Merge branch 'linus' into x86/asm

[mirror_ubuntu-artful-kernel.git] / arch / x86 / kernel / entry_64.S

/*
 *  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.
 *
 * Normal syscalls and interrupts don't save a full stack frame, this is
 * only done for syscall tracing, signals or fork/exec et.al.
 *
 * A note on terminology:
 * - top of stack: Architecture defined interrupt frame from SS to RIP
 * at the top of the kernel process stack.
 * - partial stack frame: partially saved registers up to R11.
 * - full stack frame: Like partial stack frame, but all register saved.
 *
 * Some macro usage:
 * - CFI macros are used to generate dwarf2 unwind information for better
 * backtraces. They don't change any code.
 * - SAVE_ALL/RESTORE_ALL - Save/restore all registers
 * - SAVE_ARGS/RESTORE_ARGS - Save/restore registers that C functions modify.
 * There are unfortunately lots of special cases where some registers
 * not touched. The macro is a big mess that should be cleaned up.
 * - SAVE_REST/RESTORE_REST - Handle the registers not saved by SAVE_ARGS.
 * Gives a full stack frame.
 * - ENTRY/END Define functions in the symbol table.
 * - FIXUP_TOP_OF_STACK/RESTORE_TOP_OF_STACK - Fix up the hardware stack
 * frame that is otherwise undefined after a SYSCALL
 * - TRACE_IRQ_* - Trace hard interrupt state for lock debugging.
 * - errorentry/paranoidentry/zeroentry - 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/ftrace.h>
#include <asm/percpu.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_FUNCTION_TRACER
#ifdef CONFIG_DYNAMIC_FTRACE
ENTRY(mcount)
        retq
END(mcount)

ENTRY(ftrace_caller)
        cmpl $0, function_trace_stop
        jne  ftrace_stub

        MCOUNT_SAVE_FRAME

        movq 0x38(%rsp), %rdi
        movq 8(%rbp), %rsi
        subq $MCOUNT_INSN_SIZE, %rdi

GLOBAL(ftrace_call)
        call ftrace_stub

        MCOUNT_RESTORE_FRAME

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
GLOBAL(ftrace_graph_call)
        jmp ftrace_stub
#endif

GLOBAL(ftrace_stub)
        retq
END(ftrace_caller)

#else /* ! CONFIG_DYNAMIC_FTRACE */
ENTRY(mcount)
        cmpl $0, function_trace_stop
        jne  ftrace_stub

        cmpq $ftrace_stub, ftrace_trace_function
        jnz trace

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
        cmpq $ftrace_stub, ftrace_graph_return
        jnz ftrace_graph_caller

        cmpq $ftrace_graph_entry_stub, ftrace_graph_entry
        jnz ftrace_graph_caller
#endif

GLOBAL(ftrace_stub)
        retq

trace:
        MCOUNT_SAVE_FRAME

        movq 0x38(%rsp), %rdi
        movq 8(%rbp), %rsi
        subq $MCOUNT_INSN_SIZE, %rdi

        call   *ftrace_trace_function

        MCOUNT_RESTORE_FRAME

        jmp ftrace_stub
END(mcount)
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_TRACER */

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ENTRY(ftrace_graph_caller)
        cmpl $0, function_trace_stop
        jne ftrace_stub

        MCOUNT_SAVE_FRAME

        leaq 8(%rbp), %rdi
        movq 0x38(%rsp), %rsi
        movq (%rbp), %rdx
        subq $MCOUNT_INSN_SIZE, %rsi

        call    prepare_ftrace_return

        MCOUNT_RESTORE_FRAME

        retq
END(ftrace_graph_caller)

GLOBAL(return_to_handler)
        subq  $24, %rsp

        /* Save the return values */
        movq %rax, (%rsp)
        movq %rdx, 8(%rsp)
        movq %rbp, %rdi

        call ftrace_return_to_handler

        movq %rax, %rdi
        movq 8(%rsp), %rdx
        movq (%rsp), %rax
        addq $24, %rsp
        jmp *%rdi
#endif


#ifndef CONFIG_PREEMPT
#define retint_kernel retint_restore_args
#endif

#ifdef CONFIG_PARAVIRT
ENTRY(native_usergs_sysret64)
        swapgs
        sysretq
ENDPROC(native_usergs_sysret64)
#endif /* CONFIG_PARAVIRT */


.macro TRACE_IRQS_IRETQ offset=ARGOFFSET
#ifdef CONFIG_TRACE_IRQFLAGS
        bt   $9,EFLAGS-\offset(%rsp)    /* interrupts off? */
        jnc  1f
        TRACE_IRQS_ON
1:
#endif
.endm

/*
 * C code is not supposed to know about undefined top of stack. Every time
 * a C function with an pt_regs argument is called from the SYSCALL based
 * fast path FIXUP_TOP_OF_STACK is needed.
 * RESTORE_TOP_OF_STACK syncs the syscall state after any possible ptregs
 * manipulation.
 */

        /* %rsp:at FRAMEEND */
        .macro FIXUP_TOP_OF_STACK tmp offset=0
        movq PER_CPU_VAR(old_rsp),\tmp
        movq \tmp,RSP+\offset(%rsp)
        movq $__USER_DS,SS+\offset(%rsp)
        movq $__USER_CS,CS+\offset(%rsp)
        movq $-1,RCX+\offset(%rsp)
        movq R11+\offset(%rsp),\tmp  /* get eflags */
        movq \tmp,EFLAGS+\offset(%rsp)
        .endm

        .macro RESTORE_TOP_OF_STACK tmp offset=0
        movq RSP+\offset(%rsp),\tmp
        movq \tmp,PER_CPU_VAR(old_rsp)
        movq EFLAGS+\offset(%rsp),\tmp
        movq \tmp,R11+\offset(%rsp)
        .endm

        .macro FAKE_STACK_FRAME child_rip
        /* push in order ss, rsp, eflags, cs, rip */
        xorl %eax, %eax
        pushq_cfi $__KERNEL_DS /* ss */
        /*CFI_REL_OFFSET        ss,0*/
        pushq_cfi %rax /* rsp */
        CFI_REL_OFFSET  rsp,0
        pushq_cfi $(X86_EFLAGS_IF|X86_EFLAGS_BIT1) /* eflags - interrupts on */
        /*CFI_REL_OFFSET        rflags,0*/
        pushq_cfi $__KERNEL_CS /* cs */
        /*CFI_REL_OFFSET        cs,0*/
        pushq_cfi \child_rip /* rip */
        CFI_REL_OFFSET  rip,0
        pushq_cfi %rax /* orig rax */
        .endm

        .macro UNFAKE_STACK_FRAME
        addq $8*6, %rsp
        CFI_ADJUST_CFA_OFFSET   -(6*8)
        .endm

/*
 * initial frame state for interrupts (and exceptions without error code)
 */
        .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, SS+8+\offset-RIP
        /*CFI_REL_OFFSET ss, SS+\offset-RIP*/
        CFI_REL_OFFSET rsp, RSP+\offset-RIP
        /*CFI_REL_OFFSET rflags, EFLAGS+\offset-RIP*/
        /*CFI_REL_OFFSET cs, CS+\offset-RIP*/
        CFI_REL_OFFSET rip, RIP+\offset-RIP
        .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, RIP+\offset-ORIG_RAX
        /*CFI_REL_OFFSET orig_rax, ORIG_RAX-ORIG_RAX*/
        .endm

/*
 * frame that enables calling into C.
 */
        .macro PARTIAL_FRAME start=1 offset=0
        XCPT_FRAME \start, ORIG_RAX+\offset-ARGOFFSET
        CFI_REL_OFFSET rdi, RDI+\offset-ARGOFFSET
        CFI_REL_OFFSET rsi, RSI+\offset-ARGOFFSET
        CFI_REL_OFFSET rdx, RDX+\offset-ARGOFFSET
        CFI_REL_OFFSET rcx, RCX+\offset-ARGOFFSET
        CFI_REL_OFFSET rax, RAX+\offset-ARGOFFSET
        CFI_REL_OFFSET r8, R8+\offset-ARGOFFSET
        CFI_REL_OFFSET r9, R9+\offset-ARGOFFSET
        CFI_REL_OFFSET r10, R10+\offset-ARGOFFSET
        CFI_REL_OFFSET r11, R11+\offset-ARGOFFSET
        .endm

/*
 * frame that enables passing a complete pt_regs to a C function.
 */
        .macro DEFAULT_FRAME start=1 offset=0
        PARTIAL_FRAME \start, R11+\offset-R15
        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

/* save partial stack frame */
        .macro SAVE_ARGS_IRQ
        cld
        /* start from rbp in pt_regs and jump over */
        movq_cfi rdi, RDI-RBP
        movq_cfi rsi, RSI-RBP
        movq_cfi rdx, RDX-RBP
        movq_cfi rcx, RCX-RBP
        movq_cfi rax, RAX-RBP
        movq_cfi  r8,  R8-RBP
        movq_cfi  r9,  R9-RBP
        movq_cfi r10, R10-RBP
        movq_cfi r11, R11-RBP

        /* Save rbp so that we can unwind from get_irq_regs() */
        movq_cfi rbp, 0

        /* Save previous stack value */
        movq %rsp, %rsi

        leaq -RBP(%rsp),%rdi    /* arg1 for handler */
        testl $3, CS-RBP(%rsi)
        je 1f
        SWAPGS
        /*
         * 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)
         */
1:      incl PER_CPU_VAR(irq_count)
        cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp
        CFI_DEF_CFA_REGISTER    rsi

        /* Store previous stack value */
        pushq %rsi
        CFI_ESCAPE      0x0f /* DW_CFA_def_cfa_expression */, 6, \
                        0x77 /* DW_OP_breg7 */, 0, \
                        0x06 /* DW_OP_deref */, \
                        0x08 /* DW_OP_const1u */, SS+8-RBP, \
                        0x22 /* DW_OP_plus */
        /* We entered an interrupt context - irqs are off: */
        TRACE_IRQS_OFF
        .endm

ENTRY(save_rest)
        PARTIAL_FRAME 1 REST_SKIP+8
        movq 5*8+16(%rsp), %r11 /* save return address */
        movq_cfi rbx, RBX+16
        movq_cfi rbp, RBP+16
        movq_cfi r12, R12+16
        movq_cfi r13, R13+16
        movq_cfi r14, R14+16
        movq_cfi r15, R15+16
        movq %r11, 8(%rsp)      /* return address */
        FIXUP_TOP_OF_STACK %r11, 16
        ret
        CFI_ENDPROC
END(save_rest)

/* save complete stack frame */
        .pushsection .kprobes.text, "ax"
ENTRY(save_paranoid)
        XCPT_FRAME 1 RDI+8
        cld
        movq_cfi rdi, RDI+8
        movq_cfi rsi, RSI+8
        movq_cfi rdx, RDX+8
        movq_cfi rcx, RCX+8
        movq_cfi rax, RAX+8
        movq_cfi r8, R8+8
        movq_cfi r9, R9+8
        movq_cfi r10, R10+8
        movq_cfi r11, R11+8
        movq_cfi rbx, RBX+8
        movq_cfi rbp, RBP+8
        movq_cfi r12, R12+8
        movq_cfi r13, R13+8
        movq_cfi r14, R14+8
        movq_cfi r15, R15+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(save_paranoid)
        .popsection

/*
 * 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 kernel_eflags(%rip)
        popfq_cfi                               # reset kernel eflags

        call schedule_tail                      # rdi: 'prev' task parameter

        GET_THREAD_INFO(%rcx)

        RESTORE_REST

        testl $3, CS-ARGOFFSET(%rsp)            # from kernel_thread?
        jz   retint_restore_args

        testl $_TIF_IA32, TI_flags(%rcx)        # 32-bit compat task needs IRET
        jnz  int_ret_from_sys_call

        RESTORE_TOP_OF_STACK %rdi, -ARGOFFSET
        jmp ret_from_sys_call                   # go to the SYSRET fastpath

        CFI_ENDPROC
END(ret_from_fork)

/*
 * System call entry. Up to 6 arguments in registers are supported.
 *
 * SYSCALL does not save anything on the stack and does not change the
 * stack pointer.
 */

/*
 * Register setup:
 * rax  system call number
 * rdi  arg0
 * rcx  return address for syscall/sysret, C arg3
 * rsi  arg1
 * rdx  arg2
 * r10  arg3    (--> moved to rcx for C)
 * r8   arg4
 * r9   arg5
 * r11  eflags for syscall/sysret, temporary for C
 * r12-r15,rbp,rbx saved by C code, not touched.
 *
 * Interrupts are off on entry.
 * Only called from user space.
 *
 * XXX  if we had a free scratch register we could save the RSP into the stack frame
 *      and report it properly in ps. Unfortunately we haven't.
 *
 * When user can change the frames 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,KERNEL_STACK_OFFSET
        CFI_REGISTER    rip,rcx
        /*CFI_REGISTER  rflags,r11*/
        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(old_rsp)
        movq    PER_CPU_VAR(kernel_stack),%rsp
        /*
         * No need to follow this irqs off/on section - it's straight
         * and short:
         */
        ENABLE_INTERRUPTS(CLBR_NONE)
        SAVE_ARGS 8,0
        movq  %rax,ORIG_RAX-ARGOFFSET(%rsp)
        movq  %rcx,RIP-ARGOFFSET(%rsp)
        CFI_REL_OFFSET rip,RIP-ARGOFFSET
        testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
        jnz tracesys
system_call_fastpath:
        cmpq $__NR_syscall_max,%rax
        ja badsys
        movq %r10,%rcx
        call *sys_call_table(,%rax,8)  # XXX:    rip relative
        movq %rax,RAX-ARGOFFSET(%rsp)
/*
 * Syscall return path ending with SYSRET (fast path)
 * Has incomplete stack frame and undefined top of stack.
 */
ret_from_sys_call:
        movl $_TIF_ALLWORK_MASK,%edi
        /* edi: flagmask */
sysret_check:
        LOCKDEP_SYS_EXIT
        DISABLE_INTERRUPTS(CLBR_NONE)
        TRACE_IRQS_OFF
        movl TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET),%edx
        andl %edi,%edx
        jnz  sysret_careful
        CFI_REMEMBER_STATE
        /*
         * sysretq will re-enable interrupts:
         */
        TRACE_IRQS_ON
        movq RIP-ARGOFFSET(%rsp),%rcx
        CFI_REGISTER    rip,rcx
        RESTORE_ARGS 1,-ARG_SKIP,0
        /*CFI_REGISTER  rflags,r11*/
        movq    PER_CPU_VAR(old_rsp), %rsp
        USERGS_SYSRET64

        CFI_RESTORE_STATE
        /* Handle reschedules */
        /* edx: work, edi: workmask */
sysret_careful:
        bt $TIF_NEED_RESCHED,%edx
        jnc sysret_signal
        TRACE_IRQS_ON
        ENABLE_INTERRUPTS(CLBR_NONE)
        pushq_cfi %rdi
        call schedule
        popq_cfi %rdi
        jmp sysret_check

        /* Handle a signal */
sysret_signal:
        TRACE_IRQS_ON
        ENABLE_INTERRUPTS(CLBR_NONE)
#ifdef CONFIG_AUDITSYSCALL
        bt $TIF_SYSCALL_AUDIT,%edx
        jc sysret_audit
#endif
        /*
         * We have a signal, or exit tracing or single-step.
         * These all wind up with the iret return path anyway,
         * so just join that path right now.
         */
        FIXUP_TOP_OF_STACK %r11, -ARGOFFSET
        jmp int_check_syscall_exit_work

badsys:
        movq $-ENOSYS,RAX-ARGOFFSET(%rsp)
        jmp ret_from_sys_call

#ifdef CONFIG_AUDITSYSCALL
        /*
         * Fast path for syscall audit without full syscall trace.
         * We just call __audit_syscall_entry() directly, and then
         * jump back to the normal fast path.
         */
auditsys:
        movq %r10,%r9                   /* 6th arg: 4th syscall arg */
        movq %rdx,%r8                   /* 5th arg: 3rd syscall arg */
        movq %rsi,%rcx                  /* 4th arg: 2nd syscall arg */
        movq %rdi,%rdx                  /* 3rd arg: 1st syscall arg */
        movq %rax,%rsi                  /* 2nd arg: syscall number */
        movl $AUDIT_ARCH_X86_64,%edi    /* 1st arg: audit arch */
        call __audit_syscall_entry
        LOAD_ARGS 0             /* reload call-clobbered registers */
        jmp system_call_fastpath

        /*
         * Return fast path for syscall audit.  Call __audit_syscall_exit()
         * directly and then jump back to the fast path with TIF_SYSCALL_AUDIT
         * masked off.
         */
sysret_audit:
        movq RAX-ARGOFFSET(%rsp),%rsi   /* second arg, syscall return value */
        cmpq $-MAX_ERRNO,%rsi   /* is it < -MAX_ERRNO? */
        setbe %al               /* 1 if so, 0 if not */
        movzbl %al,%edi         /* zero-extend that into %edi */
        call __audit_syscall_exit
        movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),%edi
        jmp sysret_check
#endif  /* CONFIG_AUDITSYSCALL */

        /* Do syscall tracing */
tracesys:
#ifdef CONFIG_AUDITSYSCALL
        testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
        jz auditsys
#endif
        SAVE_REST
        movq $-ENOSYS,RAX(%rsp) /* ptrace can change this for a bad syscall */
        FIXUP_TOP_OF_STACK %rdi
        movq %rsp,%rdi
        call syscall_trace_enter
        /*
         * Reload arg registers from stack in case ptrace changed them.
         * We don't reload %rax because syscall_trace_enter() returned
         * the value it wants us to use in the table lookup.
         */
        LOAD_ARGS ARGOFFSET, 1
        RESTORE_REST
        cmpq $__NR_syscall_max,%rax
        ja   int_ret_from_sys_call      /* RAX(%rsp) set to -ENOSYS above */
        movq %r10,%rcx  /* fixup for C */
        call *sys_call_table(,%rax,8)
        movq %rax,RAX-ARGOFFSET(%rsp)
        /* Use IRET because user could have changed frame */

/*
 * Syscall return path ending with IRET.
 * Has correct top of stack, but partial stack frame.
 */
GLOBAL(int_ret_from_sys_call)
        DISABLE_INTERRUPTS(CLBR_NONE)
        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   retint_swapgs

        /* 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
        call schedule
        popq_cfi %rdi
        DISABLE_INTERRUPTS(CLBR_NONE)
        TRACE_IRQS_OFF
        jmp int_with_check

        /* handle signals and tracing -- both require a full stack frame */
int_very_careful:
        TRACE_IRQS_ON
        ENABLE_INTERRUPTS(CLBR_NONE)
int_check_syscall_exit_work:
        SAVE_REST
        /* 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_REST
        DISABLE_INTERRUPTS(CLBR_NONE)
        TRACE_IRQS_OFF
        jmp int_with_check
        CFI_ENDPROC
END(system_call)

/*
 * Certain special system calls that need to save a complete full stack frame.
 */
        .macro PTREGSCALL label,func,arg
ENTRY(\label)
        PARTIAL_FRAME 1 8               /* offset 8: return address */
        subq $REST_SKIP, %rsp
        CFI_ADJUST_CFA_OFFSET REST_SKIP
        call save_rest
        DEFAULT_FRAME 0 8               /* offset 8: return address */
        leaq 8(%rsp), \arg      /* pt_regs pointer */
        call \func
        jmp ptregscall_common
        CFI_ENDPROC
END(\label)
        .endm

        PTREGSCALL stub_clone, sys_clone, %r8
        PTREGSCALL stub_fork, sys_fork, %rdi
        PTREGSCALL stub_vfork, sys_vfork, %rdi
        PTREGSCALL stub_sigaltstack, sys_sigaltstack, %rdx
        PTREGSCALL stub_iopl, sys_iopl, %rsi

ENTRY(ptregscall_common)
        DEFAULT_FRAME 1 8       /* offset 8: return address */
        RESTORE_TOP_OF_STACK %r11, 8
        movq_cfi_restore R15+8, r15
        movq_cfi_restore R14+8, r14
        movq_cfi_restore R13+8, r13
        movq_cfi_restore R12+8, r12
        movq_cfi_restore RBP+8, rbp
        movq_cfi_restore RBX+8, rbx
        ret $REST_SKIP          /* pop extended registers */
        CFI_ENDPROC
END(ptregscall_common)

ENTRY(stub_execve)
        CFI_STARTPROC
        addq $8, %rsp
        PARTIAL_FRAME 0
        SAVE_REST
        FIXUP_TOP_OF_STACK %r11
        movq %rsp, %rcx
        call sys_execve
        RESTORE_TOP_OF_STACK %r11
        movq %rax,RAX(%rsp)
        RESTORE_REST
        jmp int_ret_from_sys_call
        CFI_ENDPROC
END(stub_execve)

/*
 * 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
        addq $8, %rsp
        PARTIAL_FRAME 0
        SAVE_REST
        movq %rsp,%rdi
        FIXUP_TOP_OF_STACK %r11
        call sys_rt_sigreturn
        movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer
        RESTORE_REST
        jmp int_ret_from_sys_call
        CFI_ENDPROC
END(stub_rt_sigreturn)

/*
 * Build the entry stubs and pointer table with some assembler magic.
 * We pack 7 stubs into a single 32-byte chunk, which will fit in a
 * single cache line on all modern x86 implementations.
 */
        .section .init.rodata,"a"
ENTRY(interrupt)
        .section .entry.text
        .p2align 5
        .p2align CONFIG_X86_L1_CACHE_SHIFT
ENTRY(irq_entries_start)
        INTR_FRAME
vector=FIRST_EXTERNAL_VECTOR
.rept (NR_VECTORS-FIRST_EXTERNAL_VECTOR+6)/7
        .balign 32
  .rept 7
    .if vector < NR_VECTORS
      .if vector <> FIRST_EXTERNAL_VECTOR
        CFI_ADJUST_CFA_OFFSET -8
      .endif
1:      pushq_cfi $(~vector+0x80)       /* Note: always in signed byte range */
      .if ((vector-FIRST_EXTERNAL_VECTOR)%7) <> 6
        jmp 2f
      .endif
      .previous
        .quad 1b
      .section .entry.text
vector=vector+1
    .endif
  .endr
2:      jmp common_interrupt
.endr
        CFI_ENDPROC
END(irq_entries_start)

.previous
END(interrupt)
.previous

/*
 * 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
        /* reserve pt_regs for scratch regs and rbp */
        subq $ORIG_RAX-RBP, %rsp
        CFI_ADJUST_CFA_OFFSET ORIG_RAX-RBP
        SAVE_ARGS_IRQ
        call \func
        .endm

/*
 * Interrupt entry/exit should be protected against kprobes
 */
        .pushsection .kprobes.text, "ax"
        /*
         * 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
        addq $-0x80,(%rsp)              /* Adjust vector to [-256,-1] range */
        interrupt do_IRQ
        /* 0(%rsp): old_rsp-ARGOFFSET */
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_REGISTER    rsi
        leaq ARGOFFSET-RBP(%rsi), %rsp
        CFI_DEF_CFA_REGISTER    rsp
        CFI_ADJUST_CFA_OFFSET   RBP-ARGOFFSET

exit_intr:
        GET_THREAD_INFO(%rcx)
        testl $3,CS-ARGOFFSET(%rsp)
        je retint_kernel

        /* Interrupt came from user space */
        /*
         * Has a correct top of stack, but a partial stack frame
         * %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_args

retint_restore_args:    /* return to kernel space */
        DISABLE_INTERRUPTS(CLBR_ANY)
        /*
         * The iretq could re-enable interrupts:
         */
        TRACE_IRQS_IRETQ
restore_args:
        RESTORE_ARGS 1,8,1

irq_return:
        INTERRUPT_RETURN

        .section __ex_table, "a"
        .quad irq_return, bad_iret
        .previous

#ifdef CONFIG_PARAVIRT
ENTRY(native_iret)
        iretq

        .section __ex_table,"a"
        .quad native_iret, bad_iret
        .previous
#endif

        .section .fixup,"ax"
bad_iret:
        /*
         * The iret traps when the %cs or %ss being restored is bogus.
         * We've lost the original trap vector and error code.
         * #GPF is the most likely one to get for an invalid selector.
         * So pretend we completed the iret and took the #GPF in user mode.
         *
         * We are now running with the kernel GS after exception recovery.
         * But error_entry expects us to have user GS to match the user %cs,
         * so swap back.
         */
        pushq $0

        SWAPGS
        jmp general_protection

        .previous

        /* 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
        call  schedule
        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_REST
        movq $-1,ORIG_RAX(%rsp)
        xorl %esi,%esi          # oldset
        movq %rsp,%rdi          # &pt_regs
        call do_notify_resume
        RESTORE_REST
        DISABLE_INTERRUPTS(CLBR_NONE)
        TRACE_IRQS_OFF
        GET_THREAD_INFO(%rcx)
        jmp retint_with_reschedule

#ifdef CONFIG_PREEMPT
        /* Returning to kernel space. Check if we need preemption */
        /* rcx:  threadinfo. interrupts off. */
ENTRY(retint_kernel)
        cmpl $0,TI_preempt_count(%rcx)
        jnz  retint_restore_args
        bt  $TIF_NEED_RESCHED,TI_flags(%rcx)
        jnc  retint_restore_args
        bt   $9,EFLAGS-ARGOFFSET(%rsp)  /* interrupts off? */
        jnc  retint_restore_args
        call preempt_schedule_irq
        jmp exit_intr
#endif

        CFI_ENDPROC
END(common_interrupt)
/*
 * End of kprobes section
 */
       .popsection

/*
 * APIC interrupts.
 */
.macro apicinterrupt num sym do_sym
ENTRY(\sym)
        INTR_FRAME
        pushq_cfi $~(\num)
.Lcommon_\sym:
        interrupt \do_sym
        jmp ret_from_intr
        CFI_ENDPROC
END(\sym)
.endm

#ifdef CONFIG_SMP
apicinterrupt IRQ_MOVE_CLEANUP_VECTOR \
        irq_move_cleanup_interrupt smp_irq_move_cleanup_interrupt
apicinterrupt REBOOT_VECTOR \
        reboot_interrupt smp_reboot_interrupt
#endif

#ifdef CONFIG_X86_UV
apicinterrupt 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_SMP
        ALIGN
        INTR_FRAME
.irp idx,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15, \
        16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31
.if NUM_INVALIDATE_TLB_VECTORS > \idx
ENTRY(invalidate_interrupt\idx)
        pushq_cfi $~(INVALIDATE_TLB_VECTOR_START+\idx)
        jmp .Lcommon_invalidate_interrupt0
        CFI_ADJUST_CFA_OFFSET -8
END(invalidate_interrupt\idx)
.endif
.endr
        CFI_ENDPROC
apicinterrupt INVALIDATE_TLB_VECTOR_START, \
        invalidate_interrupt0, smp_invalidate_interrupt
#endif

apicinterrupt THRESHOLD_APIC_VECTOR \
        threshold_interrupt smp_threshold_interrupt
apicinterrupt THERMAL_APIC_VECTOR \
        thermal_interrupt smp_thermal_interrupt

#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.
 */
.macro zeroentry sym do_sym
ENTRY(\sym)
        INTR_FRAME
        PARAVIRT_ADJUST_EXCEPTION_FRAME
        pushq_cfi $-1           /* ORIG_RAX: no syscall to restart */
        subq $ORIG_RAX-R15, %rsp
        CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
        call error_entry
        DEFAULT_FRAME 0
        movq %rsp,%rdi          /* pt_regs pointer */
        xorl %esi,%esi          /* no error code */
        call \do_sym
        jmp error_exit          /* %ebx: no swapgs flag */
        CFI_ENDPROC
END(\sym)
.endm

.macro paranoidzeroentry sym do_sym
ENTRY(\sym)
        INTR_FRAME
        PARAVIRT_ADJUST_EXCEPTION_FRAME
        pushq_cfi $-1           /* ORIG_RAX: no syscall to restart */
        subq $ORIG_RAX-R15, %rsp
        CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
        call save_paranoid
        TRACE_IRQS_OFF
        movq %rsp,%rdi          /* pt_regs pointer */
        xorl %esi,%esi          /* no error code */
        call \do_sym
        jmp paranoid_exit       /* %ebx: no swapgs flag */
        CFI_ENDPROC
END(\sym)
.endm

#define INIT_TSS_IST(x) PER_CPU_VAR(init_tss) + (TSS_ist + ((x) - 1) * 8)
.macro paranoidzeroentry_ist sym do_sym ist
ENTRY(\sym)
        INTR_FRAME
        PARAVIRT_ADJUST_EXCEPTION_FRAME
        pushq_cfi $-1           /* ORIG_RAX: no syscall to restart */
        subq $ORIG_RAX-R15, %rsp
        CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
        call save_paranoid
        TRACE_IRQS_OFF
        movq %rsp,%rdi          /* pt_regs pointer */
        xorl %esi,%esi          /* no error code */
        subq $EXCEPTION_STKSZ, INIT_TSS_IST(\ist)
        call \do_sym
        addq $EXCEPTION_STKSZ, INIT_TSS_IST(\ist)
        jmp paranoid_exit       /* %ebx: no swapgs flag */
        CFI_ENDPROC
END(\sym)
.endm

.macro errorentry sym do_sym
ENTRY(\sym)
        XCPT_FRAME
        PARAVIRT_ADJUST_EXCEPTION_FRAME
        subq $ORIG_RAX-R15, %rsp
        CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
        call error_entry
        DEFAULT_FRAME 0
        movq %rsp,%rdi                  /* pt_regs pointer */
        movq ORIG_RAX(%rsp),%rsi        /* get error code */
        movq $-1,ORIG_RAX(%rsp)         /* no syscall to restart */
        call \do_sym
        jmp error_exit                  /* %ebx: no swapgs flag */
        CFI_ENDPROC
END(\sym)
.endm

        /* error code is on the stack already */
.macro paranoiderrorentry sym do_sym
ENTRY(\sym)
        XCPT_FRAME
        PARAVIRT_ADJUST_EXCEPTION_FRAME
        subq $ORIG_RAX-R15, %rsp
        CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
        call save_paranoid
        DEFAULT_FRAME 0
        TRACE_IRQS_OFF
        movq %rsp,%rdi                  /* pt_regs pointer */
        movq ORIG_RAX(%rsp),%rsi        /* get error code */
        movq $-1,ORIG_RAX(%rsp)         /* no syscall to restart */
        call \do_sym
        jmp paranoid_exit               /* %ebx: no swapgs flag */
        CFI_ENDPROC
END(\sym)
.endm

zeroentry divide_error do_divide_error
zeroentry overflow do_overflow
zeroentry bounds do_bounds
zeroentry invalid_op do_invalid_op
zeroentry device_not_available do_device_not_available
paranoiderrorentry double_fault do_double_fault
zeroentry coprocessor_segment_overrun do_coprocessor_segment_overrun
errorentry invalid_TSS do_invalid_TSS
errorentry segment_not_present do_segment_not_present
zeroentry spurious_interrupt_bug do_spurious_interrupt_bug
zeroentry coprocessor_error do_coprocessor_error
errorentry alignment_check do_alignment_check
zeroentry simd_coprocessor_error do_simd_coprocessor_error


        /* 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)

        .section __ex_table,"a"
        .align 8
        .quad gs_change,bad_gs
        .previous
        .section .fixup,"ax"
        /* running with kernelgs */
bad_gs:
        SWAPGS                  /* switch back to user gs */
        xorl %eax,%eax
        movl %eax,%gs
        jmp  2b
        .previous

ENTRY(kernel_thread_helper)
        pushq $0                # fake return address
        CFI_STARTPROC
        /*
         * Here we are in the child and the registers are set as they were
         * at kernel_thread() invocation in the parent.
         */
        call *%rsi
        # exit
        mov %eax, %edi
        call do_exit
        ud2                     # padding for call trace
        CFI_ENDPROC
END(kernel_thread_helper)

/*
 * execve(). This function needs to use IRET, not SYSRET, to set up all state properly.
 *
 * C extern interface:
 *       extern long execve(const char *name, char **argv, char **envp)
 *
 * asm input arguments:
 *      rdi: name, rsi: argv, rdx: envp
 *
 * We want to fallback into:
 *      extern long sys_execve(const char *name, char **argv,char **envp, struct pt_regs *regs)
 *
 * do_sys_execve asm fallback arguments:
 *      rdi: name, rsi: argv, rdx: envp, rcx: fake frame on the stack
 */
ENTRY(kernel_execve)
        CFI_STARTPROC
        FAKE_STACK_FRAME $0
        SAVE_ALL
        movq %rsp,%rcx
        call sys_execve
        movq %rax, RAX(%rsp)
        RESTORE_REST
        testq %rax,%rax
        je int_ret_from_sys_call
        RESTORE_ARGS
        UNFAKE_STACK_FRAME
        ret
        CFI_ENDPROC
END(kernel_execve)

/* Call softirq on interrupt stack. Interrupts are off. */
ENTRY(call_softirq)
        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(call_softirq)

#ifdef CONFIG_XEN
zeroentry xen_hypervisor_callback xen_do_hypervisor_callback

/*
 * 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)
        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 $0
        SAVE_ALL
        jmp error_exit
        CFI_ENDPROC
END(xen_failsafe_callback)

apicinterrupt XEN_HVM_EVTCHN_CALLBACK \
        xen_hvm_callback_vector xen_evtchn_do_upcall

#endif /* CONFIG_XEN */

/*
 * Some functions should be protected against kprobes
 */
        .pushsection .kprobes.text, "ax"

paranoidzeroentry_ist debug do_debug DEBUG_STACK
paranoidzeroentry_ist int3 do_int3 DEBUG_STACK
paranoiderrorentry stack_segment do_stack_segment
#ifdef CONFIG_XEN
zeroentry xen_debug do_debug
zeroentry xen_int3 do_int3
errorentry xen_stack_segment do_stack_segment
#endif
errorentry general_protection do_general_protection
errorentry page_fault do_page_fault
#ifdef CONFIG_KVM_GUEST
errorentry async_page_fault do_async_page_fault
#endif
#ifdef CONFIG_X86_MCE
paranoidzeroentry machine_check *machine_check_vector(%rip)
#endif

        /*
         * "Paranoid" exit path from exception stack.
         * Paranoid because this is used by NMIs and cannot take
         * any kernel state for granted.
         * We don't do kernel preemption checks here, because only
         * NMI should be common and it does not enable IRQs and
         * cannot get reschedule ticks.
         *
         * "trace" is 0 for the NMI handler only, because irq-tracing
         * is fundamentally NMI-unsafe. (we cannot change the soft and
         * hard flags at once, atomically)
         */

        /* ebx: no swapgs flag */
ENTRY(paranoid_exit)
        DEFAULT_FRAME
        DISABLE_INTERRUPTS(CLBR_NONE)
        TRACE_IRQS_OFF
        testl %ebx,%ebx                         /* swapgs needed? */
        jnz paranoid_restore
        testl $3,CS(%rsp)
        jnz   paranoid_userspace
paranoid_swapgs:
        TRACE_IRQS_IRETQ 0
        SWAPGS_UNSAFE_STACK
        RESTORE_ALL 8
        jmp irq_return
paranoid_restore:
        TRACE_IRQS_IRETQ 0
        RESTORE_ALL 8
        jmp irq_return
paranoid_userspace:
        GET_THREAD_INFO(%rcx)
        movl TI_flags(%rcx),%ebx
        andl $_TIF_WORK_MASK,%ebx
        jz paranoid_swapgs
        movq %rsp,%rdi                  /* &pt_regs */
        call sync_regs
        movq %rax,%rsp                  /* switch stack for scheduling */
        testl $_TIF_NEED_RESCHED,%ebx
        jnz paranoid_schedule
        movl %ebx,%edx                  /* arg3: thread flags */
        TRACE_IRQS_ON
        ENABLE_INTERRUPTS(CLBR_NONE)
        xorl %esi,%esi                  /* arg2: oldset */
        movq %rsp,%rdi                  /* arg1: &pt_regs */
        call do_notify_resume
        DISABLE_INTERRUPTS(CLBR_NONE)
        TRACE_IRQS_OFF
        jmp paranoid_userspace
paranoid_schedule:
        TRACE_IRQS_ON
        ENABLE_INTERRUPTS(CLBR_ANY)
        call schedule
        DISABLE_INTERRUPTS(CLBR_ANY)
        TRACE_IRQS_OFF
        jmp paranoid_userspace
        CFI_ENDPROC
END(paranoid_exit)

/*
 * Exception entry point. This expects an error code/orig_rax on the stack.
 * returns in "no swapgs flag" in %ebx.
 */
ENTRY(error_entry)
        XCPT_FRAME
        CFI_ADJUST_CFA_OFFSET 15*8
        /* oldrax contains error code */
        cld
        movq_cfi rdi, RDI+8
        movq_cfi rsi, RSI+8
        movq_cfi rdx, RDX+8
        movq_cfi rcx, RCX+8
        movq_cfi rax, RAX+8
        movq_cfi  r8,  R8+8
        movq_cfi  r9,  R9+8
        movq_cfi r10, R10+8
        movq_cfi r11, R11+8
        movq_cfi rbx, RBX+8
        movq_cfi rbp, RBP+8
        movq_cfi r12, R12+8
        movq_cfi r13, R13+8
        movq_cfi r14, R14+8
        movq_cfi r15, R15+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. The exception handlers after iret run with
 * kernel gs again, so don't set the user space flag. B stepping K8s
 * sometimes report an truncated RIP for IRET exceptions returning to
 * compat mode. Check for these here too.
 */
error_kernelspace:
        incl %ebx
        leaq irq_return(%rip),%rcx
        cmpq %rcx,RIP+8(%rsp)
        je error_swapgs
        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)
        jmp error_swapgs
        CFI_ENDPROC
END(error_entry)


/* ebx: no swapgs flag (1: don't need swapgs, 0: need it) */
ENTRY(error_exit)
        DEFAULT_FRAME
        movl %ebx,%eax
        RESTORE_REST
        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)

/*
 * Test if a given stack is an NMI stack or not.
 */
        .macro test_in_nmi reg stack nmi_ret normal_ret
        cmpq %\reg, \stack
        ja \normal_ret
        subq $EXCEPTION_STKSZ, %\reg
        cmpq %\reg, \stack
        jb \normal_ret
        jmp \nmi_ret
        .endm

        /* 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 out temp variable throughout */
        pushq_cfi %rdx

        /*
         * 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
        test_in_nmi rdx, 4*8(%rsp), nested_nmi, first_nmi

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 -6*8(%rsp), %rdx
        movq %rdx, %rsp
        CFI_ADJUST_CFA_OFFSET 6*8
        pushq_cfi $__KERNEL_DS
        pushq_cfi %rdx
        pushfq_cfi
        pushq_cfi $__KERNEL_CS
        pushq_cfi $repeat_nmi

        /* Put stack back */
        addq $(11*8), %rsp
        CFI_ADJUST_CFA_OFFSET -11*8

nested_nmi_out:
        popq_cfi %rdx

        /* No need to check faults here */
        INTERRUPT_RETURN

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  |
         * +-------------------------+
         * | Saved SS                |
         * | Saved Return RSP        |
         * | Saved RFLAGS            |
         * | Saved CS                |
         * | Saved RIP               |
         * +-------------------------+
         * | copied SS               |
         * | copied Return RSP       |
         * | copied RFLAGS           |
         * | copied CS               |
         * | copied RIP              |
         * +-------------------------+
         * | pt_regs                 |
         * +-------------------------+
         *
         * The saved RIP is used to fix up the copied RIP that a nested
         * NMI may zero out. The original stack frame and the temp storage
         * is also used by nested NMIs and can not be trusted on exit.
         */
        /* Set the NMI executing variable on the stack. */
        pushq_cfi $1

        /* Copy the stack frame to the Saved frame */
        .rept 5
        pushq_cfi 6*8(%rsp)
        .endr

        /* Make another copy, this one may be modified by nested NMIs */
        .rept 5
        pushq_cfi 4*8(%rsp)
        .endr

        /* Do not pop rdx, nested NMIs will corrupt it */
        movq 11*8(%rsp), %rdx

        /*
         * Everything below this point can be preempted by a nested
         * NMI if the first NMI took an exception. Repeated NMIs
         * caused by an exception and nested NMI will start here, and
         * can still be preempted by another NMI.
         */
restart_nmi:
        pushq_cfi $-1           /* ORIG_RAX: no syscall to restart */
        subq $ORIG_RAX-R15, %rsp
        CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
        /*
         * Use save_paranoid 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 save_paranoid
        DEFAULT_FRAME 0
        /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
        movq %rsp,%rdi
        movq $-1,%rsi
        call do_nmi
        testl %ebx,%ebx                         /* swapgs needed? */
        jnz nmi_restore
nmi_swapgs:
        SWAPGS_UNSAFE_STACK
nmi_restore:
        RESTORE_ALL 8
        /* Clear the NMI executing stack variable */
        movq $0, 10*8(%rsp)
        jmp irq_return
        CFI_ENDPROC
END(nmi)

        /*
         * If an NMI hit an iret because of an exception or breakpoint,
         * it can lose its NMI context, and a nested NMI may come in.
         * In that case, the nested NMI will change the preempted NMI's
         * stack to jump to here when it does the final iret.
         */
repeat_nmi:
        INTR_FRAME
        /* Update the stack variable to say we are still in NMI */
        movq $1, 5*8(%rsp)

        /* copy the saved stack back to copy stack */
        .rept 5
        pushq_cfi 4*8(%rsp)
        .endr

        jmp restart_nmi
        CFI_ENDPROC
end_repeat_nmi:

ENTRY(ignore_sysret)
        CFI_STARTPROC
        mov $-ENOSYS,%eax
        sysret
        CFI_ENDPROC
END(ignore_sysret)

/*
 * End of kprobes section
 */
        .popsection