3 files changed, 37 insertions, 38 deletions

diff --git a/fs_mgr/fs_mgr_boot_config.cpp b/fs_mgr/fs_mgr_boot_config.cpp
index 9decb27f3..5b2f21814 100644
--- a/fs_mgr/fs_mgr_boot_config.cpp
+++ b/fs_mgr/fs_mgr_boot_config.cpp
@@ -49,15 +49,8 @@ bool fs_mgr_get_boot_config(const std::string& key, std::string* out_val) {
     }
 
     // lastly, check the device tree
-    std::string file_name = kAndroidDtDir + "/compatible";
-    std::string dt_value;
-    if (android::base::ReadFileToString(file_name, &dt_value)) {
-        if (dt_value != "android,firmware") {
-            LERROR << "Error finding compatible android DT node";
-            return false;
-        }
-
-        file_name = kAndroidDtDir + "/" + key;
+    if (is_dt_compatible()) {
+        std::string file_name = kAndroidDtDir + "/" + key;
         // DT entries terminate with '\0' but so do the properties
         if (android::base::ReadFileToString(file_name, out_val)) {
             return true;
diff --git a/fs_mgr/fs_mgr_fstab.cpp b/fs_mgr/fs_mgr_fstab.cpp
index f98978780..5b0243d0e 100644
--- a/fs_mgr/fs_mgr_fstab.cpp
+++ b/fs_mgr/fs_mgr_fstab.cpp
@@ -135,6 +135,24 @@ static uint64_t parse_size(const char *arg)
     return size;
 }
 
+/* fills 'dt_value' with the underlying device tree value string without
+ * the trailing '\0'. Returns true if 'dt_value' has a valid string, 'false'
+ * otherwise.
+ */
+static bool read_dt_file(const std::string& file_name, std::string* dt_value)
+{
+    if (android::base::ReadFileToString(file_name, dt_value)) {
+        if (!dt_value->empty()) {
+            // trim the trailing '\0' out, otherwise the comparison
+            // will produce false-negatives.
+            dt_value->resize(dt_value->size() - 1);
+            return true;
+        }
+    }
+
+    return false;
+}
+
 static int parse_flags(char *flags, struct flag_list *fl,
                        struct fs_mgr_flag_values *flag_vals,
                        char *fs_options, int fs_options_len)
@@ -295,29 +313,10 @@ static int parse_flags(char *flags, struct flag_list *fl,
     return f;
 }
 
-static bool is_dt_compatible() {
-    std::string file_name = kAndroidDtDir + "/compatible";
-    std::string dt_value;
-    if (android::base::ReadFileToString(file_name, &dt_value)) {
-        // trim the trailing '\0' out, otherwise the comparison
-        // will produce false-negatives.
-        dt_value.resize(dt_value.size() - 1);
-        if (dt_value == "android,firmware") {
-            return true;
-        }
-    }
-
-    return false;
-}
-
 static bool is_dt_fstab_compatible() {
     std::string dt_value;
     std::string file_name = kAndroidDtDir + "/fstab/compatible";
-
-    if (android::base::ReadFileToString(file_name, &dt_value)) {
-        // trim the trailing '\0' out, otherwise the comparison
-        // will produce false-negatives.
-        dt_value.resize(dt_value.size() - 1);
+    if (read_dt_file(file_name, &dt_value)) {
         if (dt_value == "android,fstab") {
             return true;
         }
@@ -354,41 +353,36 @@ static std::string read_fstab_from_dt() {
         std::string file_name;
         std::string value;
         file_name = android::base::StringPrintf("%s/%s/dev", fstabdir_name.c_str(), dp->d_name);
-        if (!android::base::ReadFileToString(file_name, &value)) {
+        if (!read_dt_file(file_name, &value)) {
             LERROR << "dt_fstab: Failed to find device for partition " << dp->d_name;
             fstab.clear();
             break;
         }
-        // trim the terminating '\0' out
-        value.resize(value.size() - 1);
         fstab_entry.push_back(value);
         fstab_entry.push_back(android::base::StringPrintf("/%s", dp->d_name));
 
         file_name = android::base::StringPrintf("%s/%s/type", fstabdir_name.c_str(), dp->d_name);
-        if (!android::base::ReadFileToString(file_name, &value)) {
+        if (!read_dt_file(file_name, &value)) {
             LERROR << "dt_fstab: Failed to find type for partition " << dp->d_name;
             fstab.clear();
             break;
         }
-        value.resize(value.size() - 1);
         fstab_entry.push_back(value);
 
         file_name = android::base::StringPrintf("%s/%s/mnt_flags", fstabdir_name.c_str(), dp->d_name);
-        if (!android::base::ReadFileToString(file_name, &value)) {
+        if (!read_dt_file(file_name, &value)) {
             LERROR << "dt_fstab: Failed to find type for partition " << dp->d_name;
             fstab.clear();
             break;
         }
-        value.resize(value.size() - 1);
         fstab_entry.push_back(value);
 
         file_name = android::base::StringPrintf("%s/%s/fsmgr_flags", fstabdir_name.c_str(), dp->d_name);
-        if (!android::base::ReadFileToString(file_name, &value)) {
+        if (!read_dt_file(file_name, &value)) {
             LERROR << "dt_fstab: Failed to find type for partition " << dp->d_name;
             fstab.clear();
             break;
         }
-        value.resize(value.size() - 1);
         fstab_entry.push_back(value);
 
         fstab += android::base::Join(fstab_entry, " ");
@@ -398,6 +392,17 @@ static std::string read_fstab_from_dt() {
     return fstab;
 }
 
+bool is_dt_compatible() {
+    std::string file_name = kAndroidDtDir + "/compatible";
+    std::string dt_value;
+    if (read_dt_file(file_name, &dt_value)) {
+        if (dt_value == "android,firmware") {
+            return true;
+        }
+    }
+
+    return false;
+}
 
 struct fstab *fs_mgr_read_fstab_file(FILE *fstab_file)
 {
diff --git a/fs_mgr/fs_mgr_priv.h b/fs_mgr/fs_mgr_priv.h
index 95295d8af..3b1c56b94 100644
--- a/fs_mgr/fs_mgr_priv.h
+++ b/fs_mgr/fs_mgr_priv.h
@@ -117,6 +117,7 @@ __BEGIN_DECLS
 int fs_mgr_set_blk_ro(const char *blockdev);
 int fs_mgr_test_access(const char *device);
 int fs_mgr_update_for_slotselect(struct fstab *fstab);
+bool is_dt_compatible();
 
 __END_DECLS