Merge remote branch 'rjy/clientids'

Xext/xselinux_hooks.c

@@ -40,6 +40,7 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include "propertyst.h"
 #include "extnsionst.h"
 #include "xacestr.h"
+#include "client.h"
 #include "../os/osdep.h"
 #define _XSELINUX_NEED_FLASK_MAP
 #include "xselinuxint.h"
@@ -129,26 +130,25 @@ SELinuxLabelClient(ClientPtr client)
 
     /* For local clients, try and determine the executable name */
     if (XaceIsLocal(client)) {
-	struct ucred creds;
+	/* Get cached command name if CLIENTIDS is enabled. */
-	socklen_t len = sizeof(creds);
+	const char *cmdname = GetClientCmdName(client);
-	char path[PATH_MAX + 1];
+	Bool cached = (cmdname != NULL);
-	size_t bytes;
+	/* If CLIENTIDS is disabled, figure out the command name from
+	 * scratch. */
+	if (!cmdname)
+	{
+	    pid_t pid = DetermineClientPid(client);
+	    if (pid != -1)
+		DetermineClientCmd(pid, &cmdname, NULL);
+	}
 
-	memset(&creds, 0, sizeof(creds));
+	if (!cmdname)
-	if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &creds, &len) < 0)
 	    goto finish;
 
-	snprintf(path, PATH_MAX + 1, "/proc/%d/cmdline", creds.pid);
+	strncpy(subj->command, cmdname, COMMAND_LEN - 1);
-	fd = open(path, O_RDONLY);
-	if (fd < 0)
-	    goto finish;
 
-	bytes = read(fd, path, PATH_MAX + 1);
+	if (!cached)
-	close(fd);
+	    free((void *) cmdname); /* const char * */
-	if (bytes <= 0)
-	    goto finish;
-
-	strncpy(subj->command, path, COMMAND_LEN - 1);
     }
 
 finish:

configure.ac

@@ -312,19 +312,6 @@ AC_CHECK_HEADER([execinfo.h],[
     ])]
 )
 
-dnl ARM needs additional compiler flags for proper backtraces if GCC is
-dnl used. Compile a dummy program with the -mapcs-frame option. If it
-dnl succeeds, we know that we are building for ARM with GCC.
-old_CFLAGS="$CFLAGS"
-CFLAGS="-mapcs-frame"
-AC_COMPILE_IFELSE(
-        AC_LANG_PROGRAM([[ ]]),
-        ARM_BACKTRACE_CFLAGS="$CFLAGS",
-        ARM_BACKTRACE_CFLAGS=""
-)
-CFLAGS="$old_CFLAGS"
-AC_SUBST(ARM_BACKTRACE_CFLAGS)
-
 dnl ---------------------------------------------------------------------------
 dnl Bus options and CPU capabilities.  Replaces logic in
 dnl hw/xfree86/os-support/bus/Makefile.am, among others.
@@ -641,6 +628,7 @@ AC_ARG_ENABLE(vbe,            AS_HELP_STRING([--enable-vbe], [Build Xorg with VB
 AC_ARG_ENABLE(int10-module,     AS_HELP_STRING([--enable-int10-module], [Build Xorg with int10 module (default: enabled)]), [INT10MODULE=$enableval], [INT10MODULE=yes])
 AC_ARG_ENABLE(windowswm,      AS_HELP_STRING([--enable-windowswm], [Build XWin with WindowsWM extension (default: no)]), [WINDOWSWM=$enableval], [WINDOWSWM=no])
 AC_ARG_ENABLE(libdrm,         AS_HELP_STRING([--enable-libdrm], [Build Xorg with libdrm support (default: enabled)]), [DRM=$enableval],[DRM=yes])
+AC_ARG_ENABLE(clientids,      AS_HELP_STRING([--disable-clientids], [Build Xorg with client ID tracking (default: enabled)]), [CLIENTIDS=$enableval], [CLIENTIDS=yes])
 
 dnl DDXes.
 AC_ARG_ENABLE(xorg,    	      AS_HELP_STRING([--enable-xorg], [Build Xorg server (default: auto)]), [XORG=$enableval], [XORG=auto])
@@ -994,6 +982,18 @@ if test "x$RES" = xyes; then
 	REQUIRED_MODULES="$REQUIRED_MODULES $RESOURCEPROTO"
 fi
 
+# The XRes extension may support client ID tracking only if it has
+# been specifically enabled. Client ID tracking is implicitly not
+# supported if XRes extension is disabled.
+AC_MSG_CHECKING([whether to track client ids])
+if test "x$RES" = xyes && test "x$CLIENTIDS" = xyes; then
+	AC_DEFINE(CLIENTIDS, 1, [Support client ID tracking])
+else
+	CLIENTIDS=no
+fi
+AC_MSG_RESULT([$CLIENTIDS])
+AM_CONDITIONAL(CLIENTIDS, [test "x$CLIENTIDS" = xyes])
+
 if test "x$GLX" = xyes; then
 	PKG_CHECK_MODULES([XLIB], [x11])
 	PKG_CHECK_MODULES([GL], $GLPROTO $LIBGL)
@@ -1525,7 +1525,7 @@ if test "x$XNEST" = xyes; then
 	if test "x$have_xnest" = xno; then
 		AC_MSG_ERROR([Xnest build explicitly requested, but required modules not found.])
 	fi
-	XNEST_LIBS="$FB_LIB $FIXES_LIB $MI_LIB $XEXT_LIB $DBE_LIB $RECORD_LIB $GLX_LIBS $RANDR_LIB $RENDER_LIB $DAMAGE_LIB $MIEXT_SYNC_LIB $MIEXT_DAMAGE_LIB $MIEXT_SHADOW_LIB $XI_LIB $XKB_LIB $XKB_STUB_LIB $COMPOSITE_LIB $DIX_LIB $MAIN_LIB $OS_LIB"
+	XNEST_LIBS="$FB_LIB $FIXES_LIB $MI_LIB $XEXT_LIB $DBE_LIB $RECORD_LIB $GLX_LIBS $RANDR_LIB $RENDER_LIB $DAMAGE_LIB $MIEXT_SYNC_LIB $MIEXT_DAMAGE_LIB $MIEXT_SHADOW_LIB $XI_LIB $XKB_LIB $XKB_STUB_LIB $COMPOSITE_LIB $MAIN_LIB $DIX_LIB $OS_LIB"
 	XNEST_SYS_LIBS="$XNESTMODULES_LIBS $GLX_SYS_LIBS"
 	AC_SUBST([XNEST_LIBS])
 	AC_SUBST([XNEST_SYS_LIBS])

dix/dispatch.c

@@ -130,6 +130,7 @@ int ProcInitialConnection();
 #include "inputstr.h"
 #include "xkbsrv.h"
 #include "site.h"
+#include "client.h"
 
 #ifdef XSERVER_DTRACE
 #include "registry.h"
@@ -3459,6 +3460,9 @@ CloseDownClient(ClientPtr client)
 	    CallCallbacks((&ClientStateCallback), (pointer)&clientinfo);
 	} 	    
 	FreeClientResources(client);
+	/* Disable client ID tracking. This must be done after
+	 * ClientStateCallback. */
+	ReleaseClientIds(client);
 #ifdef XSERVER_DTRACE
 	XSERVER_CLIENT_DISCONNECT(client->index);
 #endif	
@@ -3496,6 +3500,7 @@ void InitClient(ClientPtr client, int i, pointer ospriv)
     client->smart_start_tick = SmartScheduleTime;
     client->smart_stop_tick = SmartScheduleTime;
     client->smart_check_tick = SmartScheduleTime;
+    client->clientIds = NULL;
 }
 
 /************************
@@ -3535,6 +3540,11 @@ ClientPtr NextAvailableClient(pointer ospriv)
 	currentMaxClients++;
     while ((nextFreeClientID < MAXCLIENTS) && clients[nextFreeClientID])
 	nextFreeClientID++;
+
+    /* Enable client ID tracking. This must be done before
+     * ClientStateCallback. */
+    ReserveClientIds(client);
+
     if (ClientStateCallback)
     {
 	NewClientInfoRec clientinfo;

dix/main.c

@@ -104,6 +104,7 @@ Equipment Corporation.
 #include "extnsionst.h"
 #include "privates.h"
 #include "registry.h"
+#include "client.h"
 #ifdef PANORAMIX
 #include "panoramiXsrv.h"
 #else
@@ -258,6 +259,7 @@ int main(int argc, char *argv[], char *envp[])
         InitCoreDevices();
 	InitInput(argc, argv);
 	InitAndStartDevices();
+	ReserveClientIds(serverClient);
 
 	dixSaveScreens(serverClient, SCREEN_SAVER_FORCER, ScreenSaverReset);
 
@@ -323,6 +325,7 @@ int main(int argc, char *argv[], char *envp[])
 	    screenInfo.numScreens = i;
 	}
 
+	ReleaseClientIds(serverClient);
 	dixFreePrivates(serverClient->devPrivates, PRIVATE_CLIENT);
 	serverClient->devPrivates = NULL;
 

hw/xfree86/loader/sdksyms.sh

@@ -259,6 +259,7 @@ cat > sdksyms.c << EOF
 #include "colormap.h"
 #include "colormapst.h"
 #include "hotplug.h"
+#include "client.h"
 #include "cursor.h"
 #include "cursorstr.h"
 #include "dix.h"

include/Makefile.am

@@ -3,6 +3,7 @@ sdk_HEADERS =		\
 	XIstubs.h	\
 	Xprintf.h	\
 	callback.h	\
+	client.h	\
 	closestr.h	\
 	closure.h	\
 	colormap.h	\

include/client.h

@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies). All
+ * rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/* Author: Rami Ylimäki <rami.ylimaki@vincit.fi> */
+
+#ifndef CLIENT_H
+#define CLIENT_H
+
+#ifdef HAVE_DIX_CONFIG_H
+#include <dix-config.h>
+#endif /* HAVE_DIX_CONFIG_H */
+#include <X11/Xfuncproto.h>
+#include <sys/types.h>
+
+/* Client IDs. Use GetClientPid, GetClientCmdName and GetClientCmdArgs
+ * instead of accessing the fields directly. */
+typedef struct {
+    pid_t pid;           /* process ID, -1 if not available */
+    const char *cmdname; /* process name, NULL if not available */
+    const char *cmdargs; /* process arguments, NULL if not available */
+} ClientIdRec, *ClientIdPtr;
+
+struct _Client;
+
+/* Initialize and clean up. */
+void ReserveClientIds(struct _Client *client);
+void ReleaseClientIds(struct _Client *client);
+
+/* Determine client IDs for caching. Exported on purpose for
+ * extensions such as SELinux. */
+extern _X_EXPORT pid_t DetermineClientPid(struct _Client *client);
+extern _X_EXPORT void DetermineClientCmd(pid_t, const char **cmdname, const char **cmdargs);
+
+/* Query cached client IDs. Exported on purpose for drivers. */
+extern _X_EXPORT pid_t GetClientPid(struct _Client *client);
+extern _X_EXPORT const char *GetClientCmdName(struct _Client *client);
+extern _X_EXPORT const char *GetClientCmdArgs(struct _Client *client);
+
+#endif /* CLIENT_H */

include/dix-config.h.in

@@ -279,6 +279,9 @@
 /* Support X resource extension */
 #undef RES
 
+/* Support client ID tracking in X resource extension */
+#undef CLIENTIDS
+
 /* Support MIT-SCREEN-SAVER extension */
 #undef SCREENSAVER
 

include/dixstruct.h

@@ -24,6 +24,7 @@ SOFTWARE.
 #ifndef DIXSTRUCT_H
 #define DIXSTRUCT_H
 
+#include "client.h"
 #include "dix.h"
 #include "resource.h"
 #include "cursor.h"
@@ -121,6 +122,7 @@ typedef struct _Client {
     long    smart_check_tick;
     
     DeviceIntPtr clientPtr;
+    ClientIdPtr  clientIds;
 }           ClientRec;
 
 /*

os/Makefile.am

@@ -1,25 +1,18 @@
-noinst_LTLIBRARIES = libos.la liblog.la
+noinst_LTLIBRARIES = libos.la
 
 AM_CFLAGS = $(DIX_CFLAGS) $(SHA1_CFLAGS)
 
 SECURERPC_SRCS = rpcauth.c
 XDMCP_SRCS = xdmcp.c
 STRLCAT_SRCS = strlcat.c strlcpy.c
-
+XORG_SRCS = log.c
-# Build a convenience library liblog.la that will be added into
-# libos.la. The split is done so that log.c can be built with
-# different compiler options.
-liblog_la_SOURCES = log.c
-# Add flags needed for proper backtraces of functions marked with GCC
-# __attribute__((noreturn)). Currently those flags are needed for
-# FatalError and AbortServer in log.c.
-liblog_la_CFLAGS = $(AM_CFLAGS) $(ARM_BACKTRACE_CFLAGS)
 
 libos_la_SOURCES = 	\
 	WaitFor.c	\
 	access.c	\
 	auth.c		\
 	backtrace.c	\
+	client.c	\
 	connection.c	\
 	io.c		\
 	mitauth.c	\
@@ -32,8 +25,9 @@ libos_la_SOURCES = 	\
 	xdmauth.c	\
 	xsha1.c		\
 	xstrans.c	\
-	xprintf.c
+	xprintf.c	\
-libos_la_LIBADD = @SHA1_LIBS@ $(DLOPEN_LIBS) liblog.la
+	$(XORG_SRCS)
+libos_la_LIBADD = @SHA1_LIBS@ $(DLOPEN_LIBS)
 
 if SECURE_RPC
 libos_la_SOURCES += $(SECURERPC_SRCS)

os/client.c

@@ -0,0 +1,310 @@
+/*
+ * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies). All
+ * rights reserved.
+ * Copyright (c) 1993, 2010, Oracle and/or its affiliates. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/**
+ * @file
+ *
+ * This file contains functionality for identifying clients by various
+ * means. The primary purpose of identification is to simply aid in
+ * finding out which clients are using X server and how they are using
+ * it. For example, it's often necessary to monitor what requests
+ * clients are executing (to spot bad behaviour) and how they are
+ * allocating resources in X server (to spot excessive resource
+ * usage).
+ *
+ * This framework automatically allocates information, that can be
+ * used for client identification, when a client connects to the
+ * server. The information is freed when the client disconnects. The
+ * allocated information is just a collection of various IDs, such as
+ * PID and process name for local clients, that are likely to be
+ * useful in analyzing X server usage.
+ *
+ * Users of the framework can query ID information about clients at
+ * any time. To avoid repeated polling of IDs the users can also
+ * subscribe for notifications about the availability of ID
+ * information. IDs have been allocated before ClientStateCallback is
+ * called with ClientStateInitial state. Similarly the IDs will be
+ * released after ClientStateCallback is called with ClientStateGone
+ * state.
+ *
+ * Author: Rami Ylimäki <rami.ylimaki@vincit.fi>
+ */
+
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "client.h"
+#include "os.h"
+#include "dixstruct.h"
+
+/**
+ * Try to determine a PID for a client from its connection
+ * information. This should be called only once when new client has
+ * connected, use GetClientPid to determine the PID at other times.
+ *
+ * @param[in] client Connection linked to some process.
+ *
+ * @return PID of the client. Error (-1) if PID can't be determined
+ *         for the client.
+ *
+ * @see GetClientPid
+ */
+pid_t DetermineClientPid(struct _Client *client)
+{
+    LocalClientCredRec *lcc = NULL;
+    pid_t pid = -1;
+
+    if (client == NullClient)
+        return pid;
+
+    if (client == serverClient)
+        return getpid();
+
+    if (GetLocalClientCreds(client, &lcc) != -1)
+    {
+        if (lcc->fieldsSet & LCC_PID_SET)
+            pid = lcc->pid;
+        FreeLocalClientCreds(lcc);
+    }
+
+    return pid;
+}
+
+/**
+ * Try to determine a command line string for a client based on its
+ * PID. Note that mapping PID to a command hasn't been implemented for
+ * some operating systems. This should be called only once when a new
+ * client has connected, use GetClientCmdName/Args to determine the
+ * string at other times.
+ *
+ * @param[in]  pid     Process ID of a client.
+
+ * @param[out] cmdname Client process name without arguments. You must
+ *                     release this by calling free. On error NULL is
+ *                     returned. Pass NULL if you aren't interested in
+ *                     this value.
+ * @param[out] cmdargs Arguments to client process. Useful for
+ *                     identifying a client that is executed from a
+ *                     launcher program. You must release this by
+ *                     calling free. On error NULL is returned. Pass
+ *                     NULL if you aren't interested in this value.
+ *
+ * @see GetClientCmdName/Args
+ */
+void DetermineClientCmd(pid_t pid, const char **cmdname, const char **cmdargs)
+{
+    char path[PATH_MAX + 1];
+    int totsize = 0;
+    int cmdsize = 0;
+    int argsize = 0;
+    int fd = 0;
+
+    if (cmdname)
+        *cmdname = NULL;
+    if (cmdargs)
+        *cmdargs = NULL;
+
+    if (pid == -1)
+        return;
+
+    /* Check if /proc/pid/cmdline exists. It's not supported on all
+     * operating systems. */
+    if (snprintf(path, sizeof(path), "/proc/%d/cmdline", pid) < 0)
+        return;
+    fd = open(path, O_RDONLY);
+    if (fd < 0)
+        return;
+
+    /* Read the contents of /proc/pid/cmdline. It should contain the
+     * process name and arguments. */
+    totsize = read(fd, path, sizeof(path));
+    if (totsize <= 0)
+        return;
+    if (close(fd) < 0)
+        return;
+    path[totsize - 1] = '\0';
+
+    /* Contruct the process name without arguments. */
+    cmdsize = strlen(path) + 1;
+    if (cmdname)
+    {
+        char *name = malloc(cmdsize);
+        if (name)
+        {
+            strncpy(name, path, cmdsize);
+            name[cmdsize - 1] = '\0';
+            *cmdname = name;
+        }
+    }
+
+    /* Construct the arguments for client process. */
+    argsize = totsize - cmdsize;
+    if (cmdargs && (argsize > 0))
+    {
+        char *args = malloc(argsize);
+        if (args)
+        {
+            int i = 0;
+            for (i = 0; i < (argsize - 1); ++i)
+            {
+                const char c = path[cmdsize + i];
+                args[i] = (c == '\0') ? ' ' : c;
+            }
+            args[argsize - 1] = '\0';
+            *cmdargs = args;
+        }
+    }
+}
+
+/**
+ * Called when a new client connects. Allocates client ID information.
+ *
+ * @param[in] client Recently connected client.
+ */
+void ReserveClientIds(struct _Client *client)
+{
+#ifdef CLIENTIDS
+    if (client == NullClient)
+        return;
+
+    assert(!client->clientIds);
+    client->clientIds = calloc(1, sizeof(ClientIdRec));
+    if (!client->clientIds)
+        return;
+
+    client->clientIds->pid = DetermineClientPid(client);
+    if (client->clientIds->pid != -1)
+        DetermineClientCmd(client->clientIds->pid, &client->clientIds->cmdname, &client->clientIds->cmdargs);
+
+    DebugF("client(%lx): Reserved pid(%d).\n",
+           client->clientAsMask, client->clientIds->pid);
+    DebugF("client(%lx): Reserved cmdname(%s) and cmdargs(%s).\n",
+           client->clientAsMask,
+           client->clientIds->cmdname ? client->clientIds->cmdname : "NULL",
+           client->clientIds->cmdargs ? client->clientIds->cmdargs : "NULL");
+#endif /* CLIENTIDS */
+}
+
+/**
+ * Called when an existing client disconnects. Frees client ID
+ * information.
+ *
+ * @param[in] client Recently disconnected client.
+ */
+void ReleaseClientIds(struct _Client *client)
+{
+#ifdef CLIENTIDS
+    if (client == NullClient)
+        return;
+
+    if (!client->clientIds)
+        return;
+
+    DebugF("client(%lx): Released pid(%d).\n",
+           client->clientAsMask, client->clientIds->pid);
+    DebugF("client(%lx): Released cmdline(%s) and cmdargs(%s).\n",
+           client->clientAsMask,
+           client->clientIds->cmdname ? client->clientIds->cmdname : "NULL",
+           client->clientIds->cmdargs ? client->clientIds->cmdargs : "NULL");
+
+    free((void *) client->clientIds->cmdname); /* const char * */
+    free((void *) client->clientIds->cmdargs); /* const char * */
+    free(client->clientIds);
+    client->clientIds = NULL;
+#endif /* CLIENTIDS */
+}
+
+/**
+ * Get cached PID of a client.
+ *
+ * param[in] client Client whose PID has been already cached.
+ *
+ * @return Cached client PID. Error (-1) if called:
+ *         - before ClientStateInitial client state notification
+ *         - after ClientStateGone client state notification
+ *         - for remote clients
+ *
+ * @see DetermineClientPid
+ */
+pid_t GetClientPid(struct _Client *client)
+{
+    if (client == NullClient)
+        return -1;
+
+    if (!client->clientIds)
+        return -1;
+
+    return client->clientIds->pid;
+}
+
+/**
+ * Get cached command name string of a client.
+ *
+ * param[in] client Client whose command line string has been already
+ *                  cached.
+ *
+ * @return Cached client command name. Error (NULL) if called:
+ *         - before ClientStateInitial client state notification
+ *         - after ClientStateGone client state notification
+ *         - for remote clients
+ *         - on OS that doesn't support mapping of PID to command line
+ *
+ * @see DetermineClientCmd
+ */
+const char *GetClientCmdName(struct _Client *client)
+{
+    if (client == NullClient)
+        return NULL;
+
+    if (!client->clientIds)
+        return NULL;
+
+    return client->clientIds->cmdname;
+}
+
+/**
+ * Get cached command arguments string of a client.
+ *
+ * param[in] client Client whose command line string has been already
+ *                  cached.
+ *
+ * @return Cached client command arguments. Error (NULL) if called:
+ *         - before ClientStateInitial client state notification
+ *         - after ClientStateGone client state notification
+ *         - for remote clients
+ *         - on OS that doesn't support mapping of PID to command line
+ *
+ * @see DetermineClientCmd
+ */
+const char *GetClientCmdArgs(struct _Client *client)
+{
+    if (client == NullClient)
+        return NULL;
+
+    if (!client->clientIds)
+        return NULL;
+
+    return client->clientIds->cmdargs;
+}