exp.c

ReactOS是一些高手根据Windows XP的内核编写出的类XP。内核实现机理和API函数调用几乎相同。甚至可以兼容XP的程序。喜欢研究系统内核的人可以看一看。

/*
 * PROJECT:         ReactOS Kernel
 * LICENSE:         GPL - See COPYING in the top level directory
 * FILE:            ntoskrnl/ke/i386/exp.c
 * PURPOSE:         Exception Dispatching and Context<->Trap Frame Conversion
 * PROGRAMMERS:     Alex Ionescu ([e-mail])
 *                  Gregor Anich
 *                  Skywing ([e-mail])
 */

/* INCLUDES ******************************************************************/

#include <ntoskrnl.h>
#define NDEBUG
#include <debug.h>

/* GLOBALS *******************************************************************/

/* DR Registers in the CONTEXT structure */
UCHAR KiDebugRegisterContextOffsets[9] =
{
    FIELD_OFFSET(CONTEXT, Dr0),
    FIELD_OFFSET(CONTEXT, Dr1),
    FIELD_OFFSET(CONTEXT, Dr2),
    FIELD_OFFSET(CONTEXT, Dr3),
    0,
    0,
    FIELD_OFFSET(CONTEXT, Dr6),
    FIELD_OFFSET(CONTEXT, Dr7),
    0,
};

/* DR Registers in the KTRAP_FRAME structure */
UCHAR KiDebugRegisterTrapOffsets[9] =
{
    FIELD_OFFSET(KTRAP_FRAME, Dr0),
    FIELD_OFFSET(KTRAP_FRAME, Dr1),
    FIELD_OFFSET(KTRAP_FRAME, Dr2),
    FIELD_OFFSET(KTRAP_FRAME, Dr3),
    0,
    0,
    FIELD_OFFSET(KTRAP_FRAME, Dr6),
    FIELD_OFFSET(KTRAP_FRAME, Dr7),
    0,
};

/* FUNCTIONS *****************************************************************/

_SEH_DEFINE_LOCALS(KiCopyInfo)
{
    volatile EXCEPTION_RECORD SehExceptRecord;
};

_SEH_FILTER(KiCopyInformation)
{
    _SEH_ACCESS_LOCALS(KiCopyInfo);

    /* Copy the exception records and return to the handler */
    RtlCopyMemory((PVOID)&_SEH_VAR(SehExceptRecord),
                  _SEH_GetExceptionPointers()->ExceptionRecord,
                  sizeof(EXCEPTION_RECORD));
    return EXCEPTION_EXECUTE_HANDLER;
}

VOID
INIT_FUNCTION
NTAPI
KeInitExceptions(VOID)
{
    ULONG i;
    USHORT FlippedSelector;
    extern KIDTENTRY KiIdt[MAXIMUM_IDTVECTOR];

    /* Loop the IDT */
    for (i = 0; i <= MAXIMUM_IDTVECTOR; i ++)
    {
        /* Save the current Selector */
        FlippedSelector = KiIdt[i].Selector;

        /* Flip Selector and Extended Offset */
        KiIdt[i].Selector = KiIdt[i].ExtendedOffset;
        KiIdt[i].ExtendedOffset = FlippedSelector;
    }
}

ULONG
FASTCALL
KiUpdateDr7(IN ULONG Dr7)
{
    ULONG DebugMask = KeGetCurrentThread()->DispatcherHeader.DebugActive;

    /* Check if debugging is enabled */
    if (DebugMask & DR_MASK(DR7_OVERRIDE_V))
    {
        /* Sanity checks */
        ASSERT((DebugMask & DR_REG_MASK) != 0);
        ASSERT((Dr7 & ~DR7_RESERVED_MASK) == DR7_OVERRIDE_MASK);
        return 0;
    }

    /* Return DR7 itself */
    return Dr7;
}

BOOLEAN
FASTCALL
KiRecordDr7(OUT PULONG Dr7Ptr,
            OUT PULONG DrMask)
{
    ULONG NewMask, Mask;
    UCHAR Result;

    /* Check if the caller gave us a mask */
    if (!DrMask)
    {
        /* He didn't use the one from the thread */
        Mask = KeGetCurrentThread()->DispatcherHeader.DebugActive;
    }
    else
    {
        /* He did, read it */
        Mask = *DrMask;
    }

    /* Sanity check */
    ASSERT((*Dr7Ptr & DR7_RESERVED_MASK) == 0);

    /* Check if DR7 is empty */
    NewMask = Mask;
    if (!(*Dr7Ptr))
    {
        /* Assume failure */
        Result = FALSE;

        /* Check the DR mask */
        NewMask &= ~(DR_MASK(7));
        if (NewMask & DR_REG_MASK)
        {
            /* Set the active mask */
            NewMask |= DR_MASK(DR7_OVERRIDE_V);

            /* Set DR7 override */
            *DrMask |= DR7_OVERRIDE_MASK;
        }
        else
        {
            /* Sanity check */
            ASSERT(NewMask == 0);
        }
    }
    else
    {
        /* Check if we have a mask or not */
        Result = NewMask ? TRUE: FALSE;

        /* Update the mask to disable debugging */
        NewMask &= ~(DR_MASK(DR7_OVERRIDE_V));
        NewMask |= DR_MASK(7);
    }

    /* Check if caller wants the new mask */
    if (DrMask)
    {
        /* Update it */
        *DrMask = NewMask;
    }
    else
    {
        /* Check if the mask changed */
        if (Mask != NewMask)
        {
            /* Update it */
            KeGetCurrentThread()->DispatcherHeader.DebugActive =
                (BOOLEAN)NewMask;
        }
    }

    /* Return the result */
    return Result;
}

ULONG
NTAPI
KiEspFromTrapFrame(IN PKTRAP_FRAME TrapFrame)
{
    /* Check if this is user-mode or V86 */
    if ((TrapFrame->SegCs & MODE_MASK) ||
        (TrapFrame->EFlags & EFLAGS_V86_MASK))
    {
        /* Return it directly */
        return TrapFrame->HardwareEsp;
    }
    else
    {
        /* Edited frame */
        if (!(TrapFrame->SegCs & FRAME_EDITED))
        {
            /* Return edited value */
            return TrapFrame->TempEsp;
        }
        else
        {
            /* Virgin frame, calculate */
            return (ULONG)&TrapFrame->HardwareEsp;
        }
    }
}

VOID
NTAPI
KiEspToTrapFrame(IN PKTRAP_FRAME TrapFrame,
                 IN ULONG Esp)
{
    KIRQL OldIrql;
    ULONG Previous;

    /* Raise to APC_LEVEL if needed */
    OldIrql = KeGetCurrentIrql();
    if (OldIrql < APC_LEVEL) KeRaiseIrql(APC_LEVEL, &OldIrql);

    /* Get the old ESP */
    Previous = KiEspFromTrapFrame(TrapFrame);

    /* Check if this is user-mode or V86 */
    if ((TrapFrame->SegCs & MODE_MASK) ||
        (TrapFrame->EFlags & EFLAGS_V86_MASK))
    {
        /* Write it directly */
        TrapFrame->HardwareEsp = Esp;
    }
    else
    {
        /* Don't allow ESP to be lowered, this is illegal */
        if (Esp < Previous) KeBugCheckEx(SET_OF_INVALID_CONTEXT,
                                         Esp,
                                         Previous,
                                         (ULONG_PTR)TrapFrame,
                                         0);

        /* Create an edit frame, check if it was alrady */
        if (!(TrapFrame->SegCs & FRAME_EDITED))
        {
            /* Update the value */
            TrapFrame->TempEsp = Esp;
        }
        else
        {
            /* Check if ESP changed */
            if (Previous != Esp)
            {
                /* Save CS */
                TrapFrame->TempSegCs = TrapFrame->SegCs;
                TrapFrame->SegCs &= ~FRAME_EDITED;

                /* Save ESP */
                TrapFrame->TempEsp = Esp;
            }
        }
    }

    /* Restore IRQL */
    if (OldIrql < APC_LEVEL) KeLowerIrql(OldIrql);
}

ULONG
NTAPI
KiSsFromTrapFrame(IN PKTRAP_FRAME TrapFrame)
{
    /* If this was V86 Mode */
    if (TrapFrame->EFlags & EFLAGS_V86_MASK)
    {
        /* Just return it */
        return TrapFrame->HardwareSegSs;
    }
    else if (TrapFrame->SegCs & MODE_MASK)
    {
        /* Usermode, return the User SS */
        return TrapFrame->HardwareSegSs | RPL_MASK;
    }
    else
    {
        /* Kernel mode */
        return KGDT_R0_DATA;
    }
}

VOID
NTAPI
KiSsToTrapFrame(IN PKTRAP_FRAME TrapFrame,
                IN ULONG Ss)
{
    /* Remove the high-bits */
    Ss &= 0xFFFF;

    /* If this was V86 Mode */
    if (TrapFrame->EFlags & EFLAGS_V86_MASK)
    {
        /* Just write it */
        TrapFrame->HardwareSegSs = Ss;
    }
    else if (TrapFrame->SegCs & MODE_MASK)
    {
        /* Usermode, save the User SS */
        TrapFrame->HardwareSegSs = Ss | RPL_MASK;
    }
}

USHORT
NTAPI
KiTagWordFnsaveToFxsave(USHORT TagWord)
{
    INT FxTagWord = ~TagWord; 

    /* 
     * Empty is now 00, any 2 bits containing 1 mean valid
     * Now convert the rest (11->0 and the rest to 1)
     */
    FxTagWord = (FxTagWord | (FxTagWord >> 1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
    FxTagWord = (FxTagWord | (FxTagWord >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
    FxTagWord = (FxTagWord | (FxTagWord >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
    FxTagWord = (FxTagWord | (FxTagWord >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
    return FxTagWord;
}

VOID
NTAPI
KeContextToTrapFrame(IN PCONTEXT Context,
                     IN OUT PKEXCEPTION_FRAME ExceptionFrame,
                     IN OUT PKTRAP_FRAME TrapFrame,
                     IN ULONG ContextFlags,
                     IN KPROCESSOR_MODE PreviousMode)
{
    PFX_SAVE_AREA FxSaveArea;
    ULONG i;
    BOOLEAN V86Switch = FALSE;
    KIRQL OldIrql;
    ULONG DrMask = 0;
    PVOID SafeDr;

    /* Do this at APC_LEVEL */
    OldIrql = KeGetCurrentIrql();
    if (OldIrql < APC_LEVEL) KeRaiseIrql(APC_LEVEL, &OldIrql);

    /* Start with the basic Registers */
    if ((ContextFlags & CONTEXT_CONTROL) == CONTEXT_CONTROL)
    {
        /* Check if we went through a V86 switch */
        if ((Context->EFlags & EFLAGS_V86_MASK) !=
            (TrapFrame->EFlags & EFLAGS_V86_MASK))
        {
            /* We did, remember this for later */
            V86Switch = TRUE;
        }

        /* Copy EFLAGS and sanitize them*/
        TrapFrame->EFlags = Ke386SanitizeFlags(Context->EFlags, PreviousMode);

        /* Copy EBP and EIP */
        TrapFrame->Ebp = Context->Ebp;
        TrapFrame->Eip = Context->Eip;