Support automatic "noresume" when importing pools R/W

Rather than just warn the user about the need to set the "noresume"
kernel argument when booting after an active suspend partition is
detected and a pool is imported R/W, ZFSBootMenu now supports rewriting
the kernel command line to remove any "resume=" arguments and append a
"noresume". This uses awk to cleanly (and, it seems, correctly) handle
the possibility of double-quoted strings in the argument list, which the
kernel docs say are permitted. (The docs do not mention single-quoted
strings, so we don't support them.)

The prior behavior has been preserved by allowing the user to type
DANGEROUS instead of the redefined NORESUME response to the resume guard
prompt, just in case there is some unexpected edge case that thwarts
automatic redirection and the user wants to assume responsibility for
pool corruption.

Closes #78.

Author: ahesford

90zfsbootmenu/module-setup.sh

@@ -79,6 +79,7 @@ install() {
     "tr"
     "tac"
     "blkid"
+    "awk"
   )
 
   for _exec in "${essential_execs[@]}"; do

90zfsbootmenu/zfsbootmenu-lib.sh

@@ -188,6 +188,43 @@ kexec_kernel() {
   cli_args="$( find_kernel_args "${fs}" "${mnt}" )"
   root_prefix="$( find_root_prefix "${fs}" "${mnt}" )"
 
+  if [ -e "${BASE}/noresume" ]; then
+    # Must replace resume= arguments and append a noresume
+    cli_args="$( awk <<<"${cli_args}" '
+      BEGIN {
+        quot = 0;
+        supp = 0;
+        ORS = " ";
+      }
+
+      {
+        for (i=1; i <= NF; i++) {
+          if ( quot == 0 ) {
+            # If unquoted, determine if output should be suppressed
+            if ( $(i) ~ /^resume=/ ) {
+              # Argument starts with "resume=", suppress
+              supp = 1;
+            } else {
+              # Nothing else is suppressed
+              supp = 0;
+            }
+          }
+
+          # If output is not suppressed, print the field
+          if ( supp == 0 && length($(i)) > 0 ) {
+            print $(i);
+          }
+
+          # If an odd number of quotes are in this field, toggle quoting
+          if ( gsub(/"/, "\"", $(i)) % 2 == 1 ) {
+            quot = (quot + 1) % 2;
+          }
+        }
+        printf "noresume";
+      }
+    ' )"
+  fi
+
   # restore kernel log level just before we kexec
   # shellcheck disable=SC2154
   echo "${printk}" > /proc/sys/kernel/printk
@@ -689,17 +726,31 @@ resume_prompt() {
 	be imported read-write. Importing read-write and then resuming
 	from an active suspend partition may DESTROY YOUR POOL.
 
-	If you are certain you want to proceed, type NORESUME. You are
-	also STRONGLY ADVISED to boot with the "noresume" option added to
-	your kernel command-line to prevent your system from attempting
-	to restore this image.
+	If you choose to proceed, ZFSBootMenu can attempt to remove any
+	"resume=" arguments from your kernel command line and append a
+	"noresume" argument to prevent your system from attempting to
+	restore from the active suspend partition.
+
+	Type NORESUME to proceed with the import, allowing ZFSBootMenu
+	to add a "noresume" argument to your kernel command line.
+
+	Type DANGEROUS to proceed with the import without allowing
+	ZFSBootMenu to modify your kernel command line. Make sure to
+	add the "noresume" argument yourself if necesary.
+
+	Type any other text, or just press enter, to abort.
 
 	Proceed [No] ?
 	EOF
 
     read -r decision
 
-    if [ "x${decision}" != "xNORESUME" ]; then
+    if [ "x${decision}" = "xDANGEROUS" ]; then
+      return 0
+    elif [ "x${decision}" = "xNORESUME" ]; then
+      : > "${BASE}/noresume"
+      return 0
+    else
       return 1
     fi
   fi