Adding upstream version 7.0.6-dfsg.upstream/7.0.6-dfsgupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1222 insertions, 0 deletions

diff --git a/include/VBox/dbg.h b/include/VBox/dbg.h
new file mode 100644
index 00000000..901b72da
--- /dev/null
+++ b/include/VBox/dbg.h
@@ -0,0 +1,1222 @@
+/** @file
+ * Debugger Interfaces. (VBoxDbg)
+ *
+ * This header covers all external interfaces of the Debugger module.
+ * However, it does not cover the DBGF interface since that part of the
+ * VMM. Use dbgf.h for that.
+ */
+
+/*
+ * Copyright (C) 2006-2022 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * The contents of this file may alternatively be used under the terms
+ * of the Common Development and Distribution License Version 1.0
+ * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
+ * in the VirtualBox distribution, in which case the provisions of the
+ * CDDL are applicable instead of those of the GPL.
+ *
+ * You may elect to license modified versions of this file under the
+ * terms and conditions of either the GPL or the CDDL or both.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
+ */
+
+#ifndef VBOX_INCLUDED_dbg_h
+#define VBOX_INCLUDED_dbg_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include <VBox/cdefs.h>
+#include <VBox/types.h>
+#include <VBox/vmm/dbgf.h>
+
+#include <iprt/stdarg.h>
+#ifdef IN_RING3
+# include <iprt/errcore.h>
+#endif
+
+RT_C_DECLS_BEGIN
+
+
+
+/** @defgroup grp_dbg       The VirtualBox Debugger
+ * @{
+ */
+
+#ifdef IN_RING3 /* The debugger stuff is ring-3 only. */
+
+/** @defgroup grp_dbgc     The Debugger Console API
+ * @{
+ */
+
+/** @def VBOX_WITH_DEBUGGER
+ * The build is with debugger module. Test if this is defined before registering
+ * external debugger commands. This is normally defined in Config.kmk.
+ */
+#ifdef DOXYGEN_RUNNING
+# define VBOX_WITH_DEBUGGER
+#endif
+
+
+/**
+ * DBGC variable category.
+ *
+ * Used to describe an argument to a command or function and a functions
+ * return value.
+ */
+typedef enum DBGCVARCAT
+{
+    /** Any type is fine. */
+    DBGCVAR_CAT_ANY = 0,
+    /** Any kind of pointer or number. */
+    DBGCVAR_CAT_POINTER_NUMBER,
+    /** Any kind of pointer or number, no range. */
+    DBGCVAR_CAT_POINTER_NUMBER_NO_RANGE,
+    /** Any kind of pointer. */
+    DBGCVAR_CAT_POINTER,
+    /** Any kind of pointer with no range option. */
+    DBGCVAR_CAT_POINTER_NO_RANGE,
+    /** GC pointer. */
+    DBGCVAR_CAT_GC_POINTER,
+    /** GC pointer with no range option. */
+    DBGCVAR_CAT_GC_POINTER_NO_RANGE,
+    /** Numeric argument. */
+    DBGCVAR_CAT_NUMBER,
+    /** Numeric argument with no range option. */
+    DBGCVAR_CAT_NUMBER_NO_RANGE,
+    /** String. */
+    DBGCVAR_CAT_STRING,
+    /** Symbol. */
+    DBGCVAR_CAT_SYMBOL,
+    /** Option. */
+    DBGCVAR_CAT_OPTION,
+    /** Option + string. */
+    DBGCVAR_CAT_OPTION_STRING,
+    /** Option + number. */
+    DBGCVAR_CAT_OPTION_NUMBER
+} DBGCVARCAT;
+
+
+/**
+ * DBGC variable type.
+ */
+typedef enum DBGCVARTYPE
+{
+    /** unknown... */
+    DBGCVAR_TYPE_UNKNOWN = 0,
+    /** Flat GC pointer. */
+    DBGCVAR_TYPE_GC_FLAT,
+    /** Segmented GC pointer. */
+    DBGCVAR_TYPE_GC_FAR,
+    /** Physical GC pointer. */
+    DBGCVAR_TYPE_GC_PHYS,
+    /** Flat HC pointer. */
+    DBGCVAR_TYPE_HC_FLAT,
+    /** Physical HC pointer. */
+    DBGCVAR_TYPE_HC_PHYS,
+    /** Number. */
+    DBGCVAR_TYPE_NUMBER,
+    /** String. */
+    DBGCVAR_TYPE_STRING,
+    /** Symbol. */
+    DBGCVAR_TYPE_SYMBOL,
+    /** Special type used when querying symbols. */
+    DBGCVAR_TYPE_ANY
+} DBGCVARTYPE;
+
+/** @todo Rename to DBGCVAR_IS_xyz. */
+
+/** Checks if the specified variable type is of a pointer persuasion. */
+#define DBGCVAR_ISPOINTER(enmType)      ((enmType) >= DBGCVAR_TYPE_GC_FLAT && enmType <= DBGCVAR_TYPE_HC_PHYS)
+/** Checks if the specified variable type is of a pointer persuasion. */
+#define DBGCVAR_IS_FAR_PTR(enmType)     ((enmType) == DBGCVAR_TYPE_GC_FAR)
+/** Checks if the specified variable type is of a pointer persuasion and of the guest context sort. */
+#define DBGCVAR_ISGCPOINTER(enmType)    ((enmType) >= DBGCVAR_TYPE_GC_FLAT && (enmType) <= DBGCVAR_TYPE_GC_PHYS)
+/** Checks if the specified variable type is of a pointer persuasion and of the host context sort. */
+#define DBGCVAR_ISHCPOINTER(enmType)    ((enmType) >= DBGCVAR_TYPE_HC_FLAT && (enmType) <= DBGCVAR_TYPE_HC_PHYS)
+
+
+/**
+ * DBGC variable range type.
+ */
+typedef enum DBGCVARRANGETYPE
+{
+    /** No range appliable or no range specified. */
+    DBGCVAR_RANGE_NONE = 0,
+    /** Number of elements. */
+    DBGCVAR_RANGE_ELEMENTS,
+    /** Number of bytes. */
+    DBGCVAR_RANGE_BYTES
+} DBGCVARRANGETYPE;
+
+
+/**
+ * Variable descriptor.
+ */
+typedef struct DBGCVARDESC
+{
+    /** The minimal number of times this argument may occur.
+     * Use 0 here to inidicate that the argument is optional. */
+    unsigned    cTimesMin;
+    /** Maximum number of occurrences.
+     * Use ~0 here to indicate infinite. */
+    unsigned    cTimesMax;
+    /** Argument category. */
+    DBGCVARCAT  enmCategory;
+    /** Flags, DBGCVD_FLAGS_* */
+    unsigned    fFlags;
+    /** Argument name. */
+    const char *pszName;
+    /** Argument name. */
+    const char *pszDescription;
+} DBGCVARDESC;
+/** Pointer to an argument descriptor. */
+typedef DBGCVARDESC *PDBGCVARDESC;
+/** Pointer to a const argument descriptor. */
+typedef const DBGCVARDESC *PCDBGCVARDESC;
+
+/** Variable descriptor flags.
+ * @{ */
+/** Indicates that the variable depends on the previous being present. */
+#define DBGCVD_FLAGS_DEP_PREV       RT_BIT(1)
+/** @} */
+
+
+/**
+ * DBGC variable.
+ */
+typedef struct DBGCVAR
+{
+    /** Pointer to the argument descriptor. */
+    PCDBGCVARDESC   pDesc;
+    /** Pointer to the next argument. */
+    struct DBGCVAR *pNext;
+
+    /** Argument type. */
+    DBGCVARTYPE     enmType;
+    /** Type specific. */
+    union
+    {
+        /** Flat GC Address.        (DBGCVAR_TYPE_GC_FLAT) */
+        RTGCPTR         GCFlat;
+        /** Far (16:32) GC Address. (DBGCVAR_TYPE_GC_FAR) */
+        RTFAR32         GCFar;
+        /** Physical GC Address.    (DBGCVAR_TYPE_GC_PHYS) */
+        RTGCPHYS        GCPhys;
+        /** Flat HC Address.        (DBGCVAR_TYPE_HC_FLAT) */
+        void           *pvHCFlat;
+        /** Physical GC Address.    (DBGCVAR_TYPE_HC_PHYS) */
+        RTHCPHYS        HCPhys;
+        /** String.                 (DBGCVAR_TYPE_STRING)
+         * The basic idea is the the this is a pointer to the expression we're
+         * parsing, so no messing with freeing. */
+        const char     *pszString;
+        /** Number.                 (DBGCVAR_TYPE_NUMBER) */
+        uint64_t        u64Number;
+    } u;
+
+    /** Range type. */
+    DBGCVARRANGETYPE    enmRangeType;
+    /** Range. The use of the content depends on the enmRangeType. */
+    uint64_t            u64Range;
+} DBGCVAR;
+/** Pointer to a command argument. */
+typedef DBGCVAR *PDBGCVAR;
+/** Pointer to a const command argument. */
+typedef const DBGCVAR *PCDBGCVAR;
+
+
+/**
+ * Macro for initializing a DBGC variable with defaults.
+ * The result is an unknown variable type without any range.
+ */
+#define DBGCVAR_INIT(pVar) \
+        do { \
+            (pVar)->pDesc = NULL;\
+            (pVar)->pNext = NULL; \
+            (pVar)->enmType = DBGCVAR_TYPE_UNKNOWN; \
+            (pVar)->u.u64Number = 0; \
+            (pVar)->enmRangeType = DBGCVAR_RANGE_NONE; \
+            (pVar)->u64Range = 0; \
+        } while (0)
+
+/**
+ * Macro for initializing a DBGC variable with a HC physical address.
+ */
+#define DBGCVAR_INIT_HC_PHYS(pVar, Phys) \
+        do { \
+            DBGCVAR_INIT(pVar); \
+            (pVar)->enmType = DBGCVAR_TYPE_HC_PHYS; \
+            (pVar)->u.HCPhys = (Phys); \
+        } while (0)
+
+/**
+ * Macro for initializing a DBGC variable with a HC flat address.
+ */
+#define DBGCVAR_INIT_HC_FLAT(pVar, Flat) \
+        do { \
+            DBGCVAR_INIT(pVar); \
+            (pVar)->enmType = DBGCVAR_TYPE_HC_FLAT; \
+            (pVar)->u.pvHCFlat = (Flat); \
+        } while (0)
+
+/**
+ * Macro for initializing a DBGC variable with a GC physical address.
+ */
+#define DBGCVAR_INIT_GC_PHYS(pVar, Phys) \
+        do { \
+            DBGCVAR_INIT(pVar); \
+            (pVar)->enmType = DBGCVAR_TYPE_GC_PHYS; \
+            (pVar)->u.GCPhys = (Phys); \
+        } while (0)
+
+/**
+ * Macro for initializing a DBGC variable with a GC flat address.
+ */
+#define DBGCVAR_INIT_GC_FLAT(pVar, Flat) \
+        do { \
+            DBGCVAR_INIT(pVar); \
+            (pVar)->enmType = DBGCVAR_TYPE_GC_FLAT; \
+            (pVar)->u.GCFlat = (Flat); \
+        } while (0)
+
+/**
+ * Macro for initializing a DBGC variable with a GC flat address.
+ */
+#define DBGCVAR_INIT_GC_FLAT_BYTE_RANGE(pVar, Flat, cbRange) \
+        do { \
+            DBGCVAR_INIT(pVar); \
+            (pVar)->enmType = DBGCVAR_TYPE_GC_FLAT; \
+            (pVar)->u.GCFlat = (Flat); \
+            DBGCVAR_SET_RANGE(pVar, DBGCVAR_RANGE_BYTES, cbRange); \
+        } while (0)
+
+/**
+ * Macro for initializing a DBGC variable with a GC far address.
+ */
+#define DBGCVAR_INIT_GC_FAR(pVar, _sel, _off) \
+        do { \
+            DBGCVAR_INIT(pVar); \
+            (pVar)->enmType = DBGCVAR_TYPE_GC_FAR; \
+            (pVar)->u.GCFar.sel = (_sel); \
+            (pVar)->u.GCFar.off = (_off); \
+        } while (0)
+
+/**
+ * Macro for initializing a DBGC variable with a number.
+ */
+#define DBGCVAR_INIT_NUMBER(pVar, Value) \
+        do { \
+            DBGCVAR_INIT(pVar); \
+            (pVar)->enmType = DBGCVAR_TYPE_NUMBER; \
+            (pVar)->u.u64Number = (Value); \
+        } while (0)
+
+/**
+ * Macro for initializing a DBGC variable with a string.
+ */
+#define DBGCVAR_INIT_STRING(pVar, a_pszString) \
+        do { \
+            DBGCVAR_INIT(pVar); \
+            (pVar)->enmType      = DBGCVAR_TYPE_STRING; \
+            (pVar)->enmRangeType = DBGCVAR_RANGE_BYTES; \
+            (pVar)->u.pszString  = (a_pszString); \
+            (pVar)->u64Range     = strlen(a_pszString); \
+        } while (0)
+
+
+/**
+ * Macro for initializing a DBGC variable with a symbol.
+ */
+#define DBGCVAR_INIT_SYMBOL(pVar, a_pszSymbol) \
+        do { \
+            DBGCVAR_INIT(pVar); \
+            (pVar)->enmType      = DBGCVAR_TYPE_SYMBOL; \
+            (pVar)->enmRangeType = DBGCVAR_RANGE_BYTES; \
+            (pVar)->u.pszString  = (a_pszSymbol); \
+            (pVar)->u64Range     = strlen(a_pszSymbol); \
+        } while (0)
+
+
+/**
+ * Macro for setting the range of a DBGC variable.
+ * @param   pVar            The variable.
+ * @param   _enmRangeType   The range type.
+ * @param   Value           The range length value.
+ */
+#define DBGCVAR_SET_RANGE(pVar, _enmRangeType, Value) \
+    do { \
+        (pVar)->enmRangeType = (_enmRangeType); \
+        (pVar)->u64Range = (Value); \
+    } while (0)
+
+
+/**
+ * Macro for setting the range of a DBGC variable.
+ * @param   a_pVar          The variable.
+ * @param   a_cbRange       The range, in bytes.
+ */
+#define DBGCVAR_SET_BYTE_RANGE(a_pVar, a_cbRange) \
+    DBGCVAR_SET_RANGE(a_pVar, DBGCVAR_RANGE_BYTES, a_cbRange)
+
+
+/**
+ * Macro for resetting the range a DBGC variable.
+ * @param   a_pVar          The variable.
+ */
+#define DBGCVAR_ZAP_RANGE(a_pVar) \
+    do { \
+        (a_pVar)->enmRangeType  = DBGCVAR_RANGE_NONE; \
+        (a_pVar)->u64Range      = 0; \
+    } while (0)
+
+
+/**
+ * Macro for assigning one DBGC variable to another.
+ * @param   a_pResult       The result (target) variable.
+ * @param   a_pVar          The source variable.
+ */
+#define DBGCVAR_ASSIGN(a_pResult, a_pVar) \
+    do { \
+        *(a_pResult) = *(a_pVar); \
+    } while (0)
+
+
+/** Pointer to a command descriptor. */
+typedef struct DBGCCMD *PDBGCCMD;
+/** Pointer to a const command descriptor. */
+typedef const struct DBGCCMD *PCDBGCCMD;
+
+/** Pointer to a function descriptor. */
+typedef struct DBGCFUNC *PDBGCFUNC;
+/** Pointer to a const function descriptor. */
+typedef const struct DBGCFUNC *PCDBGCFUNC;
+
+/** Pointer to helper functions for commands. */
+typedef struct DBGCCMDHLP *PDBGCCMDHLP;
+
+
+/**
+ * Helper functions for commands.
+ */
+typedef struct DBGCCMDHLP
+{
+    /** Magic value (DBGCCMDHLP_MAGIC). */
+    uint32_t                u32Magic;
+
+    /**
+     * Command helper for writing formatted text to the debug console.
+     *
+     * @returns VBox status.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pcbWritten  Where to store the number of bytes written.
+     *                      This is optional.
+     * @param   pszFormat   The format string.  This may use all IPRT extensions as
+     *                      well as the debugger ones.
+     * @param   ...         Arguments specified in the format string.
+     */
+    DECLCALLBACKMEMBER(int, pfnPrintf,(PDBGCCMDHLP pCmdHlp, size_t *pcbWritten,
+                                       const char *pszFormat, ...)) RT_IPRT_FORMAT_ATTR(3, 4);
+
+    /**
+     * Command helper for writing formatted text to the debug console.
+     *
+     * @returns VBox status.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pcbWritten  Where to store the number of bytes written.
+     *                      This is optional.
+     * @param   pszFormat   The format string.  This may use all IPRT extensions as
+     *                      well as the debugger ones.
+     * @param   args        Arguments specified in the format string.
+     */
+    DECLCALLBACKMEMBER(int, pfnPrintfV,(PDBGCCMDHLP pCmdHlp, size_t *pcbWritten,
+                                        const char *pszFormat, va_list args)) RT_IPRT_FORMAT_ATTR(3, 0);
+
+    /**
+     * Command helper for formatting a string with debugger format specifiers.
+     *
+     * @returns The number of bytes written.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pszBuf      The output buffer.
+     * @param   cbBuf       The size of the output buffer.
+     * @param   pszFormat   The format string.  This may use all IPRT extensions as
+     *                      well as the debugger ones.
+     * @param   ...         Arguments specified in the format string.
+     */
+    DECLCALLBACKMEMBER(size_t, pfnStrPrintf,(PDBGCCMDHLP pCmdHlp, char *pszBuf, size_t cbBuf,
+                                             const char *pszFormat, ...)) RT_IPRT_FORMAT_ATTR(4, 5);
+
+    /**
+     * Command helper for formatting a string with debugger format specifiers.
+     *
+     * @returns The number of bytes written.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pszBuf      The output buffer.
+     * @param   cbBuf       The size of the output buffer.
+     * @param   pszFormat   The format string.  This may use all IPRT extensions as
+     *                      well as the debugger ones.
+     * @param   va          Arguments specified in the format string.
+     */
+    DECLCALLBACKMEMBER(size_t, pfnStrPrintfV,(PDBGCCMDHLP pCmdHlp, char *pszBuf, size_t cbBuf,
+                                              const char *pszFormat, va_list va)) RT_IPRT_FORMAT_ATTR(4, 0);
+
+    /**
+     * Command helper for formatting and error message for a VBox status code.
+     *
+     * @returns VBox status code appropriate to return from a command.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   rc          The VBox status code.
+     * @param   pszFormat   Format string for additional messages. Can be NULL.
+     * @param   ...         Format arguments, optional.
+     */
+    DECLCALLBACKMEMBER(int, pfnVBoxError,(PDBGCCMDHLP pCmdHlp, int rc, const char *pszFormat, ...)) RT_IPRT_FORMAT_ATTR(3, 4);
+
+    /**
+     * Command helper for formatting and error message for a VBox status code.
+     *
+     * @returns VBox status code appropriate to return from a command.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   rc          The VBox status code.
+     * @param   pszFormat   Format string for additional messages. Can be NULL.
+     * @param   args        Format arguments, optional.
+     */
+    DECLCALLBACKMEMBER(int, pfnVBoxErrorV,(PDBGCCMDHLP pCmdHlp, int rc,
+                                           const char *pszFormat, va_list args)) RT_IPRT_FORMAT_ATTR(3, 0);
+
+    /**
+     * Command helper for reading memory specified by a DBGC variable.
+     *
+     * @returns VBox status code appropriate to return from a command.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pvBuffer    Where to store the read data.
+     * @param   cbRead      Number of bytes to read.
+     * @param   pVarPointer DBGC variable specifying where to start reading.
+     * @param   pcbRead     Where to store the number of bytes actually read.
+     *                      This optional, but it's useful when read GC virtual memory where a
+     *                      page in the requested range might not be present.
+     *                      If not specified not-present failure or end of a HC physical page
+     *                      will cause failure.
+     */
+    DECLCALLBACKMEMBER(int, pfnMemRead,(PDBGCCMDHLP pCmdHlp, void *pvBuffer, size_t cbRead, PCDBGCVAR pVarPointer, size_t *pcbRead));
+
+    /**
+     * Command helper for writing memory specified by a DBGC variable.
+     *
+     * @returns VBox status code appropriate to return from a command.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pvBuffer    What to write.
+     * @param   cbWrite     Number of bytes to write.
+     * @param   pVarPointer DBGC variable specifying where to start reading.
+     * @param   pcbWritten  Where to store the number of bytes written.
+     *                      This is optional. If NULL be aware that some of the buffer
+     *                      might have been written to the specified address.
+     */
+    DECLCALLBACKMEMBER(int, pfnMemWrite,(PDBGCCMDHLP pCmdHlp, const void *pvBuffer, size_t cbWrite, PCDBGCVAR pVarPointer, size_t *pcbWritten));
+
+    /**
+     * Executes command an expression.
+     * (Hopefully the parser and functions are fully reentrant.)
+     *
+     * @returns VBox status code appropriate to return from a command.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pszExpr     The expression. Format string with the format DBGC extensions.
+     * @param   ...         Format arguments.
+     */
+    DECLCALLBACKMEMBER(int, pfnExec,(PDBGCCMDHLP pCmdHlp, const char *pszExpr, ...)) RT_IPRT_FORMAT_ATTR(2, 3);
+
+    /**
+     * Evaluates an expression.
+     * (Hopefully the parser and functions are fully reentrant.)
+     *
+     * @returns VBox status code appropriate to return from a command.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pResult     Where to store the result.
+     * @param   pszExpr     The expression. Format string with the format DBGC extensions.
+     * @param   va          Format arguments.
+     */
+    DECLCALLBACKMEMBER(int, pfnEvalV,(PDBGCCMDHLP pCmdHlp, PDBGCVAR pResult,
+                                      const char *pszExpr, va_list va)) RT_IPRT_FORMAT_ATTR(3, 0);
+
+    /**
+     * Print an error and fail the current command.
+     *
+     * @returns VBox status code to pass upwards.
+     *
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pCmd        The failing command.
+     * @param   pszFormat   The error message format string.
+     * @param   va          Format arguments.
+     */
+    DECLCALLBACKMEMBER(int, pfnFailV,(PDBGCCMDHLP pCmdHlp, PCDBGCCMD pCmd,
+                                      const char *pszFormat, va_list va)) RT_IPRT_FORMAT_ATTR(3, 0);
+
+    /**
+     * Print an error and fail the current command.
+     *
+     * @returns VBox status code to pass upwards.
+     *
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pCmd        The failing command.
+     * @param   rc          The status code indicating the failure.  This will
+     *                      be appended to the message after a colon (': ').
+     * @param   pszFormat   The error message format string.
+     * @param   va          Format arguments.
+     *
+     * @see     DBGCCmdHlpFailRc
+     */
+    DECLCALLBACKMEMBER(int, pfnFailRcV,(PDBGCCMDHLP pCmdHlp, PCDBGCCMD pCmd, int rc,
+                                        const char *pszFormat, va_list va)) RT_IPRT_FORMAT_ATTR(4, 0);
+
+    /**
+     * Parser error.
+     *
+     * @returns VBox status code to pass upwards.
+     *
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pCmd        The failing command, can be NULL but shouldn't.
+     * @param   iArg        The offending argument, -1 when lazy.
+     * @param   pszExpr     The expression.
+     * @param   iLine       The line number.
+     */
+    DECLCALLBACKMEMBER(int, pfnParserError,(PDBGCCMDHLP pCmdHlp, PCDBGCCMD pCmd, int iArg, const char *pszExpr, unsigned iLine));
+
+    /**
+     * Converts a DBGC variable to a DBGF address structure.
+     *
+     * @returns VBox status code.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pVar        The variable to convert.
+     * @param   pAddress    The target address.
+     */
+    DECLCALLBACKMEMBER(int, pfnVarToDbgfAddr,(PDBGCCMDHLP pCmdHlp, PCDBGCVAR pVar, PDBGFADDRESS pAddress));
+
+    /**
+     * Converts a DBGF address structure to a DBGC variable.
+     *
+     * @returns VBox status code.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pAddress    The source address.
+     * @param   pResult     The result variable.
+     */
+    DECLCALLBACKMEMBER(int, pfnVarFromDbgfAddr,(PDBGCCMDHLP pCmdHlp, PCDBGFADDRESS pAddress, PDBGCVAR pResult));
+
+    /**
+     * Converts a DBGC variable to a 64-bit number.
+     *
+     * @returns VBox status code.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pVar        The variable to convert.
+     * @param   pu64Number  Where to store the number.
+     */
+    DECLCALLBACKMEMBER(int, pfnVarToNumber,(PDBGCCMDHLP pCmdHlp, PCDBGCVAR pVar, uint64_t *pu64Number));
+
+    /**
+     * Converts a DBGC variable to a boolean.
+     *
+     * @returns VBox status code.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pVar        The variable to convert.
+     * @param   pf          Where to store the boolean.
+     */
+    DECLCALLBACKMEMBER(int, pfnVarToBool,(PDBGCCMDHLP pCmdHlp, PCDBGCVAR pVar, bool *pf));
+
+    /**
+     * Get the range of a variable in bytes, resolving symbols if necessary.
+     *
+     * @returns VBox status code.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pVar        The variable to convert.
+     * @param   cbElement   Conversion factor for element ranges.
+     * @param   cbDefault   The default range.
+     * @param   pcbRange    The length of the range.
+     */
+    DECLCALLBACKMEMBER(int, pfnVarGetRange,(PDBGCCMDHLP pCmdHlp, PCDBGCVAR pVar, uint64_t cbElement, uint64_t cbDefault,
+                                            uint64_t *pcbRange));
+
+    /**
+     * Converts a variable to one with the specified type.
+     *
+     * This preserves the range.
+     *
+     * @returns VBox status code.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   pVar        The variable to convert.
+     * @param   enmToType   The target type.
+     * @param   fConvSyms   If @c true, then attempt to resolve symbols.
+     * @param   pResult     The output variable. Can be the same as @a pVar.
+     */
+    DECLCALLBACKMEMBER(int, pfnVarConvert,(PDBGCCMDHLP pCmdHlp, PCDBGCVAR pVar, DBGCVARTYPE enmToType, bool fConvSyms,
+                                           PDBGCVAR pResult));
+
+    /**
+     * Gets a DBGF output helper that directs the output to the debugger
+     * console.
+     *
+     * @returns Pointer to the helper structure.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     */
+    DECLCALLBACKMEMBER(PCDBGFINFOHLP, pfnGetDbgfOutputHlp,(PDBGCCMDHLP pCmdHlp));
+
+    /**
+     * Gets the ID currently selected CPU.
+     *
+     * @returns Current CPU ID.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     */
+    DECLCALLBACKMEMBER(VMCPUID, pfnGetCurrentCpu,(PDBGCCMDHLP pCmdHlp));
+
+    /**
+     * Gets the mode the currently selected CPU is running in, in the current
+     * context.
+     *
+     * @returns Current CPU mode.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     */
+    DECLCALLBACKMEMBER(CPUMMODE, pfnGetCpuMode,(PDBGCCMDHLP pCmdHlp));
+
+    /**
+     * Prints the register set of the given CPU.
+     *
+     * @returns VBox status code.
+     * @param   pCmdHlp     Pointer to the command callback structure.
+     * @param   idCpu       The CPU ID to print the register set of.
+     * @param   f64BitMode  True to dump 64-bit state, false to dump 32-bit state,
+     *                      -1 to use the current CPU mode.
+     * @param   fTerse      Flag to indicate whether to dump the complete register set.
+     */
+    DECLCALLBACKMEMBER(int, pfnRegPrintf, (PDBGCCMDHLP pCmdHlp, VMCPUID idCpu, int f64BitMode, bool fTerse));
+
+    /** End marker (DBGCCMDHLP_MAGIC). */
+    uint32_t                u32EndMarker;
+} DBGCCMDHLP;
+
+/** Magic value for DBGCCMDHLP::u32Magic. (Fyodor Mikhaylovich Dostoyevsky) */
+#define DBGCCMDHLP_MAGIC    UINT32_C(18211111)
+
+
+#if defined(IN_RING3) || defined(IN_SLICKEDIT)
+
+/**
+ * Command helper for writing formatted text to the debug console.
+ *
+ * @returns VBox status.
+ * @param   pCmdHlp     Pointer to the command callback structure.
+ * @param   pszFormat   The format string.  This may use all IPRT extensions as
+ *                      well as the debugger ones.
+ * @param   ...         Arguments specified in the format string.
+ */
+DECLINLINE(int) RT_IPRT_FORMAT_ATTR(2, 3) DBGCCmdHlpPrintf(PDBGCCMDHLP pCmdHlp, const char *pszFormat, ...)
+{
+    va_list va;
+    int     rc;
+
+    va_start(va, pszFormat);
+    rc = pCmdHlp->pfnPrintfV(pCmdHlp, NULL, pszFormat, va);
+    va_end(va);
+
+    return rc;
+}
+
+/**
+ * Command helper for writing formatted text to the debug console.
+ *
+ * @returns VBox status.
+ * @param   pCmdHlp     Pointer to the command callback structure.
+ * @param   pcbWritten  Where to store the amount of written characters on success.
+ * @param   pszFormat   The format string.  This may use all IPRT extensions as
+ *                      well as the debugger ones.
+ * @param   ...         Arguments specified in the format string.
+ */
+DECLINLINE(int) RT_IPRT_FORMAT_ATTR(3, 4) DBGCCmdHlpPrintfEx(PDBGCCMDHLP pCmdHlp, size_t *pcbWritten,
+                                                             const char *pszFormat, ...)
+{
+    va_list va;
+    int     rc;
+
+    va_start(va, pszFormat);
+    rc = pCmdHlp->pfnPrintfV(pCmdHlp, pcbWritten, pszFormat, va);
+    va_end(va);
+
+    return rc;
+}
+
+/**
+ * Command helper for writing formatted text to the debug console.
+ *
+ * @returns Number of bytes written.
+ * @param   pCmdHlp     Pointer to the command callback structure.
+ * @param   pszFormat   The format string.  This may use all IPRT extensions as
+ *                      well as the debugger ones.
+ * @param   ...         Arguments specified in the format string.
+ */
+DECLINLINE(size_t) RT_IPRT_FORMAT_ATTR(2, 3) DBGCCmdHlpPrintfLen(PDBGCCMDHLP pCmdHlp, const char *pszFormat, ...)
+{
+    va_list va;
+    int     rc;
+    size_t  cbWritten = 0;
+
+    va_start(va, pszFormat);
+    rc = pCmdHlp->pfnPrintfV(pCmdHlp, &cbWritten, pszFormat, va);
+    va_end(va);
+
+    return RT_SUCCESS(rc) ? cbWritten : 0;
+}
+
+/**
+ * @copydoc DBGCCMDHLP::pfnStrPrintf
+ */
+DECLINLINE(size_t) RT_IPRT_FORMAT_ATTR(4, 5) DBGCCmdHlpStrPrintf(PDBGCCMDHLP pCmdHlp, char *pszBuf, size_t cbBuf,
+                                                                 const char *pszFormat, ...)
+{
+    va_list va;
+    size_t  cch;
+
+    va_start(va, pszFormat);
+    cch = pCmdHlp->pfnStrPrintfV(pCmdHlp, pszBuf, cbBuf, pszFormat, va);
+    va_end(va);
+
+    return cch;
+}
+
+/**
+ * @copydoc DBGCCMDHLP::pfnVBoxError
+ */
+DECLINLINE(int) RT_IPRT_FORMAT_ATTR(3, 4) DBGCCmdHlpVBoxError(PDBGCCMDHLP pCmdHlp, int rc, const char *pszFormat, ...)
+{
+    va_list va;
+
+    va_start(va, pszFormat);
+    rc = pCmdHlp->pfnVBoxErrorV(pCmdHlp, rc, pszFormat, va);
+    va_end(va);
+
+    return rc;
+}
+
+/**
+ * @copydoc DBGCCMDHLP::pfnMemRead
+ */
+DECLINLINE(int) DBGCCmdHlpMemRead(PDBGCCMDHLP pCmdHlp, void *pvBuffer, size_t cbRead, PCDBGCVAR pVarPointer, size_t *pcbRead)
+{
+    return pCmdHlp->pfnMemRead(pCmdHlp, pvBuffer, cbRead, pVarPointer, pcbRead);
+}
+
+/**
+ * Evaluates an expression.
+ * (Hopefully the parser and functions are fully reentrant.)
+ *
+ * @returns VBox status code appropriate to return from a command.
+ * @param   pCmdHlp     Pointer to the command callback structure.
+ * @param   pResult     Where to store the result.
+ * @param   pszExpr     The expression. Format string with the format DBGC extensions.
+ * @param   ...         Format arguments.
+ */
+DECLINLINE(int) RT_IPRT_FORMAT_ATTR(3, 4) DBGCCmdHlpEval(PDBGCCMDHLP pCmdHlp, PDBGCVAR pResult, const char *pszExpr, ...)
+{
+    va_list va;
+    int     rc;
+
+    va_start(va, pszExpr);
+    rc = pCmdHlp->pfnEvalV(pCmdHlp, pResult, pszExpr, va);
+    va_end(va);
+
+    return rc;
+}
+
+/**
+ * Print an error and fail the current command.
+ *
+ * @returns VBox status code to pass upwards.
+ *
+ * @param   pCmdHlp     Pointer to the command callback structure.
+ * @param   pCmd        The failing command.
+ * @param   pszFormat   The error message format string.
+ * @param   ...         Format arguments.
+ */
+DECLINLINE(int) RT_IPRT_FORMAT_ATTR(3, 4) DBGCCmdHlpFail(PDBGCCMDHLP pCmdHlp, PCDBGCCMD pCmd, const char *pszFormat, ...)
+{
+    va_list va;
+    int     rc;
+
+    va_start(va, pszFormat);
+    rc = pCmdHlp->pfnFailV(pCmdHlp, pCmd, pszFormat, va);
+    va_end(va);
+
+    return rc;
+}
+
+/**
+ * Print an error and fail the current command.
+ *
+ * Usage example:
+ * @code
+    int rc = VMMR3Something(pVM);
+    if (RT_FAILURE(rc))
+        return DBGCCmdHlpFailRc(pCmdHlp, pCmd, rc, "VMMR3Something");
+    return VINF_SUCCESS;
+ * @endcode
+ *
+ * @returns VBox status code to pass upwards.
+ *
+ * @param   pCmdHlp     Pointer to the command callback structure.
+ * @param   pCmd        The failing command.
+ * @param   rc          The status code indicating the failure.
+ * @param   pszFormat   The error message format string.
+ * @param   ...         Format arguments.
+ */
+DECLINLINE(int) RT_IPRT_FORMAT_ATTR(4, 5) DBGCCmdHlpFailRc(PDBGCCMDHLP pCmdHlp, PCDBGCCMD pCmd, int rc,
+                                                           const char *pszFormat, ...)
+{
+    va_list va;
+
+    va_start(va, pszFormat);
+    rc = pCmdHlp->pfnFailRcV(pCmdHlp, pCmd, rc, pszFormat, va);
+    va_end(va);
+
+    return rc;
+}
+
+/**
+ * @copydoc DBGCCMDHLP::pfnParserError
+ */
+DECLINLINE(int) DBGCCmdHlpParserError(PDBGCCMDHLP pCmdHlp, PCDBGCCMD pCmd, int iArg, const char *pszExpr, unsigned iLine)
+{
+    return pCmdHlp->pfnParserError(pCmdHlp, pCmd, iArg, pszExpr, iLine);
+}
+
+/** Assert+return like macro for checking parser sanity.
+ * Returns with failure if the precodition is not met. */
+#define DBGC_CMDHLP_ASSERT_PARSER_RET(pCmdHlp, pCmd, iArg, expr) \
+    do { \
+        if (!(expr)) \
+            return DBGCCmdHlpParserError(pCmdHlp, pCmd, iArg, #expr, __LINE__); \
+    } while (0)
+
+/** Assert+return like macro that the VM handle is present.
+ * Returns with failure if the VM handle is NIL.  */
+#define DBGC_CMDHLP_REQ_UVM_RET(pCmdHlp, pCmd, pUVM) \
+    do { \
+        if (!(pUVM)) \
+            return DBGCCmdHlpFail(pCmdHlp, pCmd, "No VM selected"); \
+    } while (0)
+
+/**
+ * @copydoc DBGCCMDHLP::pfnVarToDbgfAddr
+ */
+DECLINLINE(int) DBGCCmdHlpVarToDbgfAddr(PDBGCCMDHLP pCmdHlp, PCDBGCVAR pVar, PDBGFADDRESS pAddress)
+{
+    return pCmdHlp->pfnVarToDbgfAddr(pCmdHlp, pVar, pAddress);
+}
+
+/**
+ * @copydoc DBGCCMDHLP::pfnVarFromDbgfAddr
+ */
+DECLINLINE(int) DBGCCmdHlpVarFromDbgfAddr(PDBGCCMDHLP pCmdHlp, PCDBGFADDRESS pAddress, PDBGCVAR pResult)
+{
+    return pCmdHlp->pfnVarFromDbgfAddr(pCmdHlp, pAddress, pResult);
+}
+
+/**
+ * Converts an variable to a flat address.
+ *
+ * @returns VBox status code.
+ * @param   pCmdHlp     Pointer to the command callback structure.
+ * @param   pVar        The variable to convert.
+ * @param   pFlatPtr    Where to store the flat address.
+ */
+DECLINLINE(int) DBGCCmdHlpVarToFlatAddr(PDBGCCMDHLP pCmdHlp, PCDBGCVAR pVar, PRTGCPTR pFlatPtr)
+{
+    DBGFADDRESS Addr;
+    int rc = pCmdHlp->pfnVarToDbgfAddr(pCmdHlp, pVar, &Addr);
+    if (RT_SUCCESS(rc))
+        *pFlatPtr = Addr.FlatPtr;
+    return rc;
+}
+
+/**
+ * @copydoc DBGCCMDHLP::pfnVarToNumber
+ */
+DECLINLINE(int) DBGCCmdHlpVarToNumber(PDBGCCMDHLP pCmdHlp, PCDBGCVAR pVar, uint64_t *pu64Number)
+{
+    return pCmdHlp->pfnVarToNumber(pCmdHlp, pVar, pu64Number);
+}
+
+/**
+ * @copydoc DBGCCMDHLP::pfnVarToBool
+ */
+DECLINLINE(int) DBGCCmdHlpVarToBool(PDBGCCMDHLP pCmdHlp, PCDBGCVAR pVar, bool *pf)
+{
+    return pCmdHlp->pfnVarToBool(pCmdHlp, pVar, pf);
+}
+
+/**
+ * @copydoc DBGCCMDHLP::pfnVarGetRange
+ */
+DECLINLINE(int) DBGCCmdHlpVarGetRange(PDBGCCMDHLP pCmdHlp, PCDBGCVAR pVar, uint64_t cbElement, uint64_t cbDefault, uint64_t *pcbRange)
+{
+    return pCmdHlp->pfnVarGetRange(pCmdHlp, pVar, cbElement, cbDefault, pcbRange);
+}
+
+/**
+ * @copydoc DBGCCMDHLP::pfnVarConvert
+ */
+DECLINLINE(int) DBGCCmdHlpConvert(PDBGCCMDHLP pCmdHlp, PCDBGCVAR pVar, DBGCVARTYPE enmToType, bool fConvSyms, PDBGCVAR pResult)
+{
+    return pCmdHlp->pfnVarConvert(pCmdHlp, pVar, enmToType, fConvSyms, pResult);
+}
+
+/**
+ * @copydoc DBGCCMDHLP::pfnGetDbgfOutputHlp
+ */
+DECLINLINE(PCDBGFINFOHLP) DBGCCmdHlpGetDbgfOutputHlp(PDBGCCMDHLP pCmdHlp)
+{
+    return pCmdHlp->pfnGetDbgfOutputHlp(pCmdHlp);
+}
+
+/**
+ * @copydoc DBGCCMDHLP::pfnGetCurrentCpu
+ */
+DECLINLINE(VMCPUID) DBGCCmdHlpGetCurrentCpu(PDBGCCMDHLP pCmdHlp)
+{
+    return pCmdHlp->pfnGetCurrentCpu(pCmdHlp);
+}
+
+/**
+ * @copydoc DBGCCMDHLP::pfnGetCpuMode
+ */
+DECLINLINE(CPUMMODE) DBGCCmdHlpGetCpuMode(PDBGCCMDHLP pCmdHlp)
+{
+    return pCmdHlp->pfnGetCpuMode(pCmdHlp);
+}
+
+/**
+ * @copydoc DBGCCMDHLP::pfnRegPrintf
+ */
+DECLINLINE(int) DBGCCmdHlpRegPrintf(PDBGCCMDHLP pCmdHlp, VMCPUID idCpu, int f64BitMode, bool fTerse)
+{
+    return pCmdHlp->pfnRegPrintf(pCmdHlp, idCpu, f64BitMode, fTerse);
+}
+
+#endif /* IN_RING3 */
+
+
+
+/**
+ * Command handler.
+ *
+ * The console will call the handler for a command once it's finished
+ * parsing the user input.  The command handler function is responsible
+ * for executing the command itself.
+ *
+ * @returns VBox status.
+ * @param   pCmd        Pointer to the command descriptor (as registered).
+ * @param   pCmdHlp     Pointer to command helper functions.
+ * @param   pUVM        The user mode VM handle, can in theory be NULL.
+ * @param   paArgs      Pointer to (readonly) array of arguments.
+ * @param   cArgs       Number of arguments in the array.
+ */
+typedef DECLCALLBACKTYPE(int, FNDBGCCMD,(PCDBGCCMD pCmd, PDBGCCMDHLP pCmdHlp, PUVM pUVM, PCDBGCVAR paArgs, unsigned cArgs));
+/** Pointer to a FNDBGCCMD() function. */
+typedef FNDBGCCMD *PFNDBGCCMD;
+
+/**
+ * DBGC command descriptor.
+ */
+typedef struct DBGCCMD
+{
+    /** Command string. */
+    const char     *pszCmd;
+    /** Minimum number of arguments. */
+    unsigned        cArgsMin;
+    /** Max number of arguments. */
+    unsigned        cArgsMax;
+    /** Argument descriptors (array). */
+    PCDBGCVARDESC   paArgDescs;
+    /** Number of argument descriptors. */
+    unsigned        cArgDescs;
+    /** flags. (reserved for now) */
+    unsigned        fFlags;
+    /** Handler function. */
+    PFNDBGCCMD      pfnHandler;
+    /** Command syntax. */
+    const char     *pszSyntax;
+    /** Command description. */
+    const char     *pszDescription;
+} DBGCCMD;
+
+/** DBGCCMD Flags.
+ * @{
+ */
+/** @} */
+
+
+/**
+ * Function handler.
+ *
+ * The console will call the handler for a command once it's finished
+ * parsing the user input.  The command handler function is responsible
+ * for executing the command itself.
+ *
+ * @returns VBox status.
+ * @param   pFunc       Pointer to the function descriptor (as registered).
+ * @param   pCmdHlp     Pointer to command helper functions.
+ * @param   pUVM        The user mode VM handle, can in theory be NULL.
+ * @param   paArgs      Pointer to (readonly) array of arguments.
+ * @param   cArgs       Number of arguments in the array.
+ * @param   pResult     Where to return the result.
+ */
+typedef DECLCALLBACKTYPE(int, FNDBGCFUNC,(PCDBGCFUNC pFunc, PDBGCCMDHLP pCmdHlp, PUVM pUVM, PCDBGCVAR paArgs, unsigned cArgs,
+                                          PDBGCVAR pResult));
+/** Pointer to a FNDBGCFUNC() function. */
+typedef FNDBGCFUNC *PFNDBGCFUNC;
+
+/**
+ * DBGC function descriptor.
+ */
+typedef struct DBGCFUNC
+{
+    /** Command string. */
+    const char     *pszFuncNm;
+    /** Minimum number of arguments. */
+    unsigned        cArgsMin;
+    /** Max number of arguments. */
+    unsigned        cArgsMax;
+    /** Argument descriptors (array). */
+    PCDBGCVARDESC   paArgDescs;
+    /** Number of argument descriptors. */
+    unsigned        cArgDescs;
+    /** flags. (reserved for now) */
+    unsigned        fFlags;
+    /** Handler function. */
+    PFNDBGCFUNC     pfnHandler;
+    /** Function syntax. */
+    const char     *pszSyntax;
+    /** Function description. */
+    const char     *pszDescription;
+} DBGCFUNC;
+
+
+/** Pointer to a const I/O callback table. */
+typedef const struct DBGCIO *PCDBGCIO;
+
+/**
+ * I/O callback table.
+ */
+typedef struct DBGCIO
+{
+    /**
+     * Destroys the given I/O instance.
+     *
+     * @returns nothing.
+     * @param   pIo         Pointer to the I/O structure supplied by the I/O provider.
+     */
+    DECLCALLBACKMEMBER(void, pfnDestroy, (PCDBGCIO pIo));
+
+    /**
+     * Wait for input available for reading.
+     *
+     * @returns Flag whether there is input ready upon return.
+     * @retval  true if there is input ready.
+     * @retval  false if there not input ready.
+     * @param   pIo         Pointer to the I/O structure supplied by
+     *                      the I/O provider. The backend can use this to find it's instance data.
+     * @param   cMillies    Number of milliseconds to wait on input data.
+     */
+    DECLCALLBACKMEMBER(bool, pfnInput, (PCDBGCIO pIo, uint32_t cMillies));
+
+    /**
+     * Read input.
+     *
+     * @returns VBox status code.
+     * @param   pIo         Pointer to the I/O structure supplied by
+     *                      the I/O provider. The backend can use this to find it's instance data.
+     * @param   pvBuf       Where to put the bytes we read.
+     * @param   cbBuf       Maximum nymber of bytes to read.
+     * @param   pcbRead     Where to store the number of bytes actually read.
+     *                      If NULL the entire buffer must be filled for a
+     *                      successful return.
+     */
+    DECLCALLBACKMEMBER(int, pfnRead, (PCDBGCIO pIo, void *pvBuf, size_t cbBuf, size_t *pcbRead));
+
+    /**
+     * Write (output).
+     *
+     * @returns VBox status code.
+     * @param   pIo         Pointer to the I/O structure supplied by
+     *                      the I/O provider. The backend can use this to find it's instance data.
+     * @param   pvBuf       What to write.
+     * @param   cbBuf       Number of bytes to write.
+     * @param   pcbWritten  Where to store the number of bytes actually written.
+     *                      If NULL the entire buffer must be successfully written.
+     */
+    DECLCALLBACKMEMBER(int, pfnWrite, (PCDBGCIO pIo, const void *pvBuf, size_t cbBuf, size_t *pcbWritten));
+
+    /**
+     * Marks the beginning of a new packet being sent - optional.
+     *
+     * @returns VBox status code.
+     * @param   pIo         Pointer to the I/O structure supplied by
+     *                      the I/O provider. The backend can use this to find it's instance data.
+     * @param   cbPktHint   Size of the packet in bytes, serves as a hint for the I/O provider to arrange buffers.
+     *                      Give 0 if size is unknown upfront.
+     */
+    DECLCALLBACKMEMBER(int, pfnPktBegin, (PCDBGCIO pIo, size_t cbPktHint));
+
+    /**
+     * Marks the end of the packet - optional.
+     *
+     * @returns VBox status code.
+     * @param   pIo         Pointer to the I/O structure supplied by
+     *                      the I/O provider. The backend can use this to find it's instance data.
+     *
+     * @note Some I/O providers might decide to send data only when this is called not in the
+     *       DBGCIO::pfnWrite callback.
+     */
+    DECLCALLBACKMEMBER(int, pfnPktEnd, (PCDBGCIO pIo));
+
+    /**
+     * Ready / busy notification.
+     *
+     * @returns nothing.
+     * @param   pIo         Pointer to the I/O structure supplied by
+     *                      the I/O provider. The backend can use this to find it's instance data.
+     * @param   fReady      Whether it's ready (true) or busy (false).
+     */
+    DECLCALLBACKMEMBER(void, pfnSetReady, (PCDBGCIO pIo, bool fReady));
+
+} DBGCIO;
+/** Pointer to an I/O callback table. */
+typedef DBGCIO *PDBGCIO;
+
+
+DBGDECL(int)    DBGCCreate(PUVM pUVM, PCDBGCIO pIo, unsigned fFlags);
+DBGDECL(int)    DBGCRegisterCommands(PCDBGCCMD paCommands, unsigned cCommands);
+DBGDECL(int)    DBGCDeregisterCommands(PCDBGCCMD paCommands, unsigned cCommands);
+
+DBGDECL(int)    DBGCIoCreate(PUVM pUVM, void **ppvData);
+DBGDECL(int)    DBGCIoTerminate(PUVM pUVM, void *pvData);
+
+/** @} */
+
+#endif /* IN_RING3 */
+
+/** @} */
+RT_C_DECLS_END
+
+#endif /* !VBOX_INCLUDED_dbg_h */