1 files changed, 147 insertions, 0 deletions
diff --git a/adb/remount_service.cpp b/adb/remount_service.cpp
new file mode 100644
index 0000000..1eaee73
--- /dev/null
+++ b/adb/remount_service.cpp
@@ -0,0 +1,147 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define TRACE_TAG TRACE_ADB
+
+#include "sysdeps.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <mntent.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <unistd.h>
+
+#include <string>
+
+#include "adb.h"
+#include "adb_io.h"
+#include "adb_utils.h"
+#include "cutils/properties.h"
+
+static int system_ro = 1;
+static int vendor_ro = 1;
+static int oem_ro = 1;
+
+/* Returns the device used to mount a directory in /proc/mounts */
+static std::string find_mount(const char *dir) {
+    FILE* fp;
+    struct mntent* mentry;
+    char* device = NULL;
+
+    if ((fp = setmntent("/proc/mounts", "r")) == NULL) {
+        return NULL;
+    }
+    while ((mentry = getmntent(fp)) != NULL) {
+        if (strcmp(dir, mentry->mnt_dir) == 0) {
+            device = mentry->mnt_fsname;
+            break;
+        }
+    }
+    endmntent(fp);
+    return device;
+}
+
+int make_block_device_writable(const std::string& dev) {
+    int fd = unix_open(dev.c_str(), O_RDONLY | O_CLOEXEC);
+    if (fd == -1) {
+        return -1;
+    }
+
+    int result = -1;
+    int OFF = 0;
+    if (!ioctl(fd, BLKROSET, &OFF)) {
+        result = 0;
+    }
+    adb_close(fd);
+
+    return result;
+}
+
+// Init mounts /system as read only, remount to enable writes.
+static int remount(const char* dir, int* dir_ro) {
+    std::string dev(find_mount(dir));
+    if (dev.empty() || make_block_device_writable(dev)) {
+        return -1;
+    }
+
+    int rc = mount(dev.c_str(), dir, "none", MS_REMOUNT, NULL);
+    *dir_ro = rc;
+    return rc;
+}
+
+static bool remount_partition(int fd, const char* partition, int* ro) {
+  if (!directory_exists(partition)) {
+    return true;
+  }
+  if (remount(partition, ro)) {
+    char buf[200];
+    snprintf(buf, sizeof(buf), "remount of %s failed: %s\n", partition, strerror(errno));
+    WriteStringFully(fd, buf);
+    return false;
+  }
+  return true;
+}
+
+void remount_service(int fd, void* cookie) {
+    char prop_buf[PROPERTY_VALUE_MAX];
+
+    if (getuid() != 0) {
+        WriteStringFully(fd, "Not running as root. Try \"adb root\" first.\n");
+        adb_close(fd);
+        return;
+    }
+
+    bool system_verified = false, vendor_verified = false;
+    property_get("partition.system.verified", prop_buf, "");
+    if (strlen(prop_buf) > 0) {
+        system_verified = true;
+    }
+
+    property_get("partition.vendor.verified", prop_buf, "");
+    if (strlen(prop_buf) > 0) {
+        vendor_verified = true;
+    }
+
+    if (system_verified || vendor_verified) {
+        // Allow remount but warn of likely bad effects
+        bool both = system_verified && vendor_verified;
+        char buffer[200];
+        snprintf(buffer, sizeof(buffer),
+                 "dm_verity is enabled on the %s%s%s partition%s.\n",
+                 system_verified ? "system" : "",
+                 both ? " and " : "",
+                 vendor_verified ? "vendor" : "",
+                 both ? "s" : "");
+        WriteStringFully(fd, buffer);
+        snprintf(buffer, sizeof(buffer),
+                 "Use \"adb disable-verity\" to disable verity.\n"
+                 "If you do not, remount may succeed, however, you will still "
+                 "not be able to write to these volumes.\n");
+        WriteStringFully(fd, buffer);
+    }
+
+    bool success = true;
+    success &= remount_partition(fd, "/system", &system_ro);
+    success &= remount_partition(fd, "/vendor", &vendor_ro);
+    success &= remount_partition(fd, "/oem", &oem_ro);
+
+    WriteStringFully(fd, success ? "remount succeeded\n" : "remount failed\n");
+
+    adb_close(fd);
+}