crosutils: add scripts/.local_mounts to allow mounting additional (RO) folders in chroot

enter_chroot.sh

Index: enter_chroot.sh
diff --git a/enter_chroot.sh b/enter_chroot.sh
index 606eaf51a6beef94cbca10047e282e08e2bf81de..d6b599d5e9e66f7908f0d741138098ca9e739cec 100755
--- a/enter_chroot.sh
+++ b/enter_chroot.sh
@@ -78,31 +78,32 @@ LOCKFILE="$FLAGS_chroot/var/lock/enter_chroot"
 
 function setup_env {
   (
+    local mounted_path
     flock 200
     echo $$ >> "$LOCKFILE"
 
     info "Mounting chroot environment."
 
     # Mount only if not already mounted
-    MOUNTED_PATH="$(readlink -f "$FLAGS_chroot/proc")"
-    if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]
+    mounted_path="$(readlink -f "$FLAGS_chroot/proc")"
+    if [ -z "$(mount | grep -F "on $mounted_path ")" ]
     then
-      sudo mount none -t proc "$MOUNTED_PATH" || \
-          die "Could not mount $MOUNTED_PATH"
+      sudo mount none -t proc "$mounted_path" || \
+          die "Could not mount $mounted_path"
     fi
 
-    MOUNTED_PATH="$(readlink -f "$FLAGS_chroot/sys")"
-    if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]
+    mounted_path="$(readlink -f "$FLAGS_chroot/sys")"
+    if [ -z "$(mount | grep -F "on $mounted_path ")" ]
     then
-      sudo mount none -t sysfs "$MOUNTED_PATH" || \
-          die "Could not mount $MOUNTED_PATH"
+      sudo mount none -t sysfs "$mounted_path" || \
+          die "Could not mount $mounted_path"
     fi
 
-    MOUNTED_PATH="$(readlink -f "${FLAGS_chroot}/dev")"
-    if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]
+    mounted_path="$(readlink -f "${FLAGS_chroot}/dev")"
+    if [ -z "$(mount | grep -F "on $mounted_path ")" ]
     then
-      sudo mount --bind /dev "$MOUNTED_PATH" || \
-          die "Could not mount $MOUNTED_PATH"
+      sudo mount --bind /dev "$mounted_path" || \
+          die "Could not mount $mounted_path"
     fi
 
     if [ $FLAGS_ssh_agent -eq $FLAGS_TRUE ]; then
@@ -119,22 +120,22 @@ function setup_env {
       fi
     fi
 
-    MOUNTED_PATH="$(readlink -f "${FLAGS_chroot}/dev/pts")"
-    if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]
+    mounted_path="$(readlink -f "${FLAGS_chroot}/dev/pts")"
+    if [ -z "$(mount | grep -F "on $mounted_path ")" ]
     then
-      sudo mount none -t devpts "$MOUNTED_PATH" || \
-          die "Could not mount $MOUNTED_PATH"
+      sudo mount none -t devpts "$mounted_path" || \
+          die "Could not mount $mounted_path"
     fi
 
-    MOUNTED_PATH="$(readlink -f "${FLAGS_chroot}$CHROOT_TRUNK_DIR")"
-    if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]
+    mounted_path="$(readlink -f "${FLAGS_chroot}$CHROOT_TRUNK_DIR")"
+    if [ -z "$(mount | grep -F "on $mounted_path ")" ]
     then
-      sudo mount --bind "$FLAGS_trunk" "$MOUNTED_PATH" || \
-          die "Could not mount $MOUNTED_PATH"
+      sudo mount --bind "$FLAGS_trunk" "$mounted_path" || \
+          die "Could not mount $mounted_path"
     fi
 
-    MOUNTED_PATH="$(readlink -f "${FLAGS_chroot}${INNER_CHROME_ROOT}")"
-    if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]
+    mounted_path="$(readlink -f "${FLAGS_chroot}${INNER_CHROME_ROOT}")"
+    if [ -z "$(mount | grep -F "on $mounted_path ")" ]
     then
       ! CHROME_ROOT="$(readlink -f "$FLAGS_chrome_root")"
       if [ -z "$CHROME_ROOT" ]; then
@@ -148,20 +149,20 @@ function setup_env {
         info "Mounting chrome source at: $INNER_CHROME_ROOT"
         echo "$CHROME_ROOT" | \
           sudo dd of="${FLAGS_chroot}${CHROME_ROOT_CONFIG}"
-        mkdir -p "$MOUNTED_PATH"
-        sudo mount --bind "$CHROME_ROOT" "$MOUNTED_PATH" || \
-          die "Could not mount $MOUNTED_PATH"
+        mkdir -p "$mounted_path"
+        sudo mount --bind "$CHROME_ROOT" "$mounted_path" || \
+          die "Could not mount $mounted_path"
       fi
     fi
 
-    MOUNTED_PATH="$(readlink -f "${FLAGS_chroot}${INNER_DEPOT_TOOLS_ROOT}")"
-    if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]
+    mounted_path="$(readlink -f "${FLAGS_chroot}${INNER_DEPOT_TOOLS_ROOT}")"
+    if [ -z "$(mount | grep -F "on $mounted_path ")" ]
     then
       if [ $(which gclient 2>/dev/null) ]; then
         info "Mounting depot_tools"
         DEPOT_TOOLS=$(dirname $(which gclient) )
-        mkdir -p "$MOUNTED_PATH"
-        if ! sudo mount --bind "$DEPOT_TOOLS" "$MOUNTED_PATH"; then
+        mkdir -p "$mounted_path"
+        if ! sudo mount --bind "$DEPOT_TOOLS" "$mounted_path"; then
           warn "depot_tools failed to mount; perhaps it's on NFS?"
           warn "This may impact chromium build."
         fi
@@ -188,12 +189,39 @@ function setup_env {
       fi
     fi
 
+    # Mount additional directories
+    local local_mounts="${FLAGS_trunk}/src/scripts/.local_mounts"
+    if [ -f "${local_mounts}" ]; then
+      info "Mounting local folders (read-only for safety concern)"
+      # format: mount_source
+      #      or mount_source mount_point
+      #      or # comments
+      local mount_source mount_point
+      cat "${local_mounts}" | while read mount_source mount_point; do
+        if [ "$(echo "${mount_source}" | cut -b 1)" = "#" ] ||
+           [ -z "${mount_source}" ]; then
+          continue
+        fi
+        # if only source is assigned, use source as mount point.
+        mount_point="${mount_point:-$mount_source}"
+        mounted_path="$(readlink -f "${FLAGS_chroot}${mount_point}")"
+        if [ -z "$(mount | grep -F "on ${mounted_path} ")" ]
+        then
+          # --bind can't be initialized as RO, so we have to use "ro,remount".
+          (sudo mount --bind "${mount_source}" "${mounted_path}" &&
+           sudo mount -o ro,remount "${mounted_path}") ||
+           die "Failed to mount ${mounted_path} from ${mount_source}."
+        fi
+      done
+    fi
+
   ) 200>>"$LOCKFILE" || die "setup_env failed"
 }
 
 function teardown_env {
   # Only teardown if we're the last enter_chroot to die
   (
+    local mounted_path
     flock 200
 
     # check each pid in $LOCKFILE to see if it's died unexpectedly
@@ -226,12 +254,12 @@ function teardown_env {
       info "At least one other pid is running in the chroot, so not"
       info "tearing down env."
     else
-      MOUNTED_PATH=$(readlink -f "$FLAGS_chroot")
+      mounted_path=$(readlink -f "$FLAGS_chroot")
       info "Unmounting chroot environment."
       # sort the list of mounts in reverse order, to ensure umount of
       # cascading mounts in proper order
       for i in \
-        $(mount | grep -F "on $MOUNTED_PATH/" | sort -r | awk '{print $3}'); do
+        $(mount | grep -F "on $mounted_path/" | sort -r | awk '{print $3}'); do
         safe_umount "$i"
       done
     fi