vold and init

android4.1

section.1

int Volume::mountVol() { dev_t deviceNodes[4]; int n, i, rc = 0; char errmsg[255]; const char* externalStorage = getenv("EXTERNAL_STORAGE");\\-----mnt/sdcard bool primaryStorage = externalStorage && !strcmp(getMountpoint(), externalStorage); char decrypt_state[PROPERTY_VALUE_MAX]; char crypto_state[PROPERTY_VALUE_MAX]; char encrypt_progress[PROPERTY_VALUE_MAX]; int flags; property_get("vold.decrypt", decrypt_state, "");//---参见《init》do_mount_all（） property_get("vold.encrypt_progress", encrypt_progress, ""); /* Don't try to mount the volumes if we have not yet entered the disk password * or are in the process of encrypting.//-----decrypt_state=1表示磁盘没有被解密 */ if ((getState() == Volume::State_NoMedia) || ((!strcmp(decrypt_state, "1") || encrypt_progress[0]) && primaryStorage)) { snprintf(errmsg, sizeof(errmsg), "Volume %s %s mount failed - no media", getLabel(), getMountpoint()); mVm->getBroadcaster()->sendBroadcast( ResponseCode::VolumeMountFailedNoMedia, errmsg, false); errno = ENODEV; return -1; } else if (getState() != Volume::State_Idle) { errno = EBUSY; if (getState() == Volume::State_Pending) { mRetryMount = true; } return -1; } if (isMountpointMounted(getMountpoint())) { SLOGW("Volume is idle but appears to be mounted - fixing"); setState(Volume::State_Mounted); // mCurrentlyMountedKdev = XXX return 0; } n = getDeviceNodes((dev_t *) &deviceNodes, 4); if (!n) { SLOGE("Failed to get device nodes (%s)\n", strerror(errno)); return -1; } /* If we're running encrypted, and the volume is marked as encryptable and nonremovable, * and vold is asking to mount the primaryStorage device, then we need to decrypt * that partition, and update the volume object to point to it's new decrypted * block device */ property_get("ro.crypto.state", crypto_state, ""); flags = getFlags(); if (primaryStorage && ((flags & (VOL_NONREMOVABLE | VOL_ENCRYPTABLE))==(VOL_NONREMOVABLE | VOL_ENCRYPTABLE)) && !strcmp(crypto_state, "encrypted") && !isDecrypted()) {//---------还没有解密呢 char new_sys_path[MAXPATHLEN]; char nodepath[256]; int new_major, new_minor; if (n != 1) { /* We only expect one device node returned when mounting encryptable volumes */ SLOGE("Too many device nodes returned when mounting %d\n", getMountpoint()); return -1; } if (cryptfs_setup_volume(getLabel(), MAJOR(deviceNodes[0]), MINOR(deviceNodes[0]),//---解密 new_sys_path, sizeof(new_sys_path), &new_major, &new_minor)) { SLOGE("Cannot setup encryption mapping for %d\n", getMountpoint()); return -1; } /* We now have the new sysfs path for the decrypted block device, and the * majore and minor numbers for it. So, create the device, update the * path to the new sysfs path, and continue. */ snprintf(nodepath, sizeof(nodepath), "/dev/block/vold/%d:%d", new_major, new_minor); if (createDeviceNode(nodepath, new_major, new_minor)) { SLOGE("Error making device node '%s' (%s)", nodepath, strerror(errno)); } // Todo: Either create sys filename from nodepath, or pass in bogus path so // vold ignores state changes on this internal device. updateDeviceInfo(nodepath, new_major, new_minor); /* Get the device nodes again, because they just changed */ n = getDeviceNodes((dev_t *) &deviceNodes, 4); if (!n) { SLOGE("Failed to get device nodes (%s)\n", strerror(errno)); return -1; } } for (i = 0; i < n; i++) { char devicePath[255]; sprintf(devicePath, "/dev/block/vold/%d:%d", MAJOR(deviceNodes[i]), MINOR(deviceNodes[i])); SLOGI("%s being considered for volume %s\n", devicePath, getLabel()); errno = 0; setState(Volume::State_Checking); if (Fat::check(devicePath)) {//--------分区检测 if (errno == ENODATA) { SLOGW("%s does not contain a FAT filesystem\n", devicePath); continue; } errno = EIO; /* Badness - abort the mount */ SLOGE("%s failed FS checks (%s)", devicePath, strerror(errno)); setState(Volume::State_Idle); return -1; } /* * Mount the device on our internal staging mountpoint so we can * muck with it before exposing it to non priviledged users. */ errno = 0; int gid; if (primaryStorage) {//-----external storage write access 1015 // Special case the primary SD card. // For this we grant write access to the SDCARD_RW group. gid = AID_SDCARD_RW; } else {//-------------internal media storage write access 1023 // For secondary external storage we keep things locked up. gid = AID_MEDIA_RW; } if (Fat::doMount(devicePath, "/mnt/secure/staging", false, false, false, AID_SYSTEM, gid, 0702, true)) { SLOGE("%s failed to mount via VFAT (%s)\n", devicePath, strerror(errno)); continue; } SLOGI("Device %s, target %s mounted @ /mnt/secure/staging", devicePath, getMountpoint()); protectFromAutorunStupidity();//--------------阻止autorun.inf文件的自动运行 // only create android_secure on primary storage if (primaryStorage && createBindMounts()) {//--------mount -bind SLOGE("Failed to create bindmounts (%s)", strerror(errno)); umount("/mnt/secure/staging"); setState(Volume::State_Idle); return -1; } /* * Now that the bindmount trickery is done, atomically move the * whole subtree to expose it to non priviledged users. */ if (doMoveMount("/mnt/secure/staging", getMountpoint(), false)) {//-------mount --move SLOGE("Failed to move mount (%s)", strerror(errno)); umount("/mnt/secure/staging"); setState(Volume::State_Idle); return -1; } setState(Volume::State_Mounted); mCurrentlyMountedKdev = deviceNodes[i]; return 0; } SLOGE("Volume %s found no suitable devices for mounting :(\n", getLabel()); setState(Volume::State_Idle); return -1; }