure > on segment reload that follows. > > Current HEAD of GRUB repository is affected, with "Clear BSS" code from > https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/arch/x86_64/boot/compressed/head.S?h=linux-2.6.17.y#n57 > wiping GDT. > > Old versions of GRUB, from before relocator was introduced, placed GDT close > to end of physical memory avoiding this issue. This patch fixes regression > by moving GDT into conventional memory. > > * grub-core/lib/i386/relocator.c: Move GDT into conventional memory > to avoid collision with BSS section of compressed Linux image for > very old kernels. > --- > grub-core/lib/i386/relocator.c | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > diff --git a/grub-core/lib/i386/relocator.c b/grub-core/lib/i386/relocator.c > index d2a1b27..ffaf25f 100644 > --- a/grub-core/lib/i386/relocator.c > +++ b/grub-core/lib/i386/relocator.c > @@ -81,10 +81,13 @@ grub_relocator32_boot (struct grub_relocator *rel, > void *relst; > grub_relocator_chunk_t ch; > > - err = grub_relocator_alloc_chunk_align (rel, &ch, 0, > - (0xffffffff - RELOCATOR_SIZEOF (32)) > - + 1, RELOCATOR_SIZEOF (32), 16, > - GRUB_RELOCATOR_PREFERENCE_NONE, > + /* Specific memory range due to Global Descriptor Table for use by payload > + that we will store in returned chunk. The address range and preference > + are based on "THE LINUX/x86 BOOT PROTOCOL" specification. */ > + err = grub_relocator_alloc_chunk_align (rel, &ch, 0x1000, > + 0x9a000 - RELOCATOR_SIZEOF (32), > + RELOCATOR_SIZEOF (32), 16, > + GRUB_RELOCATOR_PREFERENCE_LOW, > avoid_efi_bootservices); > if (err) > return err; >
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