From d6eba89f83a4028a4b25e44dc0f8bc59dd6ad70a Mon Sep 17 00:00:00 2001
From: Daniel Rosenberg <drosen@google.com>
Date: Mon, 29 Jun 2015 17:30:28 -0700
Subject: [PATCH] Fix "adb remount" for when the root directory is in
 system.img

When the root directory has been built into system.img, it is
mounted at /.

Change-Id: If01d12efeaa53b4ae59e801a6e9b802a9ae5882d
---
 adb/remount_service.cpp | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/adb/remount_service.cpp b/adb/remount_service.cpp
index 3a4d2da7b..28932636d 100644
--- a/adb/remount_service.cpp
+++ b/adb/remount_service.cpp
@@ -33,9 +33,12 @@
 #include "adb_io.h"
 #include "adb_utils.h"
 #include "cutils/properties.h"
+#include "fs_mgr.h"
+
+const std::string kFstab_Prefix = "/fstab.";
 
 // Returns the device used to mount a directory in /proc/mounts.
-static std::string find_mount(const char* dir) {
+static std::string find_proc_mount(const char* dir) {
     std::unique_ptr<FILE, int(*)(FILE*)> fp(setmntent("/proc/mounts", "r"), endmntent);
     if (!fp) {
         return "";
@@ -50,6 +53,29 @@ static std::string find_mount(const char* dir) {
     return "";
 }
 
+// Returns the device used to mount a directory in the fstab.
+static std::string find_fstab_mount(const char* dir) {
+    char propbuf[PROPERTY_VALUE_MAX];
+
+    property_get("ro.hardware", propbuf, "");
+    std::string fstab_filename = kFstab_Prefix + propbuf;
+    struct fstab* fstab = fs_mgr_read_fstab(fstab_filename.c_str());
+    struct fstab_rec* rec = fs_mgr_get_entry_for_mount_point(fstab, dir);
+    std::string dev = rec ? std::string(rec->blk_device) : "";
+    fs_mgr_free_fstab(fstab);
+    return dev;
+}
+
+// The proc entry for / is full of lies, so check fstab instead.
+// /proc/mounts lists rootfs and /dev/root, neither of which is what we want.
+static std::string find_mount(const char* dir) {
+    if (strcmp(dir, "/") == 0) {
+       return find_fstab_mount(dir);
+    } else {
+       return find_proc_mount(dir);
+    }
+}
+
 bool make_block_device_writable(const std::string& dev) {
     int fd = unix_open(dev.c_str(), O_RDONLY | O_CLOEXEC);
     if (fd == -1) {
@@ -112,7 +138,13 @@ void remount_service(int fd, void* cookie) {
     }
 
     bool success = true;
-    success &= remount_partition(fd, "/system");
+    property_get("ro.build.system_root_image", prop_buf, "");
+    bool system_root = !strcmp(prop_buf, "true");
+    if (system_root) {
+        success &= remount_partition(fd, "/");
+    } else {
+        success &= remount_partition(fd, "/system");
+    }
     success &= remount_partition(fd, "/vendor");
     success &= remount_partition(fd, "/oem");