Commit 32d00913 authored Feb 02, 2020 by Arvind Sankar Committed by Ard Biesheuvel Feb 22, 2020

x86/boot: Reload GDTR after copying to the end of the buffer

The GDT may get overwritten during the copy or during extract_kernel,
which will cause problems if any segment register is touched before the
GDTR is reloaded by the decompressed kernel. For safety update the GDTR
to point to the GDT within the copied kernel.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200202171353.3736319-4-nivedita@alum.mit.edu

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

parent 90ff2262

arch/x86/boot/compressed/head_64.S

+10 −0

Original line number	Diff line number	Diff line
		@@ -439,6 +439,16 @@ trampoline_return:
		cld
		popq %rsi

		/*
		* 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.
		*/
		leaq gdt64(%rbx), %rax
		subq %rbp, 2(%rax)
		addq %rbx, 2(%rax)
		lgdt (%rax)

		/*
		* Jump to the relocated address.
		*/