add dracut_args option to kdump.conf

mkdumprd call dracut to rebuilding kdump initrd, sometimes passing extra
dracut args is helpful. For example user can enable debug output with
--debug, --printsize to print roughly increased initramfs size by each module,
--omit-drivers to omit kernel modules, etc.

This patch enables dracut_args option for passing extra args to dracut.
Also it modifies add_dracut_arg() to treat a string with-in quote as single
string because for dracut options which has its own args, the args need to be
quoted and space seperated.

If add_dracut_arg() gets an string read from kdump.conf and if that string
contains double quotes, then while converting to positional parameters
those double quotes are not interpreted. Hence if /etc/kdump.conf contains
following.

dracut_args --add-drivers "driver1 driver2"

then add_dracut_args() sees following positional parameters

$1= --add-drivers
$2= "driver1
$3= driver2"

Notice, double quotes have been ignored and parameters have been broken
based on white space.

Modify add_dracut_arg() to look for parameters starting with " and
if one is found, it tries to merge all the next parameters till one
is found with ending double quote. Hence effectively simulating
following behavior.

$1= --add-drivers
$2= "driver1 driver2"

[v1->v2]: address quoted substring in dracut_args, also handle the leading
and ending spaces in substring.
[v2->v3]: fix dracut arguments seperator in kdump.conf.
[v3->v4]: improve changelog, thanks vivek.
[v4->v5]: make the manpage more verbose [vivek].

Tested with below dracut_args test cases:
1. dracut_args --add-drivers "pcspkr virtio_net" --omit-drivers "sdhci-pci hid-logitech-dj e1000"
2. dracut_args --add-drivers "   pcspkr virtio_net   " --omit-drivers "sdhci-pci hid-logitech-dj e1000"

Signed-off-by: Dave Young <dyoung@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>

kdump.conf

@@ -119,6 +119,10 @@
 #			Specifying 1 means though block target is unresettable, user
 #			understand this situation and want to try dumping. By default,
 #			it's set to 0, means not to try a destined failure.
+#
+# dracut_args <arg(s)>
+#			- Pass extra dracut options when rebuilding kdump
+#			  initrd.
 
 #raw /dev/vg/lv_kdump
 #ext4 /dev/vg/lv_kdump
@@ -136,3 +140,4 @@ path /var/crash
 #extra_modules gfs2
 #default shell
 #force_rebuild 1
+#dracut_args --omit-drivers "cfg80211 snd" --add-drivers "ext2 ext3"

kdump.conf.5

@@ -171,6 +171,12 @@ to try dumping. By default, it's set to 0, means not to try a destined failure.
 .RE
 
 
+.B dracut_args <arg(s)>
+.RS
+Kdump uses dracut to generate initramfs for second kernel. This option
+allows a user to pass arguments to dracut directly.
+.RE
+
 .SH DEPRECATED OPTIONS
 
 .B net <nfs mount>|<user@server>

kdumpctl

@@ -86,7 +86,7 @@ function check_config()
 		case "$config_opt" in
 		\#* | "")
 			;;
-		raw|ext2|ext3|ext4|minix|btrfs|xfs|nfs|ssh|sshkey|path|core_collector|kdump_post|kdump_pre|extra_bins|extra_modules|default|force_rebuild)
+		raw|ext2|ext3|ext4|minix|btrfs|xfs|nfs|ssh|sshkey|path|core_collector|kdump_post|kdump_pre|extra_bins|extra_modules|default|force_rebuild|dracut_args)
 			[ -z "$config_val" ] && {
 				echo "Invalid kdump config value for option $config_opt."
 				return 1;

mkdumprd

@@ -45,9 +45,29 @@ get_persistent_dev() {
 }
 
 add_dracut_arg() {
+    local arg qarg is_quoted=0
     while [ $# -gt 0 ];
     do
-        dracut_args+=("$1")
+        arg="${1//\'/\"}"
+        #Handle quoted substring properly for passing it to dracut_args array.
+        if [ $is_quoted -eq 0 ]; then
+            if [[ "$arg" == "\"" ]] || [[ $arg != ${arg#\"} ]]; then
+                is_quoted=1
+                arg=${arg#\"}
+            fi
+        fi
+        if [ $is_quoted -eq 1 ]; then
+            qarg="$qarg $arg"
+            if [[ "$arg" == "\"" ]] || [[ $arg != ${arg%\"} ]]; then
+                is_quoted=0
+                arg=${qarg%\"}
+                qarg=""
+            else
+                shift
+                continue
+            fi
+        fi
+        dracut_args+=("$arg")
         shift
     done
 }
@@ -500,6 +520,9 @@ do
     core_collector)
         verify_core_collector "$config_val"
         ;;
+    dracut_args)
+        add_dracut_arg $config_val
+        ;;
     *)
         if [ -n $(echo $config_opt | grep "^#.*$") ]
         then