x86/entry/64: Make cpu_entry_area.tss read-only

[mirror_ubuntu-artful-kernel.git] / arch / x86 / entry / entry_32.S

/*
 *  Copyright (C) 1991,1992  Linus Torvalds
 *
 * entry_32.S contains the system-call and low-level fault and trap handling routines.
 *
 * Stack layout while running C code:
 *      ptrace needs to have all registers on the stack.
 *      If the order here is changed, it needs to be
 *      updated in fork.c:copy_process(), signal.c:do_signal(),
 *      ptrace.c and ptrace.h
 *
 *       0(%esp) - %ebx
 *       4(%esp) - %ecx
 *       8(%esp) - %edx
 *       C(%esp) - %esi
 *      10(%esp) - %edi
 *      14(%esp) - %ebp
 *      18(%esp) - %eax
 *      1C(%esp) - %ds
 *      20(%esp) - %es
 *      24(%esp) - %fs
 *      28(%esp) - %gs          saved iff !CONFIG_X86_32_LAZY_GS
 *      2C(%esp) - orig_eax
 *      30(%esp) - %eip
 *      34(%esp) - %cs
 *      38(%esp) - %eflags
 *      3C(%esp) - %oldesp
 *      40(%esp) - %oldss
 */

#include <linux/linkage.h>
#include <linux/err.h>
#include <asm/thread_info.h>
#include <asm/irqflags.h>
#include <asm/errno.h>
#include <asm/segment.h>
#include <asm/smp.h>
#include <asm/percpu.h>
#include <asm/processor-flags.h>
#include <asm/irq_vectors.h>
#include <asm/cpufeatures.h>
#include <asm/alternative-asm.h>
#include <asm/asm.h>
#include <asm/smap.h>
#include <asm/frame.h>

        .section .entry.text, "ax"

/*
 * We use macros for low-level operations which need to be overridden
 * for paravirtualization.  The following will never clobber any registers:
 *   INTERRUPT_RETURN (aka. "iret")
 *   GET_CR0_INTO_EAX (aka. "movl %cr0, %eax")
 *   ENABLE_INTERRUPTS_SYSEXIT (aka "sti; sysexit").
 *
 * For DISABLE_INTERRUPTS/ENABLE_INTERRUPTS (aka "cli"/"sti"), you must
 * specify what registers can be overwritten (CLBR_NONE, CLBR_EAX/EDX/ECX/ANY).
 * Allowing a register to be clobbered can shrink the paravirt replacement
 * enough to patch inline, increasing performance.
 */

#ifdef CONFIG_PREEMPT
# define preempt_stop(clobbers) DISABLE_INTERRUPTS(clobbers); TRACE_IRQS_OFF
#else
# define preempt_stop(clobbers)
# define resume_kernel          restore_all
#endif

.macro TRACE_IRQS_IRET
#ifdef CONFIG_TRACE_IRQFLAGS
        testl   $X86_EFLAGS_IF, PT_EFLAGS(%esp)     # interrupts off?
        jz      1f
        TRACE_IRQS_ON
1:
#endif
.endm

/*
 * User gs save/restore
 *
 * %gs is used for userland TLS and kernel only uses it for stack
 * canary which is required to be at %gs:20 by gcc.  Read the comment
 * at the top of stackprotector.h for more info.
 *
 * Local labels 98 and 99 are used.
 */
#ifdef CONFIG_X86_32_LAZY_GS

 /* unfortunately push/pop can't be no-op */
.macro PUSH_GS
        pushl   $0
.endm
.macro POP_GS pop=0
        addl    $(4 + \pop), %esp
.endm
.macro POP_GS_EX
.endm

 /* all the rest are no-op */
.macro PTGS_TO_GS
.endm
.macro PTGS_TO_GS_EX
.endm
.macro GS_TO_REG reg
.endm
.macro REG_TO_PTGS reg
.endm
.macro SET_KERNEL_GS reg
.endm

#else   /* CONFIG_X86_32_LAZY_GS */

.macro PUSH_GS
        pushl   %gs
.endm

.macro POP_GS pop=0
98:     popl    %gs
  .if \pop <> 0
        add     $\pop, %esp
  .endif
.endm
.macro POP_GS_EX
.pushsection .fixup, "ax"
99:     movl    $0, (%esp)
        jmp     98b
.popsection
        _ASM_EXTABLE(98b, 99b)
.endm

.macro PTGS_TO_GS
98:     mov     PT_GS(%esp), %gs
.endm
.macro PTGS_TO_GS_EX
.pushsection .fixup, "ax"
99:     movl    $0, PT_GS(%esp)
        jmp     98b
.popsection
        _ASM_EXTABLE(98b, 99b)
.endm

.macro GS_TO_REG reg
        movl    %gs, \reg
.endm
.macro REG_TO_PTGS reg
        movl    \reg, PT_GS(%esp)
.endm
.macro SET_KERNEL_GS reg
        movl    $(__KERNEL_STACK_CANARY), \reg
        movl    \reg, %gs
.endm

#endif /* CONFIG_X86_32_LAZY_GS */

.macro SAVE_ALL pt_regs_ax=%eax
        cld
        PUSH_GS
        pushl   %fs
        pushl   %es
        pushl   %ds
        pushl   \pt_regs_ax
        pushl   %ebp
        pushl   %edi
        pushl   %esi
        pushl   %edx
        pushl   %ecx
        pushl   %ebx
        movl    $(__USER_DS), %edx
        movl    %edx, %ds
        movl    %edx, %es
        movl    $(__KERNEL_PERCPU), %edx
        movl    %edx, %fs
        SET_KERNEL_GS %edx
.endm

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

.macro RESTORE_INT_REGS
        popl    %ebx
        popl    %ecx
        popl    %edx
        popl    %esi
        popl    %edi
        popl    %ebp
        popl    %eax
.endm

.macro RESTORE_REGS pop=0
        RESTORE_INT_REGS
1:      popl    %ds
2:      popl    %es
3:      popl    %fs
        POP_GS \pop
.pushsection .fixup, "ax"
4:      movl    $0, (%esp)
        jmp     1b
5:      movl    $0, (%esp)
        jmp     2b
6:      movl    $0, (%esp)
        jmp     3b
.popsection
        _ASM_EXTABLE(1b, 4b)
        _ASM_EXTABLE(2b, 5b)
        _ASM_EXTABLE(3b, 6b)
        POP_GS_EX
.endm

/*
 * %eax: prev task
 * %edx: next task
 */
ENTRY(__switch_to_asm)
        /*
         * Save callee-saved registers
         * This must match the order in struct inactive_task_frame
         */
        pushl   %ebp
        pushl   %ebx
        pushl   %edi
        pushl   %esi

        /* switch stack */
        movl    %esp, TASK_threadsp(%eax)
        movl    TASK_threadsp(%edx), %esp

#ifdef CONFIG_CC_STACKPROTECTOR
        movl    TASK_stack_canary(%edx), %ebx
        movl    %ebx, PER_CPU_VAR(stack_canary)+stack_canary_offset
#endif

        /* restore callee-saved registers */
        popl    %esi
        popl    %edi
        popl    %ebx
        popl    %ebp

        jmp     __switch_to
END(__switch_to_asm)

/*
 * The unwinder expects the last frame on the stack to always be at the same
 * offset from the end of the page, which allows it to validate the stack.
 * Calling schedule_tail() directly would break that convention because its an
 * asmlinkage function so its argument has to be pushed on the stack.  This
 * wrapper creates a proper "end of stack" frame header before the call.
 */
ENTRY(schedule_tail_wrapper)
        FRAME_BEGIN

        pushl   %eax
        call    schedule_tail
        popl    %eax

        FRAME_END
        ret
ENDPROC(schedule_tail_wrapper)
/*
 * A newly forked process directly context switches into this address.
 *
 * eax: prev task we switched from
 * ebx: kernel thread func (NULL for user thread)
 * edi: kernel thread arg
 */
ENTRY(ret_from_fork)
        call    schedule_tail_wrapper

        testl   %ebx, %ebx
        jnz     1f              /* kernel threads are uncommon */

2:
        /* When we fork, we trace the syscall return in the child, too. */
        movl    %esp, %eax
        call    syscall_return_slowpath
        jmp     restore_all

        /* kernel thread */
1:      movl    %edi, %eax
        call    *%ebx
        /*
         * A kernel thread is allowed to return here after successfully
         * calling do_execve().  Exit to userspace to complete the execve()
         * syscall.
         */
        movl    $0, PT_EAX(%esp)
        jmp     2b
END(ret_from_fork)

/*
 * Return to user mode is not as complex as all this looks,
 * but we want the default path for a system call return to
 * go as quickly as possible which is why some of this is
 * less clear than it otherwise should be.
 */

        # userspace resumption stub bypassing syscall exit tracing
        ALIGN
ret_from_exception:
        preempt_stop(CLBR_ANY)
ret_from_intr:
#ifdef CONFIG_VM86
        movl    PT_EFLAGS(%esp), %eax           # mix EFLAGS and CS
        movb    PT_CS(%esp), %al
        andl    $(X86_EFLAGS_VM | SEGMENT_RPL_MASK), %eax
#else
        /*
         * We can be coming here from child spawned by kernel_thread().
         */
        movl    PT_CS(%esp), %eax
        andl    $SEGMENT_RPL_MASK, %eax
#endif
        cmpl    $USER_RPL, %eax
        jb      resume_kernel                   # not returning to v8086 or userspace

ENTRY(resume_userspace)
        DISABLE_INTERRUPTS(CLBR_ANY)
        TRACE_IRQS_OFF
        movl    %esp, %eax
        call    prepare_exit_to_usermode
        jmp     restore_all
END(ret_from_exception)

#ifdef CONFIG_PREEMPT
ENTRY(resume_kernel)
        DISABLE_INTERRUPTS(CLBR_ANY)
.Lneed_resched:
        cmpl    $0, PER_CPU_VAR(__preempt_count)
        jnz     restore_all
        testl   $X86_EFLAGS_IF, PT_EFLAGS(%esp) # interrupts off (exception path) ?
        jz      restore_all
        call    preempt_schedule_irq
        jmp     .Lneed_resched
END(resume_kernel)
#endif

GLOBAL(__begin_SYSENTER_singlestep_region)
/*
 * All code from here through __end_SYSENTER_singlestep_region is subject
 * to being single-stepped if a user program sets TF and executes SYSENTER.
 * There is absolutely nothing that we can do to prevent this from happening
 * (thanks Intel!).  To keep our handling of this situation as simple as
 * possible, we handle TF just like AC and NT, except that our #DB handler
 * will ignore all of the single-step traps generated in this range.
 */

#ifdef CONFIG_XEN
/*
 * Xen doesn't set %esp to be precisely what the normal SYSENTER
 * entry point expects, so fix it up before using the normal path.
 */
ENTRY(xen_sysenter_target)
        addl    $5*4, %esp                      /* remove xen-provided frame */
        jmp     .Lsysenter_past_esp
#endif

/*
 * 32-bit SYSENTER entry.
 *
 * 32-bit system calls through the vDSO's __kernel_vsyscall enter here
 * if X86_FEATURE_SEP is available.  This is the preferred system call
 * entry on 32-bit systems.
 *
 * The SYSENTER instruction, in principle, should *only* occur in the
 * vDSO.  In practice, a small number of Android devices were shipped
 * with a copy of Bionic that inlined a SYSENTER instruction.  This
 * never happened in any of Google's Bionic versions -- it only happened
 * in a narrow range of Intel-provided versions.
 *
 * SYSENTER loads SS, ESP, CS, and EIP from previously programmed MSRs.
 * IF and VM in RFLAGS are cleared (IOW: interrupts are off).
 * SYSENTER does not save anything on the stack,
 * and does not save old EIP (!!!), ESP, or EFLAGS.
 *
 * To avoid losing track of EFLAGS.VM (and thus potentially corrupting
 * user and/or vm86 state), we explicitly disable the SYSENTER
 * instruction in vm86 mode by reprogramming the MSRs.
 *
 * Arguments:
 * eax  system call number
 * ebx  arg1
 * ecx  arg2
 * edx  arg3
 * esi  arg4
 * edi  arg5
 * ebp  user stack
 * 0(%ebp) arg6
 */
ENTRY(entry_SYSENTER_32)
        movl    TSS_sysenter_sp0(%esp), %esp
.Lsysenter_past_esp:
        pushl   $__USER_DS              /* pt_regs->ss */
        pushl   %ebp                    /* pt_regs->sp (stashed in bp) */
        pushfl                          /* pt_regs->flags (except IF = 0) */
        orl     $X86_EFLAGS_IF, (%esp)  /* Fix IF */
        pushl   $__USER_CS              /* pt_regs->cs */
        pushl   $0                      /* pt_regs->ip = 0 (placeholder) */
        pushl   %eax                    /* pt_regs->orig_ax */
        SAVE_ALL pt_regs_ax=$-ENOSYS    /* save rest */

        /*
         * SYSENTER doesn't filter flags, so we need to clear NT, AC
         * and TF ourselves.  To save a few cycles, we can check whether
         * either was set instead of doing an unconditional popfq.
         * This needs to happen before enabling interrupts so that
         * we don't get preempted with NT set.
         *
         * If TF is set, we will single-step all the way to here -- do_debug
         * will ignore all the traps.  (Yes, this is slow, but so is
         * single-stepping in general.  This allows us to avoid having
         * a more complicated code to handle the case where a user program
         * forces us to single-step through the SYSENTER entry code.)
         *
         * NB.: .Lsysenter_fix_flags is a label with the code under it moved
         * out-of-line as an optimization: NT is unlikely to be set in the
         * majority of the cases and instead of polluting the I$ unnecessarily,
         * we're keeping that code behind a branch which will predict as
         * not-taken and therefore its instructions won't be fetched.
         */
        testl   $X86_EFLAGS_NT|X86_EFLAGS_AC|X86_EFLAGS_TF, PT_EFLAGS(%esp)
        jnz     .Lsysenter_fix_flags
.Lsysenter_flags_fixed:

        /*
         * User mode is traced as though IRQs are on, and SYSENTER
         * turned them off.
         */
        TRACE_IRQS_OFF

        movl    %esp, %eax
        call    do_fast_syscall_32
        /* XEN PV guests always use IRET path */
        ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \
                    "jmp .Lsyscall_32_done", X86_FEATURE_XENPV

/* Opportunistic SYSEXIT */
        TRACE_IRQS_ON                   /* User mode traces as IRQs on. */
        movl    PT_EIP(%esp), %edx      /* pt_regs->ip */
        movl    PT_OLDESP(%esp), %ecx   /* pt_regs->sp */
1:      mov     PT_FS(%esp), %fs
        PTGS_TO_GS
        popl    %ebx                    /* pt_regs->bx */
        addl    $2*4, %esp              /* skip pt_regs->cx and pt_regs->dx */
        popl    %esi                    /* pt_regs->si */
        popl    %edi                    /* pt_regs->di */
        popl    %ebp                    /* pt_regs->bp */
        popl    %eax                    /* pt_regs->ax */

        /*
         * Restore all flags except IF. (We restore IF separately because
         * STI gives a one-instruction window in which we won't be interrupted,
         * whereas POPF does not.)
         */
        addl    $PT_EFLAGS-PT_DS, %esp  /* point esp at pt_regs->flags */
        btr     $X86_EFLAGS_IF_BIT, (%esp)
        popfl

        /*
         * Return back to the vDSO, which will pop ecx and edx.
         * Don't bother with DS and ES (they already contain __USER_DS).
         */
        sti
        sysexit

.pushsection .fixup, "ax"
2:      movl    $0, PT_FS(%esp)
        jmp     1b
.popsection
        _ASM_EXTABLE(1b, 2b)
        PTGS_TO_GS_EX

.Lsysenter_fix_flags:
        pushl   $X86_EFLAGS_FIXED
        popfl
        jmp     .Lsysenter_flags_fixed
GLOBAL(__end_SYSENTER_singlestep_region)
ENDPROC(entry_SYSENTER_32)

/*
 * 32-bit legacy system call entry.
 *
 * 32-bit x86 Linux system calls traditionally used the INT $0x80
 * instruction.  INT $0x80 lands here.
 *
 * This entry point can be used by any 32-bit perform system calls.
 * Instances of INT $0x80 can be found inline in various programs and
 * libraries.  It is also used by the vDSO's __kernel_vsyscall
 * fallback for hardware that doesn't support a faster entry method.
 * Restarted 32-bit system calls also fall back to INT $0x80
 * regardless of what instruction was originally used to do the system
 * call.  (64-bit programs can use INT $0x80 as well, but they can
 * only run on 64-bit kernels and therefore land in
 * entry_INT80_compat.)
 *
 * This is considered a slow path.  It is not used by most libc
 * implementations on modern hardware except during process startup.
 *
 * Arguments:
 * eax  system call number
 * ebx  arg1
 * ecx  arg2
 * edx  arg3
 * esi  arg4
 * edi  arg5
 * ebp  arg6
 */
ENTRY(entry_INT80_32)
        ASM_CLAC
        pushl   %eax                    /* pt_regs->orig_ax */
        SAVE_ALL pt_regs_ax=$-ENOSYS    /* save rest */

        /*
         * User mode is traced as though IRQs are on, and the interrupt gate
         * turned them off.
         */
        TRACE_IRQS_OFF

        movl    %esp, %eax
        call    do_int80_syscall_32
.Lsyscall_32_done:

restore_all:
        TRACE_IRQS_IRET
.Lrestore_all_notrace:
#ifdef CONFIG_X86_ESPFIX32
        ALTERNATIVE     "jmp .Lrestore_nocheck", "", X86_BUG_ESPFIX

        movl    PT_EFLAGS(%esp), %eax           # mix EFLAGS, SS and CS
        /*
         * Warning: PT_OLDSS(%esp) contains the wrong/random values if we
         * are returning to the kernel.
         * See comments in process.c:copy_thread() for details.
         */
        movb    PT_OLDSS(%esp), %ah
        movb    PT_CS(%esp), %al
        andl    $(X86_EFLAGS_VM | (SEGMENT_TI_MASK << 8) | SEGMENT_RPL_MASK), %eax
        cmpl    $((SEGMENT_LDT << 8) | USER_RPL), %eax
        je .Lldt_ss                             # returning to user-space with LDT SS
#endif
.Lrestore_nocheck:
        RESTORE_REGS 4                          # skip orig_eax/error_code
.Lirq_return:
        INTERRUPT_RETURN

.section .fixup, "ax"
ENTRY(iret_exc  )
        pushl   $0                              # no error code
        pushl   $do_iret_error
        jmp     common_exception
.previous
        _ASM_EXTABLE(.Lirq_return, iret_exc)

#ifdef CONFIG_X86_ESPFIX32
.Lldt_ss:
/*
 * Setup and switch to ESPFIX stack
 *
 * We're returning to userspace with a 16 bit stack. The CPU will not
 * restore the high word of ESP for us on executing iret... This is an
 * "official" bug of all the x86-compatible CPUs, which we can work
 * around to make dosemu and wine happy. We do this by preloading the
 * high word of ESP with the high word of the userspace ESP while
 * compensating for the offset by changing to the ESPFIX segment with
 * a base address that matches for the difference.
 */
#define GDT_ESPFIX_SS PER_CPU_VAR(gdt_page) + (GDT_ENTRY_ESPFIX_SS * 8)
        mov     %esp, %edx                      /* load kernel esp */
        mov     PT_OLDESP(%esp), %eax           /* load userspace esp */
        mov     %dx, %ax                        /* eax: new kernel esp */
        sub     %eax, %edx                      /* offset (low word is 0) */
        shr     $16, %edx
        mov     %dl, GDT_ESPFIX_SS + 4          /* bits 16..23 */
        mov     %dh, GDT_ESPFIX_SS + 7          /* bits 24..31 */
        pushl   $__ESPFIX_SS
        pushl   %eax                            /* new kernel esp */
        /*
         * Disable interrupts, but do not irqtrace this section: we
         * will soon execute iret and the tracer was already set to
         * the irqstate after the IRET:
         */
        DISABLE_INTERRUPTS(CLBR_ANY)
        lss     (%esp), %esp                    /* switch to espfix segment */
        jmp     .Lrestore_nocheck
#endif
ENDPROC(entry_INT80_32)

.macro FIXUP_ESPFIX_STACK
/*
 * Switch back for ESPFIX stack to the normal zerobased stack
 *
 * We can't call C functions using the ESPFIX stack. This code reads
 * the high word of the segment base from the GDT and swiches to the
 * normal stack and adjusts ESP with the matching offset.
 */
#ifdef CONFIG_X86_ESPFIX32
        /* fixup the stack */
        mov     GDT_ESPFIX_SS + 4, %al /* bits 16..23 */
        mov     GDT_ESPFIX_SS + 7, %ah /* bits 24..31 */
        shl     $16, %eax
        addl    %esp, %eax                      /* the adjusted stack pointer */
        pushl   $__KERNEL_DS
        pushl   %eax
        lss     (%esp), %esp                    /* switch to the normal stack segment */
#endif
.endm
.macro UNWIND_ESPFIX_STACK
#ifdef CONFIG_X86_ESPFIX32
        movl    %ss, %eax
        /* see if on espfix stack */
        cmpw    $__ESPFIX_SS, %ax
        jne     27f
        movl    $__KERNEL_DS, %eax
        movl    %eax, %ds
        movl    %eax, %es
        /* switch to normal stack */
        FIXUP_ESPFIX_STACK
27:
#endif
.endm

/*
 * Build the entry stubs with some assembler magic.
 * We pack 1 stub into every 8-byte block.
 */
        .align 8
ENTRY(irq_entries_start)
    vector=FIRST_EXTERNAL_VECTOR
    .rept (FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR)
        pushl   $(~vector+0x80)                 /* Note: always in signed byte range */
    vector=vector+1
        jmp     common_interrupt
        .align  8
    .endr
END(irq_entries_start)

/*
 * the CPU automatically disables interrupts when executing an IRQ vector,
 * so IRQ-flags tracing has to follow that:
 */
        .p2align CONFIG_X86_L1_CACHE_SHIFT
common_interrupt:
        ASM_CLAC
        addl    $-0x80, (%esp)                  /* Adjust vector into the [-256, -1] range */
        SAVE_ALL
        ENCODE_FRAME_POINTER
        TRACE_IRQS_OFF
        movl    %esp, %eax
        call    do_IRQ
        jmp     ret_from_intr
ENDPROC(common_interrupt)

#define BUILD_INTERRUPT3(name, nr, fn)  \
ENTRY(name)                             \
        ASM_CLAC;                       \
        pushl   $~(nr);                 \
        SAVE_ALL;                       \
        ENCODE_FRAME_POINTER;           \
        TRACE_IRQS_OFF                  \
        movl    %esp, %eax;             \
        call    fn;                     \
        jmp     ret_from_intr;          \
ENDPROC(name)


#ifdef CONFIG_TRACING
# define TRACE_BUILD_INTERRUPT(name, nr)        BUILD_INTERRUPT3(trace_##name, nr, smp_trace_##name)
#else
# define TRACE_BUILD_INTERRUPT(name, nr)
#endif

#define BUILD_INTERRUPT(name, nr)               \
        BUILD_INTERRUPT3(name, nr, smp_##name); \
        TRACE_BUILD_INTERRUPT(name, nr)

/* The include is where all of the SMP etc. interrupts come from */
#include <asm/entry_arch.h>

ENTRY(coprocessor_error)
        ASM_CLAC
        pushl   $0
        pushl   $do_coprocessor_error
        jmp     common_exception
END(coprocessor_error)

ENTRY(simd_coprocessor_error)
        ASM_CLAC
        pushl   $0
#ifdef CONFIG_X86_INVD_BUG
        /* AMD 486 bug: invd from userspace calls exception 19 instead of #GP */
        ALTERNATIVE "pushl      $do_general_protection",        \
                    "pushl      $do_simd_coprocessor_error",    \
                    X86_FEATURE_XMM
#else
        pushl   $do_simd_coprocessor_error
#endif
        jmp     common_exception
END(simd_coprocessor_error)

ENTRY(device_not_available)
        ASM_CLAC
        pushl   $-1                             # mark this as an int
        pushl   $do_device_not_available
        jmp     common_exception
END(device_not_available)

#ifdef CONFIG_PARAVIRT
ENTRY(native_iret)
        iret
        _ASM_EXTABLE(native_iret, iret_exc)
END(native_iret)
#endif

ENTRY(overflow)
        ASM_CLAC
        pushl   $0
        pushl   $do_overflow
        jmp     common_exception
END(overflow)

ENTRY(bounds)
        ASM_CLAC
        pushl   $0
        pushl   $do_bounds
        jmp     common_exception
END(bounds)

ENTRY(invalid_op)
        ASM_CLAC
        pushl   $0
        pushl   $do_invalid_op
        jmp     common_exception
END(invalid_op)

ENTRY(coprocessor_segment_overrun)
        ASM_CLAC
        pushl   $0
        pushl   $do_coprocessor_segment_overrun
        jmp     common_exception
END(coprocessor_segment_overrun)

ENTRY(invalid_TSS)
        ASM_CLAC
        pushl   $do_invalid_TSS
        jmp     common_exception
END(invalid_TSS)

ENTRY(segment_not_present)
        ASM_CLAC
        pushl   $do_segment_not_present
        jmp     common_exception
END(segment_not_present)

ENTRY(stack_segment)
        ASM_CLAC
        pushl   $do_stack_segment
        jmp     common_exception
END(stack_segment)

ENTRY(alignment_check)
        ASM_CLAC
        pushl   $do_alignment_check
        jmp     common_exception
END(alignment_check)

ENTRY(divide_error)
        ASM_CLAC
        pushl   $0                              # no error code
        pushl   $do_divide_error
        jmp     common_exception
END(divide_error)

#ifdef CONFIG_X86_MCE
ENTRY(machine_check)
        ASM_CLAC
        pushl   $0
        pushl   machine_check_vector
        jmp     common_exception
END(machine_check)
#endif

ENTRY(spurious_interrupt_bug)
        ASM_CLAC
        pushl   $0
        pushl   $do_spurious_interrupt_bug
        jmp     common_exception
END(spurious_interrupt_bug)

#ifdef CONFIG_XEN
ENTRY(xen_hypervisor_callback)
        pushl   $-1                             /* orig_ax = -1 => not a system call */
        SAVE_ALL
        ENCODE_FRAME_POINTER
        TRACE_IRQS_OFF

        /*
         * Check to see if we got the event in the critical
         * region in xen_iret_direct, after we've reenabled
         * events and checked for pending events.  This simulates
         * iret instruction's behaviour where it delivers a
         * pending interrupt when enabling interrupts:
         */
        movl    PT_EIP(%esp), %eax
        cmpl    $xen_iret_start_crit, %eax
        jb      1f
        cmpl    $xen_iret_end_crit, %eax
        jae     1f

        jmp     xen_iret_crit_fixup

ENTRY(xen_do_upcall)
1:      mov     %esp, %eax
        call    xen_evtchn_do_upcall
#ifndef CONFIG_PREEMPT
        call    xen_maybe_preempt_hcall
#endif
        jmp     ret_from_intr
ENDPROC(xen_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 fix up by reattempting the load, and zeroing the segment
 * register if the load fails.
 * Category 2 we fix up by jumping to do_iret_error. 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 maintaining a status value in EAX.
 */
ENTRY(xen_failsafe_callback)
        pushl   %eax
        movl    $1, %eax
1:      mov     4(%esp), %ds
2:      mov     8(%esp), %es
3:      mov     12(%esp), %fs
4:      mov     16(%esp), %gs
        /* EAX == 0 => Category 1 (Bad segment)
           EAX != 0 => Category 2 (Bad IRET) */
        testl   %eax, %eax
        popl    %eax
        lea     16(%esp), %esp
        jz      5f
        jmp     iret_exc
5:      pushl   $-1                             /* orig_ax = -1 => not a system call */
        SAVE_ALL
        ENCODE_FRAME_POINTER
        jmp     ret_from_exception

.section .fixup, "ax"
6:      xorl    %eax, %eax
        movl    %eax, 4(%esp)
        jmp     1b
7:      xorl    %eax, %eax
        movl    %eax, 8(%esp)
        jmp     2b
8:      xorl    %eax, %eax
        movl    %eax, 12(%esp)
        jmp     3b
9:      xorl    %eax, %eax
        movl    %eax, 16(%esp)
        jmp     4b
.previous
        _ASM_EXTABLE(1b, 6b)
        _ASM_EXTABLE(2b, 7b)
        _ASM_EXTABLE(3b, 8b)
        _ASM_EXTABLE(4b, 9b)
ENDPROC(xen_failsafe_callback)

BUILD_INTERRUPT3(xen_hvm_callback_vector, HYPERVISOR_CALLBACK_VECTOR,
                xen_evtchn_do_upcall)

#endif /* CONFIG_XEN */

#if IS_ENABLED(CONFIG_HYPERV)

BUILD_INTERRUPT3(hyperv_callback_vector, HYPERVISOR_CALLBACK_VECTOR,
        hyperv_vector_handler)

#endif /* CONFIG_HYPERV */

ENTRY(page_fault)
        ASM_CLAC
        pushl   $do_page_fault
        ALIGN
        jmp common_exception
END(page_fault)

common_exception:
        /* the function address is in %gs's slot on the stack */
        pushl   %fs
        pushl   %es
        pushl   %ds
        pushl   %eax
        pushl   %ebp
        pushl   %edi
        pushl   %esi
        pushl   %edx
        pushl   %ecx
        pushl   %ebx
        ENCODE_FRAME_POINTER
        cld
        movl    $(__KERNEL_PERCPU), %ecx
        movl    %ecx, %fs
        UNWIND_ESPFIX_STACK
        GS_TO_REG %ecx
        movl    PT_GS(%esp), %edi               # get the function address
        movl    PT_ORIG_EAX(%esp), %edx         # get the error code
        movl    $-1, PT_ORIG_EAX(%esp)          # no syscall to restart
        REG_TO_PTGS %ecx
        SET_KERNEL_GS %ecx
        movl    $(__USER_DS), %ecx
        movl    %ecx, %ds
        movl    %ecx, %es
        TRACE_IRQS_OFF
        movl    %esp, %eax                      # pt_regs pointer
        call    *%edi
        jmp     ret_from_exception
END(common_exception)

ENTRY(debug)
        /*
         * #DB can happen at the first instruction of
         * entry_SYSENTER_32 or in Xen's SYSENTER prologue.  If this
         * happens, then we will be running on a very small stack.  We
         * need to detect this condition and switch to the thread
         * stack before calling any C code at all.
         *
         * If you edit this code, keep in mind that NMIs can happen in here.
         */
        ASM_CLAC
        pushl   $-1                             # mark this as an int
        SAVE_ALL
        ENCODE_FRAME_POINTER
        xorl    %edx, %edx                      # error code 0
        movl    %esp, %eax                      # pt_regs pointer

        /* Are we currently on the SYSENTER stack? */
        movl    PER_CPU_VAR(cpu_entry_area), %ecx
        addl    $CPU_ENTRY_AREA_SYSENTER_stack + SIZEOF_SYSENTER_stack, %ecx
        subl    %eax, %ecx      /* ecx = (end of SYSENTER_stack) - esp */
        cmpl    $SIZEOF_SYSENTER_stack, %ecx
        jb      .Ldebug_from_sysenter_stack

        TRACE_IRQS_OFF
        call    do_debug
        jmp     ret_from_exception

.Ldebug_from_sysenter_stack:
        /* We're on the SYSENTER stack.  Switch off. */
        movl    %esp, %ebx
        movl    PER_CPU_VAR(cpu_current_top_of_stack), %esp
        TRACE_IRQS_OFF
        call    do_debug
        movl    %ebx, %esp
        jmp     ret_from_exception
END(debug)

/*
 * NMI is doubly nasty.  It can happen on the first instruction of
 * entry_SYSENTER_32 (just like #DB), but it can also interrupt the beginning
 * of the #DB handler even if that #DB in turn hit before entry_SYSENTER_32
 * switched stacks.  We handle both conditions by simply checking whether we
 * interrupted kernel code running on the SYSENTER stack.
 */
ENTRY(nmi)
        ASM_CLAC
#ifdef CONFIG_X86_ESPFIX32
        pushl   %eax
        movl    %ss, %eax
        cmpw    $__ESPFIX_SS, %ax
        popl    %eax
        je      .Lnmi_espfix_stack
#endif

        pushl   %eax                            # pt_regs->orig_ax
        SAVE_ALL
        ENCODE_FRAME_POINTER
        xorl    %edx, %edx                      # zero error code
        movl    %esp, %eax                      # pt_regs pointer

        /* Are we currently on the SYSENTER stack? */
        movl    PER_CPU_VAR(cpu_entry_area), %ecx
        addl    $CPU_ENTRY_AREA_SYSENTER_stack + SIZEOF_SYSENTER_stack, %ecx
        subl    %eax, %ecx      /* ecx = (end of SYSENTER_stack) - esp */
        cmpl    $SIZEOF_SYSENTER_stack, %ecx
        jb      .Lnmi_from_sysenter_stack

        /* Not on SYSENTER stack. */
        call    do_nmi
        jmp     .Lrestore_all_notrace

.Lnmi_from_sysenter_stack:
        /*
         * We're on the SYSENTER stack.  Switch off.  No one (not even debug)
         * is using the thread stack right now, so it's safe for us to use it.
         */
        movl    %esp, %ebx
        movl    PER_CPU_VAR(cpu_current_top_of_stack), %esp
        call    do_nmi
        movl    %ebx, %esp
        jmp     .Lrestore_all_notrace

#ifdef CONFIG_X86_ESPFIX32
.Lnmi_espfix_stack:
        /*
         * create the pointer to lss back
         */
        pushl   %ss
        pushl   %esp
        addl    $4, (%esp)
        /* copy the iret frame of 12 bytes */
        .rept 3
        pushl   16(%esp)
        .endr
        pushl   %eax
        SAVE_ALL
        ENCODE_FRAME_POINTER
        FIXUP_ESPFIX_STACK                      # %eax == %esp
        xorl    %edx, %edx                      # zero error code
        call    do_nmi
        RESTORE_REGS
        lss     12+4(%esp), %esp                # back to espfix stack
        jmp     .Lirq_return
#endif
END(nmi)

ENTRY(int3)
        ASM_CLAC
        pushl   $-1                             # mark this as an int
        SAVE_ALL
        ENCODE_FRAME_POINTER
        TRACE_IRQS_OFF
        xorl    %edx, %edx                      # zero error code
        movl    %esp, %eax                      # pt_regs pointer
        call    do_int3
        jmp     ret_from_exception
END(int3)

ENTRY(general_protection)
        pushl   $do_general_protection
        jmp     common_exception
END(general_protection)

#ifdef CONFIG_KVM_GUEST
ENTRY(async_page_fault)
        ASM_CLAC
        pushl   $do_async_page_fault
        jmp     common_exception
END(async_page_fault)
#endif

ENTRY(rewind_stack_do_exit)
        /* Prevent any naive code from trying to unwind to our caller. */
        xorl    %ebp, %ebp

        movl    PER_CPU_VAR(cpu_current_top_of_stack), %esi
        leal    -TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%esi), %esp

        call    do_exit
1:      jmp 1b
END(rewind_stack_do_exit)