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Commit b65bef40 authored by Joerg Roedel's avatar Joerg Roedel Committed by Thomas Gleixner
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x86/entry/32: Add PTI CR3 switches to NMI handler code 



The NMI handler is special, as it needs to leave with the same CR3 as it
was entered with. This is required because the NMI can happen within kernel
context but with user CR3 already loaded, i.e. after switching to user CR3
but before returning to user space.

Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarPavel Machek <pavel@ucw.cz>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Waiman Long <llong@redhat.com>
Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca>
Cc: joro@8bytes.org
Link: https://lkml.kernel.org/r/1531906876-13451-14-git-send-email-joro@8bytes.org
parent e464fb9f

arch/x86/entry/entry_32.S

+33 −6
Original line number Diff line number Diff line
@@ -210,8 +210,19 @@ 


.endm



.macro SAVE_ALL_NMI

.macro SAVE_ALL_NMI cr3_reg:req

	SAVE_ALL



	/*

	 * Now switch the CR3 when PTI is enabled.

	 *

	 * We can enter with either user or kernel cr3, the code will

	 * store the old cr3 in \cr3_reg and switches to the kernel cr3

	 * if necessary.

	 */

	SWITCH_TO_KERNEL_CR3 scratch_reg=\cr3_reg



.Lend_\@:

.endm

/*

 * This is a sneaky trick to help the unwinder find pt_regs on the stack.  The
@@ -259,7 +270,23 @@ 
	POP_GS_EX

.endm



.macro RESTORE_ALL_NMI pop=0

.macro RESTORE_ALL_NMI cr3_reg:req pop=0

	/*

	 * Now switch the CR3 when PTI is enabled.

	 *

	 * We enter with kernel cr3 and switch the cr3 to the value

	 * stored on \cr3_reg, which is either a user or a kernel cr3.

	 */

	ALTERNATIVE "jmp .Lswitched_\@", "", X86_FEATURE_PTI



	testl	$PTI_SWITCH_MASK, \cr3_reg

	jz	.Lswitched_\@



	/* User cr3 in \cr3_reg - write it to hardware cr3 */

	movl	\cr3_reg, %cr3



.Lswitched_\@:



	RESTORE_REGS pop=\pop

.endm
@@ -1331,7 +1358,7 @@ ENTRY(nmi) 
#endif



	pushl	%eax				# pt_regs->orig_ax

	SAVE_ALL_NMI

	SAVE_ALL_NMI cr3_reg=%edi

	ENCODE_FRAME_POINTER

	xorl	%edx, %edx			# zero error code

	movl	%esp, %eax			# pt_regs pointer
@@ -1359,7 +1386,7 @@ ENTRY(nmi) 


.Lnmi_return:

	CHECK_AND_APPLY_ESPFIX

	RESTORE_ALL_NMI pop=4

	RESTORE_ALL_NMI cr3_reg=%edi pop=4

	jmp	.Lirq_return



#ifdef CONFIG_X86_ESPFIX32
@@ -1375,12 +1402,12 @@ ENTRY(nmi) 
	pushl	16(%esp)

	.endr

	pushl	%eax

	SAVE_ALL_NMI

	SAVE_ALL_NMI cr3_reg=%edi

	ENCODE_FRAME_POINTER

	FIXUP_ESPFIX_STACK			# %eax == %esp

	xorl	%edx, %edx			# zero error code

	call	do_nmi

	RESTORE_ALL_NMI

	RESTORE_ALL_NMI cr3_reg=%edi

	lss	12+4(%esp), %esp		# back to espfix stack

	jmp	.Lirq_return

#endif