trusty/fuzz/counters.cpp

/*
 * Copyright (C) 2020 The Android Open Sourete Project
 *
 * 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.
 */

#define LOG_TAG "trusty-fuzz-counters"

#include <trusty/fuzz/counters.h>

#include <android-base/logging.h>
#include <assert.h>
#include <log/log.h>
#include <string.h>
#include <trusty/coverage/coverage.h>
#include <trusty/coverage/tipc.h>

using android::base::ErrnoError;
using android::base::Error;
using android::base::Result;

/*
 * We don't know how many counters the coverage record will contain. So, eyeball
 * the size of this section.
 */
static const size_t kMaxNumCounters = 0x10000;
__attribute__((section("__libfuzzer_extra_counters"))) volatile uint8_t counters[kMaxNumCounters];

namespace android {
namespace trusty {
namespace fuzz {

ExtraCounters::ExtraCounters(coverage::CoverageRecord* record) : record_(record) {
    if (!record_->IsOpen()) {
        return;
    }

    volatile uint8_t* begin = NULL;
    volatile uint8_t* end = NULL;
    record_->GetRawCounts(&begin, &end);
    assert(end - begin <= sizeof(counters));
}

ExtraCounters::~ExtraCounters() {
    if (!record_->IsOpen()) {
        return;
    }

    Flush();
}

void ExtraCounters::Reset() {
    if (!record_->IsOpen()) {
        return;
    }
    record_->ResetCounts();
    memset_explicit(const_cast<uint8_t*>(counters), 0, sizeof(counters));
}

void ExtraCounters::Flush() {
    volatile uint8_t* begin = NULL;
    volatile uint8_t* end = NULL;

    record_->GetRawCounts(&begin, &end);
    if (!begin || !end) {
        ALOGE("Could not get raw counts from coverage record\n");
        return;
    }

    size_t num_counters = end - begin;
    if (num_counters > kMaxNumCounters) {
        ALOGE("Too many counters (%zu) to fit in the extra counters section!\n", num_counters);
        num_counters = kMaxNumCounters;
    }
    for (size_t i = 0; i < num_counters; i++) {
        *(counters + i) = *(begin + i);
    }
}

}  // namespace fuzz
}  // namespace trusty
}  // namespace android