From f4e7422c65d5d38267e71f49be926bfdc7c8c27e Mon Sep 17 00:00:00 2001
From: Mark Salyzyn <salyzyn@google.com>
Date: Thu, 24 Jan 2019 11:08:10 -0800
Subject: [PATCH] fs_mgr: remount: add partition argument list

Can supply a specific partition to remount.  Partitions can be
specified by name or mount point.  Some extra work to differentiate
an unknown partition, invalid partition, or one that is covered by
overlayfs.

Test: adb-remount-test.sh
Bug: 122602260
Change-Id: Iab6f51c2b5ebe01f1cea3fb235445d5e2f495365
---
 fs_mgr/fs_mgr_remount.cpp        | 60 ++++++++++++++++++++++++++------
 fs_mgr/tests/adb-remount-test.sh | 10 ++++--
 2 files changed, 57 insertions(+), 13 deletions(-)

diff --git a/fs_mgr/fs_mgr_remount.cpp b/fs_mgr/fs_mgr_remount.cpp
index c0e0ccd8f..631273457 100644
--- a/fs_mgr/fs_mgr_remount.cpp
+++ b/fs_mgr/fs_mgr_remount.cpp
@@ -42,13 +42,14 @@ namespace {
 
 [[noreturn]] void usage(int exit_status) {
     LOG(INFO) << getprogname()
-              << " [-h] [-R] [-T fstab_file]\n"
+              << " [-h] [-R] [-T fstab_file] [partition]...\n"
                  "\t-h --help\tthis help\n"
                  "\t-R --reboot\tdisable verity & reboot to facilitate remount\n"
                  "\t-T --fstab\tcustom fstab file location\n"
+                 "\tpartition\tspecific partition(s) (empty does all)\n"
                  "\n"
-                 "Remount all partitions read-write.\n"
-                 "-R notwithstanding, verity must be disabled.";
+                 "Remount specified partition(s) read-write, by name or mount point.\n"
+                 "-R notwithstanding, verity must be disabled on partition(s).";
 
     ::exit(exit_status);
 }
@@ -138,6 +139,8 @@ int main(int argc, char* argv[]) {
         BADARG,
         NOT_ROOT,
         NO_FSTAB,
+        UNKNOWN_PARTITION,
+        INVALID_PARTITION,
         VERITY_PARTITION,
         BAD_OVERLAY,
         NO_MOUNTS,
@@ -183,11 +186,6 @@ int main(int argc, char* argv[]) {
         }
     }
 
-    if (argc > optind) {
-        LOG(ERROR) << "Bad Argument " << argv[optind];
-        usage(BADARG);
-    }
-
     // Make sure we are root.
     if (::getuid() != 0) {
         LOG(ERROR) << "must be run as root";
@@ -211,16 +209,58 @@ int main(int argc, char* argv[]) {
     auto overlayfs_candidates = fs_mgr_overlayfs_candidate_list(fstab);
 
     // Generate the all remountable partitions sub-list
-    android::fs_mgr::Fstab partitions;
+    android::fs_mgr::Fstab all;
     for (auto const& entry : fstab) {
         if (!remountable_partition(entry)) continue;
         if (overlayfs_candidates.empty() ||
             GetEntryForMountPoint(&overlayfs_candidates, entry.mount_point) ||
             (is_wrapped(overlayfs_candidates, entry) == nullptr)) {
-            partitions.emplace_back(entry);
+            all.emplace_back(entry);
         }
     }
 
+    // Parse the unique list of valid partition arguments.
+    android::fs_mgr::Fstab partitions;
+    for (; argc > optind; ++optind) {
+        auto partition = std::string(argv[optind]);
+        if (partition.empty()) continue;
+        if (partition == "/") partition = "/system";
+        auto find_part = [&partition](const auto& entry) {
+            const auto mount_point = system_mount_point(entry);
+            if (partition == mount_point) return true;
+            if (partition == android::base::Basename(mount_point)) return true;
+            return false;
+        };
+        // Do we know about the partition?
+        auto it = std::find_if(fstab.begin(), fstab.end(), find_part);
+        if (it == fstab.end()) {
+            LOG(ERROR) << "Unknown partition " << partition << ", skipping";
+            retval = UNKNOWN_PARTITION;
+            continue;
+        }
+        // Is that one covered by an existing overlayfs?
+        auto wrap = is_wrapped(overlayfs_candidates, *it);
+        if (wrap) {
+            LOG(INFO) << "partition " << partition << " covered by overlayfs for "
+                      << wrap->mount_point << ", switching";
+            partition = system_mount_point(*wrap);
+        }
+        // Is it a remountable partition?
+        it = std::find_if(all.begin(), all.end(), find_part);
+        if (it == all.end()) {
+            LOG(ERROR) << "Invalid partition " << partition << ", skipping";
+            retval = INVALID_PARTITION;
+            continue;
+        }
+        if (GetEntryForMountPoint(&partitions, it->mount_point) == nullptr) {
+            partitions.emplace_back(*it);
+        }
+    }
+
+    if (partitions.empty() && !retval) {
+        partitions = all;
+    }
+
     // Check verity and optionally setup overlayfs backing.
     auto reboot_later = false;
     for (auto it = partitions.begin(); it != partitions.end();) {
diff --git a/fs_mgr/tests/adb-remount-test.sh b/fs_mgr/tests/adb-remount-test.sh
index 1ded95441..a6baf1d32 100755
--- a/fs_mgr/tests/adb-remount-test.sh
+++ b/fs_mgr/tests/adb-remount-test.sh
@@ -620,7 +620,7 @@ if [ "orange" = "`get_property ro.boot.verifiedbootstate`" -a \
 
   echo "${GREEN}[ RUN      ]${NORMAL} Testing adb shell su root remount -R command" >&2
 
-  adb_su remount -R </dev/null || true
+  adb_su remount -R system </dev/null || true
   sleep 2
   adb_wait 2m ||
     die "waiting for device after remount -R `usb_status`"
@@ -1159,10 +1159,12 @@ adb_reboot &&
   die "lost device after reboot to ro state (USB stack broken?)"
 adb_sh grep " /vendor .* rw," /proc/mounts >/dev/null </dev/null &&
   die "/vendor is not read-only"
-adb_su remount </dev/null ||
+adb_su remount vendor </dev/null ||
   die "remount command"
 adb_sh grep " /vendor .* rw," /proc/mounts >/dev/null </dev/null ||
   die "/vendor is not read-write"
+adb_sh grep " /system .* rw," /proc/mounts >/dev/null </dev/null &&
+  die "/vendor is not read-only"
 echo "${GREEN}[       OK ]${NORMAL} remount command works from setup" >&2
 
 # Prerequisite is an overlayfs deconstructed device but with verity disabled.
@@ -1177,10 +1179,12 @@ adb_reboot &&
   die "lost device after reboot after wipe (USB stack broken?)"
 adb_sh grep " /vendor .* rw," /proc/mounts >/dev/null </dev/null &&
   die "/vendor is not read-only"
-adb_su remount </dev/null ||
+adb_su remount vendor </dev/null ||
   die "remount command"
 adb_sh grep " /vendor .* rw," /proc/mounts >/dev/null </dev/null ||
   die "/vendor is not read-write"
+adb_sh grep " /system .* rw," /proc/mounts >/dev/null </dev/null &&
+  die "/system is not read-only"
 echo "${GREEN}[       OK ]${NORMAL} remount command works from scratch" >&2
 
 restore