arch/x86/entry/calling.h - kernel/msm-4.19 - Gitiles

 /* SPDX-License-Identifier: GPL-2.0 */
 #include <linux/jump_label.h>
 #include <asm/unwind_hints.h>
 #include <asm/cpufeatures.h>
 #include <asm/page_types.h>
 #include <asm/percpu.h>
 #include <asm/asm-offsets.h>
 #include <asm/processor-flags.h>

 /*

  x86 function call convention, 64-bit:
  -------------------------------------
   arguments           |  callee-saved      | extra caller-saved | return
  [callee-clobbered]   |                    | [callee-clobbered] |
  ---------------------------------------------------------------------------
  rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11             | rax, rdx [**]

  ( rsp is obviously invariant across normal function calls. (gcc can 'merge'
    functions when it sees tail-call optimization possibilities) rflags is
    clobbered. Leftover arguments are passed over the stack frame.)

  [*]  In the frame-pointers case rbp is fixed to the stack frame.

  [**] for struct return values wider than 64 bits the return convention is a
       bit more complex: up to 128 bits width we return small structures
       straight in rax, rdx. For structures larger than that (3 words or
       larger) the caller puts a pointer to an on-stack return struct
       [allocated in the caller's stack frame] into the first argument - i.e.
       into rdi. All other arguments shift up by one in this case.
       Fortunately this case is rare in the kernel.

 For 32-bit we have the following conventions - kernel is built with
 -mregparm=3 and -freg-struct-return:

  x86 function calling convention, 32-bit:
  ----------------------------------------
   arguments         | callee-saved        | extra caller-saved | return
  [callee-clobbered] |                     | [callee-clobbered] |
  -------------------------------------------------------------------------
  eax edx ecx        | ebx edi esi ebp [*] | <none>             | eax, edx [**]

  ( here too esp is obviously invariant across normal function calls. eflags
    is clobbered. Leftover arguments are passed over the stack frame. )

  [*]  In the frame-pointers case ebp is fixed to the stack frame.

  [**] We build with -freg-struct-return, which on 32-bit means similar
       semantics as on 64-bit: edx can be used for a second return value
       (i.e. covering integer and structure sizes up to 64 bits) - after that
       it gets more complex and more expensive: 3-word or larger struct returns
       get done in the caller's frame and the pointer to the return struct goes
       into regparm0, i.e. eax - the other arguments shift up and the
       function's register parameters degenerate to regparm=2 in essence.

 */

 #ifdef CONFIG_X86_64

 /*
  * 64-bit system call stack frame layout defines and helpers,
  * for assembly code:
  */

 /* The layout forms the "struct pt_regs" on the stack: */
 /*
  * C ABI says these regs are callee-preserved. They aren't saved on kernel entry
  * unless syscall needs a complete, fully filled "struct pt_regs".
  */
 #define R15		0*8
 #define R14		1*8
 #define R13		2*8
 #define R12		3*8
 #define RBP		4*8
 #define RBX		5*8
 /* These regs are callee-clobbered. Always saved on kernel entry. */
 #define R11		6*8
 #define R10		7*8
 #define R9		8*8
 #define R8		9*8
 #define RAX		10*8
 #define RCX		11*8
 #define RDX		12*8
 #define RSI		13*8
 #define RDI		14*8
 /*
  * On syscall entry, this is syscall#. On CPU exception, this is error code.
  * On hw interrupt, it's IRQ number:
  */
 #define ORIG_RAX	15*8
 /* Return frame for iretq */
 #define RIP		16*8
 #define CS		17*8
 #define EFLAGS		18*8
 #define RSP		19*8
 #define SS		20*8

 #define SIZEOF_PTREGS	21*8

 	.macro ALLOC_PT_GPREGS_ON_STACK
 	addq	$-(15*8), %rsp
 	.endm

 	.macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1
 	.if \r11
 	movq %r11, 6*8+\offset(%rsp)
 	.endif
 	.if \r8910
 	movq %r10, 7*8+\offset(%rsp)
 	movq %r9,  8*8+\offset(%rsp)
 	movq %r8,  9*8+\offset(%rsp)
 	.endif
 	.if \rax
 	movq %rax, 10*8+\offset(%rsp)
 	.endif
 	.if \rcx
 	movq %rcx, 11*8+\offset(%rsp)
 	.endif
 	movq %rdx, 12*8+\offset(%rsp)
 	movq %rsi, 13*8+\offset(%rsp)
 	movq %rdi, 14*8+\offset(%rsp)
 	UNWIND_HINT_REGS offset=\offset extra=0
 	.endm
 	.macro SAVE_C_REGS offset=0
 	SAVE_C_REGS_HELPER \offset, 1, 1, 1, 1
 	.endm
 	.macro SAVE_C_REGS_EXCEPT_RAX_RCX offset=0
 	SAVE_C_REGS_HELPER \offset, 0, 0, 1, 1
 	.endm
 	.macro SAVE_C_REGS_EXCEPT_R891011
 	SAVE_C_REGS_HELPER 0, 1, 1, 0, 0
 	.endm
 	.macro SAVE_C_REGS_EXCEPT_RCX_R891011
 	SAVE_C_REGS_HELPER 0, 1, 0, 0, 0
 	.endm
 	.macro SAVE_C_REGS_EXCEPT_RAX_RCX_R11
 	SAVE_C_REGS_HELPER 0, 0, 0, 1, 0
 	.endm

 	.macro SAVE_EXTRA_REGS offset=0
 	movq %r15, 0*8+\offset(%rsp)
 	movq %r14, 1*8+\offset(%rsp)
 	movq %r13, 2*8+\offset(%rsp)
 	movq %r12, 3*8+\offset(%rsp)
 	movq %rbp, 4*8+\offset(%rsp)
 	movq %rbx, 5*8+\offset(%rsp)
 	UNWIND_HINT_REGS offset=\offset
 	.endm

 	.macro POP_EXTRA_REGS
 	popq %r15
 	popq %r14
 	popq %r13
 	popq %r12
 	popq %rbp
 	popq %rbx
 	.endm

 	.macro POP_C_REGS
 	popq %r11
 	popq %r10
 	popq %r9
 	popq %r8
 	popq %rax
 	popq %rcx
 	popq %rdx
 	popq %rsi
 	popq %rdi
 	.endm

 	.macro icebp
 	.byte 0xf1
 	.endm

 /*
  * This is a sneaky trick to help the unwinder find pt_regs on the stack.  The
  * frame pointer is replaced with an encoded pointer to pt_regs.  The encoding
  * is just setting the LSB, which makes it an invalid stack address and is also
  * a signal to the unwinder that it's a pt_regs pointer in disguise.
  *
  * NOTE: This macro must be used *after* SAVE_EXTRA_REGS because it corrupts
  * the original rbp.
  */
 .macro ENCODE_FRAME_POINTER ptregs_offset=0
 #ifdef CONFIG_FRAME_POINTER
 	.if \ptregs_offset
 		leaq \ptregs_offset(%rsp), %rbp
 	.else
 		mov %rsp, %rbp
 	.endif
 	orq	$0x1, %rbp
 #endif
 .endm

 #ifdef CONFIG_PAGE_TABLE_ISOLATION

 /*
  * PAGE_TABLE_ISOLATION PGDs are 8k.  Flip bit 12 to switch between the two
  * halves:
  */
 #define PTI_USER_PGTABLE_BIT		PAGE_SHIFT
 #define PTI_USER_PGTABLE_MASK		(1 << PTI_USER_PGTABLE_BIT)
 #define PTI_USER_PCID_BIT		X86_CR3_PTI_PCID_USER_BIT
 #define PTI_USER_PCID_MASK		(1 << PTI_USER_PCID_BIT)
 #define PTI_USER_PGTABLE_AND_PCID_MASK  (PTI_USER_PCID_MASK | PTI_USER_PGTABLE_MASK)

 .macro SET_NOFLUSH_BIT	reg:req
 	bts	$X86_CR3_PCID_NOFLUSH_BIT, \reg
 .endm

 .macro ADJUST_KERNEL_CR3 reg:req
 	ALTERNATIVE "", "SET_NOFLUSH_BIT \reg", X86_FEATURE_PCID
 	/* Clear PCID and "PAGE_TABLE_ISOLATION bit", point CR3 at kernel pagetables: */
 	andq    $(~PTI_USER_PGTABLE_AND_PCID_MASK), \reg
 .endm

 .macro SWITCH_TO_KERNEL_CR3 scratch_reg:req
 	ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI
 	mov	%cr3, \scratch_reg
 	ADJUST_KERNEL_CR3 \scratch_reg
 	mov	\scratch_reg, %cr3
 .Lend_\@:
 .endm

 #define THIS_CPU_user_pcid_flush_mask   \
 	PER_CPU_VAR(cpu_tlbstate) + TLB_STATE_user_pcid_flush_mask

 .macro SWITCH_TO_USER_CR3_NOSTACK scratch_reg:req scratch_reg2:req
 	ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI
 	mov	%cr3, \scratch_reg

 	ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID

 	/*
 	 * Test if the ASID needs a flush.
 	 */
 	movq	\scratch_reg, \scratch_reg2
 	andq	$(0x7FF), \scratch_reg		/* mask ASID */
 	bt	\scratch_reg, THIS_CPU_user_pcid_flush_mask
 	jnc	.Lnoflush_\@

 	/* Flush needed, clear the bit */
 	btr	\scratch_reg, THIS_CPU_user_pcid_flush_mask
 	movq	\scratch_reg2, \scratch_reg
 	jmp	.Lwrcr3_pcid_\@

 .Lnoflush_\@:
 	movq	\scratch_reg2, \scratch_reg
 	SET_NOFLUSH_BIT \scratch_reg

 .Lwrcr3_pcid_\@:
 	/* Flip the ASID to the user version */
 	orq	$(PTI_USER_PCID_MASK), \scratch_reg

 .Lwrcr3_\@:
 	/* Flip the PGD to the user version */
 	orq     $(PTI_USER_PGTABLE_MASK), \scratch_reg
 	mov	\scratch_reg, %cr3
 .Lend_\@:
 .endm

 .macro SWITCH_TO_USER_CR3_STACK	scratch_reg:req
 	pushq	%rax
 	SWITCH_TO_USER_CR3_NOSTACK scratch_reg=\scratch_reg scratch_reg2=%rax
 	popq	%rax
 .endm

 .macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req
 	ALTERNATIVE "jmp .Ldone_\@", "", X86_FEATURE_PTI
 	movq	%cr3, \scratch_reg
 	movq	\scratch_reg, \save_reg
 	/*
 	 * Test the user pagetable bit. If set, then the user page tables
 	 * are active. If clear CR3 already has the kernel page table
 	 * active.
 	 */
 	bt	$PTI_USER_PGTABLE_BIT, \scratch_reg
 	jnc	.Ldone_\@

 	ADJUST_KERNEL_CR3 \scratch_reg
 	movq	\scratch_reg, %cr3

 .Ldone_\@:
 .endm

 .macro RESTORE_CR3 scratch_reg:req save_reg:req
 	ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI

 	ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID

 	/*
 	 * KERNEL pages can always resume with NOFLUSH as we do
 	 * explicit flushes.
 	 */
 	bt	$PTI_USER_PGTABLE_BIT, \save_reg
 	jnc	.Lnoflush_\@

 	/*
 	 * Check if there's a pending flush for the user ASID we're
 	 * about to set.
 	 */
 	movq	\save_reg, \scratch_reg
 	andq	$(0x7FF), \scratch_reg
 	bt	\scratch_reg, THIS_CPU_user_pcid_flush_mask
 	jnc	.Lnoflush_\@

 	btr	\scratch_reg, THIS_CPU_user_pcid_flush_mask
 	jmp	.Lwrcr3_\@

 .Lnoflush_\@:
 	SET_NOFLUSH_BIT \save_reg

 .Lwrcr3_\@:
 	/*
 	 * The CR3 write could be avoided when not changing its value,
 	 * but would require a CR3 read *and* a scratch register.
 	 */
 	movq	\save_reg, %cr3
 .Lend_\@:
 .endm

 #else /* CONFIG_PAGE_TABLE_ISOLATION=n: */

 .macro SWITCH_TO_KERNEL_CR3 scratch_reg:req
 .endm
 .macro SWITCH_TO_USER_CR3_NOSTACK scratch_reg:req scratch_reg2:req
 .endm
 .macro SWITCH_TO_USER_CR3_STACK scratch_reg:req
 .endm
 .macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req
 .endm
 .macro RESTORE_CR3 scratch_reg:req save_reg:req
 .endm

 #endif

 #endif /* CONFIG_X86_64 */

 /*
  * This does 'call enter_from_user_mode' unless we can avoid it based on
  * kernel config or using the static jump infrastructure.
  */
 .macro CALL_enter_from_user_mode
 #ifdef CONFIG_CONTEXT_TRACKING
 #ifdef HAVE_JUMP_LABEL
 	STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0
 #endif
 	call enter_from_user_mode
 .Lafter_call_\@:
 #endif
 .endm
	/* SPDX-License-Identifier: GPL-2.0 */
	#include <linux/jump_label.h>
	#include <asm/unwind_hints.h>
	#include <asm/cpufeatures.h>
	#include <asm/page_types.h>
	#include <asm/percpu.h>
	#include <asm/asm-offsets.h>
	#include <asm/processor-flags.h>

	/*

	x86 function call convention, 64-bit:
	-------------------------------------
	arguments \| callee-saved \| extra caller-saved \| return
	[callee-clobbered] \| \| [callee-clobbered] \|
	---------------------------------------------------------------------------
	rdi rsi rdx rcx r8-9 \| rbx rbp [] r12-15 \| r10-11 \| rax, rdx [*]

	( rsp is obviously invariant across normal function calls. (gcc can 'merge'
	functions when it sees tail-call optimization possibilities) rflags is
	clobbered. Leftover arguments are passed over the stack frame.)

	[*] In the frame-pointers case rbp is fixed to the stack frame.

	[**] for struct return values wider than 64 bits the return convention is a
	bit more complex: up to 128 bits width we return small structures
	straight in rax, rdx. For structures larger than that (3 words or
	larger) the caller puts a pointer to an on-stack return struct
	[allocated in the caller's stack frame] into the first argument - i.e.
	into rdi. All other arguments shift up by one in this case.
	Fortunately this case is rare in the kernel.

	For 32-bit we have the following conventions - kernel is built with
	-mregparm=3 and -freg-struct-return:

	x86 function calling convention, 32-bit:
	----------------------------------------
	arguments \| callee-saved \| extra caller-saved \| return
	[callee-clobbered] \| \| [callee-clobbered] \|
	-------------------------------------------------------------------------
	eax edx ecx \| ebx edi esi ebp [] \| <none> \| eax, edx [*]

	( here too esp is obviously invariant across normal function calls. eflags
	is clobbered. Leftover arguments are passed over the stack frame. )

	[*] In the frame-pointers case ebp is fixed to the stack frame.

	[**] We build with -freg-struct-return, which on 32-bit means similar
	semantics as on 64-bit: edx can be used for a second return value
	(i.e. covering integer and structure sizes up to 64 bits) - after that
	it gets more complex and more expensive: 3-word or larger struct returns
	get done in the caller's frame and the pointer to the return struct goes
	into regparm0, i.e. eax - the other arguments shift up and the
	function's register parameters degenerate to regparm=2 in essence.

	*/

	#ifdef CONFIG_X86_64

	/*
	* 64-bit system call stack frame layout defines and helpers,
	* for assembly code:
	*/

	/* The layout forms the "struct pt_regs" on the stack: */
	/*
	* C ABI says these regs are callee-preserved. They aren't saved on kernel entry
	* unless syscall needs a complete, fully filled "struct pt_regs".
	*/
	#define R15 0*8
	#define R14 1*8
	#define R13 2*8
	#define R12 3*8
	#define RBP 4*8
	#define RBX 5*8
	/* These regs are callee-clobbered. Always saved on kernel entry. */
	#define R11 6*8
	#define R10 7*8
	#define R9 8*8
	#define R8 9*8
	#define RAX 10*8
	#define RCX 11*8
	#define RDX 12*8
	#define RSI 13*8
	#define RDI 14*8
	/*
	* On syscall entry, this is syscall#. On CPU exception, this is error code.
	* On hw interrupt, it's IRQ number:
	*/
	#define ORIG_RAX 15*8
	/* Return frame for iretq */
	#define RIP 16*8
	#define CS 17*8
	#define EFLAGS 18*8
	#define RSP 19*8
	#define SS 20*8

	#define SIZEOF_PTREGS 21*8

	.macro ALLOC_PT_GPREGS_ON_STACK
	addq $-(15*8), %rsp
	.endm

	.macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1
	.if \r11
	movq %r11, 6*8+\offset(%rsp)
	.endif
	.if \r8910
	movq %r10, 7*8+\offset(%rsp)
	movq %r9, 8*8+\offset(%rsp)
	movq %r8, 9*8+\offset(%rsp)
	.endif
	.if \rax
	movq %rax, 10*8+\offset(%rsp)
	.endif
	.if \rcx
	movq %rcx, 11*8+\offset(%rsp)
	.endif
	movq %rdx, 12*8+\offset(%rsp)
	movq %rsi, 13*8+\offset(%rsp)
	movq %rdi, 14*8+\offset(%rsp)
	UNWIND_HINT_REGS offset=\offset extra=0
	.endm
	.macro SAVE_C_REGS offset=0
	SAVE_C_REGS_HELPER \offset, 1, 1, 1, 1
	.endm
	.macro SAVE_C_REGS_EXCEPT_RAX_RCX offset=0
	SAVE_C_REGS_HELPER \offset, 0, 0, 1, 1
	.endm
	.macro SAVE_C_REGS_EXCEPT_R891011
	SAVE_C_REGS_HELPER 0, 1, 1, 0, 0
	.endm
	.macro SAVE_C_REGS_EXCEPT_RCX_R891011
	SAVE_C_REGS_HELPER 0, 1, 0, 0, 0
	.endm
	.macro SAVE_C_REGS_EXCEPT_RAX_RCX_R11
	SAVE_C_REGS_HELPER 0, 0, 0, 1, 0
	.endm

	.macro SAVE_EXTRA_REGS offset=0
	movq %r15, 0*8+\offset(%rsp)
	movq %r14, 1*8+\offset(%rsp)
	movq %r13, 2*8+\offset(%rsp)
	movq %r12, 3*8+\offset(%rsp)
	movq %rbp, 4*8+\offset(%rsp)
	movq %rbx, 5*8+\offset(%rsp)
	UNWIND_HINT_REGS offset=\offset
	.endm

	.macro POP_EXTRA_REGS
	popq %r15
	popq %r14
	popq %r13
	popq %r12
	popq %rbp
	popq %rbx
	.endm

	.macro POP_C_REGS
	popq %r11
	popq %r10
	popq %r9
	popq %r8
	popq %rax
	popq %rcx
	popq %rdx
	popq %rsi
	popq %rdi
	.endm

	.macro icebp
	.byte 0xf1
	.endm

	/*
	* This is a sneaky trick to help the unwinder find pt_regs on the stack. The
	* frame pointer is replaced with an encoded pointer to pt_regs. The encoding
	* is just setting the LSB, which makes it an invalid stack address and is also
	* a signal to the unwinder that it's a pt_regs pointer in disguise.
	*
	* NOTE: This macro must be used after SAVE_EXTRA_REGS because it corrupts
	* the original rbp.
	*/
	.macro ENCODE_FRAME_POINTER ptregs_offset=0
	#ifdef CONFIG_FRAME_POINTER
	.if \ptregs_offset
	leaq \ptregs_offset(%rsp), %rbp
	.else
	mov %rsp, %rbp
	.endif
	orq $0x1, %rbp
	#endif
	.endm

	#ifdef CONFIG_PAGE_TABLE_ISOLATION

	/*
	* PAGE_TABLE_ISOLATION PGDs are 8k. Flip bit 12 to switch between the two
	* halves:
	*/
	#define PTI_USER_PGTABLE_BIT PAGE_SHIFT
	#define PTI_USER_PGTABLE_MASK (1 << PTI_USER_PGTABLE_BIT)
	#define PTI_USER_PCID_BIT X86_CR3_PTI_PCID_USER_BIT
	#define PTI_USER_PCID_MASK (1 << PTI_USER_PCID_BIT)
	#define PTI_USER_PGTABLE_AND_PCID_MASK (PTI_USER_PCID_MASK \| PTI_USER_PGTABLE_MASK)

	.macro SET_NOFLUSH_BIT reg:req
	bts $X86_CR3_PCID_NOFLUSH_BIT, \reg
	.endm

	.macro ADJUST_KERNEL_CR3 reg:req
	ALTERNATIVE "", "SET_NOFLUSH_BIT \reg", X86_FEATURE_PCID
	/* Clear PCID and "PAGE_TABLE_ISOLATION bit", point CR3 at kernel pagetables: */
	andq $(~PTI_USER_PGTABLE_AND_PCID_MASK), \reg
	.endm

	.macro SWITCH_TO_KERNEL_CR3 scratch_reg:req
	ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI
	mov %cr3, \scratch_reg
	ADJUST_KERNEL_CR3 \scratch_reg
	mov \scratch_reg, %cr3
	.Lend_\@:
	.endm

	#define THIS_CPU_user_pcid_flush_mask \
	PER_CPU_VAR(cpu_tlbstate) + TLB_STATE_user_pcid_flush_mask

	.macro SWITCH_TO_USER_CR3_NOSTACK scratch_reg:req scratch_reg2:req
	ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI
	mov %cr3, \scratch_reg

	ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID

	/*
	* Test if the ASID needs a flush.
	*/
	movq \scratch_reg, \scratch_reg2
	andq $(0x7FF), \scratch_reg /* mask ASID */
	bt \scratch_reg, THIS_CPU_user_pcid_flush_mask
	jnc .Lnoflush_\@

	/* Flush needed, clear the bit */
	btr \scratch_reg, THIS_CPU_user_pcid_flush_mask
	movq \scratch_reg2, \scratch_reg
	jmp .Lwrcr3_pcid_\@

	.Lnoflush_\@:
	movq \scratch_reg2, \scratch_reg
	SET_NOFLUSH_BIT \scratch_reg

	.Lwrcr3_pcid_\@:
	/* Flip the ASID to the user version */
	orq $(PTI_USER_PCID_MASK), \scratch_reg

	.Lwrcr3_\@:
	/* Flip the PGD to the user version */
	orq $(PTI_USER_PGTABLE_MASK), \scratch_reg
	mov \scratch_reg, %cr3
	.Lend_\@:
	.endm

	.macro SWITCH_TO_USER_CR3_STACK scratch_reg:req
	pushq %rax
	SWITCH_TO_USER_CR3_NOSTACK scratch_reg=\scratch_reg scratch_reg2=%rax
	popq %rax
	.endm

	.macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req
	ALTERNATIVE "jmp .Ldone_\@", "", X86_FEATURE_PTI
	movq %cr3, \scratch_reg
	movq \scratch_reg, \save_reg
	/*
	* Test the user pagetable bit. If set, then the user page tables
	* are active. If clear CR3 already has the kernel page table
	* active.
	*/
	bt $PTI_USER_PGTABLE_BIT, \scratch_reg
	jnc .Ldone_\@

	ADJUST_KERNEL_CR3 \scratch_reg
	movq \scratch_reg, %cr3

	.Ldone_\@:
	.endm

	.macro RESTORE_CR3 scratch_reg:req save_reg:req
	ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI

	ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID

	/*
	* KERNEL pages can always resume with NOFLUSH as we do
	* explicit flushes.
	*/
	bt $PTI_USER_PGTABLE_BIT, \save_reg
	jnc .Lnoflush_\@

	/*
	* Check if there's a pending flush for the user ASID we're
	* about to set.
	*/
	movq \save_reg, \scratch_reg
	andq $(0x7FF), \scratch_reg
	bt \scratch_reg, THIS_CPU_user_pcid_flush_mask
	jnc .Lnoflush_\@

	btr \scratch_reg, THIS_CPU_user_pcid_flush_mask
	jmp .Lwrcr3_\@

	.Lnoflush_\@:
	SET_NOFLUSH_BIT \save_reg

	.Lwrcr3_\@:
	/*
	* The CR3 write could be avoided when not changing its value,
	* but would require a CR3 read and a scratch register.
	*/
	movq \save_reg, %cr3
	.Lend_\@:
	.endm

	#else /* CONFIG_PAGE_TABLE_ISOLATION=n: */

	.macro SWITCH_TO_KERNEL_CR3 scratch_reg:req
	.endm
	.macro SWITCH_TO_USER_CR3_NOSTACK scratch_reg:req scratch_reg2:req
	.endm
	.macro SWITCH_TO_USER_CR3_STACK scratch_reg:req
	.endm
	.macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req
	.endm
	.macro RESTORE_CR3 scratch_reg:req save_reg:req
	.endm

	#endif

	#endif /* CONFIG_X86_64 */

	/*
	* This does 'call enter_from_user_mode' unless we can avoid it based on
	* kernel config or using the static jump infrastructure.
	*/
	.macro CALL_enter_from_user_mode
	#ifdef CONFIG_CONTEXT_TRACKING
	#ifdef HAVE_JUMP_LABEL
	STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0
	#endif
	call enter_from_user_mode
	.Lafter_call_\@:
	#endif
	.endm