fs_mgr: Use ro.boot.veritymode

If verity state is managed by bootloader, it will pass the verity
mode to the kernel in the androidboot.veritymode command line
parameter. Init copies the value to the ro.boot.veritymode property.

Check for ro.boot.veritymode in fs_mgr and use the value to set
dm-verity mode. If this property is not set, store verity state in
metadata as before, if a storage location is specified in fstab.

Change-Id: Ife3c978c133248432c302583d3b70e179605fe42
diff --git a/fs_mgr/fs_mgr_verity.c b/fs_mgr/fs_mgr_verity.c
index 81c7c9a..0a945a3 100644
--- a/fs_mgr/fs_mgr_verity.c
+++ b/fs_mgr/fs_mgr_verity.c
@@ -767,8 +767,24 @@
 
 static int load_verity_state(struct fstab_rec *fstab, int *mode)
 {
-    off64_t offset = 0;
+    char propbuf[PROPERTY_VALUE_MAX];
     int match = 0;
+    off64_t offset = 0;
+
+    /* use the kernel parameter if set */
+    property_get("ro.boot.veritymode", propbuf, "");
+
+    if (*propbuf != '\0') {
+        if (!strcmp(propbuf, "enforcing")) {
+            *mode = VERITY_MODE_DEFAULT;
+            return 0;
+        } else if (!strcmp(propbuf, "logging")) {
+            *mode = VERITY_MODE_LOGGING;
+            return 0;
+        } else {
+            INFO("Unknown value %s for veritymode; ignoring", propbuf);
+        }
+    }
 
     if (get_verity_state_offset(fstab, &offset) < 0) {
         /* fall back to stateless behavior */
@@ -855,6 +871,13 @@
     struct dm_ioctl *io = (struct dm_ioctl *) buffer;
     struct fstab *fstab = NULL;
 
+    /* check if we need to store the state */
+    property_get("ro.boot.veritymode", propbuf, "");
+
+    if (*propbuf != '\0') {
+        return 0; /* state is kept by the bootloader */
+    }
+
     fd = TEMP_FAILURE_RETRY(open("/dev/device-mapper", O_RDWR | O_CLOEXEC));
 
     if (fd == -1) {