ulib/fvm-host/fvm-info.cpp

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "fvm-host/format.h"
#include "fvm-host/fvm-info.h"

zx_status_t FvmInfo::Reset(size_t disk_size, size_t slice_size) {
    valid_ = false;

    if (slice_size == 0) {
        fprintf(stderr, "Invalid slice size\n");
        return ZX_ERR_INVALID_ARGS;
    }

    // Even if disk size is 0, this will default to at least FVM_BLOCK_SIZE
    metadata_size_ = fvm::MetadataSize(disk_size, slice_size);
    metadata_.reset(new uint8_t[metadata_size_ * 2]);

    // Clear entire primary copy of metadata
    memset(metadata_.get(), 0, metadata_size_);

    // Superblock
    fvm::fvm_t* sb = SuperBlock();
    sb->magic = FVM_MAGIC;
    sb->version = FVM_VERSION;
    sb->pslice_count = fvm::UsableSlicesCount(disk_size, slice_size);
    sb->slice_size = slice_size;
    sb->fvm_partition_size = disk_size;
    sb->vpartition_table_size = fvm::kVPartTableLength;
    sb->allocation_table_size = fvm::AllocTableLength(disk_size, slice_size);
    sb->generation = 0;

    if (sb->pslice_count == 0) {
        fprintf(stderr, "No space available for slices\n");
        return ZX_ERR_NO_SPACE;
    }

    valid_ = true;
    dirty_ = true;

    xprintf("fvm_init: Success\n");
    xprintf("fvm_init: Slice Count: %" PRIu64 ", size: %" PRIu64 "\n", sb->pslice_count,
            sb->slice_size);
    xprintf("fvm_init: Vpart offset: %zu, length: %zu\n",
            fvm::kVPartTableOffset, fvm::kVPartTableLength);
    xprintf("fvm_init: Atable offset: %zu, length: %zu\n",
            fvm::kAllocTableOffset, fvm::AllocTableLength(disk_size_, slice_size_));
    xprintf("fvm_init: Backup meta starts at: %zu\n",
            fvm::BackupStart(disk_size_, slice_size_));
    xprintf("fvm_init: Slices start at %zu, there are %zu of them\n",
            fvm::SlicesStart(disk_size_, slice_size_),
            fvm::UsableSlicesCount(disk_size_, slice_size_));

    return ZX_OK;
}

zx_status_t FvmInfo::Load(const fbl::unique_fd& fd, uint64_t disk_offset, uint64_t disk_size) {
    valid_ = false;

    if (disk_size == 0) {
        return ZX_OK;
    }

    // For now just reset this to the fvm header size - we can grow it to the full metadata size
    // later.
    metadata_.reset(new uint8_t[sizeof(fvm::fvm_t)]);

    // If Container already exists, read metadata from disk.
    // Read superblock first so we can determine if container has a different slice size.
    ssize_t result = pread(fd.get(), metadata_.get(), sizeof(fvm::fvm_t), disk_offset);
    if (result != static_cast<ssize_t>(sizeof(fvm::fvm_t))) {
        fprintf(stderr, "Superblock read failed: expected %ld, actual %ld\n",
                sizeof(fvm::fvm_t), result);
        return ZX_ERR_IO;
    }

    // If the image is obviously not an FVM header, bail out early.
    // Otherwise, we go through the effort of ensuring the header is
    // valid before using it.
    if (SuperBlock()->magic != FVM_MAGIC) {
        return ZX_OK;
    }

    if (DiskSize() != disk_size) {
        fprintf(stderr, "Disk size does not match expected");
        return ZX_ERR_BAD_STATE;
    }

    // Recalculate metadata size.
    size_t old_slice_size = SuperBlock()->slice_size;
    size_t old_metadata_size = fvm::MetadataSize(disk_size, old_slice_size);
    fbl::unique_ptr<uint8_t[]> old_metadata =
        fbl::make_unique<uint8_t[]>(old_metadata_size * 2);

    // Read remainder of metadata.
    result = pread(fd.get(), old_metadata.get(), old_metadata_size * 2, disk_offset);
    if (result != static_cast<ssize_t>(old_metadata_size * 2)) {
        fprintf(stderr, "Metadata read failed: expected %ld, actual %ld\n",
                old_metadata_size * 2, result);
        return ZX_ERR_IO;
    }

    metadata_size_ = old_metadata_size;
    metadata_.reset(old_metadata.release());

    if (Validate() == ZX_OK) {
        valid_ = true;
    }

    return ZX_OK;
}

zx_status_t FvmInfo::Validate() const {
    const void* primary = nullptr;
    const void* backup = reinterpret_cast<void*>(
        reinterpret_cast<uintptr_t>(metadata_.get()) + metadata_size_);
    zx_status_t status = fvm_validate_header(metadata_.get(), backup, metadata_size_, &primary);

    if (status != ZX_OK) {
        fprintf(stderr, "Header validation failed with status %d\n", status);
        return status;
    }

    if (primary != metadata_.get()) {
        fprintf(stderr, "Can only update FVM with valid primary as first copy\n");
        return ZX_ERR_NOT_SUPPORTED;
    }

    return ZX_OK;
}

zx_status_t FvmInfo::Write(const fbl::unique_fd& fd, size_t disk_offset, size_t disk_size) {
    fvm::fvm_t* sb = SuperBlock();
    if (disk_size != sb->fvm_partition_size) {
        // If disk size has changed, update and attempt to grow metadata.
        sb->pslice_count = fvm::UsableSlicesCount(disk_size, SliceSize());
        sb->fvm_partition_size = disk_size;
        sb->allocation_table_size = fvm::AllocTableLength(disk_size, SliceSize());

        size_t new_metadata_size = fvm::MetadataSize(disk_size, SliceSize());
        zx_status_t status = Grow(new_metadata_size);
        if (status != ZX_OK) {
            return status;
        }
    }

    fvm_update_hash(metadata_.get(), metadata_size_);

    if (Validate() != ZX_OK) {
        fprintf(stderr, "Metadata is invalid");
        return ZX_ERR_BAD_STATE;
    }

    if (lseek(fd.get(), disk_offset, SEEK_SET) < 0) {
        fprintf(stderr, "Error seeking disk\n");
        return ZX_ERR_IO;
    }

    if (write(fd.get(), metadata_.get(), metadata_size_) != static_cast<ssize_t>(metadata_size_)) {
        fprintf(stderr, "Error writing metadata to disk\n");
        return ZX_ERR_IO;
    }

    if (write(fd.get(), metadata_.get(), metadata_size_) != static_cast<ssize_t>(metadata_size_)) {
        fprintf(stderr, "Error writing metadata to disk\n");
        return ZX_ERR_IO;
    }

    return ZX_OK;
}

void FvmInfo::CheckValid() const {
    if (!valid_) {
        fprintf(stderr, "Error: FVM is invalid\n");
        exit(-1);
    }
}

zx_status_t FvmInfo::Grow(size_t new_size) {
    if (new_size <= metadata_size_) {
        return ZX_OK;
    }

    xprintf("Growing metadata from %zu to %zu\n", metadata_size_, new_size);
    fbl::unique_ptr<uint8_t[]> new_metadata(new uint8_t[new_size * 2]);

    memcpy(new_metadata.get(), metadata_.get(), metadata_size_);
    memset(new_metadata.get() + metadata_size_, 0, new_size - metadata_size_);

    metadata_.reset(new_metadata.release());
    metadata_size_ = new_size;
    return ZX_OK;
}

zx_status_t FvmInfo::GrowForSlices(size_t slice_count) {
    size_t required_size = fvm::kAllocTableOffset + (pslice_hint_ + slice_count)
                           * sizeof(fvm::slice_entry_t);
    return Grow(required_size);
}

zx_status_t FvmInfo::AllocatePartition(const fvm::partition_descriptor_t* partition, uint8_t* guid,
                                       uint32_t* vpart_index) {
    CheckValid();
    for (unsigned index = vpart_hint_; index < FVM_MAX_ENTRIES; index++) {
        zx_status_t status;
        fvm::vpart_entry_t* vpart = nullptr;
        if ((status = GetPartition(index, &vpart)) != ZX_OK) {
            fprintf(stderr, "Failed to retrieve partition %u\n", index);
            return status;
        }

        // Make sure this vpartition has not already been allocated
        if (vpart->slices == 0) {
            vpart->init(partition->type, guid, 0, reinterpret_cast<const char*>(partition->name),
                        partition->flags);
            vpart_hint_ = index + 1;
            dirty_ = true;
            *vpart_index = index;
            return ZX_OK;
        }
    }

    fprintf(stderr, "Unable to find any free partitions\n");
    return ZX_ERR_INTERNAL;
}

zx_status_t FvmInfo::AllocateSlice(uint32_t vpart, uint32_t vslice, uint32_t* pslice) {
    CheckValid();
    fvm::fvm_t* sb = SuperBlock();

    for (uint32_t index = pslice_hint_; index <= sb->pslice_count; index++) {
        zx_status_t status;
        fvm::slice_entry_t* slice = nullptr;
        if ((status = GetSlice(index, &slice)) != ZX_OK) {
            fprintf(stderr, "Failed to retrieve slice %u\n", index);
            return status;
        }

        if (slice->Vpart() != FVM_SLICE_ENTRY_FREE) {
            continue;
        }

        pslice_hint_ = index + 1;

        fvm::vpart_entry_t* partition;
        if ((status = GetPartition(vpart, &partition)) != ZX_OK) {
            return status;
        }

        slice->SetVpart(vpart);
        slice->SetVslice(vslice);
        partition->slices++;

        dirty_ = true;
        *pslice = index;
        return ZX_OK;
    }

    fprintf(stderr, "Unable to find any free slices\n");
    return ZX_ERR_INTERNAL;
}

zx_status_t FvmInfo::GetPartition(size_t index, fvm::vpart_entry_t** out) const {
    CheckValid();

    if (index < 1 || index > FVM_MAX_ENTRIES) {
        return ZX_ERR_OUT_OF_RANGE;
    }

    uintptr_t metadata_start = reinterpret_cast<uintptr_t>(metadata_.get());
    uintptr_t offset = static_cast<uintptr_t>(fvm::kVPartTableOffset +
                                              index * sizeof(fvm::vpart_entry_t));
    *out = reinterpret_cast<fvm::vpart_entry_t*>(metadata_start + offset);
    return ZX_OK;
}

zx_status_t FvmInfo::GetSlice(size_t index, fvm::slice_entry_t** out) const {
    CheckValid();

    if (index < 1 || index > SuperBlock()->pslice_count) {
        return ZX_ERR_OUT_OF_RANGE;
    }

    uintptr_t metadata_start = reinterpret_cast<uintptr_t>(metadata_.get());
    uintptr_t offset = static_cast<uintptr_t>(fvm::kAllocTableOffset +
                                              index * sizeof(fvm::slice_entry_t));
    *out = reinterpret_cast<fvm::slice_entry_t*>(metadata_start + offset);
    return ZX_OK;
}

fvm::fvm_t* FvmInfo::SuperBlock() const {
    return static_cast<fvm::fvm_t*>((void*)metadata_.get());
}