Commit de085ddd authored by David Woodhouse's avatar David Woodhouse Committed by Ingo Molnar
Browse files

x86/kexec: Invalidate GDT/IDT from relocate_kernel() instead of earlier 



Reduce the window during which exceptions are unhandled, by leaving the
GDT/IDT in place all the way into the relocate_kernel() function, until
the moment that %cr3 gets replaced.

Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250326142404.256980-4-dwmw2@infradead.org
parent 7516e721

arch/x86/kernel/machine_kexec_64.c

+2 −8
Original line number Diff line number Diff line
@@ -434,16 +434,10 @@ void __nocfi machine_kexec(struct kimage *image) 
	 * with from a table in memory.  At no other time is the

	 * descriptor table in memory accessed.

	 *

	 * I take advantage of this here by force loading the

	 * segments, before I zap the gdt with an invalid value.

	 * Take advantage of this here by force loading the segments,

	 * before the GDT is zapped with an invalid value.

	 */

	load_segments();

	/*

	 * The gdt & idt are now invalid.

	 * If you want to load them you must set up your own idt & gdt.

	 */

	native_idt_invalidate();

	native_gdt_invalidate();



	/* now call it */

	image->start = relocate_kernel_ptr((unsigned long)image->head,

arch/x86/kernel/relocate_kernel_64.S

+7 −2
Original line number Diff line number Diff line
@@ -79,8 +79,13 @@ SYM_CODE_START_NOALIGN(relocate_kernel) 
	pushq %r15

	pushf



	/* zero out flags, and disable interrupts */

	/* Invalidate GDT/IDT, zero out flags */

	pushq	$0

	pushq	$0



	lidt	(%rsp)

	lgdt	(%rsp)

	addq	$8, %rsp

	popfq



	/* Switch to the identity mapped page tables */