unwind.c

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/*
 * COPYRIGHT:       See COPYING in the top level directory
 * PROJECT:         ReactOS system libraries
 * PURPOSE:         Unwinding related functions
 * PROGRAMMER:      Timo Kreuzer (timo.kreuzer@reactos.org)
 */

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

#include <rtl.h>

#define NDEBUG
#include <debug.h>

#define UNWIND_HISTORY_TABLE_NONE 0
#define UNWIND_HISTORY_TABLE_GLOBAL 1
#define UNWIND_HISTORY_TABLE_LOCAL 2

#define UWOP_PUSH_NONVOL 0
#define UWOP_ALLOC_LARGE 1
#define UWOP_ALLOC_SMALL 2
#define UWOP_SET_FPREG 3
#define UWOP_SAVE_NONVOL 4
#define UWOP_SAVE_NONVOL_FAR 5
#define UWOP_SAVE_XMM 6
#define UWOP_SAVE_XMM_FAR 7
#define UWOP_SAVE_XMM128 8
#define UWOP_SAVE_XMM128_FAR 9
#define UWOP_PUSH_MACHFRAME 10


typedef unsigned char UBYTE;

typedef union _UNWIND_CODE
{
    struct
    {
        UBYTE CodeOffset;
        UBYTE UnwindOp:4;
        UBYTE OpInfo:4;
    };
    USHORT FrameOffset;
} UNWIND_CODE, *PUNWIND_CODE;

typedef struct _UNWIND_INFO
{
    UBYTE Version:3;
    UBYTE Flags:5;
    UBYTE SizeOfProlog;
    UBYTE CountOfCodes;
    UBYTE FrameRegister:4;
    UBYTE FrameOffset:4;
    UNWIND_CODE UnwindCode[1];
/*    union {
        OPTIONAL ULONG ExceptionHandler;
        OPTIONAL ULONG FunctionEntry;
    };
    OPTIONAL ULONG ExceptionData[];
*/
} UNWIND_INFO, *PUNWIND_INFO;

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

PRUNTIME_FUNCTION
NTAPI
RtlLookupFunctionTable(
    IN DWORD64 ControlPc,
    OUT PDWORD64 ImageBase,
    OUT PULONG Length)
{
    PVOID Table;
    ULONG Size;

    /* Find corresponding file header from code address */
    if (!RtlPcToFileHeader((PVOID)ControlPc, (PVOID*)ImageBase))
    {
        /* Nothing found */
        return NULL;
    }

    /* Locate the exception directory */
    Table = RtlImageDirectoryEntryToData((PVOID)*ImageBase,
                                         TRUE,
                                         IMAGE_DIRECTORY_ENTRY_EXCEPTION,
                                         &Size);

    /* Return the number of entries */
    *Length = Size / sizeof(RUNTIME_FUNCTION);

    /* Return the address of the table */
    return Table;
}

PRUNTIME_FUNCTION
NTAPI
RtlLookupFunctionEntry(
    IN DWORD64 ControlPc,
    OUT PDWORD64 ImageBase,
    OUT PUNWIND_HISTORY_TABLE HistoryTable)
{
    PRUNTIME_FUNCTION FunctionTable, FunctionEntry;
    ULONG TableLength;
    ULONG IndexLo, IndexHi, IndexMid;

    /* Find the corresponding table */
    FunctionTable = RtlLookupFunctionTable(ControlPc, ImageBase, &TableLength);

    /* Fail, if no table is found */
    if (!FunctionTable)
    {
        return NULL;
    }

    /* Use relative virtual address */
    ControlPc -= *ImageBase;

    /* Do a binary search */
    IndexLo = 0;
    IndexHi = TableLength;
    while (IndexHi > IndexLo)
    {
        IndexMid = (IndexLo + IndexHi) / 2;
        FunctionEntry = &FunctionTable[IndexMid];

        if (ControlPc < FunctionEntry->BeginAddress)
        {
            /* Continue search in lower half */
            IndexHi = IndexMid;
        }
        else if (ControlPc >= FunctionEntry->EndAddress)
        {
            /* Continue search in upper half */
            IndexLo = IndexMid + 1;
        }
        else
        {
            /* ControlPc is within limits, return entry */
            return FunctionEntry;
        }
    }

    /* Nothing found, return NULL */
    return NULL;
}

BOOLEAN
NTAPI
RtlAddFunctionTable(
    IN PRUNTIME_FUNCTION FunctionTable,
    IN DWORD EntryCount,
    IN DWORD64 BaseAddress)
{
    UNIMPLEMENTED;
    return FALSE;
}

BOOLEAN
NTAPI
RtlDeleteFunctionTable(
    IN PRUNTIME_FUNCTION FunctionTable)
{
    UNIMPLEMENTED;
    return FALSE;
}

BOOLEAN
NTAPI
RtlInstallFunctionTableCallback(
    IN DWORD64 TableIdentifier,
    IN DWORD64 BaseAddress,
    IN DWORD Length,
    IN PGET_RUNTIME_FUNCTION_CALLBACK Callback,
    IN PVOID Context,
    IN PCWSTR OutOfProcessCallbackDll)
{
    UNIMPLEMENTED;
    return FALSE;
}

void
FORCEINLINE
SetReg(PCONTEXT Context, BYTE Reg, DWORD64 Value)
{
    ((DWORD64*)(&Context->Rax))[Reg] = Value;
}

DWORD64
FORCEINLINE
GetReg(PCONTEXT Context, BYTE Reg)
{
    return ((DWORD64*)(&Context->Rax))[Reg];
}

void
FORCEINLINE
PopReg(PCONTEXT Context, BYTE Reg)
{
    DWORD64 Value = *(DWORD64*)Context->Rsp;
    Context->Rsp += 8;
    SetReg(Context, Reg, Value);
}

BOOLEAN
static
__inline
RtlpTryToUnwindEpilog(
    PCONTEXT Context,
    ULONG64 ImageBase,
    PRUNTIME_FUNCTION FunctionEntry)
{
    CONTEXT LocalContext;
    BYTE *InstrPtr;
    DWORD Instr;
    BYTE Reg, Mod;
    ULONG64 EndAddress;

    /* Make a local copy of the context */
    LocalContext = *Context;

    InstrPtr = (BYTE*)LocalContext.Rip;

    /* Check if first instruction of epilog is "add rsp, x" */
    Instr = *(DWORD*)InstrPtr;
    if ( (Instr & 0x00fffdff) == 0x00c48148 )
    {
        if ( (Instr & 0x0000ff00) == 0x8300 )
        {
            /* This is "add rsp, 0x??" */
            LocalContext.Rsp += Instr >> 24;
            InstrPtr += 4;
        }
        else
        {
            /* This is "add rsp, 0x???????? */
            LocalContext.Rsp += *(DWORD*)(InstrPtr + 3);
            InstrPtr += 7;
        }
    }
    /* Check if first instruction of epilog is "lea rsp, ..." */
    else if ( (Instr & 0x38fffe) == 0x208d48 )
    {
        /* Get the register */
        Reg = ((Instr << 8) | (Instr >> 16)) & 0x7;

        LocalContext.Rsp = GetReg(&LocalContext, Reg);

        /* Get adressing mode */
        Mod = (Instr >> 22) & 0x3;
        if (Mod == 0)
        {
            /* No displacement */
            InstrPtr += 3;
        }
        else if (Mod == 1)
        {
            /* 1 byte displacement */
            LocalContext.Rsp += Instr >> 24;
            InstrPtr += 4;
        }
        else if (Mod == 2)
        {
            /* 4 bytes displacement */
            LocalContext.Rsp += *(DWORD*)(InstrPtr + 3);
            InstrPtr += 7;
        }
    }

    /* Loop the following instructions before the ret */
    EndAddress = FunctionEntry->EndAddress + ImageBase - 1;
    while ((DWORD64)InstrPtr < EndAddress)
    {
        Instr = *(DWORD*)InstrPtr;

        /* Check for a simple pop */
        if ( (Instr & 0xf8) == 0x58 )
        {
            /* Opcode pops a basic register from stack */
            Reg = Instr & 0x7;
            PopReg(&LocalContext, Reg);
            InstrPtr++;
            continue;
        }

        /* Check for REX + pop */
        if ( (Instr & 0xf8fb) == 0x5841 )
        {
            /* Opcode is pop r8 .. r15 */
            Reg = ((Instr >> 8) & 0x7) + 8;
            PopReg(&LocalContext, Reg);
            InstrPtr += 2;
            continue;
        }

        /* Opcode not allowed for Epilog */
        return FALSE;
    }

    /* Check if we are at the ret instruction */
    if ((DWORD64)InstrPtr != EndAddress)
    {
        /* If we went past the end of the function, something is broken! */
        ASSERT((DWORD64)InstrPtr <= EndAddress);
        return FALSE;
    }

    /* Make sure this is really a ret instruction */
    if (*InstrPtr != 0xc3)
    {
        ASSERT(FALSE);
        return FALSE;
    }

    /* Unwind is finished, pop new Rip from Stack */
    LocalContext.Rip = *(DWORD64*)LocalContext.Rsp;
    LocalContext.Rsp += sizeof(DWORD64);

    *Context = LocalContext;
    return TRUE;
}

PEXCEPTION_ROUTINE
NTAPI
RtlVirtualUnwind(
    _In_ ULONG HandlerType,
    _In_ ULONG64 ImageBase,
    _In_ ULONG64 ControlPc,
    _In_ PRUNTIME_FUNCTION FunctionEntry,
    _Inout_ PCONTEXT Context,
    _Outptr_ PVOID *HandlerData,
    _Out_ PULONG64 EstablisherFrame,
    _Inout_ PKNONVOLATILE_CONTEXT_POINTERS ContextPointers)
{
    PUNWIND_INFO UnwindInfo;
    ULONG_PTR CodeOffset;
    ULONG i;
    UNWIND_CODE UnwindCode;
    BYTE Reg;

    /* Use relative virtual address */
    ControlPc -= ImageBase;

    /* Sanity checks */
    if ( (ControlPc < FunctionEntry->BeginAddress) ||
         (ControlPc >= FunctionEntry->EndAddress) )
    {
        return NULL;
    }

    /* Get a pointer to the unwind info */
    UnwindInfo = RVA(ImageBase, FunctionEntry->UnwindData);

    /* Calculate relative offset to function start */
    CodeOffset = ControlPc - FunctionEntry->BeginAddress;

    /* Check if we are in the function epilog and try to finish it */
    if (CodeOffset > UnwindInfo->SizeOfProlog)
    {
        if (RtlpTryToUnwindEpilog(Context, ImageBase, FunctionEntry))
        {
            /* There's no exception routine */
            return NULL;
        }
    }

    /* Skip all Ops with an offset greater than the current Offset */
    i = 0;
    while (i < UnwindInfo->CountOfCodes &&
           CodeOffset < UnwindInfo->UnwindCode[i].CodeOffset)
    {
        UnwindCode = UnwindInfo->UnwindCode[i];
        switch (UnwindCode.UnwindOp)
        {
            case UWOP_SAVE_NONVOL:
            case UWOP_SAVE_XMM:
            case UWOP_SAVE_XMM128:
                i += 2;
                break;

            case UWOP_SAVE_NONVOL_FAR:
            case UWOP_SAVE_XMM_FAR:
            case UWOP_SAVE_XMM128_FAR:
                i += 3;
                break;

            case UWOP_ALLOC_LARGE:
                i += UnwindCode.OpInfo ? 3 : 2;
                break;

            default:
                i++;
        }
    }

    /* Process the remaining unwind ops */
    while (i < UnwindInfo->CountOfCodes)
    {
        UnwindCode = UnwindInfo->UnwindCode[i];
        switch (UnwindCode.UnwindOp)
        {
            case UWOP_PUSH_NONVOL:
                Reg = UnwindCode.OpInfo;
                SetReg(Context, Reg, *(DWORD64*)Context->Rsp);
                Context->Rsp += sizeof(DWORD64);
                i++;
                break;

            case UWOP_ALLOC_LARGE:
                if (UnwindCode.OpInfo)
                {
                    ULONG Offset = *(ULONG*)(&UnwindInfo->UnwindCode[i+1]);
                    Context->Rsp += Offset;
                    i += 3;
                }
                else
                {
                    USHORT Offset = UnwindInfo->UnwindCode[i+1].FrameOffset;
                    Context->Rsp += Offset * 8;
                    i += 2;
                }
                break;

            case UWOP_ALLOC_SMALL:
                Context->Rsp += (UnwindCode.OpInfo + 1) * 8;
                i++;
                break;

            case UWOP_SET_FPREG:
                i++;
                break;

            case UWOP_SAVE_NONVOL:
                i += 2;
                break;

            case UWOP_SAVE_NONVOL_FAR:
                i += 3;
                break;

            case UWOP_SAVE_XMM:
                i += 2;
                break;

            case UWOP_SAVE_XMM_FAR:
                i += 3;
                break;

            case UWOP_SAVE_XMM128:
                i += 2;
                break;

            case UWOP_SAVE_XMM128_FAR:
                i += 3;
                break;

            case UWOP_PUSH_MACHFRAME:
                i += 1;
                break;
        }
    }

    /* Unwind is finished, pop new Rip from Stack */
    Context->Rip = *(DWORD64*)Context->Rsp;
    Context->Rsp += sizeof(DWORD64);

    return 0;
}

VOID
NTAPI
RtlUnwindEx(
    _In_opt_ PVOID TargetFrame,
    _In_opt_ PVOID TargetIp,
    _In_opt_ PEXCEPTION_RECORD ExceptionRecord,
    _In_ PVOID ReturnValue,
    _In_ PCONTEXT ContextRecord,
    _In_opt_ struct _UNWIND_HISTORY_TABLE *HistoryTable)
{
    __debugbreak();
    return;
}

VOID
NTAPI
RtlUnwind(
  IN PVOID TargetFrame,
  IN PVOID TargetIp,
  IN PEXCEPTION_RECORD ExceptionRecord,
  IN PVOID ReturnValue)
{
    UNIMPLEMENTED;
    return;
}

ULONG
NTAPI
RtlWalkFrameChain(OUT PVOID *Callers,
                  IN ULONG Count,
                  IN ULONG Flags)
{
    CONTEXT Context;
    ULONG64 ControlPc, ImageBase, EstablisherFrame;
    ULONG64 StackLow, StackHigh;
    PVOID HandlerData;
    ULONG i, FramesToSkip;
    PRUNTIME_FUNCTION FunctionEntry;

    DPRINT("Enter RtlWalkFrameChain\n");

    /* The upper bits in Flags define how many frames to skip */
    FramesToSkip = Flags >> 8;

    /* Capture the current Context */
    RtlCaptureContext(&Context);
    ControlPc = Context.Rip;

    /* Get the stack limits */
    RtlpGetStackLimits(&StackLow, &StackHigh);

    /* Check if we want the user-mode stack frame */
    if (Flags & 1)
    {
    }

    /* Loop the frames */
    for (i = 0; i < FramesToSkip + Count; i++)
    {
        /* Lookup the FunctionEntry for the current ControlPc */
        FunctionEntry = RtlLookupFunctionEntry(ControlPc, &ImageBase, NULL);

        /* Is this a leaf function? */
        if (!FunctionEntry)
        {
            Context.Rip = *(DWORD64*)Context.Rsp;
            Context.Rsp += sizeof(DWORD64);
            DPRINT("leaf funtion, new Rip = %p, new Rsp = %p\n", (PVOID)Context.Rip, (PVOID)Context.Rsp);
        }
        else
        {
            RtlVirtualUnwind(0,
                             ImageBase,
                             ControlPc,
                             FunctionEntry,
                             &Context,
                             &HandlerData,
                             &EstablisherFrame,
                             NULL);
            DPRINT("normal funtion, new Rip = %p, new Rsp = %p\n", (PVOID)Context.Rip, (PVOID)Context.Rsp);
        }

        /* Check if new Rip is valid */
        if (!Context.Rip)
        {
            break;
        }

        /* Check, if we have left our stack */
        if ((Context.Rsp < StackLow) || (Context.Rsp > StackHigh))
        {
            break;
        }

        /* Continue with new Rip */
        ControlPc = Context.Rip;

        /* Save value, if we are past the frames to skip */
        if (i >= FramesToSkip)
        {
            Callers[i - FramesToSkip] = (PVOID)ControlPc;
        }
    }

    DPRINT("RtlWalkFrameChain returns %ld\n", i);
    return i;
}

#undef RtlGetCallersAddress
VOID
NTAPI
RtlGetCallersAddress(
    OUT PVOID *CallersAddress,
    OUT PVOID *CallersCaller )
{
    PVOID Callers[4];
    ULONG Number;

    /* Get callers:
     * RtlWalkFrameChain -> RtlGetCallersAddress -> x -> y */
    Number = RtlWalkFrameChain(Callers, 4, 0);

    *CallersAddress = (Number >= 3) ? Callers[2] : NULL;
    *CallersCaller = (Number == 4) ? Callers[3] : NULL;

    return;
}

// FIXME: move to different file
VOID
NTAPI
RtlRaiseException(IN PEXCEPTION_RECORD ExceptionRecord)
{
    CONTEXT Context;
    NTSTATUS Status = STATUS_INVALID_DISPOSITION;
    ULONG64 ImageBase;
    PRUNTIME_FUNCTION FunctionEntry;
    PVOID HandlerData;
    ULONG64 EstablisherFrame;

    /* Capture the context */
    RtlCaptureContext(&Context);

    /* Get the function entry for this function */
    FunctionEntry = RtlLookupFunctionEntry(Context.Rip,
                                           &ImageBase,
                                           NULL);

    /* Check if we found it */
    if (FunctionEntry)
    {
        /* Unwind to the caller of this function */
        RtlVirtualUnwind(UNW_FLAG_NHANDLER,
                         ImageBase,
                         Context.Rip,
                         FunctionEntry,
                         &Context,
                         &HandlerData,
                         &EstablisherFrame,
                         NULL);

        /* Save the exception address */
        ExceptionRecord->ExceptionAddress = (PVOID)Context.Rip;

        /* Write the context flag */
        Context.ContextFlags = CONTEXT_FULL;

        /* Check if user mode debugger is active */
        if (RtlpCheckForActiveDebugger())
        {
            /* Raise an exception immediately */
            Status = ZwRaiseException(ExceptionRecord, &Context, TRUE);
        }
        else
        {
            /* Dispatch the exception and check if we should continue */
            if (!RtlDispatchException(ExceptionRecord, &Context))
            {
                /* Raise the exception */
                Status = ZwRaiseException(ExceptionRecord, &Context, FALSE);
            }
            else
            {
                /* Continue, go back to previous context */
                Status = ZwContinue(&Context, FALSE);
            }
        }
    }

    /* If we returned, raise a status */
    RtlRaiseStatus(Status);
}