am dc4fa7f6: Merge "Fix "adb remount" for when the root directory is in system.img"

#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 "";

    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) {

    }

    bool success = true;

    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");