Commit b7155dfd authored by David Woodhouse's avatar David Woodhouse Committed by Ingo Molnar
Browse files

x86/kexec: Eliminate writes through kernel mapping of relocate_kernel page 



All writes to the relocate_kernel control page are now done *after* the
%cr3 switch via simple %rip-relative addressing, which means the DATA()
macro with its pointer arithmetic can also now be removed.

Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20241205153343.3275139-12-dwmw2@infradead.org
parent b3adabae

arch/x86/kernel/relocate_kernel_64.S

+14 −15
Original line number Diff line number Diff line
@@ -61,21 +61,24 @@ SYM_CODE_START_NOALIGN(relocate_kernel) 
	pushq %r15

	pushf



	movq	%rsp, saved_rsp(%rip)

	movq	%cr0, %rax

	movq	%rax, saved_cr0(%rip)

	movq	%cr3, %rax

	movq	%rax, saved_cr3(%rip)

	movq	%cr4, %rax

	movq	%rax, saved_cr4(%rip)



	/* Save CR4. Required to enable the right paging mode later. */

	movq	%rax, %r13



	/* zero out flags, and disable interrupts */

	pushq $0

	popfq



	/* Switch to the identity mapped page tables */

	movq	%cr3, %rax

	movq	kexec_pa_table_page(%rip), %r9

	movq	%r9, %cr3



	/* Save %rsp and CRs. */

	movq    %rsp, saved_rsp(%rip)

	movq	%rax, saved_cr3(%rip)

	movq	%cr0, %rax

	movq	%rax, saved_cr0(%rip)

	/* Leave CR4 in %r13 to enable the right paging mode later. */

	movq	%cr4, %r13

	movq	%r13, saved_cr4(%rip)



	/* Save SME active flag */

	movq	%r8, %r12
@@ -85,10 +88,6 @@ SYM_CODE_START_NOALIGN(relocate_kernel) 
	/* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */

	movq	%rcx, %r11



	/* Switch to the identity mapped page tables */

	movq	kexec_pa_table_page(%rip), %r9

	movq	%r9, %cr3



	/* Physical address of control page */

	movq    %rsi, %r8