Initial import

1 files changed, 1653 insertions, 0 deletions

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
new file mode 100644
index 000000000..02c2eff74
--- /dev/null
+++ b/arch/x86/kernel/entry_64.S
@@ -0,0 +1,1653 @@
+/*
+ *  linux/arch/x86_64/entry.S
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *  Copyright (C) 2000, 2001, 2002  Andi Kleen SuSE Labs
+ *  Copyright (C) 2000  Pavel Machek <pavel@suse.cz>
+ */
+
+/*
+ * entry.S contains the system-call and fault low-level handling routines.
+ *
+ * Some of this is documented in Documentation/x86/entry_64.txt
+ *
+ * NOTE: This code handles signal-recognition, which happens every time
+ * after an interrupt and after each system call.
+ *
+ * A note on terminology:
+ * - iret frame: Architecture defined interrupt frame from SS to RIP
+ * at the top of the kernel process stack.
+ *
+ * Some macro usage:
+ * - CFI macros are used to generate dwarf2 unwind information for better
+ * backtraces. They don't change any code.
+ * - ENTRY/END Define functions in the symbol table.
+ * - TRACE_IRQ_* - Trace hard interrupt state for lock debugging.
+ * - idtentry - Define exception entry points.
+ */
+
+#include <linux/linkage.h>
+#include <asm/segment.h>
+#include <asm/cache.h>
+#include <asm/errno.h>
+#include <asm/dwarf2.h>
+#include <asm/calling.h>
+#include <asm/asm-offsets.h>
+#include <asm/msr.h>
+#include <asm/unistd.h>
+#include <asm/thread_info.h>
+#include <asm/hw_irq.h>
+#include <asm/page_types.h>
+#include <asm/irqflags.h>
+#include <asm/paravirt.h>
+#include <asm/percpu.h>
+#include <asm/asm.h>
+#include <asm/context_tracking.h>
+#include <asm/smap.h>
+#include <asm/pgtable_types.h>
+#include <linux/err.h>
+
+/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this.  */
+#include <linux/elf-em.h>
+#define AUDIT_ARCH_X86_64	(EM_X86_64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
+#define __AUDIT_ARCH_64BIT 0x80000000
+#define __AUDIT_ARCH_LE	   0x40000000
+
+	.code64
+	.section .entry.text, "ax"
+
+
+#ifdef CONFIG_PARAVIRT
+ENTRY(native_usergs_sysret64)
+	swapgs
+	sysretq
+ENDPROC(native_usergs_sysret64)
+#endif /* CONFIG_PARAVIRT */
+
+
+.macro TRACE_IRQS_IRETQ
+#ifdef CONFIG_TRACE_IRQFLAGS
+	bt   $9,EFLAGS(%rsp)	/* interrupts off? */
+	jnc  1f
+	TRACE_IRQS_ON
+1:
+#endif
+.endm
+
+/*
+ * When dynamic function tracer is enabled it will add a breakpoint
+ * to all locations that it is about to modify, sync CPUs, update
+ * all the code, sync CPUs, then remove the breakpoints. In this time
+ * if lockdep is enabled, it might jump back into the debug handler
+ * outside the updating of the IST protection. (TRACE_IRQS_ON/OFF).
+ *
+ * We need to change the IDT table before calling TRACE_IRQS_ON/OFF to
+ * make sure the stack pointer does not get reset back to the top
+ * of the debug stack, and instead just reuses the current stack.
+ */
+#if defined(CONFIG_DYNAMIC_FTRACE) && defined(CONFIG_TRACE_IRQFLAGS)
+
+.macro TRACE_IRQS_OFF_DEBUG
+	call debug_stack_set_zero
+	TRACE_IRQS_OFF
+	call debug_stack_reset
+.endm
+
+.macro TRACE_IRQS_ON_DEBUG
+	call debug_stack_set_zero
+	TRACE_IRQS_ON
+	call debug_stack_reset
+.endm
+
+.macro TRACE_IRQS_IRETQ_DEBUG
+	bt   $9,EFLAGS(%rsp)	/* interrupts off? */
+	jnc  1f
+	TRACE_IRQS_ON_DEBUG
+1:
+.endm
+
+#else
+# define TRACE_IRQS_OFF_DEBUG		TRACE_IRQS_OFF
+# define TRACE_IRQS_ON_DEBUG		TRACE_IRQS_ON
+# define TRACE_IRQS_IRETQ_DEBUG		TRACE_IRQS_IRETQ
+#endif
+
+/*
+ * empty frame
+ */
+	.macro EMPTY_FRAME start=1 offset=0
+	.if \start
+	CFI_STARTPROC simple
+	CFI_SIGNAL_FRAME
+	CFI_DEF_CFA rsp,8+\offset
+	.else
+	CFI_DEF_CFA_OFFSET 8+\offset
+	.endif
+	.endm
+
+/*
+ * initial frame state for interrupts (and exceptions without error code)
+ */
+	.macro INTR_FRAME start=1 offset=0
+	EMPTY_FRAME \start, 5*8+\offset
+	/*CFI_REL_OFFSET ss, 4*8+\offset*/
+	CFI_REL_OFFSET rsp, 3*8+\offset
+	/*CFI_REL_OFFSET rflags, 2*8+\offset*/
+	/*CFI_REL_OFFSET cs, 1*8+\offset*/
+	CFI_REL_OFFSET rip, 0*8+\offset
+	.endm
+
+/*
+ * initial frame state for exceptions with error code (and interrupts
+ * with vector already pushed)
+ */
+	.macro XCPT_FRAME start=1 offset=0
+	INTR_FRAME \start, 1*8+\offset
+	.endm
+
+/*
+ * frame that enables passing a complete pt_regs to a C function.
+ */
+	.macro DEFAULT_FRAME start=1 offset=0
+	XCPT_FRAME \start, ORIG_RAX+\offset
+	CFI_REL_OFFSET rdi, RDI+\offset
+	CFI_REL_OFFSET rsi, RSI+\offset
+	CFI_REL_OFFSET rdx, RDX+\offset
+	CFI_REL_OFFSET rcx, RCX+\offset
+	CFI_REL_OFFSET rax, RAX+\offset
+	CFI_REL_OFFSET r8, R8+\offset
+	CFI_REL_OFFSET r9, R9+\offset
+	CFI_REL_OFFSET r10, R10+\offset
+	CFI_REL_OFFSET r11, R11+\offset
+	CFI_REL_OFFSET rbx, RBX+\offset
+	CFI_REL_OFFSET rbp, RBP+\offset
+	CFI_REL_OFFSET r12, R12+\offset
+	CFI_REL_OFFSET r13, R13+\offset
+	CFI_REL_OFFSET r14, R14+\offset
+	CFI_REL_OFFSET r15, R15+\offset
+	.endm
+
+/*
+ * 64bit SYSCALL instruction entry. Up to 6 arguments in registers.
+ *
+ * 64bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11,
+ * then loads new ss, cs, and rip from previously programmed MSRs.
+ * rflags gets masked by a value from another MSR (so CLD and CLAC
+ * are not needed). SYSCALL does not save anything on the stack
+ * and does not change rsp.
+ *
+ * Registers on entry:
+ * rax  system call number
+ * rcx  return address
+ * r11  saved rflags (note: r11 is callee-clobbered register in C ABI)
+ * rdi  arg0
+ * rsi  arg1
+ * rdx  arg2
+ * r10  arg3 (needs to be moved to rcx to conform to C ABI)
+ * r8   arg4
+ * r9   arg5
+ * (note: r12-r15,rbp,rbx are callee-preserved in C ABI)
+ *
+ * Only called from user space.
+ *
+ * When user can change pt_regs->foo always force IRET. That is because
+ * it deals with uncanonical addresses better. SYSRET has trouble
+ * with them due to bugs in both AMD and Intel CPUs.
+ */
+
+ENTRY(system_call)
+	CFI_STARTPROC	simple
+	CFI_SIGNAL_FRAME
+	CFI_DEF_CFA	rsp,0
+	CFI_REGISTER	rip,rcx
+	/*CFI_REGISTER	rflags,r11*/
+
+	/*
+	 * Interrupts are off on entry.
+	 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
+	 * it is too small to ever cause noticeable irq latency.
+	 */
+	SWAPGS_UNSAFE_STACK
+	/*
+	 * A hypervisor implementation might want to use a label
+	 * after the swapgs, so that it can do the swapgs
+	 * for the guest and jump here on syscall.
+	 */
+GLOBAL(system_call_after_swapgs)
+
+	movq	%rsp,PER_CPU_VAR(rsp_scratch)
+	movq	PER_CPU_VAR(kernel_stack),%rsp
+
+	/* Construct struct pt_regs on stack */
+	pushq_cfi $__USER_DS			/* pt_regs->ss */
+	pushq_cfi PER_CPU_VAR(rsp_scratch)	/* pt_regs->sp */
+	/*
+	 * Re-enable interrupts.
+	 * We use 'rsp_scratch' as a scratch space, hence irq-off block above
+	 * must execute atomically in the face of possible interrupt-driven
+	 * task preemption. We must enable interrupts only after we're done
+	 * with using rsp_scratch:
+	 */
+	ENABLE_INTERRUPTS(CLBR_NONE)
+	pushq_cfi	%r11			/* pt_regs->flags */
+	pushq_cfi	$__USER_CS		/* pt_regs->cs */
+	pushq_cfi	%rcx			/* pt_regs->ip */
+	CFI_REL_OFFSET rip,0
+	pushq_cfi_reg	rax			/* pt_regs->orig_ax */
+	pushq_cfi_reg	rdi			/* pt_regs->di */
+	pushq_cfi_reg	rsi			/* pt_regs->si */
+	pushq_cfi_reg	rdx			/* pt_regs->dx */
+	pushq_cfi_reg	rcx			/* pt_regs->cx */
+	pushq_cfi	$-ENOSYS		/* pt_regs->ax */
+	pushq_cfi_reg	r8			/* pt_regs->r8 */
+	pushq_cfi_reg	r9			/* pt_regs->r9 */
+	pushq_cfi_reg	r10			/* pt_regs->r10 */
+	pushq_cfi_reg	r11			/* pt_regs->r11 */
+	sub	$(6*8),%rsp /* pt_regs->bp,bx,r12-15 not saved */
+	CFI_ADJUST_CFA_OFFSET 6*8
+
+	testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+	jnz tracesys
+system_call_fastpath:
+#if __SYSCALL_MASK == ~0
+	cmpq $__NR_syscall_max,%rax
+#else
+	andl $__SYSCALL_MASK,%eax
+	cmpl $__NR_syscall_max,%eax
+#endif
+	ja	1f	/* return -ENOSYS (already in pt_regs->ax) */
+	movq %r10,%rcx
+	call *sys_call_table(,%rax,8)
+	movq %rax,RAX(%rsp)
+1:
+/*
+ * Syscall return path ending with SYSRET (fast path).
+ * Has incompletely filled pt_regs.
+ */
+	LOCKDEP_SYS_EXIT
+	/*
+	 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
+	 * it is too small to ever cause noticeable irq latency.
+	 */
+	DISABLE_INTERRUPTS(CLBR_NONE)
+
+	/*
+	 * We must check ti flags with interrupts (or at least preemption)
+	 * off because we must *never* return to userspace without
+	 * processing exit work that is enqueued if we're preempted here.
+	 * In particular, returning to userspace with any of the one-shot
+	 * flags (TIF_NOTIFY_RESUME, TIF_USER_RETURN_NOTIFY, etc) set is
+	 * very bad.
+	 */
+	testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+	jnz int_ret_from_sys_call_irqs_off	/* Go to the slow path */
+
+	CFI_REMEMBER_STATE
+
+	RESTORE_C_REGS_EXCEPT_RCX_R11
+	movq	RIP(%rsp),%rcx
+	CFI_REGISTER	rip,rcx
+	movq	EFLAGS(%rsp),%r11
+	/*CFI_REGISTER	rflags,r11*/
+	movq	RSP(%rsp),%rsp
+	/*
+	 * 64bit SYSRET restores rip from rcx,
+	 * rflags from r11 (but RF and VM bits are forced to 0),
+	 * cs and ss are loaded from MSRs.
+	 * Restoration of rflags re-enables interrupts.
+	 *
+	 * NB: On AMD CPUs with the X86_BUG_SYSRET_SS_ATTRS bug, the ss
+	 * descriptor is not reinitialized.  This means that we should
+	 * avoid SYSRET with SS == NULL, which could happen if we schedule,
+	 * exit the kernel, and re-enter using an interrupt vector.  (All
+	 * interrupt entries on x86_64 set SS to NULL.)  We prevent that
+	 * from happening by reloading SS in __switch_to.  (Actually
+	 * detecting the failure in 64-bit userspace is tricky but can be
+	 * done.)
+	 */
+	USERGS_SYSRET64
+
+	CFI_RESTORE_STATE
+
+	/* Do syscall entry tracing */
+tracesys:
+	movq %rsp, %rdi
+	movl $AUDIT_ARCH_X86_64, %esi
+	call syscall_trace_enter_phase1
+	test %rax, %rax
+	jnz tracesys_phase2		/* if needed, run the slow path */
+	RESTORE_C_REGS_EXCEPT_RAX	/* else restore clobbered regs */
+	movq ORIG_RAX(%rsp), %rax
+	jmp system_call_fastpath	/*      and return to the fast path */
+
+tracesys_phase2:
+	SAVE_EXTRA_REGS
+	movq %rsp, %rdi
+	movl $AUDIT_ARCH_X86_64, %esi
+	movq %rax,%rdx
+	call syscall_trace_enter_phase2
+
+	/*
+	 * Reload registers from stack in case ptrace changed them.
+	 * We don't reload %rax because syscall_trace_entry_phase2() returned
+	 * the value it wants us to use in the table lookup.
+	 */
+	RESTORE_C_REGS_EXCEPT_RAX
+	RESTORE_EXTRA_REGS
+#if __SYSCALL_MASK == ~0
+	cmpq $__NR_syscall_max,%rax
+#else
+	andl $__SYSCALL_MASK,%eax
+	cmpl $__NR_syscall_max,%eax
+#endif
+	ja	1f	/* return -ENOSYS (already in pt_regs->ax) */
+	movq %r10,%rcx	/* fixup for C */
+	call *sys_call_table(,%rax,8)
+	movq %rax,RAX(%rsp)
+1:
+	/* Use IRET because user could have changed pt_regs->foo */
+
+/*
+ * Syscall return path ending with IRET.
+ * Has correct iret frame.
+ */
+GLOBAL(int_ret_from_sys_call)
+	DISABLE_INTERRUPTS(CLBR_NONE)
+int_ret_from_sys_call_irqs_off: /* jumps come here from the irqs-off SYSRET path */
+	TRACE_IRQS_OFF
+	movl $_TIF_ALLWORK_MASK,%edi
+	/* edi:	mask to check */
+GLOBAL(int_with_check)
+	LOCKDEP_SYS_EXIT_IRQ
+	GET_THREAD_INFO(%rcx)
+	movl TI_flags(%rcx),%edx
+	andl %edi,%edx
+	jnz   int_careful
+	andl	$~TS_COMPAT,TI_status(%rcx)
+	jmp	syscall_return
+
+	/* Either reschedule or signal or syscall exit tracking needed. */
+	/* First do a reschedule test. */
+	/* edx:	work, edi: workmask */
+int_careful:
+	bt $TIF_NEED_RESCHED,%edx
+	jnc  int_very_careful
+	TRACE_IRQS_ON
+	ENABLE_INTERRUPTS(CLBR_NONE)
+	pushq_cfi %rdi
+	SCHEDULE_USER
+	popq_cfi %rdi
+	DISABLE_INTERRUPTS(CLBR_NONE)
+	TRACE_IRQS_OFF
+	jmp int_with_check
+
+	/* handle signals and tracing -- both require a full pt_regs */
+int_very_careful:
+	TRACE_IRQS_ON
+	ENABLE_INTERRUPTS(CLBR_NONE)
+	SAVE_EXTRA_REGS
+	/* Check for syscall exit trace */
+	testl $_TIF_WORK_SYSCALL_EXIT,%edx
+	jz int_signal
+	pushq_cfi %rdi
+	leaq 8(%rsp),%rdi	# &ptregs -> arg1
+	call syscall_trace_leave
+	popq_cfi %rdi
+	andl $~(_TIF_WORK_SYSCALL_EXIT|_TIF_SYSCALL_EMU),%edi
+	jmp int_restore_rest
+
+int_signal:
+	testl $_TIF_DO_NOTIFY_MASK,%edx
+	jz 1f
+	movq %rsp,%rdi		# &ptregs -> arg1
+	xorl %esi,%esi		# oldset -> arg2
+	call do_notify_resume
+1:	movl $_TIF_WORK_MASK,%edi
+int_restore_rest:
+	RESTORE_EXTRA_REGS
+	DISABLE_INTERRUPTS(CLBR_NONE)
+	TRACE_IRQS_OFF
+	jmp int_with_check
+
+syscall_return:
+	/* The IRETQ could re-enable interrupts: */
+	DISABLE_INTERRUPTS(CLBR_ANY)
+	TRACE_IRQS_IRETQ
+
+	/*
+	 * Try to use SYSRET instead of IRET if we're returning to
+	 * a completely clean 64-bit userspace context.
+	 */
+	movq RCX(%rsp),%rcx
+	cmpq %rcx,RIP(%rsp)		/* RCX == RIP */
+	jne opportunistic_sysret_failed
+
+	/*
+	 * On Intel CPUs, SYSRET with non-canonical RCX/RIP will #GP
+	 * in kernel space.  This essentially lets the user take over
+	 * the kernel, since userspace controls RSP.  It's not worth
+	 * testing for canonicalness exactly -- this check detects any
+	 * of the 17 high bits set, which is true for non-canonical
+	 * or kernel addresses.  (This will pessimize vsyscall=native.
+	 * Big deal.)
+	 *
+	 * If virtual addresses ever become wider, this will need
+	 * to be updated to remain correct on both old and new CPUs.
+	 */
+	.ifne __VIRTUAL_MASK_SHIFT - 47
+	.error "virtual address width changed -- SYSRET checks need update"
+	.endif
+	shr $__VIRTUAL_MASK_SHIFT, %rcx
+	jnz opportunistic_sysret_failed
+
+	cmpq $__USER_CS,CS(%rsp)	/* CS must match SYSRET */
+	jne opportunistic_sysret_failed
+
+	movq R11(%rsp),%r11
+	cmpq %r11,EFLAGS(%rsp)		/* R11 == RFLAGS */
+	jne opportunistic_sysret_failed
+
+	/*
+	 * SYSRET can't restore RF.  SYSRET can restore TF, but unlike IRET,
+	 * restoring TF results in a trap from userspace immediately after
+	 * SYSRET.  This would cause an infinite loop whenever #DB happens
+	 * with register state that satisfies the opportunistic SYSRET
+	 * conditions.  For example, single-stepping this user code:
+	 *
+	 *           movq $stuck_here,%rcx
+	 *           pushfq
+	 *           popq %r11
+	 *   stuck_here:
+	 *
+	 * would never get past 'stuck_here'.
+	 */
+	testq $(X86_EFLAGS_RF|X86_EFLAGS_TF), %r11
+	jnz opportunistic_sysret_failed
+
+	/* nothing to check for RSP */
+
+	cmpq $__USER_DS,SS(%rsp)	/* SS must match SYSRET */
+	jne opportunistic_sysret_failed
+
+	/*
+	 * We win!  This label is here just for ease of understanding
+	 * perf profiles.  Nothing jumps here.
+	 */
+syscall_return_via_sysret:
+	CFI_REMEMBER_STATE
+	/* r11 is already restored (see code above) */
+	RESTORE_C_REGS_EXCEPT_R11
+	movq RSP(%rsp),%rsp
+	USERGS_SYSRET64
+	CFI_RESTORE_STATE
+
+opportunistic_sysret_failed:
+	SWAPGS
+	jmp	restore_c_regs_and_iret
+	CFI_ENDPROC
+END(system_call)
+
+
+	.macro FORK_LIKE func
+ENTRY(stub_\func)
+	CFI_STARTPROC
+	DEFAULT_FRAME 0, 8		/* offset 8: return address */
+	SAVE_EXTRA_REGS 8
+	jmp sys_\func
+	CFI_ENDPROC
+END(stub_\func)
+	.endm
+
+	FORK_LIKE  clone
+	FORK_LIKE  fork
+	FORK_LIKE  vfork
+
+ENTRY(stub_execve)
+	CFI_STARTPROC
+	DEFAULT_FRAME 0, 8
+	call	sys_execve
+return_from_execve:
+	testl	%eax, %eax
+	jz	1f
+	/* exec failed, can use fast SYSRET code path in this case */
+	ret
+1:
+	/* must use IRET code path (pt_regs->cs may have changed) */
+	addq	$8, %rsp
+	CFI_ADJUST_CFA_OFFSET -8
+	ZERO_EXTRA_REGS
+	movq	%rax,RAX(%rsp)
+	jmp	int_ret_from_sys_call
+	CFI_ENDPROC
+END(stub_execve)
+/*
+ * Remaining execve stubs are only 7 bytes long.
+ * ENTRY() often aligns to 16 bytes, which in this case has no benefits.
+ */
+	.align	8
+GLOBAL(stub_execveat)
+	CFI_STARTPROC
+	DEFAULT_FRAME 0, 8
+	call	sys_execveat
+	jmp	return_from_execve
+	CFI_ENDPROC
+END(stub_execveat)
+
+#ifdef CONFIG_X86_X32_ABI
+	.align	8
+GLOBAL(stub_x32_execve)
+	CFI_STARTPROC
+	DEFAULT_FRAME 0, 8
+	call	compat_sys_execve
+	jmp	return_from_execve
+	CFI_ENDPROC
+END(stub_x32_execve)
+	.align	8
+GLOBAL(stub_x32_execveat)
+	CFI_STARTPROC
+	DEFAULT_FRAME 0, 8
+	call	compat_sys_execveat
+	jmp	return_from_execve
+	CFI_ENDPROC
+END(stub_x32_execveat)
+#endif
+
+#ifdef CONFIG_IA32_EMULATION
+	.align	8
+GLOBAL(stub32_execve)
+	CFI_STARTPROC
+	call	compat_sys_execve
+	jmp	return_from_execve
+	CFI_ENDPROC
+END(stub32_execve)
+	.align	8
+GLOBAL(stub32_execveat)
+	CFI_STARTPROC
+	call	compat_sys_execveat
+	jmp	return_from_execve
+	CFI_ENDPROC
+END(stub32_execveat)
+#endif
+
+/*
+ * sigreturn is special because it needs to restore all registers on return.
+ * This cannot be done with SYSRET, so use the IRET return path instead.
+ */
+ENTRY(stub_rt_sigreturn)
+	CFI_STARTPROC
+	DEFAULT_FRAME 0, 8
+	/*
+	 * SAVE_EXTRA_REGS result is not normally needed:
+	 * sigreturn overwrites all pt_regs->GPREGS.
+	 * But sigreturn can fail (!), and there is no easy way to detect that.
+	 * To make sure RESTORE_EXTRA_REGS doesn't restore garbage on error,
+	 * we SAVE_EXTRA_REGS here.
+	 */
+	SAVE_EXTRA_REGS 8
+	call sys_rt_sigreturn
+return_from_stub:
+	addq	$8, %rsp
+	CFI_ADJUST_CFA_OFFSET -8
+	RESTORE_EXTRA_REGS
+	movq %rax,RAX(%rsp)
+	jmp int_ret_from_sys_call
+	CFI_ENDPROC
+END(stub_rt_sigreturn)
+
+#ifdef CONFIG_X86_X32_ABI
+ENTRY(stub_x32_rt_sigreturn)
+	CFI_STARTPROC
+	DEFAULT_FRAME 0, 8
+	SAVE_EXTRA_REGS 8
+	call sys32_x32_rt_sigreturn
+	jmp  return_from_stub
+	CFI_ENDPROC
+END(stub_x32_rt_sigreturn)
+#endif
+
+/*
+ * A newly forked process directly context switches into this address.
+ *
+ * rdi: prev task we switched from
+ */
+ENTRY(ret_from_fork)
+	DEFAULT_FRAME
+
+	LOCK ; btr $TIF_FORK,TI_flags(%r8)
+
+	pushq_cfi $0x0002
+	popfq_cfi				# reset kernel eflags
+
+	call schedule_tail			# rdi: 'prev' task parameter
+
+	RESTORE_EXTRA_REGS
+
+	testl $3,CS(%rsp)			# from kernel_thread?
+
+	/*
+	 * By the time we get here, we have no idea whether our pt_regs,
+	 * ti flags, and ti status came from the 64-bit SYSCALL fast path,
+	 * the slow path, or one of the ia32entry paths.
+	 * Use IRET code path to return, since it can safely handle
+	 * all of the above.
+	 */
+	jnz	int_ret_from_sys_call
+
+	/* We came from kernel_thread */
+	/* nb: we depend on RESTORE_EXTRA_REGS above */
+	movq %rbp, %rdi
+	call *%rbx
+	movl $0, RAX(%rsp)
+	RESTORE_EXTRA_REGS
+	jmp int_ret_from_sys_call
+	CFI_ENDPROC
+END(ret_from_fork)
+
+/*
+ * Build the entry stubs with some assembler magic.
+ * We pack 1 stub into every 8-byte block.
+ */
+	.align 8
+ENTRY(irq_entries_start)
+	INTR_FRAME
+    vector=FIRST_EXTERNAL_VECTOR
+    .rept (FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR)
+	pushq_cfi $(~vector+0x80)	/* Note: always in signed byte range */
+    vector=vector+1
+	jmp	common_interrupt
+	CFI_ADJUST_CFA_OFFSET -8
+	.align	8
+    .endr
+	CFI_ENDPROC
+END(irq_entries_start)
+
+/*
+ * Interrupt entry/exit.
+ *
+ * Interrupt entry points save only callee clobbered registers in fast path.
+ *
+ * Entry runs with interrupts off.
+ */
+
+/* 0(%rsp): ~(interrupt number) */
+	.macro interrupt func
+	cld
+	/*
+	 * Since nothing in interrupt handling code touches r12...r15 members
+	 * of "struct pt_regs", and since interrupts can nest, we can save
+	 * four stack slots and simultaneously provide
+	 * an unwind-friendly stack layout by saving "truncated" pt_regs
+	 * exactly up to rbp slot, without these members.
+	 */
+	ALLOC_PT_GPREGS_ON_STACK -RBP
+	SAVE_C_REGS -RBP
+	/* this goes to 0(%rsp) for unwinder, not for saving the value: */
+	SAVE_EXTRA_REGS_RBP -RBP
+
+	leaq -RBP(%rsp),%rdi	/* arg1 for \func (pointer to pt_regs) */
+
+	testl $3, CS-RBP(%rsp)
+	je 1f
+	SWAPGS
+1:
+	/*
+	 * Save previous stack pointer, optionally switch to interrupt stack.
+	 * irq_count is used to check if a CPU is already on an interrupt stack
+	 * or not. While this is essentially redundant with preempt_count it is
+	 * a little cheaper to use a separate counter in the PDA (short of
+	 * moving irq_enter into assembly, which would be too much work)
+	 */
+	movq %rsp, %rsi
+	incl PER_CPU_VAR(irq_count)
+	cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp
+	CFI_DEF_CFA_REGISTER	rsi
+	pushq %rsi
+	/*
+	 * For debugger:
+	 * "CFA (Current Frame Address) is the value on stack + offset"
+	 */
+	CFI_ESCAPE	0x0f /* DW_CFA_def_cfa_expression */, 6, \
+			0x77 /* DW_OP_breg7 (rsp) */, 0, \
+			0x06 /* DW_OP_deref */, \
+			0x08 /* DW_OP_const1u */, SIZEOF_PTREGS-RBP, \
+			0x22 /* DW_OP_plus */
+	/* We entered an interrupt context - irqs are off: */
+	TRACE_IRQS_OFF
+
+	call \func
+	.endm
+
+	/*
+	 * The interrupt stubs push (~vector+0x80) onto the stack and
+	 * then jump to common_interrupt.
+	 */
+	.p2align CONFIG_X86_L1_CACHE_SHIFT
+common_interrupt:
+	XCPT_FRAME
+	ASM_CLAC
+	addq $-0x80,(%rsp)		/* Adjust vector to [-256,-1] range */
+	interrupt do_IRQ
+	/* 0(%rsp): old RSP */
+ret_from_intr:
+	DISABLE_INTERRUPTS(CLBR_NONE)
+	TRACE_IRQS_OFF
+	decl PER_CPU_VAR(irq_count)
+
+	/* Restore saved previous stack */
+	popq %rsi
+	CFI_DEF_CFA rsi,SIZEOF_PTREGS-RBP /* reg/off reset after def_cfa_expr */
+	/* return code expects complete pt_regs - adjust rsp accordingly: */
+	leaq -RBP(%rsi),%rsp
+	CFI_DEF_CFA_REGISTER	rsp
+	CFI_ADJUST_CFA_OFFSET	RBP
+
+	testl $3,CS(%rsp)
+	je retint_kernel
+	/* Interrupt came from user space */
+
+	GET_THREAD_INFO(%rcx)
+	/*
+	 * %rcx: thread info. Interrupts off.
+	 */
+retint_with_reschedule:
+	movl $_TIF_WORK_MASK,%edi
+retint_check:
+	LOCKDEP_SYS_EXIT_IRQ
+	movl TI_flags(%rcx),%edx
+	andl %edi,%edx
+	CFI_REMEMBER_STATE
+	jnz  retint_careful
+
+retint_swapgs:		/* return to user-space */
+	/*
+	 * The iretq could re-enable interrupts:
+	 */
+	DISABLE_INTERRUPTS(CLBR_ANY)
+	TRACE_IRQS_IRETQ
+
+	SWAPGS
+	jmp	restore_c_regs_and_iret
+
+/* Returning to kernel space */
+retint_kernel:
+#ifdef CONFIG_PREEMPT
+	/* Interrupts are off */
+	/* Check if we need preemption */
+	bt	$9,EFLAGS(%rsp)	/* interrupts were off? */
+	jnc	1f
+0:	cmpl	$0,PER_CPU_VAR(__preempt_count)
+	jnz	1f
+	call	preempt_schedule_irq
+	jmp	0b
+1:
+#endif
+	/*
+	 * The iretq could re-enable interrupts:
+	 */
+	TRACE_IRQS_IRETQ
+
+/*
+ * At this label, code paths which return to kernel and to user,
+ * which come from interrupts/exception and from syscalls, merge.
+ */
+restore_c_regs_and_iret:
+	RESTORE_C_REGS
+	REMOVE_PT_GPREGS_FROM_STACK 8
+
+irq_return:
+	INTERRUPT_RETURN
+
+ENTRY(native_iret)
+	/*
+	 * Are we returning to a stack segment from the LDT?  Note: in
+	 * 64-bit mode SS:RSP on the exception stack is always valid.
+	 */
+#ifdef CONFIG_X86_ESPFIX64
+	testb $4,(SS-RIP)(%rsp)
+	jnz native_irq_return_ldt
+#endif
+
+.global native_irq_return_iret
+native_irq_return_iret:
+	/*
+	 * This may fault.  Non-paranoid faults on return to userspace are
+	 * handled by fixup_bad_iret.  These include #SS, #GP, and #NP.
+	 * Double-faults due to espfix64 are handled in do_double_fault.
+	 * Other faults here are fatal.
+	 */
+	iretq
+
+#ifdef CONFIG_X86_ESPFIX64
+native_irq_return_ldt:
+	pushq_cfi %rax
+	pushq_cfi %rdi
+	SWAPGS
+	movq PER_CPU_VAR(espfix_waddr),%rdi
+	movq %rax,(0*8)(%rdi)	/* RAX */
+	movq (2*8)(%rsp),%rax	/* RIP */
+	movq %rax,(1*8)(%rdi)
+	movq (3*8)(%rsp),%rax	/* CS */
+	movq %rax,(2*8)(%rdi)
+	movq (4*8)(%rsp),%rax	/* RFLAGS */
+	movq %rax,(3*8)(%rdi)
+	movq (6*8)(%rsp),%rax	/* SS */
+	movq %rax,(5*8)(%rdi)
+	movq (5*8)(%rsp),%rax	/* RSP */
+	movq %rax,(4*8)(%rdi)
+	andl $0xffff0000,%eax
+	popq_cfi %rdi
+	orq PER_CPU_VAR(espfix_stack),%rax
+	SWAPGS
+	movq %rax,%rsp
+	popq_cfi %rax
+	jmp native_irq_return_iret
+#endif
+
+	/* edi: workmask, edx: work */
+retint_careful:
+	CFI_RESTORE_STATE
+	bt    $TIF_NEED_RESCHED,%edx
+	jnc   retint_signal
+	TRACE_IRQS_ON
+	ENABLE_INTERRUPTS(CLBR_NONE)
+	pushq_cfi %rdi
+	SCHEDULE_USER
+	popq_cfi %rdi
+	GET_THREAD_INFO(%rcx)
+	DISABLE_INTERRUPTS(CLBR_NONE)
+	TRACE_IRQS_OFF
+	jmp retint_check
+
+retint_signal:
+	testl $_TIF_DO_NOTIFY_MASK,%edx
+	jz    retint_swapgs
+	TRACE_IRQS_ON
+	ENABLE_INTERRUPTS(CLBR_NONE)
+	SAVE_EXTRA_REGS
+	movq $-1,ORIG_RAX(%rsp)
+	xorl %esi,%esi		# oldset
+	movq %rsp,%rdi		# &pt_regs
+	call do_notify_resume
+	RESTORE_EXTRA_REGS
+	DISABLE_INTERRUPTS(CLBR_NONE)
+	TRACE_IRQS_OFF
+	GET_THREAD_INFO(%rcx)
+	jmp retint_with_reschedule
+
+	CFI_ENDPROC
+END(common_interrupt)
+
+/*
+ * APIC interrupts.
+ */
+.macro apicinterrupt3 num sym do_sym
+ENTRY(\sym)
+	INTR_FRAME
+	ASM_CLAC
+	pushq_cfi $~(\num)
+.Lcommon_\sym:
+	interrupt \do_sym
+	jmp ret_from_intr
+	CFI_ENDPROC
+END(\sym)
+.endm
+
+#ifdef CONFIG_TRACING
+#define trace(sym) trace_##sym
+#define smp_trace(sym) smp_trace_##sym
+
+.macro trace_apicinterrupt num sym
+apicinterrupt3 \num trace(\sym) smp_trace(\sym)
+.endm
+#else
+.macro trace_apicinterrupt num sym do_sym
+.endm
+#endif
+
+.macro apicinterrupt num sym do_sym
+apicinterrupt3 \num \sym \do_sym
+trace_apicinterrupt \num \sym
+.endm
+
+#ifdef CONFIG_SMP
+apicinterrupt3 IRQ_MOVE_CLEANUP_VECTOR \
+	irq_move_cleanup_interrupt smp_irq_move_cleanup_interrupt
+apicinterrupt3 REBOOT_VECTOR \
+	reboot_interrupt smp_reboot_interrupt
+#endif
+
+#ifdef CONFIG_X86_UV
+apicinterrupt3 UV_BAU_MESSAGE \
+	uv_bau_message_intr1 uv_bau_message_interrupt
+#endif
+apicinterrupt LOCAL_TIMER_VECTOR \
+	apic_timer_interrupt smp_apic_timer_interrupt
+apicinterrupt X86_PLATFORM_IPI_VECTOR \
+	x86_platform_ipi smp_x86_platform_ipi
+
+#ifdef CONFIG_HAVE_KVM
+apicinterrupt3 POSTED_INTR_VECTOR \
+	kvm_posted_intr_ipi smp_kvm_posted_intr_ipi
+#endif
+
+#ifdef CONFIG_X86_MCE_THRESHOLD
+apicinterrupt THRESHOLD_APIC_VECTOR \
+	threshold_interrupt smp_threshold_interrupt
+#endif
+
+#ifdef CONFIG_X86_THERMAL_VECTOR
+apicinterrupt THERMAL_APIC_VECTOR \
+	thermal_interrupt smp_thermal_interrupt
+#endif
+
+#ifdef CONFIG_SMP
+apicinterrupt CALL_FUNCTION_SINGLE_VECTOR \
+	call_function_single_interrupt smp_call_function_single_interrupt
+apicinterrupt CALL_FUNCTION_VECTOR \
+	call_function_interrupt smp_call_function_interrupt
+apicinterrupt RESCHEDULE_VECTOR \
+	reschedule_interrupt smp_reschedule_interrupt
+#endif
+
+apicinterrupt ERROR_APIC_VECTOR \
+	error_interrupt smp_error_interrupt
+apicinterrupt SPURIOUS_APIC_VECTOR \
+	spurious_interrupt smp_spurious_interrupt
+
+#ifdef CONFIG_IRQ_WORK
+apicinterrupt IRQ_WORK_VECTOR \
+	irq_work_interrupt smp_irq_work_interrupt
+#endif
+
+/*
+ * Exception entry points.
+ */
+#define CPU_TSS_IST(x) PER_CPU_VAR(cpu_tss) + (TSS_ist + ((x) - 1) * 8)
+
+.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1
+ENTRY(\sym)
+	/* Sanity check */
+	.if \shift_ist != -1 && \paranoid == 0
+	.error "using shift_ist requires paranoid=1"
+	.endif
+
+	.if \has_error_code
+	XCPT_FRAME
+	.else
+	INTR_FRAME
+	.endif
+
+	ASM_CLAC
+	PARAVIRT_ADJUST_EXCEPTION_FRAME
+
+	.ifeq \has_error_code
+	pushq_cfi $-1			/* ORIG_RAX: no syscall to restart */
+	.endif
+
+	ALLOC_PT_GPREGS_ON_STACK
+
+	.if \paranoid
+	.if \paranoid == 1
+	CFI_REMEMBER_STATE
+	testl $3, CS(%rsp)		/* If coming from userspace, switch */
+	jnz 1f				/* stacks. */
+	.endif
+	call paranoid_entry
+	.else
+	call error_entry
+	.endif
+	/* returned flag: ebx=0: need swapgs on exit, ebx=1: don't need it */
+
+	DEFAULT_FRAME 0
+
+	.if \paranoid
+	.if \shift_ist != -1
+	TRACE_IRQS_OFF_DEBUG		/* reload IDT in case of recursion */
+	.else
+	TRACE_IRQS_OFF
+	.endif
+	.endif
+
+	movq %rsp,%rdi			/* pt_regs pointer */
+
+	.if \has_error_code
+	movq ORIG_RAX(%rsp),%rsi	/* get error code */
+	movq $-1,ORIG_RAX(%rsp)		/* no syscall to restart */
+	.else
+	xorl %esi,%esi			/* no error code */
+	.endif
+
+	.if \shift_ist != -1
+	subq $EXCEPTION_STKSZ, CPU_TSS_IST(\shift_ist)
+	.endif
+
+	call \do_sym
+
+	.if \shift_ist != -1
+	addq $EXCEPTION_STKSZ, CPU_TSS_IST(\shift_ist)
+	.endif
+
+	/* these procedures expect "no swapgs" flag in ebx */
+	.if \paranoid
+	jmp paranoid_exit
+	.else
+	jmp error_exit
+	.endif
+
+	.if \paranoid == 1
+	CFI_RESTORE_STATE
+	/*
+	 * Paranoid entry from userspace.  Switch stacks and treat it
+	 * as a normal entry.  This means that paranoid handlers
+	 * run in real process context if user_mode(regs).
+	 */
+1:
+	call error_entry
+
+	DEFAULT_FRAME 0
+
+	movq %rsp,%rdi			/* pt_regs pointer */
+	call sync_regs
+	movq %rax,%rsp			/* switch stack */
+
+	movq %rsp,%rdi			/* pt_regs pointer */
+
+	.if \has_error_code
+	movq ORIG_RAX(%rsp),%rsi	/* get error code */
+	movq $-1,ORIG_RAX(%rsp)		/* no syscall to restart */
+	.else
+	xorl %esi,%esi			/* no error code */
+	.endif
+
+	call \do_sym
+
+	jmp error_exit			/* %ebx: no swapgs flag */
+	.endif
+
+	CFI_ENDPROC
+END(\sym)
+.endm
+
+#ifdef CONFIG_TRACING
+.macro trace_idtentry sym do_sym has_error_code:req
+idtentry trace(\sym) trace(\do_sym) has_error_code=\has_error_code
+idtentry \sym \do_sym has_error_code=\has_error_code
+.endm
+#else
+.macro trace_idtentry sym do_sym has_error_code:req
+idtentry \sym \do_sym has_error_code=\has_error_code
+.endm
+#endif
+
+idtentry divide_error do_divide_error has_error_code=0
+idtentry overflow do_overflow has_error_code=0
+idtentry bounds do_bounds has_error_code=0
+idtentry invalid_op do_invalid_op has_error_code=0
+idtentry device_not_available do_device_not_available has_error_code=0
+idtentry double_fault do_double_fault has_error_code=1 paranoid=2
+idtentry coprocessor_segment_overrun do_coprocessor_segment_overrun has_error_code=0
+idtentry invalid_TSS do_invalid_TSS has_error_code=1
+idtentry segment_not_present do_segment_not_present has_error_code=1
+idtentry spurious_interrupt_bug do_spurious_interrupt_bug has_error_code=0
+idtentry coprocessor_error do_coprocessor_error has_error_code=0
+idtentry alignment_check do_alignment_check has_error_code=1
+idtentry simd_coprocessor_error do_simd_coprocessor_error has_error_code=0
+
+
+	/* Reload gs selector with exception handling */
+	/* edi:  new selector */
+ENTRY(native_load_gs_index)
+	CFI_STARTPROC
+	pushfq_cfi
+	DISABLE_INTERRUPTS(CLBR_ANY & ~CLBR_RDI)
+	SWAPGS
+gs_change:
+	movl %edi,%gs
+2:	mfence		/* workaround */
+	SWAPGS
+	popfq_cfi
+	ret
+	CFI_ENDPROC
+END(native_load_gs_index)
+
+	_ASM_EXTABLE(gs_change,bad_gs)
+	.section .fixup,"ax"
+	/* running with kernelgs */
+bad_gs:
+	SWAPGS			/* switch back to user gs */
+	xorl %eax,%eax
+	movl %eax,%gs
+	jmp  2b
+	.previous
+
+/* Call softirq on interrupt stack. Interrupts are off. */
+ENTRY(do_softirq_own_stack)
+	CFI_STARTPROC
+	pushq_cfi %rbp
+	CFI_REL_OFFSET rbp,0
+	mov  %rsp,%rbp
+	CFI_DEF_CFA_REGISTER rbp
+	incl PER_CPU_VAR(irq_count)
+	cmove PER_CPU_VAR(irq_stack_ptr),%rsp
+	push  %rbp			# backlink for old unwinder
+	call __do_softirq
+	leaveq
+	CFI_RESTORE		rbp
+	CFI_DEF_CFA_REGISTER	rsp
+	CFI_ADJUST_CFA_OFFSET   -8
+	decl PER_CPU_VAR(irq_count)
+	ret
+	CFI_ENDPROC
+END(do_softirq_own_stack)
+
+#ifdef CONFIG_XEN
+idtentry xen_hypervisor_callback xen_do_hypervisor_callback has_error_code=0
+
+/*
+ * A note on the "critical region" in our callback handler.
+ * We want to avoid stacking callback handlers due to events occurring
+ * during handling of the last event. To do this, we keep events disabled
+ * until we've done all processing. HOWEVER, we must enable events before
+ * popping the stack frame (can't be done atomically) and so it would still
+ * be possible to get enough handler activations to overflow the stack.
+ * Although unlikely, bugs of that kind are hard to track down, so we'd
+ * like to avoid the possibility.
+ * So, on entry to the handler we detect whether we interrupted an
+ * existing activation in its critical region -- if so, we pop the current
+ * activation and restart the handler using the previous one.
+ */
+ENTRY(xen_do_hypervisor_callback)   # do_hypervisor_callback(struct *pt_regs)
+	CFI_STARTPROC
+/*
+ * Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will
+ * see the correct pointer to the pt_regs
+ */
+	movq %rdi, %rsp            # we don't return, adjust the stack frame
+	CFI_ENDPROC
+	DEFAULT_FRAME
+11:	incl PER_CPU_VAR(irq_count)
+	movq %rsp,%rbp
+	CFI_DEF_CFA_REGISTER rbp
+	cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp
+	pushq %rbp			# backlink for old unwinder
+	call xen_evtchn_do_upcall
+	popq %rsp
+	CFI_DEF_CFA_REGISTER rsp
+	decl PER_CPU_VAR(irq_count)
+#ifndef CONFIG_PREEMPT
+	call xen_maybe_preempt_hcall
+#endif
+	jmp  error_exit
+	CFI_ENDPROC
+END(xen_do_hypervisor_callback)
+
+/*
+ * Hypervisor uses this for application faults while it executes.
+ * We get here for two reasons:
+ *  1. Fault while reloading DS, ES, FS or GS
+ *  2. Fault while executing IRET
+ * Category 1 we do not need to fix up as Xen has already reloaded all segment
+ * registers that could be reloaded and zeroed the others.
+ * Category 2 we fix up by killing the current process. We cannot use the
+ * normal Linux return path in this case because if we use the IRET hypercall
+ * to pop the stack frame we end up in an infinite loop of failsafe callbacks.
+ * We distinguish between categories by comparing each saved segment register
+ * with its current contents: any discrepancy means we in category 1.
+ */
+ENTRY(xen_failsafe_callback)
+	INTR_FRAME 1 (6*8)
+	/*CFI_REL_OFFSET gs,GS*/
+	/*CFI_REL_OFFSET fs,FS*/
+	/*CFI_REL_OFFSET es,ES*/
+	/*CFI_REL_OFFSET ds,DS*/
+	CFI_REL_OFFSET r11,8
+	CFI_REL_OFFSET rcx,0
+	movw %ds,%cx
+	cmpw %cx,0x10(%rsp)
+	CFI_REMEMBER_STATE
+	jne 1f
+	movw %es,%cx
+	cmpw %cx,0x18(%rsp)
+	jne 1f
+	movw %fs,%cx
+	cmpw %cx,0x20(%rsp)
+	jne 1f
+	movw %gs,%cx
+	cmpw %cx,0x28(%rsp)
+	jne 1f
+	/* All segments match their saved values => Category 2 (Bad IRET). */
+	movq (%rsp),%rcx
+	CFI_RESTORE rcx
+	movq 8(%rsp),%r11
+	CFI_RESTORE r11
+	addq $0x30,%rsp
+	CFI_ADJUST_CFA_OFFSET -0x30
+	pushq_cfi $0	/* RIP */
+	pushq_cfi %r11
+	pushq_cfi %rcx
+	jmp general_protection
+	CFI_RESTORE_STATE
+1:	/* Segment mismatch => Category 1 (Bad segment). Retry the IRET. */
+	movq (%rsp),%rcx
+	CFI_RESTORE rcx
+	movq 8(%rsp),%r11
+	CFI_RESTORE r11
+	addq $0x30,%rsp
+	CFI_ADJUST_CFA_OFFSET -0x30
+	pushq_cfi $-1 /* orig_ax = -1 => not a system call */
+	ALLOC_PT_GPREGS_ON_STACK
+	SAVE_C_REGS
+	SAVE_EXTRA_REGS
+	jmp error_exit
+	CFI_ENDPROC
+END(xen_failsafe_callback)
+
+apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
+	xen_hvm_callback_vector xen_evtchn_do_upcall
+
+#endif /* CONFIG_XEN */
+
+#if IS_ENABLED(CONFIG_HYPERV)
+apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
+	hyperv_callback_vector hyperv_vector_handler
+#endif /* CONFIG_HYPERV */
+
+idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK
+idtentry int3 do_int3 has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK
+idtentry stack_segment do_stack_segment has_error_code=1
+#ifdef CONFIG_XEN
+idtentry xen_debug do_debug has_error_code=0
+idtentry xen_int3 do_int3 has_error_code=0
+idtentry xen_stack_segment do_stack_segment has_error_code=1
+#endif
+idtentry general_protection do_general_protection has_error_code=1
+trace_idtentry page_fault do_page_fault has_error_code=1
+#ifdef CONFIG_KVM_GUEST
+idtentry async_page_fault do_async_page_fault has_error_code=1
+#endif
+#ifdef CONFIG_X86_MCE
+idtentry machine_check has_error_code=0 paranoid=1 do_sym=*machine_check_vector(%rip)
+#endif
+
+/*
+ * Save all registers in pt_regs, and switch gs if needed.
+ * Use slow, but surefire "are we in kernel?" check.
+ * Return: ebx=0: need swapgs on exit, ebx=1: otherwise
+ */
+ENTRY(paranoid_entry)
+	XCPT_FRAME 1 15*8
+	cld
+	SAVE_C_REGS 8
+	SAVE_EXTRA_REGS 8
+	movl $1,%ebx
+	movl $MSR_GS_BASE,%ecx
+	rdmsr
+	testl %edx,%edx
+	js 1f	/* negative -> in kernel */
+	SWAPGS
+	xorl %ebx,%ebx
+1:	ret
+	CFI_ENDPROC
+END(paranoid_entry)
+
+/*
+ * "Paranoid" exit path from exception stack.  This is invoked
+ * only on return from non-NMI IST interrupts that came
+ * from kernel space.
+ *
+ * We may be returning to very strange contexts (e.g. very early
+ * in syscall entry), so checking for preemption here would
+ * be complicated.  Fortunately, we there's no good reason
+ * to try to handle preemption here.
+ */
+/* On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it) */
+ENTRY(paranoid_exit)
+	DEFAULT_FRAME
+	DISABLE_INTERRUPTS(CLBR_NONE)
+	TRACE_IRQS_OFF_DEBUG
+	testl %ebx,%ebx				/* swapgs needed? */
+	jnz paranoid_exit_no_swapgs
+	TRACE_IRQS_IRETQ
+	SWAPGS_UNSAFE_STACK
+	jmp paranoid_exit_restore
+paranoid_exit_no_swapgs:
+	TRACE_IRQS_IRETQ_DEBUG
+paranoid_exit_restore:
+	RESTORE_EXTRA_REGS
+	RESTORE_C_REGS
+	REMOVE_PT_GPREGS_FROM_STACK 8
+	INTERRUPT_RETURN
+	CFI_ENDPROC
+END(paranoid_exit)
+
+/*
+ * Save all registers in pt_regs, and switch gs if needed.
+ * Return: ebx=0: need swapgs on exit, ebx=1: otherwise
+ */
+ENTRY(error_entry)
+	XCPT_FRAME 1 15*8
+	cld
+	SAVE_C_REGS 8
+	SAVE_EXTRA_REGS 8
+	xorl %ebx,%ebx
+	testl $3,CS+8(%rsp)
+	je error_kernelspace
+error_swapgs:
+	SWAPGS
+error_sti:
+	TRACE_IRQS_OFF
+	ret
+
+	/*
+	 * There are two places in the kernel that can potentially fault with
+	 * usergs. Handle them here.  B stepping K8s sometimes report a
+	 * truncated RIP for IRET exceptions returning to compat mode. Check
+	 * for these here too.
+	 */
+error_kernelspace:
+	CFI_REL_OFFSET rcx, RCX+8
+	incl %ebx
+	leaq native_irq_return_iret(%rip),%rcx
+	cmpq %rcx,RIP+8(%rsp)
+	je error_bad_iret
+	movl %ecx,%eax	/* zero extend */
+	cmpq %rax,RIP+8(%rsp)
+	je bstep_iret
+	cmpq $gs_change,RIP+8(%rsp)
+	je error_swapgs
+	jmp error_sti
+
+bstep_iret:
+	/* Fix truncated RIP */
+	movq %rcx,RIP+8(%rsp)
+	/* fall through */
+
+error_bad_iret:
+	SWAPGS
+	mov %rsp,%rdi
+	call fixup_bad_iret
+	mov %rax,%rsp
+	decl %ebx	/* Return to usergs */
+	jmp error_sti
+	CFI_ENDPROC
+END(error_entry)
+
+
+/* On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it) */
+ENTRY(error_exit)
+	DEFAULT_FRAME
+	movl %ebx,%eax
+	RESTORE_EXTRA_REGS
+	DISABLE_INTERRUPTS(CLBR_NONE)
+	TRACE_IRQS_OFF
+	GET_THREAD_INFO(%rcx)
+	testl %eax,%eax
+	jne retint_kernel
+	LOCKDEP_SYS_EXIT_IRQ
+	movl TI_flags(%rcx),%edx
+	movl $_TIF_WORK_MASK,%edi
+	andl %edi,%edx
+	jnz retint_careful
+	jmp retint_swapgs
+	CFI_ENDPROC
+END(error_exit)
+
+/* Runs on exception stack */
+ENTRY(nmi)
+	INTR_FRAME
+	PARAVIRT_ADJUST_EXCEPTION_FRAME
+	/*
+	 * We allow breakpoints in NMIs. If a breakpoint occurs, then
+	 * the iretq it performs will take us out of NMI context.
+	 * This means that we can have nested NMIs where the next
+	 * NMI is using the top of the stack of the previous NMI. We
+	 * can't let it execute because the nested NMI will corrupt the
+	 * stack of the previous NMI. NMI handlers are not re-entrant
+	 * anyway.
+	 *
+	 * To handle this case we do the following:
+	 *  Check the a special location on the stack that contains
+	 *  a variable that is set when NMIs are executing.
+	 *  The interrupted task's stack is also checked to see if it
+	 *  is an NMI stack.
+	 *  If the variable is not set and the stack is not the NMI
+	 *  stack then:
+	 *    o Set the special variable on the stack
+	 *    o Copy the interrupt frame into a "saved" location on the stack
+	 *    o Copy the interrupt frame into a "copy" location on the stack
+	 *    o Continue processing the NMI
+	 *  If the variable is set or the previous stack is the NMI stack:
+	 *    o Modify the "copy" location to jump to the repeate_nmi
+	 *    o return back to the first NMI
+	 *
+	 * Now on exit of the first NMI, we first clear the stack variable
+	 * The NMI stack will tell any nested NMIs at that point that it is
+	 * nested. Then we pop the stack normally with iret, and if there was
+	 * a nested NMI that updated the copy interrupt stack frame, a
+	 * jump will be made to the repeat_nmi code that will handle the second
+	 * NMI.
+	 */
+
+	/* Use %rdx as our temp variable throughout */
+	pushq_cfi %rdx
+	CFI_REL_OFFSET rdx, 0
+
+	/*
+	 * If %cs was not the kernel segment, then the NMI triggered in user
+	 * space, which means it is definitely not nested.
+	 */
+	cmpl $__KERNEL_CS, 16(%rsp)
+	jne first_nmi
+
+	/*
+	 * Check the special variable on the stack to see if NMIs are
+	 * executing.
+	 */
+	cmpl $1, -8(%rsp)
+	je nested_nmi
+
+	/*
+	 * Now test if the previous stack was an NMI stack.
+	 * We need the double check. We check the NMI stack to satisfy the
+	 * race when the first NMI clears the variable before returning.
+	 * We check the variable because the first NMI could be in a
+	 * breakpoint routine using a breakpoint stack.
+	 */
+	lea	6*8(%rsp), %rdx
+	/* Compare the NMI stack (rdx) with the stack we came from (4*8(%rsp)) */
+	cmpq	%rdx, 4*8(%rsp)
+	/* If the stack pointer is above the NMI stack, this is a normal NMI */
+	ja	first_nmi
+	subq	$EXCEPTION_STKSZ, %rdx
+	cmpq	%rdx, 4*8(%rsp)
+	/* If it is below the NMI stack, it is a normal NMI */
+	jb	first_nmi
+	/* Ah, it is within the NMI stack, treat it as nested */
+
+	CFI_REMEMBER_STATE
+
+nested_nmi:
+	/*
+	 * Do nothing if we interrupted the fixup in repeat_nmi.
+	 * It's about to repeat the NMI handler, so we are fine
+	 * with ignoring this one.
+	 */
+	movq $repeat_nmi, %rdx
+	cmpq 8(%rsp), %rdx
+	ja 1f
+	movq $end_repeat_nmi, %rdx
+	cmpq 8(%rsp), %rdx
+	ja nested_nmi_out
+
+1:
+	/* Set up the interrupted NMIs stack to jump to repeat_nmi */
+	leaq -1*8(%rsp), %rdx
+	movq %rdx, %rsp
+	CFI_ADJUST_CFA_OFFSET 1*8
+	leaq -10*8(%rsp), %rdx
+	pushq_cfi $__KERNEL_DS
+	pushq_cfi %rdx
+	pushfq_cfi
+	pushq_cfi $__KERNEL_CS
+	pushq_cfi $repeat_nmi
+
+	/* Put stack back */
+	addq $(6*8), %rsp
+	CFI_ADJUST_CFA_OFFSET -6*8
+
+nested_nmi_out:
+	popq_cfi %rdx
+	CFI_RESTORE rdx
+
+	/* No need to check faults here */
+	INTERRUPT_RETURN
+
+	CFI_RESTORE_STATE
+first_nmi:
+	/*
+	 * Because nested NMIs will use the pushed location that we
+	 * stored in rdx, we must keep that space available.
+	 * Here's what our stack frame will look like:
+	 * +-------------------------+
+	 * | original SS             |
+	 * | original Return RSP     |
+	 * | original RFLAGS         |
+	 * | original CS             |
+	 * | original RIP            |
+	 * +-------------------------+
+	 * | temp storage for rdx    |
+	 * +-------------------------+
+	 * | NMI executing variable  |
+	 * +-------------------------+
+	 * | copied SS               |
+	 * | copied Return RSP       |
+	 * | copied RFLAGS           |
+	 * | copied CS               |
+	 * | copied RIP              |
+	 * +-------------------------+
+	 * | Saved SS                |
+	 * | Saved Return RSP        |
+	 * | Saved RFLAGS            |
+	 * | Saved CS                |
+	 * | Saved RIP               |
+	 * +-------------------------+
+	 * | pt_regs                 |
+	 * +-------------------------+
+	 *
+	 * The saved stack frame is used to fix up the copied stack frame
+	 * that a nested NMI may change to make the interrupted NMI iret jump
+	 * to the repeat_nmi. The original stack frame and the temp storage
+	 * is also used by nested NMIs and can not be trusted on exit.
+	 */
+	/* Do not pop rdx, nested NMIs will corrupt that part of the stack */
+	movq (%rsp), %rdx
+	CFI_RESTORE rdx
+
+	/* Set the NMI executing variable on the stack. */
+	pushq_cfi $1
+
+	/*
+	 * Leave room for the "copied" frame
+	 */
+	subq $(5*8), %rsp
+	CFI_ADJUST_CFA_OFFSET 5*8
+
+	/* Copy the stack frame to the Saved frame */
+	.rept 5
+	pushq_cfi 11*8(%rsp)
+	.endr
+	CFI_DEF_CFA_OFFSET 5*8
+
+	/* Everything up to here is safe from nested NMIs */
+
+	/*
+	 * If there was a nested NMI, the first NMI's iret will return
+	 * here. But NMIs are still enabled and we can take another
+	 * nested NMI. The nested NMI checks the interrupted RIP to see
+	 * if it is between repeat_nmi and end_repeat_nmi, and if so
+	 * it will just return, as we are about to repeat an NMI anyway.
+	 * This makes it safe to copy to the stack frame that a nested
+	 * NMI will update.
+	 */
+repeat_nmi:
+	/*
+	 * Update the stack variable to say we are still in NMI (the update
+	 * is benign for the non-repeat case, where 1 was pushed just above
+	 * to this very stack slot).
+	 */
+	movq $1, 10*8(%rsp)
+
+	/* Make another copy, this one may be modified by nested NMIs */
+	addq $(10*8), %rsp
+	CFI_ADJUST_CFA_OFFSET -10*8
+	.rept 5
+	pushq_cfi -6*8(%rsp)
+	.endr
+	subq $(5*8), %rsp
+	CFI_DEF_CFA_OFFSET 5*8
+end_repeat_nmi:
+
+	/*
+	 * Everything below this point can be preempted by a nested
+	 * NMI if the first NMI took an exception and reset our iret stack
+	 * so that we repeat another NMI.
+	 */
+	pushq_cfi $-1		/* ORIG_RAX: no syscall to restart */
+	ALLOC_PT_GPREGS_ON_STACK
+
+	/*
+	 * Use paranoid_entry to handle SWAPGS, but no need to use paranoid_exit
+	 * as we should not be calling schedule in NMI context.
+	 * Even with normal interrupts enabled. An NMI should not be
+	 * setting NEED_RESCHED or anything that normal interrupts and
+	 * exceptions might do.
+	 */
+	call paranoid_entry
+	DEFAULT_FRAME 0
+
+	/*
+	 * Save off the CR2 register. If we take a page fault in the NMI then
+	 * it could corrupt the CR2 value. If the NMI preempts a page fault
+	 * handler before it was able to read the CR2 register, and then the
+	 * NMI itself takes a page fault, the page fault that was preempted
+	 * will read the information from the NMI page fault and not the
+	 * origin fault. Save it off and restore it if it changes.
+	 * Use the r12 callee-saved register.
+	 */
+	movq %cr2, %r12
+
+	/* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
+	movq %rsp,%rdi
+	movq $-1,%rsi
+	call do_nmi
+
+	/* Did the NMI take a page fault? Restore cr2 if it did */
+	movq %cr2, %rcx
+	cmpq %rcx, %r12
+	je 1f
+	movq %r12, %cr2
+1:
+	
+	testl %ebx,%ebx				/* swapgs needed? */
+	jnz nmi_restore
+nmi_swapgs:
+	SWAPGS_UNSAFE_STACK
+nmi_restore:
+	RESTORE_EXTRA_REGS
+	RESTORE_C_REGS
+	/* Pop the extra iret frame at once */
+	REMOVE_PT_GPREGS_FROM_STACK 6*8
+
+	/* Clear the NMI executing stack variable */
+	movq $0, 5*8(%rsp)
+	jmp irq_return
+	CFI_ENDPROC
+END(nmi)
+
+ENTRY(ignore_sysret)
+	CFI_STARTPROC
+	mov $-ENOSYS,%eax
+	sysret
+	CFI_ENDPROC
+END(ignore_sysret)
+