kernel/object/bus_transaction_initiator_dispatcher.cpp

// Copyright 2017 The Fuchsia Authors
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT

#include <object/bus_transaction_initiator_dispatcher.h>

#include <dev/iommu.h>
#include <err.h>
#include <vm/vm_object.h>
#include <zircon/rights.h>
#include <zxcpp/new.h>
#include <fbl/auto_lock.h>

zx_status_t BusTransactionInitiatorDispatcher::Create(fbl::RefPtr<Iommu> iommu, uint64_t bti_id,
                                                      fbl::RefPtr<Dispatcher>* dispatcher,
                                                      zx_rights_t* rights) {

    if (!iommu->IsValidBusTxnId(bti_id)) {
        return ZX_ERR_INVALID_ARGS;
    }

    fbl::AllocChecker ac;
    auto disp = new (&ac) BusTransactionInitiatorDispatcher(fbl::move(iommu), bti_id);
    if (!ac.check()) {
        return ZX_ERR_NO_MEMORY;
    }

    *rights = ZX_DEFAULT_BTI_RIGHTS;
    *dispatcher = fbl::AdoptRef<Dispatcher>(disp);
    return ZX_OK;
}

BusTransactionInitiatorDispatcher::BusTransactionInitiatorDispatcher(fbl::RefPtr<Iommu> iommu,
                                                                     uint64_t bti_id)
        : iommu_(fbl::move(iommu)), bti_id_(bti_id), zero_handles_(false) {}

BusTransactionInitiatorDispatcher::~BusTransactionInitiatorDispatcher() {
    DEBUG_ASSERT(pinned_memory_.is_empty());
}

zx_status_t BusTransactionInitiatorDispatcher::Pin(fbl::RefPtr<VmObject> vmo, uint64_t offset,
                                                   uint64_t size, uint32_t perms,
                                                   fbl::RefPtr<Dispatcher>* pmt,
                                                   zx_rights_t* pmt_rights) {

    DEBUG_ASSERT(IS_PAGE_ALIGNED(offset));
    DEBUG_ASSERT(IS_PAGE_ALIGNED(size));

    if (size == 0) {
        return ZX_ERR_INVALID_ARGS;
    }

    fbl::AutoLock guard(&lock_);

    if (zero_handles_) {
        return ZX_ERR_BAD_STATE;
    }

    return PinnedMemoryTokenDispatcher::Create(fbl::WrapRefPtr(this), fbl::move(vmo),
                                               offset, size, perms, pmt, pmt_rights);
}

void BusTransactionInitiatorDispatcher::ClearQuarantine() {
    QuarantineList tmp;

    // The PMT dtor will call RemovePmo, which will reacquire this BTI's lock.
    // To avoid deadlock, drop the lock before letting the quarantined PMTs go.
    {
        fbl::AutoLock guard(&lock_);
        quarantine_.swap(tmp);
    }
}

void BusTransactionInitiatorDispatcher::on_zero_handles() {
    fbl::AutoLock guard(&lock_);
    // Prevent new pinning from happening.  The Dispatcher will stick around
    // until all of the PMTs are closed.
    zero_handles_ = true;

    // Do not clear out the quarantine list.  PMTs hold a reference to the BTI
    // and the BTI holds a reference to each quarantined PMT.  We intentionally
    // leak the BTI, all quarantined PMTs, and their underlying VMOs.  We could
    // get away with freeing the BTI and the PMTs, but for safety we must leak
    // at least the pinned parts of the VMOs, since we have no assurance that
    // hardware is not still reading/writing to it.
    if (!quarantine_.is_empty()) {
        PrintQuarantineWarningLocked();
    }
}

void BusTransactionInitiatorDispatcher::AddPmoLocked(PinnedMemoryTokenDispatcher* pmt) {
    DEBUG_ASSERT(!pmt->dll_pmt_.InContainer());
    pinned_memory_.push_back(pmt);
}

void BusTransactionInitiatorDispatcher::RemovePmo(PinnedMemoryTokenDispatcher* pmt) {
    fbl::AutoLock guard(&lock_);
    DEBUG_ASSERT(pmt->dll_pmt_.InContainer());
    pinned_memory_.erase(*pmt);
}

void BusTransactionInitiatorDispatcher::Quarantine(fbl::RefPtr<PinnedMemoryTokenDispatcher> pmt) {
    fbl::AutoLock guard(&lock_);

    DEBUG_ASSERT(pmt->dll_pmt_.InContainer());
    quarantine_.push_back(fbl::move(pmt));

    if (zero_handles_) {
        // If we quarantine when at zero handles, this PMT will be leaked.  See
        // the comment in on_zero_handles().
        PrintQuarantineWarningLocked();
    }
}

void BusTransactionInitiatorDispatcher::PrintQuarantineWarningLocked() {
    uint64_t leaked_pages = 0;
    size_t num_entries = 0;
    for (const auto& pmt : quarantine_) {
        leaked_pages += pmt.size() / PAGE_SIZE;
        num_entries++;
    }
    printf("Bus Transaction Initiator 0x%lx has leaked %" PRIu64 " pages in %zu VMOs\n",
           bti_id_, leaked_pages, num_entries);
}