fs/Exfat.cpp

/*
 * Copyright (C) 2018 The Android Open Source Project
 * Copyright (C) 2010-2021 Tuxera Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <fcntl.h>
#include <sys/mount.h>

#define LOG_TAG "Vold::Exfat"

#include <android-base/logging.h>
#include <android-base/stringprintf.h>

#include <logwrap/logwrap.h>

#include "Exfat.h"
#include "Utils.h"

using android::base::StringPrintf;

namespace android {
namespace vold {
namespace exfat {

static const char* kMkfsPath = "/system/bin/mkexfat";
static const char* kFsckPath = "/system/bin/exfatck";

status_t Detect(const std::string& source, bool *outResult) {
    const char *const fsPath = source.c_str();

    int retval = -1;

    int fd = open(fsPath, O_RDONLY | O_CLOEXEC);
    if (fd != -1) {
        loff_t seek_res = lseek64(fd, 0, SEEK_SET);
        if (seek_res == 0) {
            char sb_region[4096];
            ssize_t read_res = read(fd, sb_region, 4096);
            if (read_res >= 512) {
                if (!memcmp(&sb_region[3], "EXFAT   ", 8)) {
                    LOG(INFO) << "exFAT filesystem detected.";
                    *outResult = true;
                }
                else if (!memcmp(&sb_region[0], "RRaAXFAT   ", 11)) {
                    LOG(INFO) << "Corrupted exFAT filesystem detected. Fixing.";
                    *outResult = true;
                }
                else {
                    LOG(VERBOSE) << "Filesystem detection failed (not an exFAT "
                                 << "filesystem).";
                    *outResult = false;
                }

                retval = 0;
            }
            else if (read_res != -1) {
                int err = errno ? errno : EIO;
                LOG(ERROR) << "Error while reading 4096 bytes from device "
                           << "offset 0: " << strerror(errno) << " (" << errno
                           << ")";
                errno = err;
            }
        }
        else if (seek_res != -1) {
            int err = errno ? errno : EIO;
            LOG(ERROR) << "Error while seeking to device offset 0: "
                       << strerror(errno) << " (" << errno << ")";
            errno = err;
        }

        close(fd);
    }

    return retval;
}

bool IsSupported() {
    return access(kMkfsPath, X_OK) == 0 && access(kFsckPath, X_OK) == 0 &&
           IsFilesystemSupported("texfat");
}

status_t Check(const std::string& source) {
    std::vector<std::string> cmd;
    cmd.push_back(kFsckPath);
    cmd.push_back("-r");
    cmd.push_back(source);

    int rc = ForkExecvp(cmd, nullptr, sFsckUntrustedContext);
    if (rc == 0) {
        LOG(INFO) << "Check OK";
        return 0;
    } else {
        LOG(ERROR) << "Check failed (code " << rc << ")";

        /* Ignore return/errno value. We know it's exFAT, so any file system
         * check/repair results should be considered a bonus. The driver should
         * be able to mount the volume in any case and deal with inconsistencies
         * appropriately. */
        errno = 0;
        return 0;
    }
}

status_t Mount(const std::string& source, const std::string& target, bool ro,
        bool remount, bool executable, int ownerUid, int ownerGid, int permMask)
{
    int rc;
    unsigned long flags;
    auto mountData = android::base::StringPrintf("utf8,uid=%d,gid=%d,fmask=%o,dmask=%o", ownerUid,
                                                 ownerGid, permMask, permMask);

    flags = MS_NODEV | MS_NOSUID | MS_DIRSYNC | MS_NOATIME;

    flags |= (executable ? 0 : MS_NOEXEC);
    flags |= (ro ? MS_RDONLY : 0);
    flags |= (remount ? MS_REMOUNT : 0);

    rc = mount(source.c_str(), target.c_str(), "texfat", flags, mountData.c_str());

    if (rc && errno == EROFS) {
        LOG(ERROR) << source << "appears to be a read only filesystem - retrying mount RO";
        flags |= MS_RDONLY;
        rc = mount(source.c_str(), target.c_str(), "texfat", flags, mountData.c_str());
    }

    return rc;
}

static status_t DoFormat(const std::string& source, unsigned long numSectors,
        bool wholeDevice, bool partitionOnly, bool wipe) {
    const char *const fsPath = source.c_str();

    if (!wholeDevice && partitionOnly) {
        LOG(ERROR) << "Cannot partition non-whole device.";
        errno = EIO;
        return -1;
    }

    LOG(INFO) << (partitionOnly ? "Partitioning" : "Formatting")
              << " SDXC " << (partitionOnly ? "card" : "exFAT file system")
              << " at \"" << fsPath << "\" as "
              << (wholeDevice ? "whole device" : "single partition") << "...";

    std::vector<std::string> cmd;
    cmd.push_back(kMkfsPath);
    if (wholeDevice)
        cmd.push_back("--sda-whole");
    cmd.push_back("--sda-strict");

    if (partitionOnly) {
        cmd.push_back("--sda-partitioning-only");
    }

    if (wipe) {
        cmd.push_back("--discard");
    }

    if (numSectors) {
        char tmp[32];
        snprintf(tmp, sizeof(tmp), "%lu", numSectors);
        cmd.push_back("--sector-count");
        cmd.push_back(tmp);
    }

    cmd.push_back(source);

    int rc = ForkExecvp(cmd);
    if (rc == 0) {
        LOG(INFO) << "Format OK";
        return 0;
    } else {
        LOG(ERROR) << "Format failed (code " << rc << ")";
        errno = EIO;
        return -1;
    }
    return 0;
}

status_t Format(const std::string& source, unsigned long numSectors) {
    return DoFormat(source, numSectors, false, false, false);
}

static int getDeviceSize(const char *const devicePath, uint64_t *const outSize)
{
    int err = 0;
    int fd = open(devicePath, O_RDONLY | O_CLOEXEC);
    if (fd == -1)
        err = errno ? errno : EIO;
    else {
        uint64_t size;
        if (ioctl(fd, BLKGETSIZE64, &size) == -1)
            err = errno ? errno : EIO;
        else
            *outSize = size;

        close(fd);
    }

    return err;
}

int CheckSize(const std::string& source, bool isPartition) {
    const char *const wholeDevicePath = source.c_str();

    const unsigned long long limit_min =
        isPartition ? 34342961152ULL : 34359738368ULL;
    const unsigned long long limit_max =
        isPartition ? 2198956146688ULL : 2199023255552ULL;

    int res;
    uint64_t size = 0;
    int err = getDeviceSize(wholeDevicePath, &size);
    if (!err) {
        if (size < limit_min || size > limit_max)
            res = 0;
        else
            res = 1;
    }
    else {
        res = -1;
        errno = err;
    }

    return res;
}

status_t PartitionDisk(const std::string& source) {
    return DoFormat(source, 0, true, true, false);
}

#ifndef VFAT_IOCTL_GET_VOLUME_ID
#define VFAT_IOCTL_GET_VOLUME_ID    _IOR('r', 0x12, __u32)
#endif

extern "C" {
    typedef struct _TUXERA_IOCTL_GET_VOLUME_LABEL_ARGS {
        __u32 size;     /* Size in bytes of volume label buffer. */
        __u8 label[];   /* Buffer to return the volume label into of size at least @size
                           bytes. */
    } __attribute__ ((packed)) TUXERA_VOLUME_LABEL;
}

#ifndef TUXERA_GET_VOLUME_LABEL
#define TUXERA_GET_VOLUME_LABEL     _IOWR('X', 2, TUXERA_VOLUME_LABEL)
#endif

int ExtractMetadata(const char *mountPoint, char **outVolumeLabel,
                    char **outVolumeUuid)
{
    int err = 0;
    __u32 returnedLabelSize;
    __u32 volumeLabelSize;
    TUXERA_VOLUME_LABEL *volumeLabel = NULL;
    __u32 volumeLabelBufferSize = 0;
    char *volumeLabelBuffer = NULL;
    __u32 volumeUuidBufferSize = 0;
    char *volumeUuidBuffer = NULL;
    int fd = -1;
    int volumeId;

    fd = open(mountPoint, O_RDONLY | O_CLOEXEC);
    if(fd == -1) {
        err = errno ? errno : ENOENT;
        LOG(ERROR) << "Error while opening mount point: " << strerror(errno)
                   << " (" << errno << ")";
        goto out;
    }

    volumeLabelSize = 4096;
    while(1) {
        TUXERA_VOLUME_LABEL *newVolumeLabel;
        int res;

        newVolumeLabel = (TUXERA_VOLUME_LABEL*) realloc(volumeLabel,
            sizeof(TUXERA_VOLUME_LABEL) + volumeLabelSize);
        if(!newVolumeLabel) {
            err = errno ? errno : ENOMEM;
            LOG(ERROR) << "Error while reallocating memory (" << volumeLabelSize
                       << " bytes) for TUXERA_VOLUME_LABEL: " << strerror(errno)
                       << " (" << errno << ")";
            goto out;
        }

        volumeLabel = newVolumeLabel;

        memset(volumeLabel, 0, sizeof(TUXERA_VOLUME_LABEL) + volumeLabelSize);
        volumeLabel->size = volumeLabelSize;

        if((res = ioctl(fd, TUXERA_GET_VOLUME_LABEL, volumeLabel)) < 0) {
            err = errno ? errno : EINVAL;
            LOG(ERROR) << "Error while issuing IOCTL to get volume label: "
                       << strerror(errno) << " (" << errno << ")";
            goto out;
        }

        returnedLabelSize = (__u32) res;

        if(volumeLabelSize >= returnedLabelSize + 1) {
            break;
        }

        volumeLabelSize = returnedLabelSize + 1;
    }

    volumeLabelBufferSize = volumeLabel->size + 1;
    volumeLabelBuffer = (char*) malloc(volumeLabelBufferSize);
    if(!volumeLabelBuffer) {
        err = errno ? errno : ENOMEM;
        LOG(ERROR) << "Error while allocating volume label buffer: "
                   << strerror(errno) << " (" << errno << ")";
        goto out;
    }

    memcpy(volumeLabelBuffer, volumeLabel->label, volumeLabel->size);
    volumeLabelBuffer[volumeLabel->size] = '\0';

    volumeUuidBufferSize = 10;
    volumeUuidBuffer = (char*) malloc(volumeUuidBufferSize);
    if(!volumeUuidBuffer) {
        err = errno ? errno : ENOMEM;
        LOG(ERROR) << "Error while allocating volume UUID buffer: "
                   << strerror(errno) << " (" << errno << ")";
        goto out;
    }

    volumeId = ioctl(fd, VFAT_IOCTL_GET_VOLUME_ID, NULL);
    if(volumeId == -1) {
        err = errno ? errno : EINVAL;
        LOG(ERROR) << "Error while issuing IOCTL to get volume ID: "
                   << strerror(errno) << " (" << errno << ")";
        goto out;
    }

    if(snprintf(volumeUuidBuffer, volumeUuidBufferSize, "%04X-%04X",
            (volumeId >> 16) & 0xFFFF, volumeId & 0xFFFF) != 9)
    {
        err = errno ? errno : EINVAL;
        LOG(ERROR) << "Error while constructing volume UUID string: "
                   << strerror(errno) << " (" << errno << ")";
        goto out;
    }

out:
    if(err) {
        if(volumeUuidBuffer) {
            free(volumeUuidBuffer);
        }

        if(volumeLabelBuffer) {
            free(volumeLabelBuffer);
        }
    }
    else {
        *outVolumeLabel = volumeLabelBuffer;
        *outVolumeUuid = volumeUuidBuffer;
    }

    if(volumeLabel) {
        free(volumeLabel);
    }

    if(fd != -1) {
        close(fd);
    }

    return err;
}

}  // namespace exfat
}  // namespace vold
}  // namespace android