utils: Introduce functions for kernel module manipulation

virKModConfig()        - Return a buffer containing kernel module configuration
virKModLoad()          - Load a specific module into the kernel configuration
virKModUnload()        - Unload a specific module from the kernel configuration
virKModIsBlacklisted() - Determine whether a module is blacklisted within
                         the kernel configuration

configure.ac

@@ -416,6 +416,8 @@ AC_PATH_PROG([UDEVSETTLE], [udevsettle], [],
 	[/sbin:/usr/sbin:/usr/local/sbin:$PATH])
 AC_PATH_PROG([MODPROBE], [modprobe], [modprobe],
 	[/sbin:/usr/sbin:/usr/local/sbin:$PATH])
+AC_PATH_PROG([RMMOD], [rmmod], [rmmod],
+	[/sbin:/usr/sbin:/usr/local/sbin:$PATH])
 AC_PATH_PROG([OVSVSCTL], [ovs-vsctl], [ovs-vsctl],
 	[/sbin:/usr/sbin:/usr/local/sbin:$PATH])
 AC_PATH_PROG([SCRUB], [scrub], [scrub],
@@ -444,6 +446,10 @@ if test -n "$MODPROBE"; then
   AC_DEFINE_UNQUOTED([MODPROBE],["$MODPROBE"],
         [Location or name of the modprobe program])
 fi
+if test -n "$RMMOD"; then
+  AC_DEFINE_UNQUOTED([RMMOD],["$RMMOD"],
+        [Location or name of the rmmod program])
+fi
 AC_DEFINE_UNQUOTED([SCRUB],["$SCRUB"],
         [Location or name of the scrub program (for wiping algorithms)])
 

src/Makefile.am

@@ -125,6 +125,7 @@ UTIL_SOURCES =							\
 		util/virnetdevvportprofile.h util/virnetdevvportprofile.c \
 		util/virnetlink.c util/virnetlink.h		\
 		util/virnodesuspend.c util/virnodesuspend.h	\
+		util/virkmod.c util/virkmod.h                   \
 		util/virnuma.c util/virnuma.h			\
 		util/virobject.c util/virobject.h		\
 		util/virpci.c util/virpci.h			\

src/libvirt_private.syms

@@ -1383,6 +1383,13 @@ virKeyFileLoadFile;
 virKeyFileNew;
 
 
+# util/virkmod.h
+virKModConfig;
+virKModIsBlacklisted;
+virKModLoad;
+virKModUnload;
+
+
 # util/virlockspace.h
 virLockSpaceAcquireResource;
 virLockSpaceCreateResource;

src/util/virkmod.c

@@ -0,0 +1,181 @@
+/*
+ * virkmod.c: helper APIs for managing kernel modules
+ *
+ * Copyright (C) 2014 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <config.h>
+#include "viralloc.h"
+#include "virkmod.h"
+#include "vircommand.h"
+#include "virstring.h"
+
+static int
+doModprobe(const char *opts, const char *module, char **outbuf, char **errbuf)
+{
+    int ret = -1;
+    virCommandPtr cmd = NULL;
+
+    cmd = virCommandNew(MODPROBE);
+    if (opts)
+        virCommandAddArg(cmd, opts);
+    if (module)
+        virCommandAddArg(cmd, module);
+    if (outbuf)
+        virCommandSetOutputBuffer(cmd, outbuf);
+    if (errbuf)
+        virCommandSetErrorBuffer(cmd, errbuf);
+
+    if (virCommandRun(cmd, NULL) < 0)
+        goto cleanup;
+
+    ret = 0;
+
+cleanup:
+    virCommandFree(cmd);
+    return ret;
+}
+
+static int
+doRmmod(const char *module, char **errbuf)
+{
+    int ret = -1;
+    virCommandPtr cmd = NULL;
+
+    cmd = virCommandNewArgList(RMMOD, module, NULL);
+    virCommandSetErrorBuffer(cmd, errbuf);
+
+    if (virCommandRun(cmd, NULL) < 0)
+        goto cleanup;
+
+    ret = 0;
+
+cleanup:
+    virCommandFree(cmd);
+    return ret;
+}
+
+/**
+ * virKModConfig:
+ *
+ * Get the current kernel module configuration
+ *
+ * Returns NULL on failure or a pointer to the output which
+ * must be VIR_FREE()'d by the caller
+ */
+char *
+virKModConfig(void)
+{
+    char *outbuf = NULL;
+
+    if (doModprobe("-c", NULL, &outbuf, NULL) < 0)
+        return NULL;
+
+    return outbuf;
+}
+
+
+/**
+ * virKModLoad:
+ * @module: Name of the module to load
+ * @useBlacklist: True if honoring blacklist
+ *
+ * Attempts to load a kernel module
+ *
+ * returns NULL in case of success and the error buffer output from the
+ * virCommandRun() on failure.  The returned buffer must be VIR_FREE()
+ * by the caller
+ */
+char *
+virKModLoad(const char *module, bool useBlacklist)
+{
+    char *errbuf = NULL;
+
+    if (doModprobe(useBlacklist ? "-b" : NULL, module, NULL, &errbuf) < 0)
+        return errbuf;
+
+    VIR_FREE(errbuf);
+    return NULL;
+}
+
+
+/**
+ * virKModUnload:
+ * @module: Name of the module to unload
+ *
+ * Remove or unload a module.
+ *
+ * NB: Do not use 'modprobe -r' here as that code will recursively
+ * unload any modules that were dependancies of the one being removed
+ * even if things still require them. e.g. it'll see the 'bridge'
+ * module has refcount of 0 and remove it, even if there are bridges
+ * created on the host
+ *
+ * returns NULL in case of success and the error buffer output from the
+ * virCommandRun() on failure.  The returned buffer must be VIR_FREE()
+ * by the caller
+ */
+char *
+virKModUnload(const char *module)
+{
+    char *errbuf = NULL;
+
+    if (doRmmod(module, &errbuf) < 0)
+        return errbuf;
+
+    VIR_FREE(errbuf);
+    return NULL;
+}
+
+
+/**
+ * virKModIsBlacklisted:
+ * @module: Name of the module to check for on the blacklist
+ *
+ * Search the output of the configuration data for the module being
+ * blacklisted.
+ *
+ * returns true when found blacklisted, false otherwise.
+ */
+bool
+virKModIsBlacklisted(const char *module)
+{
+    bool retval = false;
+    size_t i;
+    char *drvblklst = NULL;
+    char *outbuf = NULL;
+
+    if (virAsprintfQuiet(&drvblklst, "blacklist %s\n", module) < 0)
+        goto cleanup;
+
+    /* modprobe will convert all '-' into '_', so we need to as well */
+    for (i = 0; i < drvblklst[i]; i++)
+        if (drvblklst[i] == '-')
+            drvblklst[i] = '_';
+
+    if (doModprobe("-c", NULL, &outbuf, NULL) < 0)
+        goto cleanup;
+
+    if (strstr(outbuf, drvblklst))
+        retval = true;
+
+cleanup:
+    VIR_FREE(drvblklst);
+    VIR_FREE(outbuf);
+    return retval;
+}

src/util/virkmod.h

@@ -0,0 +1,34 @@
+/*
+ * virkmod.h: helper APIs for managing kernel modprobe
+ *
+ * Copyright (C) 2014 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef __VIR_KMOD_H__
+# define __VIR_KMOD_H__
+
+# include "internal.h"
+
+char *virKModConfig(void);
+char *virKModLoad(const char *, bool)
+    ATTRIBUTE_NONNULL(1);
+char *virKModUnload(const char *)
+    ATTRIBUTE_NONNULL(1);
+bool virKModIsBlacklisted(const char *)
+    ATTRIBUTE_NONNULL(1);
+#endif /* __VIR_KMOD_H__ */