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

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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: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Ingo 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
This commit is contained in:
David Woodhouse 2025-03-26 14:16:03 +00:00 committed by Ingo Molnar
parent 7516e7216b
commit de085ddd49
2 changed files with 9 additions and 10 deletions
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10
arch/x86/kernel/machine_kexec_64.c
View File

@ -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,

9
arch/x86/kernel/relocate_kernel_64.S
View File

@ -79,8 +79,13 @@ SYM_CODE_START_NOALIGN(relocate_kernel)
pushq %r15
pushf
/* zero out flags, and disable interrupts */
pushq $0
/* 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 */