| Message ID | 20200226204515.2752095-2-nivedita@alum.mit.edu |
|---|---|
| State | New |
| Headers | show |
| Series | [1/1] x86/boot/compressed/32: Fix reloading of GDTR post-relocation | expand |
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index 356060c5332c..2f8138b71ea9 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -139,12 +139,11 @@ SYM_FUNC_START(startup_32) /* * The GDT may get overwritten either during the copy we just did or * during extract_kernel below. To avoid any issues, repoint the GDTR - * to the new copy of the GDT. EAX still contains the previously - * calculated relocation offset of init_size - _end. + * to the new copy of the GDT. */ - leal gdt(%ebx), %edx - addl %eax, 2(%edx) - lgdt (%edx) + leal gdt(%ebx), %eax + movl %eax, 2(%eax) + lgdt (%eax) /* * Jump to the relocated address.
Commit ef5a7b5eb13e ("efi/x86: Remove GDT setup from efi_main") introduced GDT setup into startup_32, and reloads the GDTR after relocating the kernel for paranoia's sake. The GDTR is adjusted by init_size - _end, however this may not be the correct offset to apply if the kernel was loaded at a misaligned address or below LOAD_PHYSICAL_ADDR, as in that case the decompression buffer has an additional offset from the original load address. This should never happen for a conformant bootloader, but we're being paranoid anyway, so just store the new GDT address in there instead of adding any offsets, which is simpler as well. Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu> Fixes: ef5a7b5eb13e ("efi/x86: Remove GDT setup from efi_main") --- arch/x86/boot/compressed/head_32.S | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)